PHENTERMINE: 1,780 Adverse Event Reports & Safety Profile

Phentermine and topiramate extended-release capsules are comprised of immediate-release phentermine hydrochloride (expressed as the weight of the free base) and extended-release topiramate. Phentermine and topiramate extended-release capsules contain phentermine hydrochloride USP, a sympathomimetic amine anorectic, and topiramate USP, a sulfamate-substituted monosaccharide.

Phentermine

Hydrochloride, USP The chemical name of phentermine hydrochloride, USP is α,α-dimethylphenethylamine hydrochloride. The molecular formula is C 10 H 15 N

• HCl and its molecular weight is 185.7 (hydrochloride salt) or 149.2 (free base). Phentermine hydrochloride, USP is a white, odorless, hygroscopic, crystalline powder that is soluble in water, methanol, and ethanol. Its structural formula is: Topiramate, USP Topiramate, USP is 2,3:4,5-di-O-isopropylidene-β-D-fructopyranose sulfamate. The molecular formula is C 12 H 21 NO 8 S and its molecular weight is 339.4. Topiramate, USP is a white to off-white crystalline powder with a bitter taste. It is freely soluble in methanol and acetone, sparingly soluble in pH 9 to pH 12 aqueous solutions and slightly soluble in pH 1 to pH 8 aqueous solutions. Its structural formula is: Phentermine and topiramate extended-release capsules are for oral administration and available in four dosage strengths: 3.75 mg/23 mg (phentermine 3.75 mg and topiramate 23 mg extended-release) (equivalent to 4.67 mg of phentermine hydrochloride, USP). 7.5 mg/46 mg (phentermine 7.5 mg and topiramate 46 mg extended-release) (equivalent to 9.33 mg of phentermine hydrochloride, USP). 11.25 mg/69 mg (phentermine 11.25 mg and topiramate 69 mg extended-release) (equivalent to 14.0 mg of phentermine hydrochloride, USP). 15 mg/92 mg (phentermine 15 mg and topiramate 92 mg extended-release) (equivalent to 18.66 mg of phentermine hydrochloride, USP). Each capsule contains the following inactive ingredients: colloidal silicon dioxide, copovidone, ethylcellulose, gelatin, hypromellose, microcrystalline cellulose, polysorbate 80, povidone K-30, sugar spheres (which contain sucrose and corn starch), talc, and titanium dioxide.

The

3.75 mg/23 mg strength also contains iron oxide red and iron oxide yellow.

The

7.5 mg/46 mg strength also contains FD&C Blue #2 and iron oxide yellow.

The

11.25 mg/69 mg strength also contains iron oxide yellow.

The

15 mg/92 mg strength also contains iron oxide red. The imprinting ink contains ammonium hydroxide, iron oxide black, propylene glycol, and shellac glaze. 1 1

1 INDICATIONS & USAGE Phentermine hydrochloride tablets USP are indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m 2 , or greater than or equal to 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). Below is a chart of body mass index (BMI) based on various heights and weights. BMI is calculated by taking the patient's weight, in kilograms (kg), divided by the patient's height, in meters (m), squared. Metric conversions are as follows: pounds ÷ 2.2 = kg; inches x 0.0254 = meters. BODY MASS INDEX (BMI), kg/m 2 Height (feet, inches) Weight (pounds) 5'0" 5'3" 5'6" 5'9" 6'0" 6'3" 140 27 25 23 21 19 18 150 29 27 24 22 20 19 160 31 28 26 24 22 20 170 33 30 28 25 23 21 180 35 32 29 27 25 23 190 37 34 31 28 26 24 200 39 36 32 30 27 25 210 41 37 34 31 29 26 220 43 39 36 33 30 28 230 45 41 37 34 31 29 240 47 43 39 36 33 30 250 49 44 40 37 34 31 The limited usefulness of agents of this class, including phentermine, [see Clinical Pharmacology ( 12.1 , 12.2 ) ] should be measured against possible risk factors inherent in their use such as those described below. Phentermine hydrochloride is a sympathomimetic amine anorectic indicated as a short-term adjunct (a few weeks) in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m 2 , or greater than or equal to 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). ( 1 ) The limited usefulness of agents of this class, including phentermine hydrochloride tablets USP, should be measured against possible risk factors inherent in their use. ( 1 )

AND ADMINISTRATION Take orally once daily in morning. Avoid administration in evening to prevent insomnia ( 2.2 ). Recommended starting dosage is 3.75 mg/23 mg (phentermine mg/topiramate mg) daily for 14 days; then increase to 7.5 mg/46 mg daily ( 2.2 ). Escalate dosage based on weight loss in adults or BMI reduction in pediatric patients. See the Full Prescribing Information for details regarding discontinuation or dosage escalation ( 2.2 ). Gradually discontinue 15 mg/92 mg dosage to prevent possible seizure ( 2.3 ). Do not exceed 7.5 mg/46 mg dosage for patients with moderate or severe renal impairment or patients with moderate hepatic impairment ( 2.4 , 2.5 ).

2.1 Recommended Testing Prior to and During Treatment with Phentermine and Topiramate Extended-Release Capsules Prior to phentermine and topiramate extended-release capsule initiation and during treatment with phentermine and topiramate extended-release capsules, the following is recommended: Obtain a negative pregnancy test before initiating phentermine and topiramate extended-release capsules in patients who can become pregnant and monthly during phentermine and topiramate extended-release capsule therapy. Phentermine and topiramate extended-release capsules are contraindicated during pregnancy <span class="opacity-50 text-xs">[see Contraindications ( 4 ), Warnings and Precautions ( 5.1 ), and Use in Specific Populations ( 8.3 )]</span> . Obtain a blood chemistry profile that includes bicarbonate, creatinine, and potassium in all patients, and glucose in patients with type 2 diabetes mellitus on antidiabetic medication prior to initiating phentermine and topiramate extended-release capsule treatment and periodically during treatment <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.7 , 5.8 , 5.12 )]</span> .

2.2 Recommended Dosage and Administration The recommended dosage, titration, and administration of phentermine and topiramate extended-release capsules are as follows: Take phentermine and topiramate extended-release capsules orally once daily in the morning with or without food. Avoid administration of phentermine and topiramate extended-release capsules in the evening due to the possibility of insomnia. The recommended starting dosage of phentermine and topiramate extended-release capsules is one capsule (containing 3.75 mg of phentermine and 23 mg of topiramate) (3.75 mg/23 mg) taken orally once daily for 14 days; after 14 days increase to the recommended dosage of phentermine and topiramate extended-release capsules 7.5 mg/46 mg orally once daily.

After

12 weeks of treatment with phentermine and topiramate extended-release capsules 7.5 mg/46 mg, evaluate weight loss for adults or BMI reduction for pediatric patients aged 12 years and older. If an adult patient has not lost at least 3% of baseline body weight or a pediatric patient has not experienced a reduction of at least 3% of baseline BMI, increase the dosage to phentermine and topiramate extended-release capsules 11.25 mg/69 mg orally once daily for 14 days; followed by an increase in the dosage to phentermine and topiramate extended-release capsules 15 mg/92 mg orally once daily.

After

12 weeks of treatment with phentermine and topiramate extended-release capsules 15 mg/92 mg, evaluate weight loss for adults or BMI reduction for pediatric patients aged 12 years and older. If an adult patient has not lost at least 5% of baseline body weight or a pediatric patient has not experienced a reduction of at least 5% of baseline BMI, discontinue phentermine and topiramate extended-release capsules [see Dosage and Administration ( 2.3 )] , as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss with continued treatment. Monitor the rate of weight loss in pediatric patients. If weight loss exceeds 2 lbs (0.9 kg)/week, consider dosage reduction.

2.3 Discontinuation of Phentermine and Topiramate Extended-Release Capsules 15 mg/92 mg Discontinue phentermine and topiramate extended-release capsules 15 mg/92 mg gradually by taking phentermine and topiramate extended-release capsules 15 mg/92 mg orally once daily every other day for at least 1 week prior to stopping treatment altogether, due to the possibility of precipitating a seizure <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.9 ) and Drug Abuse and Dependence ( 9.3 )]</span> .

2.4 Recommended Dosage in Patients with Renal Impairment The recommended dosage in patients with mild (CrCl greater or equal to 50 and less than 80 mL/min) renal impairment is the same as the recommended dosage for patients with normal renal function <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.9 ), Use in Specific Populations ( 8.6 ), and Clinical Pharmacology ( 12.3 )]</span> . In patients with severe [creatinine clearance (CrCl) less than 30 mL/min] or moderate (CrCl greater than or equal to 30 and less than 50 mL/min) renal impairment (CrCl calculated using the Cockcroft-Gault equation with actual body weight), the maximum recommended dosage is phentermine and topiramate extended-release capsules 7.5 mg/46 mg once daily. Avoid use of phentermine and topiramate extended-release capsules in patients with end-stage renal disease on dialysis.

2.5 Recommended Dosage in Patients with Hepatic Impairment The recommended dosage of phentermine and topiramate extended-release capsules in patients with mild hepatic impairment (Child-Pugh 5 to 6) is the same as the recommended dosage in patients with normal hepatic function <span class="opacity-50 text-xs">[see Use in Specific Populations ( 8.7 ), and Clinical Pharmacology ( 12.3 )]</span> . In patients with moderate hepatic impairment (Child-Pugh score 7 to 9), the maximum recommended dosage is phentermine and topiramate extended-release capsules 7.5 mg/46 mg orally once daily. Avoid use of phentermine and topiramate extended-release capsules in patients with severe hepatic impairment (Child-Pugh score 10 to 15).

4 CONTRAINDICATIONS

• History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension)
• During or within 14 days following the administration of monoamine oxidase inhibitors
• Hyperthyroidism
• Glaucoma
• Agitated states
• History of drug abuse
• Pregnancy [ see Use in Specific Populations ( Error! Hyperlink reference not valid. ) ]
• Nursing [ see Use in Specific Populations ( 8.3 ) ]
• Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines
• History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) ( Error! Hyperlink reference not valid. )
• During or within 14 days following the administration of monoamine oxidase inhibitors ( 4 )
• Hyperthyroidism ( 4 )
• Glaucoma ( 4 )
• Agitated states ( 4 )
• History of drug abuse ( 4 )
• Pregnancy ( 4 , 8.1 )
• Nursing ( 4 , Error! Hyperlink reference not valid. )
• Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines ( 4 )

REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: Embryo-Fetal Toxicity [see Warnings and Precautions (5.1) and Use in Specific Populations (8.1 , 8.6) ]

Suicidal

Behavior and Ideation [see Warnings and Precautions (5.2) ] Risk of Ophthalmologic Adverse Reactions [see Warnings and Precautions (5.3) ] Mood and Sleep Disorders [see Warnings and Precautions (5.4) ]

Cognitive

Impairment [see Warnings and Precautions (5.5) ] Slowing of Linear Growth [see Warnings and Precautions (5.6) ]

Metabolic

Acidosis [see Warnings and Precautions (5.7) ] Decrease in Renal Function [see Warnings and Precautions (5.8) ] Risk of Seizures with Abrupt Withdrawal of phentermine and topiramate extended-release capsules [see Warnings and Precautions (5.9) ]

Kidney

Stones [see Warnings and Precautions (5.10) ] Oligohydrosis and Hyperthermia [see Warnings and Precautions (5.11) ] Hypokalemia [see Warnings and Precautions (5.12) ]

Serious Skin

Reactions [see Warnings and Precautions (5.13) ] Most common adverse reactions in: Adults (incidence ≥ 5% and at least 1.5 times placebo) are: paraesthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth ( 6.1 ). Pediatric patients aged 12 years and older (incidence ≥4% and greater than placebo) are: depression, dizziness, arthralgia, pyrexia, influenza, and ligament sprain ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact VIVUS LLC, at 1-888-998-4887 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice. The data described herein reflect exposure to phentermine and topiramate extended-release capsules in two 1-year, randomized, double-blind, placebo-controlled, multicenter clinical trials and two supportive trials in 2,318 adult patients with overweight or obesity [936 (40%) patients with hypertension, 309 (13%) patients with type 2 diabetes mellitus, 808 (35%) patients with BMI greater than 40 kg/m 2 ] exposed for a mean duration of 298 days. Data in this section also describe adverse reactions from a 1-year, randomized, double-blind, placebo-controlled multicenter clinical trial that evaluated 223 pediatric patients (12 to 17 years old) with obesity <span class="opacity-50 text-xs">[see Clinical Studies (14) ]</span> .

Adults

Adverse reactions occurring at greater than or equal to 5% and at least 1.5 times placebo in adults include paraesthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth. Adverse reactions reported in greater than or equal to 2% of phentermine and topiramate extended-release capsule-treated adults and more frequently than in the placebo group are shown in Table 1 .

Table

1.

Adverse Reactions

Reported in ≥2% of Phentermine and Topiramate Extended-Release Capsule-Treated Adults with Overweight or Obesity and More Frequently than Placebo in Overall Study Population of 1 Year Duration Adverse Reaction Placebo (N = 1561) % Phentermine and Topiramate Extended- Release Capsules 3.75 mg/23 mg (N = 240) % Phentermine and Topiramate Extended- Release Capsules 7.5 mg/46 mg (N = 498) % Phentermine and Topiramate Extended- Release Capsules 15 mg/92 mg (N = 1,580) % Paraesthesia 2 4 14 20 Dry Mouth 3 7 14 19 Constipation 6 8 15 16 Upper Respiratory Tract Infection 13 16 12 14 Headache 9 10 7 11 Dysgeusia 1 1 7 9 Insomnia 5 5 6 9 Nasopharyngitis 8 13 11 9 Dizziness 3 3 7 9 Sinusitis 6 8 7 8 Nausea 4 6 4 7 Back Pain 5 5 6 7 Fatigue 4 5 4 6 Diarrhea 5 5 6 6 Vision Blurred 4 6 4 5 Bronchitis 4 7 4 5 Urinary Tract Infection 4 3 5 5 Cough 4 3 4 5 Influenza 4 8 5 4 Depression 2 3 3 4 Anxiety 2 3 2 4 Hypoesthesia 1 1 4 4 Irritability 1 2 3 4 Alopecia 1 2 3 4 Disturbance in Attention 1 0 2 4 Pain in Extremity 3 2 3 3 Muscle Spasms 2 3 3 3 Dyspepsia 2 2 2 3 Gastroesophageal Reflux Disease 1 1 3 3 Rash 2 2 2 3 Hypokalemia 0 0 1 3 Dry Eye 1 1 1 3 Gastroenteritis 2 1 2 3 Pharyngolaryngeal Pain 2 3 1 2 Paraesthesia Oral 0 0 1 2 Eye Pain 1 2 2 2 Nasal Congestion 1 2 1 2 Thirst 1 2 2 2 Sinus Congestion 2 3 3 2 Procedural Pain 2 2 2 2 Palpitations 1 1 2 2 Musculoskeletal Pain 1 1 3 2 Decreased Appetite 1 2 2 2 Neck Pain 1 1 2 1 Dysmenorrhea 0 2 0 1 Chest Discomfort 0 2 0 1 Pediatric Patients Aged 12 Years and Older Adverse reactions occurring in pediatric patients treated with either phentermine and topiramate extended-release capsules 15 mg/92 mg or phentermine and topiramate extended-release capsules 7.5 mg/46 mg at greater than or equal to 4% and higher than placebo include depression, pyrexia, dizziness, arthralgia, influenza, and ligament sprain. Adverse reactions reported in greater than or equal to 2% of phentermine and topiramate extended-release capsule-treated pediatric patients and more frequently than in the placebo group from a study in pediatric patients aged 12 years and older are shown in Table 2 .

Table

2.

Adverse Reactions

Reported in ≥2% of Phentermine and Topiramate Extended-Release Capsule-Treated Pediatric Patients Aged 12 to 17 Years and More Frequently than Placebo during 56 Weeks of Treatment Adverse Reaction Placebo (N = 56) % Phentermine and Topiramate Extended- Release Capsules 7.5 mg/46 mg (N = 54) % Phentermine and Topiramate Extended- Release Capsules 15 mg/92 mg (N = 113) % Depression 0 2 4 Nausea 4 4 4 Pyrexia 2 2 4 Dizziness 0 2 4 Arthralgia 0 2 4 Paraesthesia 0 2 3 Anxiety 0 2 3 Abdominal Pain Upper 0 0 3 Fatigue 2 0 3 Ear Infection 0 2 3 Musculoskeletal Chest Pain 0 0 3 Influenza 0 4 2 Ligament Sprain 0 4 2 Increase in Heart Rate In adult and pediatric clinical trials, there was a higher incidence of heart rate elevations observed in phentermine and topiramate extended-release capsule-treated compared to placebo-treated patients. In an 8-week ambulatory blood pressure monitoring (ABPM) study in adults, phentermine and topiramate extended-release capsules increased the 24-hr average heart rate by 3.6 beats per minute (bpm) (95% CI 2.1, 5.2) compared to the placebo group [see Clinical Pharmacology (12.2) ] . In clinical trials, a higher percentage of phentermine and topiramate extended-release capsule-treated adults and pediatric patients aged 12 years and older experienced heart rate increases from baseline of more than 5, 10, 15, and 20 bpm compared to placebo-treated patients.

Table

3 and Table 4 provide the numbers and percentages of adult and pediatric patients, respectively, with elevations in heart rate in clinical studies of up to one year.

Table

3. Number and Percentage of Adults with Overweight or Obesity with an Increase in Heart Rate at a Single Time Point from Baseline Placebo N=1561 n (%) Phentermine and Topiramate Extended- Release Capsules 3.75 mg/23 mg N=240 n (%) Phentermine and Topiramate Extended- Release Capsules 7.5 mg/46 mg N=498 n (%) Phentermine and Topiramate Extended- Release Capsules 15 mg/92 mg N=1580 n (%) Greater than 5 bpm 1021 (65.4) 168 (70.0) 372 (74.7) 1228 (77.7) Greater than 10 bpm 657 (42.1) 120 (50.0) 251 (50.4) 887 (56.1) Greater than 15 bpm 410 (26.3) 79 (32.9) 165 (33.1) 590 (37.3) Greater than 20 bpm 186 (11.9) 36 (15.0) 67 (13.5) 309 (19.6)

Table

4. Number and Percentage of Pediatric Patients with an Increase in Heart Rate at a Single Time Point from Baseline Placebo N=56 n (%) Phentermine and Topiramate Extended- Release Capsules 7.5 mg/46 mg N=54 n (%) Phentermine and Topiramate Extended- Release Capsules 15 mg/92 mg N=113 n (%) Greater than 5 bpm 37 (66.1) 38 (70.4) 92 (81.4) Greater than 10 bpm 26 (46.4) 30 (55.6) 73 (64.6) Greater than 15 bpm 17 (30.4) 18 (33.3) 48 (42.5) Greater than 20 bpm 10 (17.9) 10 (18.5) 27 (23.9) Paraesthesia/Dysgeusia In adult clinical trials, reports of paraesthesia, characterized as tingling in hands, feet, or face, and dysgeusia, characterized as a metallic taste, occurred (see Table 1 ). Adverse reactions of paraesthesia were also reported in pediatric patients (see Table 2 ). Phentermine and topiramate extended-release capsule-treated adult patients discontinued treatment due to these adverse reactions (1% for paraesthesia and 0.6% for dysgeusia); no pediatric patients discontinued treatment due to paraesthesia or dysgeusia. Mood and Sleep Disorders The proportion of adult patients in 1-year controlled trials of phentermine and topiramate extended-release capsules reporting one or more adverse reactions related to mood and sleep disorders was 15% and 21% with phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 15 mg/92 mg, respectively, compared to 10% with placebo. These events were further categorized into sleep disorders, anxiety, and depression. Reports of sleep disorders were typically characterized as insomnia and occurred in 8.1% and 11% of patients treated with phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 15 mg/92 mg, respectively, compared to 5.8% of patients treated with placebo. Reports of anxiety occurred in 4.8% and 7.9% of patients treated with phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 15 mg/92 mg, respectively, compared to 2.6% of patients treated with placebo. Reports of depression/mood problems occurred in 3.8% and 7.6% of patients treated with phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 15 mg/92 mg, respectively, compared to 3.4% of patients treated with placebo. Mood and sleep disorder adverse reactions occurred in patients with and without a history of depression. In a pediatric clinical trial, higher proportions of phentermine and topiramate extended-release capsule-treated patients reported one or more adverse reactions related to mood (e.g., depression, anxiety) and sleep disorders (e.g., insomnia) compared to placebo-treated patients (see Table 2 ).

Cognitive

Disorders In the 1-year controlled trials of phentermine and topiramate extended-release capsules in adults, the proportion of patients who experienced one or more cognitive-related adverse reactions was 5.0% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 7.6% for phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 1.5% for placebo. These adverse reactions were comprised primarily of reports of problems with attention/concentration, memory, and language (word-finding). These events occurred at any time during treatment with phentermine and topiramate extended-release capsules. Slowing of Linear Growth Phentermine and topiramate extended-release capsules are associated with a reduction in height velocity (centimeters of height gained per year) in obese pediatric patients 12 to 17 years of age. In a 56-week study, average height increased from baseline in both phentermine and topiramate extended-release capsules and placebo-treated patients; however, a lower height velocity of -1.3 to -1.4 cm/year was observed in phentermine and topiramate extended-release capsule-treated compared to placebo-treated patients. Decrease in Bone Mineral Density Phentermine and topiramate extended-release capsules are associated with less bone mineral acquisition in pediatric patients 12 to 17 years of age. In a substudy (n=66) evaluating bone mineralization via dual-energy X-ray absorptiometry (DEXA), increases in bone mineral density (BMD) at the lumbar spine and total body less head (TBLH) were smaller in pediatric patients treated with phentermine and topiramate extended-release capsules compared to those treated with placebo after 1 year of treatment. Declines in BMD Z-scores of -0.5 or greater from baseline for TBLH were observed in 9% of phentermine and topiramate extended-release capsules 7.5 mg/46 mg-treated patients and 30% of phentermine and topiramate extended-release capsules 15 mg/92 mg-treated patients, compared to 0% of placebo-treated patients. The sample size and study duration were too small to determine if fracture risk is increased. Decreased BMD was not correlated with decreased serum bicarbonate, which commonly occurs with phentermine and topiramate extended-release capsules treatment, or changes in body weight. No patient had a BMD Z-score that went below -2.0 during the trial. Similar findings were observed in a 1 year, active-controlled trial of topiramate in pediatric patients with another condition. Nephrolithiasis In the 1-year controlled trials of phentermine and topiramate extended-release capsules in adults, the incidence of nephrolithiasis was 0.2% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 1.2% for phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 0.3% for placebo.

Laboratory Abnormalities Serum

Bicarbonate In the 1-year controlled trials of phentermine and topiramate extended-release capsules in adults, the incidence of persistent decreases in serum bicarbonate below the normal range (levels of less than 21 mEq/L at 2 consecutive visits or at the final visit) was 6.4% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 12.8% for phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 2.1% for placebo. The incidence of persistent, markedly low serum bicarbonate values (levels of less than 17 mEq/L on 2 consecutive visits or at the final visit) was 0.2% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg dose and 0.7% for phentermine and topiramate extended-release capsules 15 mg/92 mg dose, compared to 0.1% for placebo. In a pediatric clinical trial, 60 to 70% phentermine and topiramate extended-release capsule-treated patients had a persistent bicarbonate level below the normal range (<21 mEq/L) compared to 43% of placebo-treated patients.

Serum

Potassium In the 1-year controlled trials of phentermine and topiramate extended-release capsules in adults, the incidence of persistent low serum potassium values (less than 3.5 mEq/L at two consecutive visits or at the final visit) during the trial was 3.6% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg dose and 4.9% for phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 1.1% for placebo. Of the subjects who experienced persistent low serum potassium, 88% were receiving treatment with a non-potassium sparing diuretic. The incidence of markedly low serum potassium (less than 3 mEq/L, and a reduction from pre-treatment of greater than 0.5 mEq/L) at any time during the trial was 0.2% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg dose and 0.7% for phentermine and topiramate extended-release capsules 15 mg/92 mg dose, compared to 0.0% for placebo. Persistent markedly low serum potassium (less than 3 mEq/L, and a reduction from pre-treatment of greater than 0.5 mEq/L at two consecutive visits or at the final visit) occurred in 0.2% receiving phentermine and topiramate extended-release capsules 7.5 mg/46 mg dose and 0.1% receiving phentermine and topiramate extended-release capsules 15 mg/92 mg dose, compared to 0.0% receiving placebo. Low serum potassium levels (<3.5 mEq/L) were not observed in a 56-week clinical trial of pediatric patients with obesity.

Serum

Creatinine In the 1-year controlled trials of phentermine and topiramate extended-release capsules in adults and pediatric patients, there was an increase in serum creatinine from baseline, peaking between Week 4 to 8 in adults and at Week 16 in pediatric patients. Serum creatinine values declined but remained elevated over baseline over 1 year of treatment. The incidence of increases in serum creatinine of greater than or equal to 0.3 mg/dL at any time during treatment in adults was 7.2% for phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 8.4% for phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 2.0% for placebo; 17% of pediatric patients treated with phentermine and topiramate extended-release capsules 7.5 mg/46 mg or phentermine and topiramate extended-release capsules 15 mg/92 mg and 0% of patients treated with placebo had a serum creatinine ≥0.3 mg/dL at any time post-randomization. Increases in serum creatinine of greater than or equal to 50% over baseline occurred in 2.0% of adult subjects receiving phentermine and topiramate extended-release capsules 7.5 mg/46 mg and 2.8% receiving phentermine and topiramate extended-release capsules 15 mg/92 mg, compared to 0.6% receiving placebo.

Serum Ammonia

Hyperammonemia with or without encephalopathy has been reported with topiramate. The risk for hyperammonemia with topiramate appears dose related and has been reported more frequently when concomitantly used with valproic acid [see Drug Interactions (7) ] . The incidence of hyperammonemia in pediatric patients 12 to 17 years of age in clinical trials of another condition was 26% in patients taking topiramate at 100 mg/day (1.1 times the maximum recommended dosage of phentermine and topiramate extended-release capsules) and 14% in patients taking topiramate at 50 mg/day (0.6 times the maximum recommended dosage of phentermine and topiramate extended-release capsules), compared to 9% in patients taking placebo. There was also an increased incidence of markedly increased hyperammonemia (defined as 50% above the upper limit of normal reference range) at the 100 mg dose.

6.2 Postmarketing Experience The following adverse reactions have been reported during post approval use of phentermine and topiramate extended-release capsules, phentermine, and topiramate. Because these reactions are reported voluntarily from a population of uncertain size it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Phentermine and Topiramate Extended-Release Capsules Psychiatric: suicidal ideation, suicidal behavior Ophthalmic: acute angle closure glaucoma, increased intraocular pressure Phentermine Allergic Reactions: urticaria Cardiovascular: elevation of blood pressure, ischemic events Central Nervous System: euphoria, psychosis, tremor Reproductive: changes in libido, impotence Topiramate Dermatologic: bullous skin reactions (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), pemphigus Gastrointestinal: pancreatitis Hepatic: hepatic failure (including fatalities), hepatitis Metabolic: hyperammonemia with or without encephalopathy has been reported with concomitant valproic acid <span class="opacity-50 text-xs">[see Drug Interactions (7) ]</span> , hypothermia Ophthalmic: maculopathy

AND PRECAUTIONS Embryo-Fetal Toxicity : Can cause fetal harm. In patients who can become pregnant, a negative pregnancy test is recommended before initiating phentermine and topiramate extended-release capsules and monthly during therapy; advise use of effective contraception. Phentermine and topiramate extended-release capsules are available through a limited program under a Risk Evaluation and Mitigation Strategy (REMS) ( 5.1 ).

Suicidal

Behavior and Ideation : Monitor for depression or suicidal thoughts. Discontinue phentermine and topiramate extended-release capsules if symptoms develop ( 5.2 ). Risk of Ophthalmologic Adverse Reactions : Acute myopia and secondary angle closure glaucoma have been reported. Immediately discontinue phentermine and topiramate extended-release capsules if symptoms develop. Consider phentermine and topiramate extended-release capsules discontinuation if visual field defects occur ( 5.3 ). Mood and Sleep Disorders : Consider dosage reduction or discontinuation for clinically significant or persistent mood or sleep disorder symptoms ( 5.4 ).

Cognitive

Impairment : May cause disturbances in attention or memory, or speech/language problems. Caution patients about operating automobiles or hazardous machinery when starting treatment ( 5.5 ). Slowing of Linear Growth : Consider dosage reduction or discontinuation if pediatric patients are not growing or gaining height as expected ( 5.6 ).

Metabolic

Acidosis : Measure electrolytes before and during treatment. If persistent metabolic acidosis develops, reduce dosage or discontinue phentermine and topiramate extended-release capsules ( 5.7 ). Decrease in Renal Function : Measure creatinine before and during treatment. For persistent creatinine elevations, reduce dosage or discontinue phentermine and topiramate extended-release capsules ( 5.8 ).

Serious Skin

Reactions: phentermine and topiramate extended-release capsules should be discontinued at the first sign of a rash, unless the rash is clearly not drug-related ( 5.13 ).

5.1 Embryo-Fetal Toxicity Phentermine and topiramate extended-release capsules can cause fetal harm. Data from pregnancy registries and epidemiologic studies indicate that a fetus exposed to topiramate in the first trimester of pregnancy has an increased risk of major congenital malformations, including but not limited to cleft lip and/or cleft palate (oral clefts), and of being small for gestational age (SGA). When multiple species of pregnant animals received topiramate at clinically relevant doses, structural malformations, including craniofacial defects, and reduced fetal weights occurred in offspring. A negative pregnancy test is recommended before initiating phentermine and topiramate extended-release capsules treatment in patients who can become pregnant and monthly during phentermine and topiramate extended-release capsules therapy. Advise patients who can become pregnant of the potential risk to a fetus and to use effective contraception during phentermine and topiramate extended-release capsules therapy <span class="opacity-50 text-xs">[see Use in Specific Populations (8.1 , 8.3) ]</span> . Phentermine and Topiramate Extended-Release Capsules Risk Evaluation and Mitigation Strategy (REMS) Because of the teratogenic risk associated with phentermine and topiramate extended-release capsules therapy, phentermine and topiramate extended-release capsules are available through a limited program under the REMS. Under the phentermine and topiramate extended-release capsules REMS, only certified pharmacies may distribute phentermine and topiramate extended-release capsules. Further information is available at www.QSYMIAREMS.com or by telephone at 1-888-998-4887.

5.2 Suicidal Behavior and Ideation Antiepileptic drugs (AEDs), including topiramate, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Pooled analyses of 199 placebo-controlled clinical studies (monotherapy and adjunctive therapy, median treatment duration 12 weeks) of 11 different AEDs across several indications showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI 1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. The estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in AED-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion about AED effect on suicide. The increased risk of suicidal thoughts or behavior with AEDs was observed as early as 1 week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed. The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed. The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age in the clinical trials analyzed. In a phentermine and topiramate extended-release capsule clinical trial of pediatric patients aged 12 years and older, 1 (0.6%) of the 167 phentermine and topiramate extended-release capsule-treated patients reported suicidal ideation and behavior which required hospitalization. No placebo-treated patients reported suicidal behavior or ideation. Monitor all patients for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. Discontinue phentermine and topiramate extended-release capsules in patients who experience suicidal thoughts or behaviors <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) ]</span> . Avoid phentermine and topiramate extended-release capsules in patients with a history of suicidal attempts or active suicidal ideation.

5.3 Risk of Ophthalmologic Adverse Reactions Acute Myopia and Secondary Angle Closure Glaucoma A syndrome consisting of acute myopia associated with secondary angle closure glaucoma has been reported in patients treated with topiramate. Symptoms include acute onset of decreased visual acuity and/or ocular pain. Ophthalmologic findings can include myopia, mydriasis, anterior chamber shallowing, ocular hyperemia (redness), choroidal detachments, retinal pigment epithelial detachments, macular striae, and increased intraocular pressure. This syndrome may be associated with supraciliary effusion resulting in anterior displacement of the lens and iris, with secondary angle closure glaucoma. Symptoms typically occur within 1 month of initiating treatment with topiramate but may occur at any time during therapy. In contrast to primary narrow angle glaucoma, which is rare under 40 years of age, secondary angle closure glaucoma associated with topiramate has been reported in pediatric patients as well as adults. The primary treatment to reverse symptoms is discontinuation of phentermine and topiramate extended-release capsules as rapidly as possible in consultation with the treating physician. Elevated intraocular pressure of any etiology, if left untreated, can lead to serious sequelae including permanent loss of vision.

Visual Field Defects

Visual field defects (independent of elevated intraocular pressure) have been reported in clinical trials and in postmarketing experience in patients receiving topiramate. In clinical trials, most of these events were reversible after topiramate discontinuation. If visual problems occur at any time during treatment, consider discontinuing phentermine and topiramate extended-release capsules.

5.4 Mood and Sleep Disorders Phentermine and topiramate extended-release capsules can cause mood disorders, including depression and anxiety, as well as insomnia. Patients with a history of depression may be at increased risk of recurrent depression or other mood disorders while taking phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Consider dosage reduction or discontinuation of phentermine and topiramate extended-release capsules if clinically significant or persistent symptoms occur. Discontinue phentermine and topiramate extended-release capsules if patients have symptoms of suicidal ideation or behavior <span class="opacity-50 text-xs">[see Warnings and Precautions (5.2) ]</span> .

5.5 Cognitive Impairment Phentermine and topiramate extended-release capsules can cause cognitive dysfunction (e.g., impairment of concentration/attention, difficulty with memory, and speech or language problems, particularly word-finding difficulties). Rapid titration or high initial doses of phentermine and topiramate extended-release capsules may be associated with higher rates of cognitive events such as attention, memory, and language/word-finding difficulties <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . The concomitant use of alcohol or central nervous system (CNS) depressant drugs with phentermine and topiramate extended-release capsules may potentiate CNS depression or other centrally mediated effects of these agents, such as dizziness, cognitive adverse reactions, drowsiness, light-headedness, impaired coordination, and somnolence. Caution patients about operating hazardous machinery, including automobiles, until they are reasonably certain phentermine and topiramate extended-release capsules therapy does not affect them adversely. Caution patients against excessive alcohol intake while receiving phentermine and topiramate extended-release capsules. If cognitive dysfunction persists, consider dosage reduction or discontinuation of phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) ]</span> .

5.6 Slowing of Linear Growth Phentermine and topiramate extended-release capsules are associated with a reduction in height velocity (centimeters of height gained per year) in obese pediatric patients 12 to 17 years of age. In a 56-week study, average height increased from baseline in both phentermine and topiramate extended-release capsules and placebo-treated patients; however, a lower height velocity of -1.3 to -1.4 cm/year was observed in phentermine and topiramate extended-release capsules-treated compared to placebo-treated patients. Monitor height velocity in pediatric patients treated with phentermine and topiramate extended-release capsules. Consider dosage reduction or discontinuation of phentermine and topiramate extended-release capsules if pediatric patients are not growing or gaining height as expected <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) ]</span> .

5.7 Metabolic Acidosis Hyperchloremic, non-anion gap, metabolic acidosis (decreased serum bicarbonate below the normal reference range in the absence of chronic respiratory alkalosis) has been reported in patients treated with phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Manifestations of acute or chronic metabolic acidosis may include hyperventilation, nonspecific symptoms such as fatigue and anorexia, or more severe sequelae including cardiac arrhythmias or stupor. Chronic, untreated metabolic acidosis may increase the risk for nephrolithiasis or nephrocalcinosis and may also result in osteomalacia (referred to as rickets in pediatric patients) and/or osteoporosis with an increased risk for fractures. Chronic metabolic acidosis in pediatric patients may also reduce growth rates, which may decrease the maximal height achieved. Conditions or therapies that predispose to acidosis (i.e., renal disease, severe respiratory disorders, status epilepticus, diarrhea, surgery, or ketogenic diet) may be additive to the bicarbonate lowering effects of phentermine and topiramate extended-release capsules. Concomitant use of phentermine and topiramate extended-release capsules and a carbonic anhydrase inhibitor may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation <span class="opacity-50 text-xs">[see Warnings and Precautions (5.10) ]</span> . Avoid use of phentermine and topiramate extended-release capsules with other carbonic anhydrase inhibitors. If concomitant use of phentermine and topiramate extended-release capsules with another carbonic anhydrase inhibitor is unavoidable, the patient should be monitored for the appearance or worsening of metabolic acidosis. Measure electrolytes including serum bicarbonate prior to starting phentermine and topiramate extended-release capsules and during phentermine and topiramate extended-release capsules treatment. In phentermine and topiramate extended-release capsules clinical trials, the peak reduction in serum bicarbonate typically occurred within 4 weeks of titration to the assigned dose, and in most patients, there was a correction of bicarbonate by week 56, without any dosage reduction. However, if persistent metabolic acidosis develops while taking phentermine and topiramate extended-release capsules, reduce the dosage or discontinue phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) ]</span> .

5.8 Decrease in Renal Function Phentermine and topiramate extended-release capsules can cause an increase in serum creatinine that reflects a decrease in renal function (glomerular filtration rate). In clinical trials, peak increases in serum creatinine were observed after 4 to 8 weeks of treatment. On average, serum creatinine gradually declined but remained elevated over baseline creatinine values. The changes in serum creatinine (and measured GFR) with short-term (4-weeks) phentermine and topiramate extended-release capsules treatment appear reversible with treatment discontinuation, but the effect of chronic treatment on renal function is not known. Measure serum creatinine prior to starting phentermine and topiramate extended-release capsules and during phentermine and topiramate extended-release capsules treatment. If persistent elevations in creatinine occur, reduce the dosage or discontinue phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) , Adverse Reactions (6.1) , and Clinical Pharmacology (12.2) ]</span> .

5.9 Risk of Seizures with Abrupt Withdrawal of Phentermine and Topiramate Extended-Release Capsules Abrupt withdrawal of topiramate has been associated with seizures in individuals without a history of seizures or epilepsy. In situations where immediate termination of phentermine and topiramate extended-release capsules are medically required, appropriate monitoring is recommended. Patients discontinuing phentermine and topiramate extended-release capsules 15 mg/92 mg should be gradually tapered to reduce the possibility of precipitating a seizure <span class="opacity-50 text-xs">[see Dosage and Administration (2.3) and Drug Abuse and Dependence (9.3) ]</span> .

5.10 Kidney Stones Phentermine and topiramate extended-release capsules have been associated with kidney stone formation <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Topiramate inhibits carbonic anhydrase activity and promotes kidney stone formation by reducing urinary citrate excretion and increasing urine pH. Patients on a ketogenic diet may be at increased risk for kidney stone formation. An increase in urinary calcium and a marked decrease in urinary citrate was observed in topiramate-treated pediatric patients in a one-year, active-controlled study. Increased ratio of urinary calcium/citrate increases the risk of kidney stones and/or nephrocalcinosis. Avoid the use of phentermine and topiramate extended-release capsules with other drugs that inhibit carbonic anhydrase <span class="opacity-50 text-xs">[see Drug Interactions (7) ]</span> . Advise patients to increase fluid intake (to increase urinary output), which may decrease the concentration of substances involved in kidney stone formation.

5.11 Oligohidrosis and Hyperthermia Oligohidrosis (decreased sweating), infrequently resulting in hospitalization, has been reported in association with the use of topiramate. Decreased sweating and an elevation in body temperature above normal characterized these cases. Some of the cases have been reported with topiramate after exposure to elevated environmental temperatures. The majority of the reports associated with topiramate have been in pediatric patients. Advise all patients and caregivers to monitor for decreased sweating and increased body temperature during physical activity, especially in hot weather. Patients on concomitant medications that predispose them to heat-related disorders may be at increased risk.

5.12 Hypokalemia Phentermine and topiramate extended-release capsules can increase the risk of hypokalemia through its inhibition of carbonic anhydrase activity. In addition, when phentermine and topiramate extended-release capsules are used in conjunction with non-potassium sparing diuretics this may further potentiate potassium-wasting. Measure potassium before and during treatment with phentermine and topiramate extended-release capsules <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) , Drug Interactions (7) , and Clinical Pharmacology (12.3) ]</span> .

5.13 Serious Skin Reactions Serious skin reactions (Stevens-Johnson Syndrome [SJS] and Toxic Epidermal Necrolysis [TEN]) have been reported in patients receiving topiramate. Phentermine and topiramate extended-release capsules should be discontinued at the first sign of a rash, unless the rash is clearly not drug-related. If signs or symptoms suggest SJS/TEN, use of this drug should not be resumed, and alternative therapy should be considered. Inform patients about the signs of serious skin reactions.

5.14 Allergic Reactions Due to Inactive Ingredient FD&amp;C Yellow No. 5 This product contains FD&amp;C Yellow No. 5 (tartrazine) which may cause allergic-type reactions (including bronchial asthma) in certain susceptible persons. Although the overall incidence of FD&amp;C Yellow No. 5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity.

PRECAUTIONS Information for Patients Patients must be informed that phentermine hydrochloride is a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity, and that coadministration of phentermine with other drugs for weight loss is not recommended (see Indications and Usage and Warnings ). Patients must be instructed on how much phentermine to take, and when and how to take it (see Dosage and Administration ). Advise pregnant women and nursing mothers not to use phentermine (see Precautions ). Patients must be informed about the risks of use of phentermine (including the risks discussed in Warnings and Precautions ), about the symptoms of potential adverse reactions and when to contact a physician and/or take other action. The risks include, but are not limited to:

• Development of primary pulmonary hypertension (see Warnings )
• Development of serious valvular heart disease (see Warnings )
• Effects on the ability to engage in potentially hazardous tasks (see Warnings )
• The risk of an increase in blood pressure (see Warnings and Adverse Reactions )
• The risk of interactions (see Contraindications , Warnings , and Precautions / Drug Interactions ) The patients must also be informed about
• the potential for developing tolerance and actions if they suspect development of tolerance (see Warnings ) and
• the risk of dependence and the potential consequences of abuse (see Warnings , Drug Abuse and Dependence , and Overdosage ). Tell patients to keep phentermine in a safe place to prevent theft, accidental overdose, misuse or abuse. Selling or giving away phentermine may harm others and is against the law.

Drug Interactions Monoamine Oxidase Inhibitors

Use of phentermine is contraindicated during or within 14 days following the administration of monoamine oxidase inhibitors because of the risk of hypertensive crisis.

Alcohol

Concomitant use of alcohol with phentermine may result in an adverse drug reaction. Insulin and Oral Hypoglycemic Medications Requirements may be altered (see Warnings )

Adrenergic Neuron Blocking Drugs

Phentermine may decrease the hypotensive effect of adrenergic neuron blocking drugs. Carcinogenesis, Mutagenesis, Impairment of Fertility Studies have not been performed with phentermine to determine the potential for carcinogenesis, mutagenesis or impairment of fertility.

Pregnancy Pregnancy

Category X Phentermine is contraindicated during pregnancy because weight loss offers no potential benefit to a pregnant woman and may result in fetal harm. A minimum weight gain, and no weight loss, is currently recommended for all pregnant women, including those who are already overweight or obese, due to obligatory weight gain that occurs in maternal tissues during pregnancy. Phentermine has pharmacologic activity similar to amphetamine (d- and dll-amphetamine) (see Clinical Pharmacology ). Animal reproduction studies have not been conducted with phentermine. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus.

Nursing

Mothers It is not known if phentermine is excreted in human milk; however, other amphetamines are present in human milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Because pediatric obesity is a chronic condition requiring long-term treatment, the use of this product, approved for short-term therapy, is not recommended.

Geriatric

Use In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

Renal Impairment

Phentermine was not studied in patients with renal impairment. Based on the reported excretion of phentermine in urine, exposure increases can be expected in patients with renal impairment. Use caution when administering phentermine to patients with renal impairment (see Clinical Pharmacology ).

INTERACTIONS Table 5 displays clinically significant drug interactions with phentermine and topiramate extended-release capsules.

Table

5.

Clinically Significant Drug

Interactions with Phentermine and Topiramate Extended-Release Capsules Monoamine Oxidase Inhibitors Clinical Impact Concomitant use of phentermine with monoamine oxidase inhibitors (MAOIs) increases the risk of hypertensive crisis.

Intervention

Concomitant use of phentermine and topiramate extended-release capsules is contraindicated during MAOI treatment and within 14 days of stopping an MAOI.

Oral Contraceptives Clinical Impact

Coadministration of multiple-dose phentermine and topiramate extended-release capsules 15 mg/92 mg once daily with a single dose of oral contraceptive containing 35 mcg ethinyl estradiol (estrogen component) and 1 mg norethindrone (progestin component), in obese otherwise healthy volunteers, decreased the exposure of ethinyl estradiol by 16% and increased the exposure of norethindrone by 22% [see Clinical Pharmacology ( 12.3 )] . Although this interaction is not anticipated to increase the risk of pregnancy, irregular bleeding (spotting) may occur more frequently due to both the increased exposure to the progestin and lower exposure to the estrogen, which tends to stabilize the endometrium.

Intervention

Inform patients not to discontinue their combination oral contraceptive if spotting occurs, but to notify their health care provider if the spotting is troubling to them.

Cns

Depressants Including Alcohol Clinical Impact The concomitant use of alcohol or CNS depressant drugs (e.g., barbiturates, benzodiazepines, and sleep medications) with phentermine or topiramate may potentiate CNS depression such as dizziness or cognitive adverse reactions, or other centrally mediated effects of these agents.

Intervention

Advise patients not to drive or operate machinery until they have gained sufficient experience on phentermine and topiramate extended-release capsules to gauge whether it adversely affects their mental performance, motor performance, and/or vision. Caution patients against excessive alcohol intake when taking phentermine and topiramate extended-release capsules. Consider phentermine and topiramate extended-release capsule dosage reduction or discontinuation if cognitive dysfunction persists [see Warnings and Precautions ( 5.5 )] . Non-Potassium Sparing Diuretics Clinical Impact Concurrent use of phentermine and topiramate extended-release capsules with non-potassium sparing diuretics may potentiate the potassium-wasting action of these diuretics. Concomitant administration of hydrochlorothiazide alone with topiramate alone has been shown to increase the C max and AUC of topiramate by 27% and 29%, respectively.

Intervention

When phentermine and topiramate extended-release capsules are used concomitantly with non-potassium-sparing diuretics, measure potassium before and during phentermine and topiramate extended-release capsule treatment [see Warnings and Precautions ( 5.12 ) and Clinical Pharmacology ( 12.3 )] .

Antiepileptic Drugs Clinical Impact

Concomitant administration of phenytoin or carbamazepine with topiramate in patients with epilepsy, decreased plasma concentrations of topiramate by 48% and 40%, respectively, when compared to topiramate given alone [see Clinical Pharmacology ( 12.3 )] . Concomitant administration of valproic acid and topiramate has been associated with hyperammonemia with and without encephalopathy. Concomitant administration of topiramate with valproic acid in patients has also been associated with hypothermia (with and without hyperammonemia).

Intervention

Consider measuring blood ammonia in patients in whom the onset of hypothermia or encephalopathy has been reported [see Clinical Pharmacology ( 12.3 )] .

Carbonic Anhydrase Inhibitors Clinical Impact

Concomitant use of topiramate with any other carbonic anhydrase inhibitor may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation.

Intervention

Avoid the use of phentermine and topiramate extended-release capsules with other drugs that inhibit carbonic anhydrase. If concomitant use of phentermine and topiramate extended-release capsules with another carbonic anhydrase inhibitor is unavoidable, monitor patient for the appearance or worsening of metabolic acidosis [see Warnings and Precautions ( 5.7 , 5.10 )] .

Pioglitazone Clinical

Impact A decrease in the exposure of pioglitazone and its active metabolites were noted with the concurrent use of pioglitazone and topiramate in a clinical trial. The clinical relevance of these observations is unknown.

Intervention

Consider increased glycemic monitoring when using pioglitazone and phentermine and topiramate extended-release capsules concomitantly [see Clinical Pharmacology ( 12.3 )] .

Amitriptyline Clinical Impact

Some patients may experience a large increase in amitriptyline concentration in the presence of topiramate.

Intervention

Any adjustments in amitriptyline dose when used with phentermine and topiramate extended-release capsules should be made according to the patient's clinical response and not on the basis of amitriptyline levels [see Clinical Pharmacology ( 12.3 )] .

Oral

Contraceptives: Altered exposure of progestin and estrogen may cause irregular bleeding, but not increased risk of pregnancy. Advise patients not to discontinue oral contraceptives if spotting occurs ( 7 ).

Cns

Depressants Including Alcohol: May potentiate CNS depressant effects. Avoid excessive use of alcohol ( 7 ). Non-potassium Sparing Diuretics: May potentiate hypokalemia. Measure potassium before and during treatment ( 7 ).