Atomoxetine Hydrochloride 003578

Categories, Drug Classes, Brand Names & Cost Of Therapy

Categories: Attention deficit hyperactivity disorder; Pregnancy Category C; FDA Approved 2002 Nov

Drug Classes: Selective norepinephrine reuptake inhibitor

Brand Names: Strattera

Description

Atomoxetine hydrochloride is a white to practically white solid, which has a solubility of 27.8 mg/ml in water.

Strattera capsules are intended for oral administration only.

Each capsule contains atomoxetine hydrochloride equivalent to 10, 18, 25, 40, or 60 mg of atomoxetine. The capsules also contain pregelatinized starch and dimethicone. The capsule shells contain gelatin, sodium lauryl sulfate, and other inactive ingredients. The capsule shells also contain 1 or more of the following: FD&C blue no. 2, synthetic yellow iron oxide, titanium dioxide. The capsules are imprinted with edible black ink.

Clinical Pharmacology

The precise mechanism by which atomoxetine produces its therapeutic effects in Attention-Deficit/Hyperactivity Disorder (ADHD) is unknown, but is thought to be related to selective inhibition of the pre-synaptic norepinephrine transporter, as determined in ex vivo uptake and neurotransmitter depletion studies.

Human Pharmacokinetics

Atomoxetine is well-absorbed after oral administration and is minimally affected by food. It is eliminated primarily by oxidative metabolism through the cytochrome P450 2D6 (CYP2D6) enzymatic pathway and subsequent glucuronidation. Atomoxetine has a half-life of about 5 hours. A fraction of the population (about 7% of Caucasians and 2% of African Americans) are poor metabolizers (PMs) of CYP2D6 metabolized drugs. These individuals have reduced activity in this pathway resulting in 10-fold higher AUCs, 5-fold higher peak plasma concentrations, and slower elimination (plasma half-life of about 24 hours) of atomoxetine compared with people with normal activity [extensive metabolizers (EMs)]. Drugs that inhibit CYP2D6, such as fluoxetine, paroxetine, and quinidine, cause similar increases in exposure.

The pharmacokinetics of atomoxetine have been evaluated in more than 400 children and adolescents in selected clinical trials, primarily using population pharmacokinetic studies. Single-dose and steady-state individual pharmacokinetic data were also obtained in children, adolescents, and adults. When doses were normalized to a mg/kg basis, similar half-life, C_max, and AUC values were observed in children, adolescents, and adults. Clearance and volume of distribution after adjustment for body weight were also similar.

Absorption and Distribution

Atomoxetine is rapidly absorbed after oral administration, with absolute bioavailability of about 63% in EMs and 94% in PMs. Maximal plasma concentrations (C_max) are reached approximately 1-2 hours after dosing.

Atomoxetine HCl can be administered with or without food. Administration of atomoxetine HCl with a standard high-fat meal in adults did not affect the extent of oral absorption of atomoxetine (AUC), but did decrease the rate of absorption, resulting in a 37% lower C_max, and delayed T_max by 3 hours. In clinical trials with children and adolescents, administration of atomoxetine HCl with food resulted in a 9% lower C_max.

The steady-state volume of distribution after intravenous administration is 0.85 L/kg indicating that atomoxetine distributes primarily into total body water. Volume of distribution is similar across the patient weight range after normalizing for body weight.

At therapeutic concentrations, 98% of atomoxetine in plasma is bound to protein, primarily albumin.

Metabolism and Elimination

Atomoxetine is metabolized primarily through the CYP2D6 enzymatic pathway. People with reduced activity in this pathway (PMs) have higher plasma concentrations of atomoxetine compared with people with normal activity (EMs). For PMs, AUC of atomoxetine is approximately 10-fold and C_ss,max is about 5-fold greater than EMs. Laboratory tests are available to identify CYP2D6 PMs. Coadministration of atomoxetine HCl with potent inhibitors of CYP2D6, such as fluoxetine, paroxetine, or quinidine, results in a substantial increase in atomoxetine plasma exposure, and dosing adjustment may be necessary (see Drug-Drug Interactions). Atomoxetine did not inhibit or induce the CYP2D6 pathway.

The major oxidative metabolite formed, regardless of CYP2D6 status, is 4-hydroxyatomoxetine, which is glucuronidated. 4-Hydroxyatomoxetine is equipotent to atomoxetine as an inhibitor of the norepinephrine transporter but circulates in plasma at much lower concentrations (1% of atomoxetine concentration in EMs and 0.1% of atomoxetine concentration in PMs). 4-Hydroxyatomoxetine is primarily formed by CYP2D6, but in PMs, 4-hydroxyatomoxetine is formed at a slower rate by several other cytochrome P450 enzymes. N-desmethylatomoxetine is formed by CYP2C19 and other cytochrome P450 enzymes, but has substantially less pharmacological activity compared with atomoxetine and circulates in plasma at lower concentrations (5% of atomoxetine concentration in EMs and 45% of atomoxetine concentration in PMs).

Mean apparent plasma clearance of atomoxetine after oral administration in adult EMs is 0.35 L/h/kg and the mean half-life is 5.2 hours. Following oral administration of atomoxetine to PMs, mean apparent plasma clearance is 0.03 L/h/kg and mean half-life is 21.6 hours. For PMs, AUC of atomoxetine is approximately 10-fold and C_ss,max is about 5-fold greater than EMs. The elimination half-life of 4-hydroxyatomoxetine is similar to that of N-desmethylatomoxetine (6-8 hours) in EM subjects, while the half-life of N-desmethylatomoxetine is much longer in PM subjects (34-40 hours).

Atomoxetine is excreted primarily as 4-hydroxyatomoxetine-O -glucuronide, mainly in the urine (greater than 80% of the dose) and to a lesser extent in the feces (less than 17% of the dose). Only a small fraction of the atomoxetine HCl dose is excreted as unchanged atomoxetine (less than 3% of the dose), indicating extensive biotransformation.

Special Populations

Hepatic Insufficiency

Atomoxetine exposure (AUC) is increased, compared with normal subjects, in EM subjects with moderate (Child-Pugh Class B) (2-fold increase) and severe (Child-Pugh Class C) (4-fold increase) hepatic insufficiency. Dosage adjustment is recommended for patients with moderate or severe hepatic insufficiency (see DOSAGE AND ADMINISTRATION).

Renal Insufficiency

EM subjects with end stage renal disease had higher systemic exposure to atomoxetine than healthy subjects (about a 65% increase), but there was no difference when exposure was corrected for mg/kg dose. Atomoxetine HCl can therefore be administered to ADHD patients with end stage renal disease or lesser degrees of renal insufficiency using the normal dosing regimen.

Geriatric

The pharmacokinetics of atomoxetine have not been evaluated in the geriatric population.

Pediatric

The pharmacokinetics of atomoxetine in children and adolescents are similar to those in adults. The pharmacokinetics of atomoxetine have not been evaluated in children under 6 years of age.

Gender

Gender did not influence atomoxetine disposition.

Ethnic Origin

Ethnic origin did not influence atomoxetine disposition (except that PMs are more common in Caucasians).

Drug-Drug Interactions

CYP2D6 Activity and Atomoxetine Plasma Concentration

Atomoxetine is primarily metabolized by the CYP2D6 pathway to 4-hydroxyatomoxetine. In EMs, inhibitors of CYP2D6 increase atomoxetine steady-state plasma concentrations to exposures similar to those observed in PMs. Dosage adjustment of atomoxetine HCl in EMs may be necessary when coadministered with CYP2D6 inhibitors, e.g., paroxetine, fluoxetine, and quinidine (see DRUG INTERACTIONS). In vitro studies suggest that coadministration of cytochrome P450 inhibitors to PMs will not increase the plasma concentrations of atomoxetine.

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.

Albuterol

Albuterol (600 µg 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 (see DRUG INTERACTIONS).

Alcohol

Consumption of ethanol with atomoxetine HCl did not change the intoxicating effects of ethanol.

Desipramine

Coadministration of atomoxetine HCl (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.

Methylphenidate

Coadministration of methylphenidate with atomoxetine HCl did not increase cardiovascular effects beyond those seen with methylphenidate alone.

Midazolam

Coadministration of atomoxetine HCl (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.

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.

Drugs That Affect Gastric pH

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

Clinical Studies

Children and Adolescents

The effectiveness of atomoxetine HCl in the treatment of ADHD was established in 4 randomized, double-blind, placebo-controlled studies of pediatric patients (ages 6-18). Approximately one-third of the patients met DSM-IV criteria for inattentive subtype and two-thirds met criteria for both inattentive and hyperactive/impulsive subtypes (see INDICATIONS AND USAGE).

Signs and symptoms of ADHD were evaluated by a comparison of mean change from baseline to endpoint for atomoxetine HCl- and placebo-treated patients using an intent-to-treat analysis of the primary outcome measure, the investigator administered and scored ADHD Rating Scale-IV-Parent Version (ADHDRS) total score including hyperactive/impulsive and inattentive sub-scales. Each item on the ADHDRS maps directly to 1 symptom criterion for ADHD in the DSM-IV.

In Study 1, an 8 week randomized, double-blind, placebo-controlled, dose-response, acute treatment study of children and adolescents aged 8-18 (n=297), patients received either a fixed dose of atomoxetine HCl (0.5, 1.2, or 1.8 mg/kg/day) or placebo. Atomoxetine HCl was administered as a divided dose in the early morning and late afternoon/early evening. At the 2 higher doses, improvements in ADHD symptoms were statistically significantly superior in atomoxetine HCl-treated patients compared with placebo-treated patients as measured on the ADHDRS scale. The 1.8 mg/kg/day atomoxetine HCl dose did not provide any additional benefit over that observed with the 1.2 mg/kg/day dose. The 0.5 mg/kg/day atomoxetine HCl dose was not superior to placebo.

In Study 2, a 6 week randomized, double-blind, placebo-controlled, acute treatment study of children and adolescents aged 6-16 (n=171), patients received either atomoxetine HCl or placebo. Atomoxetine HCl was administered as a single dose in the early morning and titrated on a weight-adjusted basis according to clinical response, up to a maximum dose of 1.5 mg/kg/day. The mean final dose of atomoxetine HCl was approximately 1.3 mg/kg/day. ADHD symptoms were statistically significantly improved on atomoxetine HCl compared with placebo, as measured on the ADHDRS scale. This study shows that atomoxetine HCl is effective when administered once daily in the morning.

In 2 identical, 9 week, acute, randomized, double-blind, placebo-controlled studies of children aged 7-13 (Study 3, n=147; Study 4, n=144), atomoxetine HCl and methylphenidate were compared with placebo. Atomoxetine HCl was administered as a divided dose in the early morning and late afternoon (after school) and titrated on a weight-adjusted basis according to clinical response. The maximum recommended atomoxetine HCl dose was 2.0 mg/kg/day. The mean final dose of atomoxetine HCl for both studies was approximately 1.6 mg/kg/day. In both studies, ADHD symptoms statistically significantly improved more on atomoxetine HCl than on placebo, as measured on the ADHDRS scale.

Examination of population subsets based on gender and age (<12 and 12-17) did not reveal any differential responsiveness on the basis of these subgroupings. There was not sufficient exposure of ethnic groups other than Caucasian to allow exploration of differences in these subgroups.

Adults

The effectiveness of atomoxetine HCl in the treatment of ADHD was established in 2 randomized, double-blind, placebo-controlled clinical studies of adult patients, age 18 and older, who met DSM-IV criteria for ADHD.

Signs and symptoms of ADHD were evaluated using the investigator-administered Conners Adult ADHD Rating Scale Screening Version (CAARS), a 30 item scale. The primary effectiveness measure was the 18 item Total ADHD Symptom score (the sum of the inattentive and hyperactivity/impulsivity subscales from the CAARS) evaluated by a comparison of mean change from baseline to endpoint using an intent-to-treat analysis.

In 2 identical, 10 week, randomized, double-blind, placebo-controlled acute treatment studies (Study 5, n=280; Study 6, n=256), patients received either atomoxetine HCl or placebo. Atomoxetine HCl was administered as a divided dose in the early morning and late afternoon/early evening and titrated according to clinical response in a range of 60-120 mg/day. The mean final dose of atomoxetine HCl for both studies was approximately 95 mg/day. In both studies, ADHD symptoms were statistically significantly improved on atomoxetine HCl, as measured on the ADHD Symptom score from the CAARS scale.

Examination of population subsets based on gender and age (<42 and ≥42) did not reveal any differential responsiveness on the basis of these subgroupings. There was not sufficient exposure of ethnic groups other than Caucasian to allow exploration of differences in these subgroups.

Indications And Usage

The effectiveness of atomoxetine HCl in the treatment of ADHD was established in 2 placebo-controlled trials in children, 2 placebo-controlled trials in children and adolescents, and 2 placebo-controlled trials in adults who met DSM-IV criteria for ADHD (see CLINICAL STUDIES).

A diagnosis of ADHD (DSM-IV) implies the presence of hyperactive-impulsive or inattentive symptoms that cause impairment and that were present before age 7 years. The symptoms must be persistent, must be more severe than is typically observed in individuals at a comparable level of development, must cause clinically significant impairment, e.g., in social, academic, or occupational functioning, and must be present in 2 or more settings, e.g., school (or work) and at home. The symptoms must not be better accounted for by another mental disorder. For the Inattentive Type, at least 6 of the following symptoms must have persisted for at least 6 months: lack of attention to details/careless mistakes, lack of sustained attention, poor listener, failure to follow through on tasks, poor organization, avoids tasks requiring sustained mental effort, loses things, easily distracted, forgetful. For the Hyperactive-Impulsive Type, at least 6 of the following symptoms must have persisted for at least 6 months: fidgeting/squirming, leaving seat, inappropriate running/climbing, difficulty with quiet activities, "on the go," excessive talking, blurting answers, can’t wait turn, intrusive. For a Combined Type diagnosis, both inattentive and hyperactive-impulsive criteria must be met.

Special Diagnostic Considerations

The specific etiology of ADHD is unknown, and there is no single diagnostic test. Adequate diagnosis requires the use not only of medical but of special psychological, educational, and social resources. Learning may or may not be impaired. The diagnosis must be based upon a complete history and evaluation of the patient and not solely on the presence of the required number of DSM-IV characteristics.

Need for Comprehensive Treatment Program

Atomoxetine HCl is indicated as an integral part of a total treatment program for ADHD that may include other measures (psychological, educational, social) for patients with this syndrome. Drug treatment may not be indicated for all patients with this syndrome. Drug treatment is not intended for use in the patient who exhibits symptoms secondary to environmental factors and/or other primary psychiatric disorders, including psychosis. Appropriate educational placement is essential in children and adolescents with this diagnosis and psychosocial intervention is often helpful. When remedial measures alone are insufficient, the decision to prescribe drug treatment medication will depend upon the physician’s assessment of the chronicity and severity of the patient’s symptoms.

Long-Term Use

The effectiveness of atomoxetine HCl for long-term use, i.e., for more than 9 weeks in child and adolescent patients and 10 weeks in adult patients, has not been systematically evaluated in controlled trials. Therefore, the physician who elects to use atomoxetine HCl for extended periods should periodically reevaluate the long-term usefulness of the drug for the individual patient (see DOSAGE AND ADMINISTRATION).

Contraindications

Atomoxetine HCl is contraindicated in patients known to be hypersensitive to atomoxetine or other constituents of the product (see WARNINGS).

Monoamine Oxidase Inhibitors (MAOI)

Atomoxetine HCl 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 HCl. 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.

Narrow Angle Glaucoma

In clinical trials, atomoxetine HCl use was associated with an increased risk of mydriasis and therefore its use is not recommended in patients with narrow angle glaucoma.

Warnings

Although uncommon, allergic reactions, including angioneurotic edema, urticaria, and rash, have been reported in patients taking atomoxetine HCl.

Growth

Growth should be monitored during treatment with atomoxetine HCl . During acute treatment studies (up to 9 weeks), atomoxetine HCl-treated patients lost an average of 0.4 kg, while placebo patients gained an average of 1.5 kg. In a controlled trial that randomized patients to placebo or 1 of 3 atomoxetine doses, 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 atomoxetine HCl dose groups, respectively. During acute treatment studies, atomoxetine HCl-treated patients grew an average of 0.9 cm, while placebo-treated patients grew an average of 1.1 cm. There are no long-term, placebo-controlled data to evaluate the effect of atomoxetine HCl on growth. Weight and height were assessed during open-label studies of 12 and 18 months, and mean rates of growth were compared to normal growth curves. Patients treated with atomoxetine HCl for at least 18 months gained an average of 6.5 kg while mean weight percentile decreased slightly from 68 to 60. For this same group of patients, the average gain in height was 9.3 cm with a slight decrease in mean height percentile from 54 to 50. Among patients treated for at least 6 months, mean weight gain was lower for poor metabolizer (PM) patients compared with extensive metabolizer (EM) patients (+0.7 kg compared with +3.0 kg), while mean growth for PM patients was 4.3 cm and mean growth for EM patients was 4.4 cm. Whether final adult height or weight is affected by treatment with atomoxetine HCl is unknown. Patients requiring long-term therapy should be monitored and consideration should be given to interrupting therapy in patients who are not growing or gaining weight satisfactorily.

Precautions

Effects on Blood Pressure and Heart Rate

Atomoxetine HCl should be used with caution in patients with hypertension, tachycardia, or cardiovascular or cerebrovascular disease because it can increase blood pressure and heart rate. Pulse and blood pressure should be measured at baseline, following atomoxetine HCl dose increases, and periodically while on therapy.

In pediatric placebo-controlled trials, atomoxetine HCl-treated subjects experienced a mean increase in heart rate of about 6 beats/min compared with placebo subjects. At the final study visit before drug discontinuation, 3.6% (12/335) of atomoxetine HCl-treated subjects had heart rate increases of at least 25 beats/min and a heart rate of at least 110 beats/min, compared with 0.5% (1/204) of placebo subjects. No pediatric subject had a heart rate increase of at least 25 beats/min and a heart rate of at least 110 beats/min on more than 1 occasion. Tachycardia was identified as an adverse event for 1.5% (5/340) of these pediatric subjects compared with 0.5% (1/207) of placebo subjects. The mean heart rate increase in extensive metabolizer (EM) patients was 6.7 beats/min, and in poor metabolizer (PM) patients 10.4 beats/min.

Atomoxetine HCl-treated pediatric subjects experienced mean increases of about 1.5 mm Hg in systolic and diastolic blood pressures compared with placebo. At the final study visit before drug discontinuation, 6.8% (22/324) of atomoxetine HCl-treated pediatric subjects had high systolic blood pressure measurements compared with 3.0% (6/197) of placebo subjects. High systolic blood pressures were measured on 2 or more occasions in 8.6% (28/324) of atomoxetine HCl-treated subjects and 3.6% (7/197) of placebo subjects. At the final study visit before drug discontinuation, 2.8% (9/326) of atomoxetine HCl-treated pediatric subjects had high diastolic blood pressure measurements compared with 0.5% (1/200) of placebo subjects. High diastolic blood pressures were measured on 2 or more occasions in 5.2% (17/326) of atomoxetine HCl-treated subjects and 1.5% (3/200) placebo subjects. (High systolic and diastolic blood pressure measurements were defined as those exceeding the 95 ^th percentile, stratified by age, gender, and height percentile — National High Blood Pressure Education Working Group on Hypertension Control in Children and Adolescents.)

In adult placebo-controlled trials, atomoxetine HCl-treated subjects experienced a mean increase in heart rate of 5 beats/min compared with placebo subjects. Tachycardia was identified as an adverse event for 3% (8/269) of these adult atomoxetine subjects compared with 0.8% (2/263) of placebo subjects.

Atomoxetine HCl-treated adult subjects experienced mean increases in systolic (about 3 mm Hg) and diastolic (about 1 mm Hg) blood pressures compared with placebo. At the final study visit before drug discontinuation, 1.9% (5/258) of atomoxetine HCl-treated adult subjects had systolic blood pressure measurements ≥150 mm Hg compared with 1.2% (3/256) of placebo subjects. At the final study visit before drug discontinuation, 0.8% (2/257) of atomoxetine HCl-treated adult subjects had diastolic blood pressure measurements ≥100 mm Hg compared with 0.4% (1/257) of placebo subjects. No adult subject had a high systolic or diastolic blood pressure detected on more than 1 occasion.

Orthostatic hypotension has been reported in subjects taking atomoxetine HCl. In short-term child- and adolescent-controlled trials, 1.8% (6/340) of atomoxetine HCl-treated subjects experienced symptoms of postural hypotension compared with 0.5% (1/207) of placebo-treated subjects. Atomoxetine HCl should be used with caution in any condition that may predispose patients to hypotension.

Effects on Urine Outflow From the Bladder

In adult ADHD controlled trials, the rates of urinary retention (3%, 7/269) and urinary hesitation (3%, 7/269) were increased among atomoxetine subjects compared with placebo subjects (0%, 0/263). 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.

Information for the Patient

Patients should consult a physician if they are taking or plan to take any prescription or over-the-counter medicines, dietary supplements, or herbal remedies.

Patients should consult a physician if they are nursing, pregnant, or thinking of becoming pregnant while taking atomoxetine HCl.

Patients may take atomoxetine HCl with or without food.

If patients miss a dose, they should take it as soon as possible, but should not take more than the prescribed total daily amount of atomoxetine HCl in any 24 hour period.

Patients should use caution when driving a car or operating hazardous machinery until they are reasonably certain that their performance is not affected by atomoxetine.

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 HCl 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 HCl (see ADVERSE REACTIONS).

Carcinogenesis, Mutagenesis, and Impairment of Fertility

Carcinogenesis

Atomoxetine HCl was not carcinogenic in rats and mice when given in the diet for 2 years at time-weighted average doses up to 47 and 458 mg/kg/day, respectively. The highest dose used in rats is approximately 8 and 5 times the maximum human dose in children and adults, respectively, on a mg/m ² basis. Plasma levels (AUC) of atomoxetine at this dose in rats are estimated to be 1.8 times (extensive metabolizers) or 0.2 times (poor metabolizers) those in humans receiving the maximum human dose. The highest dose used in mice is approximately 39 and 26 times the maximum human dose in children and adults, respectively, on a mg/m ² basis.

Mutagenesis

Atomoxetine HCl was negative in a battery of genotoxicity studies that included a reverse point mutation assay (Ames Test), an in vitro mouse lymphoma assay, a chromosomal aberration test in Chinese hamster ovary cells, an unscheduled DNA synthesis test in rat hepatocytes, and an in vivo micronucleus test in mice. However, there was a slight increase in the percentage of Chinese hamster ovary cells with diplochromosomes, suggesting endoreduplication (numerical aberration).

The metabolite N-desmethylatomoxetine HCl was negative in the Ames Test, mouse lymphoma assay, and unscheduled DNA synthesis test.

Impairment of Fertility

Atomoxetine HCl did not impair fertility in rats when given in the diet at doses of up to 57 mg/kg/day, which is approximately 6 times the maximum human dose on a mg/m ² basis.

Pregnancy Category C

Pregnant rabbits were treated with up to 100 mg/kg/day of atomoxetine by gavage throughout the period of organogenesis. At this dose, in 1 of 3 studies, a decrease in live fetuses and an increase in early resorptions was observed. Slight increases in the incidences of atypical origin of carotid artery and absent subclavian artery were observed. These findings were observed at doses that caused slight maternal toxicity. The no-effect dose for these findings was 30 mg/kg/day. The 100 mg/kg dose is approximately 23 times the maximum human dose on a mg/m ² basis; plasma levels (AUC) of atomoxetine at this dose in rabbits are estimated to be 3.3 times (extensive metabolizers) or 0.4 times (poor metabolizers) those in humans receiving the maximum human dose.

Rats were treated with up to approximately 50 mg/kg/day of atomoxetine (approximately 6 times the maximum human dose on a mg/m ² basis) in the diet from 2 (females) or 10 (males) weeks prior to mating through the periods of organogenesis and lactation. In 1 of 2 studies, decreases in pup weight and pup survival were observed. The decreased pup survival was also seen at 25 mg/kg (but not at 13 mg/kg). In a study in which rats were treated with atomoxetine in the diet from 2 (females) or 10 (males) weeks prior to mating throughout the period of organogenesis, a decrease in fetal (female only) weight and an increase in the incidence of incomplete ossification of the vertebral arch in fetuses were observed at 40 mg/kg/day (approximately 5 times the maximum human dose on a mg/m ² basis) but not at 20 mg/kg/day.

No adverse fetal effects were seen when pregnant rats were treated with up to 150 mg/kg/day (approximately 17 times the maximum human dose on a mg/m ² basis) by gavage throughout the period of organogenesis.

No adequate and well-controlled studies have been conducted in pregnant women. Atomoxetine HCl should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus.

Labor and Delivery

Parturition in rats was not affected by atomoxetine. The effect of atomoxetine HCl on labor and delivery in humans is unknown.

Nursing Mothers

Atomoxetine and/or its metabolites were excreted in the milk of rats. It is not known if atomoxetine is excreted in human milk. Caution should be exercised if atomoxetine HCl is administered to a nursing woman.

Pediatric Use

The safety and efficacy of atomoxetine HCl in pediatric patients less than 6 years of age have not been established. The efficacy of atomoxetine HCl beyond 9 weeks and safety of atomoxetine HCl beyond 1 year of treatment have not been systematically evaluated.

A study was conducted in young rats to evaluate the effects of atomoxetine on growth and neurobehavioral and sexual development. Rats were treated with 1, 10, or 50 mg/kg/day (approximately 0.2, 2, and 8 times, respectively, the maximum human dose on a mg/m ² basis) of atomoxetine given by gavage from the early postnatal period (Day 10 of age) through adulthood. Slight delays in onset of vaginal patency (all doses) and preputial separation (10 and 50 mg/kg), slight decreases in epididymal weight and sperm number (10 and 50 mg/kg), and a slight decrease in corpora lutea (50 mg/kg) were seen, but there were no effects on fertility or reproductive performance. A slight delay in onset of incisor eruption was seen at 50 mg/kg. A slight increase in motor activity was seen on Day 15 (males at 10 and 50 and females at 50 mg/kg) and on Day 30 (females at 50 mg/kg) but not on Day 60 of age. There were no effects on learning and memory tests. The significance of these findings to humans is unknown.

Geriatric Use

The safety and efficacy of atomoxetine HCl in geriatric patients have not been established.

Drug Interactions

Atomoxetine HCl should be administered with caution to patients being treated with albuterol (or other beta₂ agonists) because the action of albuterol on the cardiovascular system can be potentiated.

CYP2D6 Inhibitors

Atomoxetine is primarily metabolized by the CYP2D6 pathway to 4-hydroxyatomoxetine. In EMs, selective inhibitors of CYP2D6 increase atomoxetine steady-state plasma concentrations to exposures similar to those observed in PMs. Dosage adjustment of atomoxetine HCl may be necessary when coadministered with CYP2D6 inhibitors, e.g., paroxetine, fluoxetine, and quinidine (see DOSAGE AND ADMINISTRATION). 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.

Monoamine Oxidase Inhibitors

See CONTRAINDICATIONS.

Pressor Agents

Because of possible effects on blood pressure, atomoxetine HCl should be used cautiously with pressor agents.

Adverse Reactions

The data in the following tables and text cannot be used to predict the incidence of side effects in the course of usual medical practice where patient characteristics and other factors differ from those that prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with data obtained from other clinical investigations involving different treatments, uses, or investigators. The cited data provide the prescribing physician with some basis for estimating the relative contribution of drug and non-drug factors to the adverse event incidence in the population studied.

Child and Adolescent Clinical Trials

Reasons for Discontinuation of Treatment Due to Adverse Events in Child and Adolescent Clinical Trials

In acute child and adolescent placebo-controlled trials, 3.5% (15/427) of atomoxetine subjects and 1.4% (4/294) placebo subjects discontinued for adverse events. For all studies, (including open-label and long-term studies), 5% of extensive metabolizer (EM) patients and 7% of poor metabolizer (PM) patients discontinued because of an adverse event. Among atomoxetine HCl-treated patients, aggression (0.5%, n=2); irritability (0.5%, n=2); somnolence (0.5%, n=2); and vomiting (0.5%, n=2) were the reasons for discontinuation reported by more than 1 patient.

Commonly Observed Adverse Events in Acute Child and Adolescent, Placebo-Controlled Trials

Commonly observed adverse events associated with the use of atomoxetine HCl (incidence of 2% or greater) and not observed at an equivalent incidence among placebo-treated patients (atomoxetine HCl incidence greater than placebo) are listed in TABLE 1 for the bid trials. Results were similar in the qd trial except as shown in TABLE 2, which shows both bid and qd results for selected adverse events. The most commonly observed adverse events in patients treated with atomoxetine HCl (incidence of 5% or greater and at least twice the incidence in placebo patients, for either bid or qd dosing) were: dyspepsia, nausea, vomiting, fatigue, appetite decreased, dizziness, and mood swings (see TABLE 1 and TABLE 2).

The following adverse events occurred in at least 2% of PM patients and were either twice as frequent or statistically significantly more frequent in PM patients compared with EM patients: decreased appetite (23% of PMs, 16% of EMs); insomnia (13% of PMs, 7% of EMs); sedation (4% of PMs, 2% of EMs); depression (6% of PMs, 2% of EMs); tremor (4% of PMs, 1% of EMs); early morning awakening (3% of PMs, 1% of EMs); pruritus (2% of PMs, 1% of EMs); mydriasis (2% of PMs, 1% of EMs).

Adult Clinical Trials

Reasons for Discontinuation of Treatment Due to Adverse Events in Acute Adult Placebo-Controlled Trials

In the acute adult placebo-controlled trials, 8.5% (23/270) atomoxetine subjects and 3.4% (9/266) placebo subjects discontinued for adverse events. Among atomoxetine HCl-treated patients, insomnia (1.1%, n=3); chest pain (0.7%, n=2); palpitations (0.7%, n=2); and urinary retention (0.7%, n=2) were the reasons for discontinuation reported by more than 1 patient.

Commonly Observed Adverse Events in Acute Adult Placebo-Controlled Trials

Commonly observed adverse events associated with the use of atomoxetine HCl (incidence of 2% or greater) and not observed at an equivalent incidence among placebo-treated patients (atomoxetine HCl incidence greater than placebo) are listed in TABLE 3. The most commonly observed adverse events in patients treated with atomoxetine HCl (incidence of 5% or greater and at least twice the incidence in placebo patients) were: constipation, dry mouth, nausea, appetite decreased, dizziness, insomnia, decreased libido, ejaculatory problems, impotence, urinary hesitation and/or urinary retention and/or difficulty in micturition, and dysmenorrhea (see TABLE 3).

Male and Female Sexual Dysfunction

Atomoxetine appears to impair sexual function in some patients. Changes in sexual desire, sexual performance, and sexual satisfaction are not well assessed in most clinical trials because they need special attention and because patients and physicians may be reluctant to discuss them. Accordingly, estimates of the incidence of untoward sexual experience and performance cited in product labeling are likely to underestimate the actual incidence. TABLE 4 displays the incidence of sexual side effects reported by at least 2% of adult patients taking atomoxetine HCl in placebo-controlled trials.

There are no adequate and well-controlled studies examining sexual dysfunction with atomoxetine HCl treatment. While it is difficult to know the precise risk of sexual dysfunction associated with the use of atomoxetine HCl, physicians should routinely inquire about such possible side effects.

Drug Abuse And Dependence

Atomoxetine HCl is not a controlled substance.

Physical and Psychological Dependence

In a randomized, double-blind, placebo-controlled, abuse-potential study in adults comparing effects of atomoxetine HCl and placebo, atomoxetine HCl was not associated with a pattern of response that suggested stimulant or euphoriant properties.

Clinical study data in over 2000 children, adolescents, and adults with ADHD and over 1200 adults with depression showed only isolated incidents of drug diversion or inappropriate self-administration associated with atomoxetine HCl. There was no evidence of symptom rebound or adverse events suggesting a drug-discontinuation or withdrawal syndrome.

Animal Experience

Drug discrimination studies in rats and monkeys showed inconsistent stimulus generalization between atomoxetine and cocaine.

Overdosage

No specific information is available on the treatment of overdose with atomoxetine. Patients who overdose with atomoxetine should be monitored carefully and receive supportive care. Gastric emptying and repeated activated charcoal (with/without cathartics) may prevent systemic absorption.

Dosage And Administration

Dosing of Children and Adolescents Up to 70 kg Body Weight

Atomoxetine HCl should be initiated at a total daily dose of approximately 0.5 mg/kg and increased after a minimum of 3 days to a target total daily dose of approximately 1.2 mg/kg administered either as a single daily dose in the morning or as evenly divided doses in the morning and late afternoon/early evening. No additional benefit has been demonstrated for doses higher than 1.2 mg/kg/day (see CLINICAL STUDIES).

The total daily dose in children and adolescents should not exceed 1.4 mg/kg or 100 mg, whichever is less.

Dosing of Children and Adolescents Over 70 kg Body Weight and Adults

Atomoxetine HCl should be initiated at a total daily dose of 40 mg and increased after a minimum of 3 days to a target total daily dose of approximately 80 mg administered either as a single daily dose in the morning or as evenly divided doses in the morning and late afternoon/early evening. After 2-4 additional weeks, the dose may be increased to a maximum of 100 mg in patients who have not achieved an optimal response. There are no data that support increased effectiveness at higher doses (see CLINICAL STUDIES).

The maximum recommended total daily dose in children and adolescents over 70 kg and adults is 100 mg.

Maintenance/Extended Treatment

There is no evidence available from controlled trials to indicate how long the patient with ADHD should be treated with atomoxetine HCl. It is generally agreed, however, that pharmacological treatment of ADHD may be needed for extended periods. Nevertheless, the physician who elects to use atomoxetine HCl for extended periods should periodically reevaluate the long-term usefulness of the drug for the individual patient.

General Dosing Information

Atomoxetine HCl may be taken with or without food.

The safety of single doses over 120 mg and total daily doses above 150 mg have not been systematically evaluated.

Dosing Adjustment for Hepatically Impaired Patients

For those ADHD patients who have hepatic insufficiency (HI), dosage adjustment is recommended as follows: For patients with moderate HI (Child-Pugh Class B), initial and target doses should be reduced to 50% of the normal dose (for patients without HI). For patients with severe HI (Child-Pugh Class C), initial dose and target doses should be reduced to 25% of normal (see CLINICAL PHARMACOLOGY, Special Populations).

Dosing Adjustment for Use With a Strong CYP2D6 Inhibitor

In children and adolescents up to 70 kg body weight administered strong CYP2D6 inhibitors, e.g., paroxetine, fluoxetine, quinidine, atomoxetine HCl should be initiated at 0.5 mg/kg/day and only increased to the usual target dose of 1.2 mg/kg/day if symptoms fail to improve after 4 weeks and the initial dose is well tolerated.

In children and adolescents over 70 kg body weight and adults administered strong CYP2D6 inhibitors, e.g., paroxetine, fluoxetine, quinidine, atomoxetine HCl should be initiated at 40 mg/day and only increased to the usual target dose of 80 mg/day if symptoms fail to improve after 4 weeks and the initial dose is well tolerated.

Atomoxetine can be discontinued without being tapered.

How Supplied

Storage: Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F).