ATOMOXETINE Drug Interactions: What You Need to Know

INTERACTIONS

• Monoamine Oxidase Inhibitors. ( 4.2 , 7.1 )
• CYP2D6 Inhibitors - Concomitant use may increase atomoxetinesteady-state plasma concentrations in EMs. (7.2)
• Antihypertensive Drugs and Pressor Agents - Possible effects on blood pressure. (7.3)
• Albuterol (or other beta 2 agonists) - Action of albuterol on cardiovascular system can be potentiated. (7.4)

7.1 Monoamine Oxidase Inhibitors With other drugs that affect brain monoamine concentrations, there have been reports of serious, sometimes fatal reactions (including hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, and mental status changes that include extreme agitation progressing to delirium and coma) when taken in combination with an MAOI. Some cases presented with features resembling neuroleptic malignant syndrome. Such reactions may occur when these drugs are given concurrently or in close proximity <span class="opacity-50 text-xs">[see Contraindications (4.2) ]</span> .

7.2 Effect of CYP2D6 Inhibitors on Atomoxetine In extensive metabolizers (EMs), inhibitors of CYP2D6 (e.g., paroxetine, fluoxetine, and quinidine) increase atomoxetine steady-state plasma concentrations to exposures similar to those observed in poor metabolizers (PMs). In EM individuals treated with paroxetine or fluoxetine, the AUC of atomoxetine is approximately 6- to 8-fold and C ss, max is about 3- to 4-fold greater than atomoxetine alone. In vitro studies suggest that coadministration of cytochrome P450 inhibitors to PMs will not increase the plasma concentrations of atomoxetine.

7.3 Antihypertensive Drugs and Pressor Agents Because of possible effects on blood pressure, atomoxetine hydrochloride should be used cautiously with antihypertensive drugs and pressor agents (e.g., dopamine, dobutamine) or other drugs that increase blood pressure.

7.4 Albuterol Atomoxetine hydrochloride should be administered with caution to patients being treated with systemically-administered (oral or intravenous) albuterol (or other beta 2 agonists) because the action of albuterol on the cardiovascular system can be potentiated resulting in increases in heart rate and blood pressure. Albuterol (600 mcg iv over 2 hours) induced increases in heart rate and blood pressure. These effects were potentiated by atomoxetine (60 mg BID for 5 days) and were most marked after the initial coadministration of albuterol and atomoxetine. However, these effects on heart rate and blood pressure were not seen in another study after the coadministration with inhaled dose of albuterol (200 to 800 mcg) and atomoxetine (80 mg QD for 5 days) in 21 healthy Asian subjects who were excluded for poor metabolizer status.

7.5 Effect of Atomoxetine on P450 Enzymes Atomoxetine did not cause clinically important inhibition or induction of cytochrome P450 enzymes, including CYP1A2, CYP3A, CYP2D6, and CYP2C9. CYP3A Substrate (e.g., Midazolam ) - Coadministration of atomoxetine hydrochloride (60 mg BID for 12 days) with midazolam, a model compound for CYP3A4 metabolized drugs (single dose of 5 mg), resulted in 15% increase in AUC of midazolam. No dose adjustment is recommended for drugs metabolized by CYP3A. CYP2D6 Substrate (e.g., Desipramine) - Coadministration of atomoxetine hydrochloride (40 or 60 mg BID for 13 days) with desipramine, a model compound for CYP2D6 metabolized drugs (single dose of 50 mg), did not alter the pharmacokinetics of desipramine. No dose adjustment is recommended for drugs metabolized by CYP2D6.

7.6 Alcohol Consumption of ethanol with atomoxetine hydrochloride did not change the intoxicating effects of ethanol.

7.7 Methylphenidate Coadministration of methylphenidate with atomoxetine hydrochloride did not increase cardiovascular effects beyond those seen with methylphenidate alone.

7.8 Drugs Highly Bound to Plasma Protein In vitro drug-displacement studies were conducted with atomoxetine and other highly-bound drugs at therapeutic concentrations. Atomoxetine did not affect the binding of warfarin, acetylsalicylic acid, phenytoin, or diazepam to human albumin. Similarly, these compounds did not affect the binding of atomoxetine to human albumin.

7.9 Drugs that Affect Gastric pH Drugs that elevate gastric pH (magnesium hydroxide/aluminum hydroxide, omeprazole) had no effect on atomoxetine hydrochloride bioavailability.

4 CONTRAINDICATIONS

• Hypersensitivity to atomoxetine or other constituents of product. (4.1)
• Atomoxetine hydrochloride use within 2 weeks after discontinuing MAOI or other drugs that affect brain monoamine concentrations. ( 4.2 , 7.1 )
• Narrow Angle Glaucoma. (4.3)
• Pheochromocytoma or history of pheochromocytoma. (4.4)
• Severe Cardiovascular Disorders that might deteriorate with clinically important increases in HR and BP. (4.5)

4.1 Hypersensitivity Atomoxetine capsules are contraindicated in patients known to be hypersensitive to atomoxetine or other constituents of the product <span class="opacity-50 text-xs">[see Warnings and Precautions (5.8) ]</span>.

4.2 Monoamine Oxidase Inhibitors (MAOI) Atomoxetine capsules should not be taken with an MAOI, or within 2 weeks after discontinuing an MAOI. Treatment with an MAOI should not be initiated within 2 weeks after discontinuing atomoxetine capsules. With other drugs that affect brain monoamine concentrations, there have been reports of serious, sometimes fatal reactions (including hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, and mental status changes that include extreme agitation progressing to delirium and coma) when taken in combination with an MAOI. Some cases presented with features resembling neuroleptic malignant syndrome. Such reactions may occur when these drugs are given concurrently or in close proximity <span class="opacity-50 text-xs">[see Drug Interactions (7.1)]</span> .

4.3 Narrow Angle Glaucoma In clinical trials, atomoxetine hydrochloride use was associated with an increased risk of mydriasis and therefore its use is not recommended in patients with narro w angle glaucoma.

4.4 Pheochromocytoma Serious reactions, including elevated blood pressure and tachyarrhythmia, have been reported in patients with pheochromocytoma or a history of pheochromocytoma who received atomoxetine hydrochloride. Therefore, atomoxetine capsules should not be taken by patients with pheochromocytoma or a history of pheochromocytoma.

4.5 Severe Cardiovascular Disorders Atomoxetine capsules should not be used in patients with severe cardiac or vascular disorders whose condition would be expected to deteriorate if they experience increases in blood pressure or heart rate that could be clinically important (for example, 15 to 20 mm Hg in blood pressure or 20 beats per minute in heart rate. <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.4 )]</span>.

AND PRECAUTIONS Suicidal Ideation - Monitor for suicidality, clinical worsening, and unusual changes in behavior. ( 5.1 )

Severe Liver

Injury - Should be discontinued and not restarted in patients with jaundice or laboratory evidence of liver injury. ( 5.2 )

Serious Cardiovascular

Events - Sudden death, stroke and myocardial infarction have been reported in association with atomoxetine treatment. Patients should have a careful history and physical exam to assess for presence of cardiovascular disease. Atomoxetine hydrochloride generally should not be used in children or adolescents with known serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other serious cardiac problems that may place them at increased vulnerability to its noradrenergic effects. Consideration should be given to not using atomoxetine hydrochloride in adults with clinically significant cardiac abnormalities. ( 5.3 )

Emergent Cardiovascular

Symptoms - Patients should undergo prompt cardiac evaluation. ( 5.3 ) Effects on Blood Pressure and Heart Rate - Increase in blood pressure and heart rate; orthostasis and syncope may occur. Use with caution in patients with hypertension, tachycardia, or cardiovascular or cerebrovascular disease. ( 5.4 )

Emergent

Psychotic or Manic Symptoms - Consider discontinuing treatment if such new symptoms occur. ( 5.5 )

Bipolar

Disorder - Screen patients to avoid possible induction of a mixed/manic episode. ( 5.6 ) Aggressive behavior or hostility should be monitored. ( 5.7 ) Possible allergic reactions, including anaphylactic reactions, angioneurotic edema, urticaria, and rash. ( 5.8 ) Effects on Urine Outflow - Urinary hesitancy and retention may occur. ( 5.9 ) Priapism - Prompt medical attention is required in the event of suspected priapism. ( 5.10 , 17.5 ) Growth - Height and weight should be monitored in pediatric patients. ( 5.11 )

Concomitant

Use of Potent CYP2D6 Inhibitors or Use in patients known to be CYP2D6 PMs - Dose adjustment of atomoxetine hydrochloride may be necessary. ( 5.13 )

5.1 Suicidal Ideation Atomoxetine hydrochloride increased the risk of suicidal ideation in short-term studies in children and adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD). Pooled analyses of short-term (6 to 18 weeks) placebo-controlled trials of atomoxetine hydrochloride in children and adolescents have revealed a greater risk of suicidal ideation early during treatment in those receiving atomoxetine hydrochloride. There were a total of 12 trials (11 in ADHD and 1 in enuresis) involving over 2200 patients (including 1357 patients receiving atomoxetine hydrochloride and 851 receiving placebo). The average risk of suicidal ideation in patients receiving atomoxetine hydrochloride was 0.4% (5/1357 patients), compared to none in placebo-treated patients. There was 1 suicide attempt among these approximately 2200 patients, occurring in a patient treated with atomoxetine hydrochloride. No suicides occurred in these trials. All reactions occurred in children 12 years of age or younger. All reactions occurred during the first month of treatment. It is unknown whether the risk of suicidal ideation in pediatric patients extends to longer-term use. A similar analysis in adult patients treated with atomoxetine hydrochloride for either ADHD or major depressive disorder (MDD) did not reveal an increased risk of suicidal ideation or behavior in association with the use of atomoxetine hydrochloride. All pediatric patients being treated with atomoxetine hydrochloride should be monitored appropriately and observed closely for clinical worsening, suicidality, and unusual changes in behavior, especially during the initial few months of a course of drug therapy, or at times of dose changes, either increases or decreases. The following symptoms have been reported with atomoxetine hydrochloride: anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania and mania. Although a causal link between the emergence of such symptoms and the emergence of suicidal impulses has not been established, there is a concern that such symptoms may represent precursors to emerging suicidality. Thus, patients being treated with atomoxetine hydrochloride should be observed for the emergence of such symptoms. Consideration should be given to changing the therapeutic regimen, including possibly discontinuing the medication, in patients who are experiencing emergent suicidality or symptoms that might be precursors to emerging suicidality, especially if these symptoms are severe or abrupt in onset, or were not part of the patient’s presenting symptoms. Families and caregivers of pediatric patients being treated with atomoxetine hydrochloride should be alerted about the need to monitor patients for the emergence of agitation, irritability, unusual changes in behavior, and the other symptoms described above, as well as the emergence of suicidality, and to report such symptoms immediately to healthcare providers. Such monitoring should include daily observation by families and caregivers.

5.2 Severe Liver Injury Postmarketing reports indicate that atomoxetine hydrochloride can cause severe liver injury. Although no evidence of liver injury was detected in clinical trials of about 6000 patients, there have been rare cases of clinically significant liver injury that were considered probably or possibly related to atomoxetine hydrochloride use in postmarketing experience. Rare cases of liver failure have also been reported, including a case that resulted in a liver transplant. Because of probable underreporting, it is impossible to provide an accurate estimate of the true incidence of these reactions. Reported cases of liver injury occurred within 120 days of initiation of atomoxetine in the majority of cases and some patients presented with markedly elevated liver enzymes [&gt; 20 X upper limit of normal (ULN)], and jaundice with significantly elevated bilirubin levels (&gt; 2 X ULN), followed by recovery upon atomoxetine discontinuation. In one patient, liver injury, manifested by elevated hepatic enzymes up to 40 X ULN and jaundice with bilirubin up to 12 X ULN, recurred upon rechallenge, and was followed by recovery upon drug discontinuation, providing evidence that atomoxetine hydrochloride likely caused the liver injury. Such reactions may occur several months after therapy is started, but laboratory abnormalities may continue to worsen for several weeks after drug is stopped. The patient described above recovered from his liver injury, and did not require a liver transplant. Atomoxetine hydrochloride should be discontinued in patients with jaundice or laboratory evidence of liver injury, and should not be restarted. Laboratory testing to determine liver enzyme levels should be done upon the first symptom or sign of liver dysfunction (e.g., pruritus, dark urine, jaundice, right upper quadrant tenderness, or unexplained “flu like” symptoms) [ see Warnings and Precautions ( 5.12 ); Patient Counseling Information ( 17.3 ) ].

5.3 Serious Cardiovascular Events Sudden Death and Pre-existing Structural Cardiac Abnormalities or Other Serious Heart Problems Children and Adolescents — Sudden death has been reported in association with atomoxetine treatment at usual doses in children and adolescents with structural cardiac abnormalities or other serious heart problems. Although some serious heart problems alone carry an increased risk of sudden death, atomoxetine generally should not be used in children or adolescents with known serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other serious cardiac problems that may place them at increased vulnerability to the noradrenergic effects of atomoxetine. Adults — Sudden deaths, stroke, and myocardial infarction have been reported in adults taking atomoxetine at usual doses for ADHD. Although the role of atomoxetine in these adult cases is also unknown, adults have a greater likelihood than children of having serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, coronary artery disease, or other serious cardiac problems. Consideration should be given to not treating adults with clinically significant cardiac abnormalities.

Assessing Cardiovascular

Status in Patients being Treated with Atomoxetine Children, adolescents, or adults who are being considered for treatment with atomoxetine should have a careful history (including assessment for a family history of sudden death or ventricular arrhythmia) and physical exam to assess for the presence of cardiac disease, and should receive further cardiac evaluation if findings suggest such disease (e.g., electrocardiogram and echocardiogram). Patients who develop symptoms such as exertional chest pain, unexplained syncope, or other symptoms suggestive of cardiac disease during atomoxetine treatment should undergo a prompt cardiac evaluation.

5.4 Effects on Blood Pressure and Heart Rate Atomoxetine hydrochloride should be used with caution in patients whose underlying medical conditions could be worsened by increases in blood pressure or heart rate such as certain patients with hypertension, tachycardia, or cardiovascular or cerebrovascular disease. It should not be used in patients with severe cardiac or vascular disorders whose condition would be expected to deteriorate if they experienced clinically important increases in blood pressure or heart rate [ see Contraindications ( 4.5 ) ]. Pulse and blood pressure should be measured at baseline, following atomoxetine hydrochloride dose increases, and periodically while on therapy to detect possible clinically important increases. The following table provides short-term, placebo-controlled clinical trial data for the proportions of patients having an increase in: diastolic blood pressure ≥ 15 mm Hg; systolic blood pressure ≥ 20 mm Hg; heart rate greater than or equal to 20 bpm, in both the pediatric and adult populations ( see Table 1).

Table

1 a Pediatric Acute Placebo-Controlled Adult Acute Placebo-Controlled Maximum b Endpoint Maximum b Endpoint Atomoxetine Placebo Atomoxetine Placebo Atomoxetine Placebo Atomoxetine Placebo % % % % % % % % DBP (≥ 15 mm Hg) 21.5 14.1 9.3 4.8 12.6 8.7 4.8

3.5 SBP (≥ 20 mm Hg) 12.5 8.7 4.9 3.3 12.4 7.8 4.2

3.2 HR (≥ 20 bpm) 23.4 11.5 12.2 3.8 22.4 8.3 10.2 2.0 a Abbreviations: bpm = beats per minute; DBP = diastolic blood pressure; HR = heart rate; mm Hg = millimeters mercury; SBP = systolic blood pressure. b Proportion of patients meeting threshold at any one time during clinical trial. In placebo-controlled registration studies involving pediatric patients, tachycardia was identified as an adverse event for 0.3% (5/1597) of these atomoxetine hydrochloride patients compared with 0% (0/934) of placebo patients. The mean heart rate increase in extensive metabolizer (EM) patients was 5.0 beats/minute, and in poor metabolizer (PM) patients 9.4 beats/minute. In adult clinical trials where EM/PM status was available, the mean heart rate increase in PM patients was significantly higher than in EM patients (11 beats/minute versus 7.5 beats/minute). The heart rate effects could be clinically important in some PM patients. In placebo-controlled registration studies involving adult patients, tachycardia was identified as an adverse event for 1.5% (8/540) of atomoxetine hydrochloride patients compared with 0.5% (2/402) of placebo patients. In adult clinical trials where EM/PM status was available, the mean change from baseline in diastolic blood pressure in PM patients was higher than in EM patients (4.21 versus 2.13 mm Hg) as was the mean change from baseline in systolic blood pressure (PM: 2.75 versus EM: 2.40 mm Hg). The blood pressure effects could be clinically important in some PM patients. Orthostatic hypotension and syncope have been reported in patients taking atomoxetine hydrochloride. In child and adolescent registration studies, 0.2% (12/5596) of atomoxetine hydrochloride-treated patients experienced orthostatic hypotension and 0.8% (46/5596) experienced syncope. In short-term child and adolescent registration studies, 1.8% (6/340) of atomoxetine hydrochloride-treated patients experienced orthostatic hypotension compared with 0.5% (1/207) of placebo-treated patients. Syncope was not reported during short-term child and adolescent placebo-controlled ADHD registration studies. Atomoxetine hydrochloride should be used with caution in any condition that may predispose patients to hypotension, or conditions associated with abrupt heart rate or blood pressure changes.

5.5 Emergence of New Psychotic or Manic Symptoms Treatment emergent psychotic or manic symptoms, e.g., hallucinations, delusional thinking, or mania in children and adolescents without a prior history of psychotic illness or mania can be caused by atomoxetine at usual doses. If such symptoms occur, consideration should be given to a possible causal role of atomoxetine, and discontinuation of treatment should be considered. In a pooled analysis of multiple short-term, placebo-controlled studies, such symptoms occurred in about 0.2% (4 patients with reactions out of 1939 exposed to atomoxetine for several weeks at usual doses) of atomoxetine-treated patients compared to 0 out of 1056 placebo-treated patients.

5.6 Screening Patients for Bipolar Disorder In general, particular care should be taken in treating ADHD in patients with comorbid bipolar disorder because of concern for possible induction of a mixed/manic episode in patients at risk for bipolar disorder. Whether any of the symptoms described above represent such a conversion is unknown. However, prior to initiating treatment with atomoxetine hydrochloride, patients with comorbid depressive symptoms should be adequately screened to determine if they are at risk for bipolar disorder; such screening should include a detailed psychiatric history, including a family history of suicide, bipolar disorder, and depression.

5.7 Aggressive Behavior or Hostility Patients beginning treatment for ADHD should be monitored for the appearance or worsening of aggressive behavior or hostility. Aggressive behavior or hostility is often observed in children and adolescents with ADHD. In pediatric short-term controlled clinical trials, 21/1308 (1.6%) of atomoxetine patients versus 9/806 (1.1%) of placebo-treated patients spontaneously reported treatment emergent hostility-related adverse events (overall risk ratio of 1.33 [95% C.I. 0.67 to 2.64 – not statistically significant]). In adult placebo-controlled clinical trials, 6/1697 (0.35%) of atomoxetine patients versus 4/1560 (0.26%) of placebo-treated patients spontaneously reported treatment emergent hostility-related adverse events (overall risk ratio of 1.38 [95% C.I. 0.39 to 4.88 – not statistically significant]). Although this is not conclusive evidence that atomoxetine hydrochloride causes aggressive behavior or hostility, these behaviors were more frequently observed in clinical trials among children, adolescents, and adults treated with atomoxetine hydrochloride compared to placebo.

5.8 Allergic Events Although uncommon, allergic reactions, including anaphylactic reactions, angioneurotic edema, urticaria, and rash, have been reported in patients taking atomoxetine hydrochloride.

5.9 Effects on Urine Outflow from the Bladder In adult ADHD controlled trials, the rates of urinary retention (1.7%, 9/540) and urinary hesitation (5.6%, 30/540) were increased among atomoxetine subjects compared with placebo subjects (0%, 0/402; 0.5%, 2/402, respectively). Two adult atomoxetine subjects and no placebo subjects discontinued from controlled clinical trials because of urinary retention. A complaint of urinary retention or urinary hesitancy should be considered potentially related to atomoxetine.

5.10 Priapism Rare postmarketing cases of priapism, defined as painful and nonpainful penile erection lasting more than 4 hours, have been reported for pediatric and adult patients treated with atomoxetine hydrochloride. The erections resolved in cases in which follow-up information was available, some following discontinuation of atomoxetine hydrochloride. Prompt medical attention is required in the event of suspected priapism.

5.11 Effects on Growth Data on the long-term effects of atomoxetine hydrochloride on growth come from open-label studies, and weight and height changes are compared to normative population data. In general, the weight and height gain of pediatric patients treated with atomoxetine hydrochloride lags behind that predicted by normative population data for about the first 9 to 12 months of treatment. Subsequently, weight gain rebounds and at about 3 years of treatment, patients treated with atomoxetine hydrochloride have gained 17.9 kg on average, 0.5 kg more than predicted by their baseline data. After about 12 months, gain in height stabilizes, and at 3 years, patients treated with atomoxetine hydrochloride have gained 19.4 cm on average, 0.4 cm less than predicted by their baseline data ( see Figure 1 below).

Figure

1: Mean Weight and Height Percentiles Over Time for Patients with Three Years of Atomoxetine Hydrochloride Treatment This growth pattern was generally similar regardless of pubertal status at the time of treatment initiation. Patients who were pre-pubertal at the start of treatment (girls ≤ 8 years old, boys ≤ 9 years old) gained an average of 2.1 kg and 1.2 cm less than predicted after three years. Patients who were pubertal (girls > 8 to ≤ 13 years old, boys > 9 to ≤ 14 years old) or late pubertal (girls > 13 years old, boys > 14 years old) had average weight and height gains that were close to or exceeded those predicted after three years of treatment. Growth followed a similar pattern in both extensive and poor metabolizers (EMs, PMs). PMs treated for at least two years gained an average of 2.4 kg and 1.1 cm less than predicted, while EMs gained an average of 0.2 kg and 0.4 cm less than predicted. In short-term controlled studies (up to 9 weeks), atomoxetine hydrochloride-treated patients lost an average of 0.4 kg and gained an average of 0.9 cm, compared to a gain of 1.5 kg and 1.1 cm in the placebo-treated patients. In a fixed-dose controlled trial, 1.3%, 7.1%, 19.3%, and 29.1% of patients lost at least 3.5% of their body weight in the placebo, 0.5, 1.2, and 1.8 mg/kg/day dose groups. Growth should be monitored during treatment with atomoxetine hydrochloride.

Figure

1

5.12 Laboratory Tests Routine laboratory tests are not required. CYP2D6 metabolism — Poor metabolizers (PMs) of CYP2D6 have a 10 fold higher AUC and a 5 fold higher peak concentration to a given dose of atomoxetine hydrochloride compared with extensive metabolizers (EMs).

Approximately

7% of a Caucasian population are PMs. Laboratory tests are available to identify CYP2D6 PMs. The blood levels in PMs are similar to those attained by taking strong inhibitors of CYP2D6. The higher blood levels in PMs lead to a higher rate of some adverse effects of atomoxetine hydrochloride [ see Adverse Reactions ( 6.1 ) ].

5.13 Concomitant Use of Potent CYP2D6 Inhibitors or Use in Patients who are known to be CYP2D6 PMs Atomoxetine is primarily metabolized by the CYP2D6 pathway to 4-hydroxyatomoxetine. Dosage adjustment of atomoxetine hydrochloride may be necessary when coadministered with potent CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, and quinidine) or when administered to CYP2D6 PMs [ see Dosage and Administration ( 2.4 ) and Drug Interactions ( 7.2 ) ].