CARBIDOPA: 302 Adverse Event Reports & Safety Profile

Carbidopa, levodopa and entacapone tablets are a combination of carbidopa, levodopa, and entacapone for the treatment of Parkinson’s disease. Carbidopa USP, an inhibitor of aromatic amino acid decarboxylation, is a white to creamy white powder, freely soluble in 3 N hydrochloric acid; slightly soluble in water and in methanol; practically insoluble in alcohol, in acetone, in chloroform and in ether, with a molecular weight of 244.3. It is designated chemically as (-)-L-(α-hydrazino-(α-methyl-β-(3,4-dihydroxybenzene) propanoic acid monohydrate. Its empirical formula is C 10 H 14 N 2 O 4

• H 2 O, and its structural formula is: Tablet content is expressed in terms of anhydrous carbidopa, which has a molecular weight of 226.3. Levodopa USP, an aromatic amino acid, is a white to off-white, crystalline powder, slightly soluble in water, freely soluble in 3 N hydrochloric acid and insoluble in alcohol, with a molecular weight of 197.2. It is designated chemically as (-)-L-α-amino-β-(3,4-dihydroxybenzene) propanoic acid. Its empirical formula is C 9 H 11 NO 4 , and its structural formula is: Entacapone USP, a COMT inhibitor, is a nitro-catechol-structured compound with a molecular weight of 305.3. The chemical name of entacapone is (E)-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)-N,N-diethyl-2-propenamide. Its empirical formula is C 14 H 15 N 3 O 5 and its structural formula is: Carbidopa, levodopa and entacapone is supplied as tablets in 6 strengths: Carbidopa, levodopa and entacapone tablets 12.5 mg/50 mg/200 mg: 12.5 mg of carbidopa USP, 50 mg of levodopa USP and 200 mg of entacapone USP. Carbidopa, levodopa and entacapone tablets 18.75 mg/75 mg/200 mg: 18.75 mg of carbidopa USP, 75 mg of levodopa USP and 200 mg of entacapone USP. Carbidopa, levodopa and entacapone tablets 25 mg/100 mg/200 mg: 25 mg of carbidopa USP, 100 mg of levodopa USP and 200 mg of entacapone USP. Carbidopa, levodopa and entacapone tablets 31.25 mg/125 mg/200 mg: 31.25 mg of carbidopa USP, 125 mg of levodopa USP and 200 mg of entacapone USP. Carbidopa, levodopa and entacapone tablets 37.5 mg/150 mg/200 mg: 37.5 mg of carbidopa USP, 150 mg of levodopa USP and 200 mg of entacapone USP. Carbidopa, levodopa and entacapone tablets 50 mg/200 mg/200 mg: 50 mg of carbidopa USP, 200 mg of levodopa USP and 200 mg of entacapone USP.

Inactive

Ingredients: Mannitol, corn starch, croscarmellose sodium, povidone (K-30), colloidal silicon dioxide, magnesium stearate, hypromellose, glycerin, titanium dioxide, iron oxide red, sucrose, polysorbate 80. Carbidopa, levodopa and entacapone tablets 12.5 mg/50 mg/200 mg, 25 mg/100 mg/200 mg, 31.25 mg/125 mg/200 mg and 37.5 mg/150 mg/200 mg also contain yellow iron oxide. carbilevoenta-carbidopa.jpg carbilevoenta-levodopa.jpg carbilevoenta-entacapone.jpg

INDICATIONS AND USAGE Carbidopa tablets are indicated for use with carbidopa-levodopa or with levodopa in the treatment of the symptoms of idiopathic Parkinson's disease (paralysis agitans), postencephalitic parkinsonism, and symptomatic parkinsonism, which may follow injury to the nervous system by carbon monoxide intoxication and/or manganese intoxication. Carbidopa tablets are for use with carbidopa-levodopa in patients for whom the dosage of carbidopa-levodopa tablets provides less than adequate daily dosage (usually 70 mg daily) of carbidopa. Carbidopa tablets are for use with levodopa in the occasional patient whose dosage requirement of carbidopa-levodopa necessitates separate titration of each medication. Carbidopa tablets are used with carbidopa-levodopa or with levodopa to permit the administration of lower doses of levodopa with reduced nausea and vomiting, more rapid dosage titration, and with a somewhat smoother response. However, patients with markedly irregular ("on-off") responses to levodopa have not been shown to benefit from the addition of carbidopa. Since carbidopa prevents the reversal of levodopa effects caused by pyridoxine, supplemental pyridoxine (vitamin B 6 ), can be given to patients when they are receiving carbidopa and levodopa concomitantly or as carbidopa-levodopa. Although the administration of carbidopa tablets permits control of parkinsonism and Parkinson's disease with much lower doses of levodopa, there is no conclusive evidence at present that this is beneficial other than in reducing nausea and vomiting, permitting more rapid titration, and providing a somewhat smoother response to levodopa. Certain patients who responded poorly to levodopa alone have improved when carbidopa-levodopa were given concurrently. This was most likely due to decreased peripheral decarboxylation of levodopa rather than to a primary effect of carbidopa tablets on the peripheral nervous system. Carbidopa has not been shown to enhance the intrinsic efficacy of levodopa. In deciding whether to give carbidopa tablets with carbidopa-levodopa or with levodopa to patients who have nausea and/or vomiting, the physician should be aware that, while many patients may be expected to improve, some may not. Since one cannot predict which patients are likely to improve, this can only be determined by a trial of therapy. It should be further noted that in controlled trials comparing carbidopa-levodopa with levodopa alone, about half the patients with nausea and/or vomiting on levodopa alone improved spontaneously despite being retained on the same dose of levodopa during the controlled portion of the trial.

AND ADMINISTRATION The maximum recommended daily dose of DUOPA is 2000 mg of levodopa (i.e., one cassette per day) administered over 16 hours ( 2.1 ) Prior to initiating DUOPA, convert patients from all forms of levodopa to oral immediate-release carbidopa-levodopa tablets (1:4 ratio) ( 2.2 ) Titrate total daily dose based on clinical response for the patient ( 2.2 ) Administer DUOPA into the jejunum through a percutaneous endoscopic gastrostomy with jejunal tube (PEG-J) with the CADD®-Legacy 1400 portable infusion pump ( 2.3 )

2.1 DUOPA Daily Dose DUOPA is administered over a 16-hour infusion period. The daily dose is determined by individualized patient titration and composed of: A Morning Dose A Continuous Dose Extra Doses The maximum recommended daily dose of DUOPA is 2000 mg of the levodopa component (i.e., one cassette per day) administered over 16 hours. At the end of the daily 16-hour infusion, patients will disconnect the pump from the PEG-J and take their night-time dose of oral immediate-release carbidopa-levodopa tablets. Treatment with DUOPA is initiated in 3 steps <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.2 ) ]</span> : Conversion of patients to oral immediate-release carbidopa-levodopa tablets in preparation for DUOPA treatment. Calculation and administration of the DUOPA starting dose (Morning Dose and Continuous Dose) for Day 1. Titration of the dose as needed based on individual clinical response and tolerability.

Extra

Doses DUOPA has an extra dose function that can be used to manage acute “Off” symptoms that are not controlled by the Morning Dose and the Continuous Dose administered over 16 hours. The extra dose function should be set at 1 mL (20 mg of levodopa) when starting DUOPA. If the amount of the extra dose needs to be adjusted, it is typically done in 0.2 mL increments. The extra dose frequency should be limited to one extra dose every 2 hours. Administration of frequent extra doses may cause or worsen dyskinesias. Once no further adjustments are required to the DUOPA Morning Dose, Continuous Dose, or Extra Dose, this dosing regimen should be administered daily. Over time, additional changes may be necessary based on the patient’s clinical response and tolerability.

2.2 Initiation and Titration Instructions Prepare for DUOPA Treatment Prior to initiating DUOPA, convert patients from all other forms of levodopa to oral immediate-release carbidopa-levodopa tablets (1:4 ratio). Patients should remain on a stable dose of their concomitant medications taken for the treatment of Parkinson&apos;s disease before initiation of DUOPA infusion. Healthcare providers should ensure patients take their oral Parkinson&apos;s disease medications the morning of the PEG-J procedure. Determine the DUOPA Starting Dose for Day 1 The steps for determining the initial DUOPA daily dosing (Morning Dose and Continuous Dose) for Day 1 are outlined below.

Step

1: Calculate and administer the DUOPA Morning Dose for Day 1 a. Determine the total amount of levodopa (in milligrams) in the first dose of oral immediate-release carbidopa-levodopa that was taken by the patient on the previous day. b. Convert the oral levodopa dose from milligrams to milliliters by multiplying the oral dose by 0.8 and dividing by 20 mg/mL. This calculation will provide the Morning Dose of DUOPA in milliliters. c.

Add

3 milliliters to the Morning Dose to fill (prime) the intestinal tube to obtain the Total Morning Dose. d.

The Total Morning

Dose is usually administered over 10 to 30 minutes. e. Program the pump to deliver the Total Morning Dose.

Step

2: Calculate and administer the DUOPA Continuous Dose for Day 1 a. Determine the amount of oral immediate-release levodopa that the patient received from oral immediate-release carbidopa-levodopa doses throughout the previous day (16 waking hours), in milligrams. Do not include the doses of oral immediate-release carbidopa-levodopa taken at night when calculating the levodopa amount. b. Subtract the first oral levodopa dose in milligrams taken by the patient on the previous day (determined in Step 1 (a)) from the total oral levodopa dose in milligrams taken over 16 waking hours (determined in Step 2 (a)). Divide the result by 20 mg/mL. This is the dose of DUOPA administered as a Continuous Dose (in mL) over 16 hours. c. The hourly infusion rate (mL per hour) is obtained by dividing the Continuous Dose by 16 (hours). This value will be programmed into the pump as the continuous rate. d. If persistent or numerous “Off” periods occur during the 16-hour infusion, consider increasing the Continuous Dose or using the Extra Dose function. If dyskinesia or DUOPA-related adverse reactions occur, consider decreasing the Continuous Dose or stopping the infusion until the adverse reactions subside.

Duopa

Titration The daily dose of DUOPA can be titrated as needed, based on the patient’s individual clinical response and tolerability after Day 1 of DUOPA treatment and until a stable daily dose is maintained. Adjustments to concomitant Parkinson’s disease medications may be needed. In the controlled trial, the average number of titration days required to establish a stable Morning and Continuous Dose was 5 days. Additional dose adjustments may be necessary over time based on the patient level of activity and disease progression. The recommendations for adjusting the DUOPA Morning and Continuous Doses are provided below.

Morning Dose

Adjustment If there was an inadequate clinical response within 1 hour of the Morning Dose on the preceding day, adjust the Morning Dose (excluding the 3 mL to fill the tube) as follows: If the Morning Dose on the preceding day was less than or equal to 6 mL, increase the Morning Dose by 1 mL. If the Morning Dose on the preceding day was greater than 6 mL, increase the Morning Dose by 2 mL. If the patient experienced dyskinesias or DUOPA-related adverse reactions within 1 hour of the Morning Dose on the preceding day, decrease the Morning Dose by 1 mL.

Continuous Dose Adjustment

Consider increasing the Continuous Dose based on the number and volume of Extra Doses of DUOPA (i.e., total amount of levodopa component) that were needed for the previous day and the patient’s clinical response. Consider decreasing the Continuous Dose if the patient experienced troublesome dyskinesia, or other troublesome DUOPA-related adverse reactions on the preceding day: For troublesome adverse reactions lasting for a period of one hour or more, decrease the Continuous Dose by 0.3 mL per hour. For troublesome adverse reactions lasting for two or more periods of one hour or more, decrease the Continuous Dose by 0.6 mL per hour.

2.3 Administration Information DUOPA should be used at room temperature. Take one DUOPA cassette out of the refrigerator and out of the carton 20 minutes prior to use; failure to use the product at room temperature may result in the patient not receiving the right amount of medication. DUOPA is delivered as a 16-hour infusion through either a naso-jejunal tube for short-term administration or through a PEG-J for long-term administration. The cassettes are for single-use only and should not be used for longer than 16 hours, even if some drug product remains. An opened cassette should not be re-used. The PEG-J should be disconnected from the pump at the end of the daily 16-hour administration period and flushed with room temperature potable water with a syringe. Long-term administration of DUOPA requires placement of a PEG-J outer transabdominal tube and inner jejunal tube by percutaneous endoscopic gastrostomy. DUOPA is dispensed from medication cassette reservoirs that are specifically designed to be connected to the CADD ® -Legacy 1400 pump. Establishment of the transabdominal port should be performed by a gastroenterologist or other healthcare provider experienced in this procedure.

See Table

1 for the recommended tubing sets for PEG-J administration. For short-term, temporary administration of DUOPA prior to PEG-J tube placement, treatment may be initiated by a naso-jejunal tube with observation of the patient’s clinical response.

See Table

2 for the recommended tubing sets for naso-jejunal administration.

Table

1.

Recommended Tubing

Sets for Long-Term PEG-J DUOPA Administration Product Name Manufacturer AbbVie PEG 15 and 20 Fr AbbVie J AbbVie Inc. AbbVie Inc.

Table

2.

Recommended Tubing

Sets for Short-Term Naso-Jejunal DUOPA Administration Product Name Manufacturer AbbVie NJ AbbVie Inc. NJFT-10 Wilson-Cook Medical, Inc. Kangaroo™ Naso-Jejunal Feeding Tube Covidien Kangaroo™ Covidien

2.4 Discontinuation of DUOPA Avoid sudden discontinuation or rapid dose reduction in patients taking DUOPA. If patients need to discontinue DUOPA, the dose should be tapered or patients should be switched to oral immediate-release carbidopa-levodopa tablets <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.7 ) ]</span> . When using a PEG-J tube, DUOPA can be discontinued by withdrawing the tube and letting the stoma heal. The removal of the tube should only be performed by a qualified healthcare provider.

CONTRAINDICATIONS Carbidopa is contraindicated in patients with known hypersensitivity to any component of this drug. Nonselective monoamine oxidase (MAO) inhibitors are contraindicated for use with levodopa or carbidopa-levodopa combination products with or without carbidopa. These inhibitors must be discontinued at least two weeks prior to initiating therapy with levodopa. Carbidopa-levodopa or levodopa may be administered concomitantly with the manufacturer's recommended dose of an MAO inhibitor with selectivity for MAO type B (e.g., selegiline hydrochloride) (see PRECAUTIONS , Drug Interactions ). Levodopa or carbidopa-levodopa products, with or without carbidopa, are contra-indicated in patients with narrow-angle glaucoma.

ADVERSE REACTIONS In controlled clinical trials, patients predominantly with moderate to severe motor fluctuations while on carbidopa and levodopa tablets were randomized to therapy with either carbidopa and levodopa tablets or carbidopa and levodopa extended-release tablets. The adverse experience frequency profile of carbidopa and levodopa extended-release tablets did not differ substantially from that of carbidopa and levodopa tablets, as shown in Table 1.

Table

1: Clinical Adverse Experiences Occurring In 1% or Greater of Patients Adverse Experience Carbidopa and Levodopa Extended-release Tablets n = 491 % Carbidopa and Levodopa Tablets n = 524 % Dyskinesia 16.5

12.2 Nausea 5.5

5.7 Hallucinations 3.9

3.2 Confusion 3.7

2.3 Dizziness 2.9

2.3 Depression 2.2

1.3 Urinary tract infection 2.2

2.3 Headache 2

1.9 Dream abnormalities 1.8

0.8 Dystonia 1.8

0.8 Vomiting 1.8

1.9 Upper respiratory infection 1.8 1 Dyspnea 1.6 0.4 ‘On-Off’ phenomena 1.6

1.1 Back pain 1.6

0.6 Dry mouth 1.4

1.1 Anorexia 1.2

1.1 Diarrhea 1.2

0.6 Insomnia 1.2 1 Orthostatic hypotension 1

1.1 Shoulder pain 1

0.6 Chest pain 1

0.8 Muscle cramps 0.8 1 Paresthesia 0.8

1.1 Urinary frequency 0.8

1.1 Dyspepsia 0.6

1.1 Constipation 0.2

1.5 Abnormal laboratory findings occurring at a frequency of 1% or greater in approximately 443 patients who received carbidopa and levodopa extended-release tablets and 475 who received carbidopa and levodopa tablets during controlled clinical trials included: decreased hemoglobin and hematocrit; elevated serum glucose; white blood cells, bacteria and blood in the urine. The adverse experiences observed in patients in uncontrolled studies were similar to those seen in controlled clinical studies. Other adverse experiences reported overall in clinical trials in 748 patients treated with carbidopa and levodopa extended-release tablets, listed by body system in order of decreasing frequency, include: Body as a Whole: Asthenia, fatigue, abdominal pain, orthostatic effects. Cardiovascular: Palpitation, hypertension, hypotension, myocardial infarction. Gastrointestinal: Gastrointestinal pain, dysphagia, heartburn. Metabolic: Weight loss. Musculoskeletal: Leg pain.

Nervous

System/Psychiatric: Chorea, somnolence, falling, anxiety, disorientation, decreased mental acuity, gait abnormalities, extrapyramidal disorder, agitation, nervousness, sleep disorders, memory impairment. Respiratory: Cough, pharyngeal pain, common cold. Skin: Rash.

Special

Senses: Blurred vision. Urogenital: Urinary incontinence.

Laboratory

Tests: Decreased white blood cell count and serum potassium; increased BUN, serum creatinine and serum LDH; protein and glucose in the urine. The following adverse experiences have been reported in post-marketing experience with carbidopa and levodopa extended-release tablets: Cardiovascular: Cardiac irregularities, syncope. Gastrointestinal: Taste alterations, dark saliva. Hypersensitivity: Angioedema, urticaria, pruritus, bullous lesions (including pemphigus-like reactions).

Nervous

System/Psychiatric: Increased tremor, peripheral neuropathy, psychotic episodes including delusions and paranoid ideation, pathological gambling, increased libido including hypersexuality, impulse control symptoms. Skin: Alopecia, flushing, dark sweat. Urogenital: Dark urine. Other adverse reactions that have been reported with levodopa alone and with various carbidopa-levodopa formulations and may occur with carbidopa and levodopa extended-release tablets are: Cardiovascular: Phlebitis. Gastrointestinal: Gastrointestinal bleeding, development of duodenal ulcer, sialorrhea, bruxism, hiccups, flatulence, burning sensation of tongue. Hematologic: Hemolytic and nonhemolytic anemia, thrombocytopenia, leukopenia, agranulocytosis. Hypersensitivity: Henoch-Schonlein purpura. Metabolic: Weight gain, edema.

Nervous

System/Psychiatric: Ataxia, depression with suicidal tendencies, dementia, euphoria, convulsions (however, a causal relationship has not been established); bradykinetic episodes, numbness, muscle twitching, blepharospasm (which may be taken as an early sign of excess dosage; consideration of dosage reduction may be made at this time), trismus, activation of latent Horner's syndrome, nightmares. Skin: Malignant melanoma (see also CONTRAINDICATIONS ), increased sweating.

Special

Senses: Oculogyric crisis, mydriasis, diplopia. Urogenital: Urinary retention, priapism. Miscellaneous: Faintness, hoarseness, malaise, hot flashes, sense of stimulation, bizarre breathing patterns.

Laboratory

Tests: Abnormalities in alkaline phosphatase, SGOT (AST), SGPT (ALT), bilirubin, Coombs test, uric acid.

In controlled clinical trials, patients predominantly with moderate to severe motor fluctuations while on carbidopa and levodopa tablets were randomized to therapy with either carbidopa and levodopa tablets or carbidopa and levodopa extended-release tablets. The adverse experience frequency profile of carbidopa and levodopa extended-release tablets did not differ substantially from that of carbidopa and levodopa tablets, as shown in Table 1.

Table

1: Clinical Adverse Experiences Occurring In 1% or Greater of Patients Adverse Experience Carbidopa and Levodopa Extended-release Tablets n = 491 % Carbidopa and Levodopa Tablets n = 524 % Dyskinesia 16.5

12.2 Nausea 5.5

5.7 Hallucinations 3.9

3.2 Confusion 3.7

2.3 Dizziness 2.9

2.3 Depression 2.2

1.3 Urinary tract infection 2.2

2.3 Headache 2

1.9 Dream abnormalities 1.8

0.8 Dystonia 1.8

0.8 Vomiting 1.8

1.9 Upper respiratory infection 1.8 1 Dyspnea 1.6 0.4 ‘On-Off’ phenomena 1.6

1.1 Back pain 1.6

0.6 Dry mouth 1.4

1.1 Anorexia 1.2

1.1 Diarrhea 1.2

0.6 Insomnia 1.2 1 Orthostatic hypotension 1

1.1 Shoulder pain 1

0.6 Chest pain 1

0.8 Muscle cramps 0.8 1 Paresthesia 0.8

1.1 Urinary frequency 0.8

1.1 Dyspepsia 0.6

1.1 Constipation 0.2

1.5 Abnormal laboratory findings occurring at a frequency of 1% or greater in approximately 443 patients who received carbidopa and levodopa extended-release tablets and 475 who received carbidopa and levodopa tablets during controlled clinical trials included: decreased hemoglobin and hematocrit; elevated serum glucose; white blood cells, bacteria and blood in the urine. The adverse experiences observed in patients in uncontrolled studies were similar to those seen in controlled clinical studies. Other adverse experiences reported overall in clinical trials in 748 patients treated with carbidopa and levodopa extended-release tablets, listed by body system in order of decreasing frequency, include: Body as a Whole: Asthenia, fatigue, abdominal pain, orthostatic effects. Cardiovascular: Palpitation, hypertension, hypotension, myocardial infarction. Gastrointestinal: Gastrointestinal pain, dysphagia, heartburn. Metabolic: Weight loss. Musculoskeletal: Leg pain.

Nervous

System/Psychiatric: Chorea, somnolence, falling, anxiety, disorientation, decreased mental acuity, gait abnormalities, extrapyramidal disorder, agitation, nervousness, sleep disorders, memory impairment. Respiratory: Cough, pharyngeal pain, common cold. Skin: Rash.

Special

Senses: Blurred vision. Urogenital: Urinary incontinence.

Laboratory

Tests: Decreased white blood cell count and serum potassium; increased BUN, serum creatinine and serum LDH; protein and glucose in the urine.

The following adverse experiences have been reported in post-marketing experience with carbidopa and levodopa extended-release tablets: Cardiovascular: Cardiac irregularities, syncope. Gastrointestinal: Taste alterations, dark saliva. Hypersensitivity: Angioedema, urticaria, pruritus, bullous lesions (including pemphigus-like reactions).

Nervous

System/Psychiatric: Increased tremor, peripheral neuropathy, psychotic episodes including delusions and paranoid ideation, pathological gambling, increased libido including hypersexuality, impulse control symptoms. Skin: Alopecia, flushing, dark sweat. Urogenital: Dark urine. Other adverse reactions that have been reported with levodopa alone and with various carbidopa-levodopa formulations and may occur with carbidopa and levodopa extended-release tablets are: Cardiovascular: Phlebitis. Gastrointestinal: Gastrointestinal bleeding, development of duodenal ulcer, sialorrhea, bruxism, hiccups, flatulence, burning sensation of tongue. Hematologic: Hemolytic and nonhemolytic anemia, thrombocytopenia, leukopenia, agranulocytosis. Hypersensitivity: Henoch-Schonlein purpura. Metabolic: Weight gain, edema.

Nervous

System/Psychiatric: Ataxia, depression with suicidal tendencies, dementia, euphoria, convulsions (however, a causal relationship has not been established); bradykinetic episodes, numbness, muscle twitching, blepharospasm (which may be taken as an early sign of excess dosage; consideration of dosage reduction may be made at this time), trismus, activation of latent Horner's syndrome, nightmares. Skin: Malignant melanoma (see also CONTRAINDICATIONS ), increased sweating.

Special

Senses: Oculogyric crisis, mydriasis, diplopia. Urogenital: Urinary retention, priapism. Miscellaneous: Faintness, hoarseness, malaise, hot flashes, sense of stimulation, bizarre breathing patterns.

Laboratory

Tests: Abnormalities in alkaline phosphatase, SGOT (AST), SGPT (ALT), bilirubin, Coombs test, uric acid.

AND PRECAUTIONS The following adverse reactions described in this section are related to at least one of the components of Carbidopa, levodopa and entacapone tablets (i.e., levodopa, carbidopa, and/or entacapone) based upon the safety experience in clinical trials (especially pivotal trials) or in postmarketing reports.

• May cause falling asleep during activities of daily living without apparent warning, and daytime drowsiness and somnolence ( 5.1 )
• May cause syncope and hypotension/orthostatic hypotension ( 5.2 )
• May cause or exacerbate dyskinesia ( 5.3 )
• May cause depression and suicidality ( 5.4 )
• May cause hallucinations and/or other psychotic-like behavior ( 5.5 )
• May cause problems with impulse control and compulsive behaviors ( 5.6 )
• Abrupt discontinuation may cause hyperpyrexia and confusion ( 5.7 )
• May cause diarrhea and/or drug-induced colitis ( 5.8 )
• May cause rhabdomyolysis ( 5.9 )

5.1 Falling Asleep During Activities of Daily Living and Somnolence Patients with Parkinson’s disease treated with Carbidopa, levodopa and entacapone tablets or other carbidopa/levodopa products have reported suddenly falling asleep without prior warning of sleepiness while engaged in activities of daily living (including the operation of motor vehicles). Some of these episodes resulted in accidents. Although many of these patients reported somnolence while taking entacapone, some did not perceive warning signs, such as excessive drowsiness, and believed that they were alert immediately prior to the event. Some of these events have been reported to occur up to one year after initiation of treatment. Somnolence was reported in 2% of patients taking entacapone and 0% in placebo in controlled trials. It is reported that falling asleep while engaged in activities of daily living always occurs in a setting of pre-existing somnolence, although patients may not give such a history. For this reason, prescribers should reassess patients for drowsiness or sleepiness especially since some of the events occur well after the start of treatment. Prescribers should also be aware that patients may not acknowledge drowsiness or sleepiness until directly questioned about drowsiness or sleepiness during specific activities. Patients who have already experienced somnolence and/or an episode of sudden sleep onset should not participate in these activities during treatment with Carbidopa, levodopa and entacapone tablets. Before initiating treatment with Carbidopa, levodopa and entacapone tablets, advise patients of the potential to develop drowsiness and specifically ask about factors that may increase this risk such as use of concomitant sedating medications and the presence of sleep disorders. If a patient develops daytime sleepiness or episodes of falling asleep during activities that require active participation (e.g., conversations, eating, etc.), Carbidopa, levodopa and entacapone tablets should ordinarily be discontinued <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.5 ) and Warnings and Precautions ( 5.7 )]</span>. If the decision is made to continue Carbidopa, levodopa and entacapone tablets, patients should be advised not to drive and to avoid other potentially dangerous activities. There is insufficient information to establish whether dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living.

5.2 Hypotension, Orthostatic Hypotension and Syncope Reports of syncope were generally more frequent in patients in both treatment groups who had had a prior episode of documented hypotension (although the episodes of syncope, obtained by history, were themselves not documented with vital sign measurement). Hypotension, orthostatic hypotension, and syncope are observed in patients treated with drugs that increase central dopaminergic tone including Carbidopa, levodopa and entacapone tablets.

5.3 Dyskinesia Dyskinesia (involuntary movements) may occur or be exacerbated at lower dosages and sooner with Carbidopa, levodopa and entacapone tablets than with preparations containing only carbidopa and levodopa. The occurrence of dyskinesias may require dosage reduction. In pivotal trials, the treatment difference incidence of dyskinesia was 10% and for carbidopa-levodopa plus 200 mg entacapone. Although decreasing the dose of levodopa may ameliorate this side effect, many patients in controlled trials continued to experience frequent dyskinesias despite a reduction in their dose of levodopa. The treatment difference incidence of study withdrawal for dyskinesia was 1% for carbidopa-levodopa-entacapone.

5.4 Depression and Suicidality All patients should be observed carefully for the development of depression with concomitant suicidal tendencies. Patients with past or current psychoses should be treated with caution.

5.5 Hallucinations and/or Psychotic-Like Behavior Dopaminergic therapy in patients with Parkinson’s disease has been associated with hallucinations. Hallucinations led to drug discontinuation and premature withdrawal from clinical trials in 0.8% and 0% of patients treated with carbidopa, levodopa, entacapone and carbidopa, levodopa, respectively. Hallucinations led to hospitalization in 1.0% and 0.3% of patients in the carbidopa, levodopa, entacapone and carbidopa, levodopa, groups, respectively. Agitation occurred in 1% of patients treated with carbidopa, levodopa, entacapone and 0% treated with carbidopa, levodopa.

5.6 Impulse Control and/or Compulsive Behaviors Postmarketing reports suggest that patients treated with anti-Parkinson medications can experience intense urges to gamble, increased sexual urges, intense urges to spend money uncontrollably, and other intense urges. Patients may be unable to control these urges while taking one or more of the medications generally used for the treatment of Parkinson’s disease and which increase central dopaminergic tone, including entacapone taken with levodopa and carbidopa. In some cases, although not all, these urges were reported to have stopped when the dose of anti-Parkinson medications was reduced or discontinued. Because patients may not recognize these behaviors as abnormal it is important for prescribers to specifically ask patients or their caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending or other urges while being treated with entacapone. Physicians should consider dose reduction or stopping Carbidopa, levodopa and entacapone tablets if a patient develops such urges while taking Carbidopa, levodopa and entacapone tablets <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.5 ), Warnings and Precautions ( 5.7 )]</span>.

5.7 Withdrawal-Emergent Hyperpyrexia and Confusion Cases of hyperpyrexia and confusion resembling neuroleptic malignant syndrome (NMS) have been reported in association with dose reduction or withdrawal of therapy with carbidopa, levodopa and entacapone. However, in some cases, hyperpyrexia and confusion were reported after initiation of treatment with entacapone. Hyperpyrexia and confusion are uncommon but they may be life-threatening with a variety of features, including hyperpyrexia/fever/hyperthermia, muscle rigidity, involuntary movements, altered consciousness/mental status changes, delirium, autonomic dysfunction, tachycardia, tachypnea, sweating, hyper-or hypotension, and abnormal laboratory findings (e.g., creatine phosphokinase elevation, leukocytosis, myoglobinuria, and increased serum myoglobin). If a patient needs to discontinue or reduce their daily dose of Carbidopa, levodopa and entacapone tablets, the dose should be decreased slowly, with supervision from a health care provider <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.5 )]</span>. Specific methods for tapering entacapone have not been systematically evaluated.

5.8 Diarrhea and Colitis In clinical trials of entacapone, diarrhea developed in 60 of 603 (10.0%) and 16 of 400 (4.0%) of patients treated with 200 mg of entacapone or placebo in combination with levodopa and dopa decarboxylase inhibitor, respectively. In patients treated with entacapone, diarrhea was generally mild to moderate in severity (8.6%) but was regarded as severe in 1.3%. Diarrhea resulted in withdrawal in 10 of 603 (1.7%) patients, 7 (1.2%) with mild and moderate diarrhea and 3 (0.5%) with severe diarrhea. Diarrhea generally resolved after discontinuation of entacapone. Two patients with diarrhea were hospitalized. Typically, diarrhea presents within 4 to 12 weeks after entacapone is started, but it may appear as early as the first week and as late as many months after the initiation of treatment. Diarrhea may be associated with weight loss, dehydration, and hypokalemia. Postmarketing experience has shown that diarrhea may be a sign of drug-induced microscopic colitis, primarily lymphocytic colitis. In these cases diarrhea has usually been moderate to severe, watery and non-bloody, at times associated with dehydration, abdominal pain, weight loss, and hypokalemia. In the majority of cases, diarrhea and other colitis-related symptoms resolved or significantly improved when entacapone treatment was stopped. In some patients with biopsy confirmed colitis, diarrhea had resolved or significantly improved after discontinuation of entacapone but recurred after retreatment with entacapone. If prolonged diarrhea is suspected to be related to Carbidopa, levodopa and entacapone tablets, the drug should be discontinued and appropriate medical therapy considered. If the cause of prolonged diarrhea remains unclear or continues after stopping entacapone, then further diagnostic investigations including colonoscopy and biopsies should be considered.

5.9 Rhabdomyolysis Cases of severe rhabdomyolysis have been reported with entacapone when used in combination with carbidopa and levodopa. Severe prolonged motor activity including dyskinesia may possibly account for rhabdomyolysis. Most of the cases were manifested by myalgia and increased values of creatine phosphokinase (CPK) and myoglobin. Some of the reactions also included fever and/or alteration of consciousness. It is also possible that rhabdomyolysis may be a result of the syndrome described in Withdrawal-Emergent Hyperpyrexia and Confusion <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.7 )]</span>.

5.10 Interaction with Drugs Metabolized by COMT Drugs known to be metabolized by COMT, such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, alpha-methyldopa, apomorphine, isoetherine, and bitolterol should be administered with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rate, arrhythmia, and/or increased blood pressure.

5.11 Fibrotic Complications Cases of retroperitoneal fibrosis, pulmonary infiltrates, pleural effusion, and pleural thickening have been reported in some patients treated with ergot derived dopaminergic agents. These complications may resolve when the drug is discontinued, but complete resolution does not always occur. Although these adverse reactions may be related to the ergoline structure of these compounds, a possible causal role of nonergot derived drugs (e.g., entacapone, levodopa), which increase dopaminergic activity, has also been considered. The expected incidence of fibrotic complications is so low that even if entacapone caused these complications at rates similar to those attributable to other dopaminergic therapies, it is unlikely that it would have been detected in a cohort of the size exposed to entacapone during its clinical development. Four cases of pulmonary fibrosis have been reported during clinical development of entacapone; 3 of these patients were also treated with pergolide and 1 with bromocriptine. The duration of treatment with entacapone ranged from 7 months to 17 months.

5.12 Peptic Ulcer Disease As with levodopa, treatment with Carbidopa, levodopa and entacapone tablets may increase the possibility of upper gastrointestinal hemorrhage in patients with a history of peptic ulcer.

5.13 Hepatic Impairment Patients with hepatic impairment should be treated with caution <span class="opacity-50 text-xs">[see Clinical Pharmacology ( 12.3 )]</span>. As with levodopa, periodic evaluation of hepatic function is recommended during extended therapy.

5.14 Laboratory Tests Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, SGOT (AST), SGPT (ALT), lactic dehydrogenase, and bilirubin. Abnormalities in blood urea nitrogen and positive Coombs test have also been reported. Commonly, levels of blood urea nitrogen, creatinine, and uric acid are lower during administration of Carbidopa, levodopa and entacapone tablets than with levodopa. Carbidopa, levodopa and entacapone tablets may cause a false-positive reaction for urinary ketone bodies when a test tape is used for determination of ketonuria. This reaction will not be altered by boiling the urine specimen. False-negative tests may result with the use of glucose-oxidase methods of testing for glucosuria. Cases of falsely diagnosed pheochromocytoma in patients on carbidopa/levodopa therapy have been reported very rarely. Caution should be exercised when interpreting the plasma and urine levels of catecholamines and their metabolites in patients on carbidopa/levodopa therapy.

PRECAUTIONS General As with levodopa, periodic evaluations of hepatic, hematopoietic, cardiovascular, and renal function are recommended during extended therapy. Patients with chronic wide-angle glaucoma may be treated cautiously with carbidopa and levodopa extended-release tablets provided the intraocular pressure is well-controlled and the patient is monitored carefully for changes in intraocular pressure during therapy.

Dyskinesia

Levodopa alone, as well as carbidopa and levodopa extended-release tablets are associated with dyskinesias. The occurrence of dyskinesias may require dosage reduction. Hallucinations / Psychotic-Like Behavior Hallucinations and psychotic-like behavior have been reported with dopaminergic medications. In general, hallucinations present shortly after the initiation of therapy and may be responsive to dose reduction in levodopa. Hallucinations may be accompanied by confusion and to a lesser extent sleep disorder (insomnia) and excessive dreaming. Carbidopa and levodopa extended-release tablets may have similar effects on thinking and behavior. This abnormal thinking and behavior may present with one or more symptoms, including paranoid ideation, delusions, hallucinations, confusion, psychotic-like behavior, disorientation, aggressive behavior, agitation, and delirium. Ordinarily, patients with a major psychotic disorder should not be treated with carbidopa and levodopa extended-release tablets, because of the risk of exacerbating psychosis. In addition, certain medications used to treat psychosis may exacerbate the symptoms of Parkinson’s disease and may decrease the effectiveness of carbidopa and levodopa extended-release tablets.

Impulse

Control / Compulsive Behaviors Reports of patients taking dopaminergic medications (medications that increase central dopaminergic tone), suggest that patients may experience an intense urge to gamble, increased sexual urges, intense urges to spend money, binge eating, and/or other intense urges, and the inability to control these urges. In some cases, although not all, these urges were reported to have stopped when the dose was reduced or the medication was discontinued. Because patients may not recognize these behaviors as abnormal, it is important for prescribers to specifically ask patients or the caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending or other urges while being treated with carbidopa and levodopa extended-release tablets. Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking carbidopa and levodopa extended-release tablets [see Information for Patients ].

Melanoma

Epidemiological studies have shown that patients with Parkinson’s disease have a higher risk (2- to approximately 6-fold higher) of developing melanoma than the general population. Whether the increased risk observed was due to Parkinson’s disease or other factors, such as drugs used to treat Parkinson’s disease, is unclear. For the reasons stated above, patients and providers are advised to monitor for melanomas frequently and on a regular basis when using carbidopa and levodopa extended-release tablets for any indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists). Information for Patients The patient should be informed that carbidopa and levodopa extended-release tablet is an extended-release formulation of carbidopa and levodopa which releases these ingredients over a 4- to 6-hour period. It is important that carbidopa and levodopa extended-release tablets be taken at regular intervals according to the schedule outlined by the physician. The patient should be cautioned not to change the prescribed dosage regimen and not to add any additional antiparkinson medications, including other carbidopa and levodopa preparations, without first consulting the physician. If abnormal involuntary movements appear or get worse during treatment with carbidopa and levodopa extended-release tablets, the physician should be notified, as dosage adjustment may be necessary. Patients should be advised that sometimes the onset of effect of the first morning dose of carbidopa and levodopa extended-release tablets may be delayed for up to 1 hour compared with the response usually obtained from the first morning dose of carbidopa and levodopa tablets. The physician should be notified if such delayed responses pose a problem in treatment. Patients should be advised that, occasionally, dark color (red, brown, or black) may appear in saliva, urine, or sweat after ingestion of carbidopa and levodopa extended-release tablets. Although the color appears to be clinically insignificant, garments may become discolored. The patient should be informed that a change in diet to foods that are high in protein may delay the absorption of levodopa and may reduce the amount taken up in the circulation. Excessive acidity also delays stomach emptying, thus delaying the absorption of levodopa. Iron salts (such as in multivitamin tablets) may also reduce the amount of levodopa available to the body. The above factors may reduce the clinical effectiveness of the levodopa or carbidopa and levodopa therapy. Patients must be advised that the whole or half tablet should be swallowed without chewing or crushing. Patients should be alerted to the possibility of sudden onset of sleep during daily activities, in some cases without awareness or warning signs, when they are taking dopaminergic agents, including levodopa. Patients should be advised to exercise caution while driving or operating machinery and that if they have experienced somnolence and/or sudden sleep onset, they must refrain from these activities. (see WARNINGS , Falling Asleep During Activities of Daily Living and Somnolence . ) There have been reports of patients experiencing intense urges to gamble, increased sexual urges, and other intense urges, and the inability to control these urges while taking one or more of the medications that increase central dopaminergic tone that are generally used for the treatment of Parkinson’s disease, including carbidopa and levodopa extended-release tablets. Although it is not proven that the medications caused these events, these urges were reported to have stopped in some cases when the dose was reduced or the medication was stopped. Prescribers should ask patients about the development of new or increased gambling urges, sexual urges or other urges while being treated with carbidopa and levodopa extended-release tablets. Patients should inform their physician if they experience new or increased gambling urges, increased sexual urges, or other intense urges while taking carbidopa and levodopa extended-release tablets. Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking carbidopa and levodopa extended-release tablets. (see PRECAUTIONS, Impulse Control / Compulsive Behaviors ).

Laboratory Tests

Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, SGOT (AST), SGPT (ALT), lactic dehydrogenase (LDH), and bilirubin. Abnormalities in blood urea nitrogen (BUN) and positive Coombs test have also been reported. Commonly, levels of blood urea nitrogen, creatinine, and uric acid are lower during administration of carbidopa and levodopa preparations than with levodopa. Carbidopa and levodopa preparations, such as carbidopa and levodopa tablets and carbidopa and levodopa extended-release tablets, may cause a false-positive reaction for urinary ketone bodies when a test tape is used for determination of ketonuria. This reaction will not be altered by boiling the urine specimen. False-negative tests may result with the use of glucose-oxidase methods of testing for glucosuria. Cases of falsely diagnosed pheochromocytoma in patients on carbidopa and levodopa therapy have been reported very rarely. Caution should be exercised when interpreting the plasma and urine levels of catecholamines and their metabolites in patients on levodopa or carbidopa and levodopa therapy.

Drug Interactions

Caution should be exercised when the following drugs are administered concomitantly with carbidopa and levodopa extended-release tablets. Symptomatic postural hypotension has occurred when carbidopa and levodopa preparations were added to the treatment of patients receiving some antihypertensive drugs. Therefore, when therapy with carbidopa and levodopa extended-release tablets is started, dosage adjustment of the antihypertensive drug may be required. For patients receiving MAO inhibitors (Type A or B), see CONTRAINDICATIONS . Concomitant therapy with selegiline and carbidopa and levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa and levodopa alone (see CONTRAINDICATIONS ). There have been rare reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa and levodopa preparations. Dopamine D 2 receptor antagonists (e.g., phenothiazines, butyrophenones, risperidone) and isoniazid may reduce the therapeutic effects of levodopa. In addition, the beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with carbidopa and levodopa extended-release tablets should be carefully observed for loss of therapeutic response. Use of carbidopa and levodopa extended-release tablets with dopamine-depleting agents (e.g., reserpine and tetrabenazine) or other drugs known to deplete monoamine stores is not recommended. Carbidopa and levodopa extended-release tablets and iron salts or multivitamins containing iron salts should be coadministered with caution. Iron salts can form chelates with levodopa and carbidopa and consequently reduce the bioavailability of carbidopa and levodopa. Although metoclopramide may increase the bioavailability of levodopa by increasing gastric emptying, metoclopramide may also adversely affect disease control by its dopamine receptor antagonistic properties. Carcinogenesis, Mutagenesis, Impairment of Fertility In a two-year bioassay of carbidopa and levodopa tablets, no evidence of carcinogenicity was found in rats receiving doses of approximately two times the maximum daily human dose of carbidopa and four times the maximum daily human dose of levodopa (equivalent to 8 carbidopa and levodopa extended-release tablets). In reproduction studies with carbidopa and levodopa tablets, no effects on fertility were found in rats receiving doses of approximately two times the maximum daily human dose of carbidopa and four times the maximum daily human dose of levodopa (equivalent to 8 carbidopa and levodopa extended-release tablets).

Pregnancy Pregnancy

Category C. No teratogenic effects were observed in a study in mice receiving up to 20 times the maximum recommended human dose of carbidopa and levodopa tablets. There was a decrease in the number of live pups delivered by rats receiving approximately two times the maximum recommended human dose of carbidopa and approximately five times the maximum recommended human dose of levodopa during organogenesis. Carbidopa and levodopa tablets caused both visceral and skeletal malformations in rabbits at all doses and ratios of carbidopa/levodopa tested, which ranged from 10 times/5 times the maximum recommended human dose of carbidopa/levodopa to 20 times/10 times the maximum recommended human dose of carbidopa/levodopa. There are no adequate or well-controlled studies in pregnant women. It has been reported from individual cases that levodopa crosses the human placental barrier, enters the fetus, and is metabolized. Carbidopa concentrations in fetal tissue appeared to be minimal. Use of carbidopa and levodopa extended-release tablets in women of childbearing potential requires that the anticipated benefits of the drug be weighed against possible hazards to mother and child.

Nursing Mothers

Levodopa has been detected in human milk. Caution should be exercised when carbidopa and levodopa extended-release tablets are administered to a nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Use of the drug in patients below the age of 18 is not recommended.

Geriatric

Use In the clinical efficacy trials for carbidopa and levodopa tablets, almost half of the patients were older than 65, but few were older than 75. No overall meaningful differences in safety or effectiveness were observed between these subjects and younger subjects, but greater sensitivity of some older individuals to adverse drug reactions such as hallucinations cannot be ruled out. There is no specific dosing recommendation based upon clinical pharmacology data as carbidopa and levodopa tablets and carbidopa and levodopa extended-release tablets are titrated as tolerated for clinical effect.

INTERACTIONS

• Drugs metabolized by COMT: use with caution ( 5.11 , 7.2 )
• Anti-hypertensive agents: dose adjustment may be required ( 7.3 )
• Tricyclic antidepressants: risk of hypertension and dyskinesia reported during concomitant use with carbidopa/levodopa ( 7.4 )
• Dopamine D2 receptor antagonists, isoniazid, phenytoin, papaverine and iron salts: may reduce efficacy of Carbidopa, levodopa and entacapone tablets ( 7.5 , 7.6 , 7.7 , 7.8 , 7.9 )
• Drugs that interfere with biliary excretion, glucuronidation and intestinal beta-glucuronidase: dose adjustment of Carbidopa, levodopa and entacapone tablets may be required ( 7.10 )
• Drugs metabolized by CYP2C9 (e.g., coumadin): dose adjustment of Carbidopa, levodopa and entacapone tablets may be required; monitor INR when initiating Carbidopa, levodopa and entacapone tablets in patients on coumadin ( 7.11 )

7.1 MAO Inhibitors Patients receiving nonselective MAO inhibitors and carbidopa, levodopa and entacapone may be at risk of increased adrenergic tone. Therefore, the use of Carbidopa, levodopa and entacapone tablets is contraindicated in patients receiving nonselective MAO inhibitors <span class="opacity-50 text-xs">[see Contraindications ( 4 )]</span>.

7.2 Drugs Metabolized by Catechol-O-Methyltransferase (COMT) Drugs known to be metabolized by COMT, such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, alpha-methyldopa, apomorphine, isoetherine, and bitolterol should be administered with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rates, possibly arrhythmias, and excessive changes in blood pressure <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.10 )]</span>.

7.3 Antihypertensive Agents Symptomatic postural hypotension has occurred when carbidopa/levodopa was added to the treatment of patients receiving antihypertensive drugs. When starting therapy with Carbidopa, levodopa and entacapone tablets, dosage adjustment of antihypertensive drug may be required.

7.4 Tricyclic Antidepressants There have been reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa/levodopa.

7.5 Dopamine D2 Receptor Antagonists Dopamine D2 receptor antagonists (e.g., metoclopramide, phenothiazines, butyrophenones, risperidone) may reduce the therapeutic effects of levodopa.

7.6 Isoniazid Isoniazid may reduce the therapeutic effects of levodopa, a dose increase may be necessary.

7.7 Phenytoin The beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin. Patients taking phenytoin with carbidopa/levodopa should be carefully observed for loss of therapeutic response. Carbidopa, levodopa and entacapone tablets dosage should be increased as clinically needed in patients receiving phenytoin.

7.8 Papaverine The beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by papaverine. Patients taking papaverine with carbidopa/levodopa should be carefully observed for loss of therapeutic response. Carbidopa, levodopa and entacapone tablets dosage should be increased as clinically needed in patients receiving papaverine.

7.9 Iron Salts Iron salts or multi vitamins containing iron salts should be coadministered with caution. Iron salts can form chelates with levodopa, carbidopa and entacapone and consequently reduce bioavailability of levodopa, carbidopa and entacapone.

7.10 Drugs Known to Interfere with Biliary Excretion, Glucuronidation, and Intestinal Beta-glucuronidase As most entacapone excretion is via the bile, caution should be exercised when drugs known to interfere with biliary excretion, glucuronidation, and intestinal beta-glucuronidase are given concurrently with entacapone. These include probenecid, cholestyramine, and some antibiotics (e.g., erythromycin, rifampicin, ampicillin and chloramphenicol).

7.11 Drugs Metabolized via CYP2C9 (e.g.,coumadin) The dosage of Carbidopa, levodopa and entacapone tablets should be adjusted as clinically needed in patients using other drugs metabolized via CYP2C9. An interaction study in healthy volunteers, entacapone increased the AUC of R-warfarin on average by 18%, and the INR values on average by 13%. Cases of increased INR in patients concomitantly using warfarin have been reported during the post-approval use of entacapone. Thus, monitoring of INR is recommended when Carbidopa, levodopa and entacapone tablets treatment is initiated for patients receiving warfarin.