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.
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)].
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 (2.5) and Drug Interactions (7.2)].
Atomoxetine hydrochloride was administered to 5382 children or adolescent patients with ADHD and 1007 adults with ADHD in clinical studies. During the ADHD clinical trials, 1625 children and adolescent patients were treated for longer than 1 year and 2529 children and adolescent patients were treated for over 6 months.
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
Reasons for discontinuation of treatment due to adverse reactions in child and adolescent clinical trials — In acute child and adolescent placebo-controlled trials, 3% (48/1613) of atomoxetine subjects and 1.4% (13/945) placebo subjects discontinued for adverse reactions. For all studies, (including open-label and long-term studies), 6.3% of extensive metabolizer (EM) patients and 11.2% of poor metabolizer (PM) patients discontinued because of an adverse reaction. Among atomoxetine hydrochloride-treated patients, irritability (0.3%, N=5); somnolence (0.3%, N=5); aggression (0.2%, N=4); nausea (0.2%, N=4); vomiting (0.2%, N=4); abdominal pain (0.2%, N=4); constipation (0.1%, N=2); fatigue (0.1%, N=2); feeling abnormal (0.1%, N=2); and headache (0.1%, N=2) were the reasons for discontinuation reported by more than 1 patient.
Seizures — Atomoxetine hydrochloride has not been systematically evaluated in pediatric patients with seizure disorder as these patients were excluded from clinical studies during the product’s premarket testing. In the clinical development program, seizures were reported in 0.2% (12/5073) of children whose average age was 10 years (range 6 to 16 years). In these clinical trials, the seizure risk among poor metabolizers was 0.3% (1/293) compared to 0.2% (11/4741) for extensive metabolizers.
Commonly observed adverse reactions in acute child and adolescent, placebo-controlled trials — Commonly observed adverse reactions associated with the use of atomoxetine hydrochloride (incidence of 2% or greater) and not observed at an equivalent incidence among placebo-treated patients (atomoxetine hydrochloride incidence greater than placebo) are listed in Table 2. Results were similar in the BID and the QD trial except as shown in Table 3, which shows both BID and QD results for selected adverse reactions based on statistically significant Breslow-Day tests. The most commonly observed adverse reactions in patients treated with atomoxetine hydrochloride (incidence of 5% or greater and at least twice the incidence in placebo patients, for either BID or QD dosing) were: nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence (see Tables 2 and 3).
Additional data from ADHD clinical trials (controlled and uncontrolled) has shown that approximately 5 to 10% of pediatric patients experienced potentially clinically important changes in heart rate (≥20 beats per min) or blood pressure (≥15 to 20 mm Hg) [see Contraindications (4) and Warnings and Precautions (5) ].
Table 2: Common Treatment-Emergent Adverse Reactions Associated with the Use of Atomoxetine Hydrochloride in Acute (up to 18 weeks) Child and Adolescent Trials
|Adverse Reactiona||Percentage of Patients Reporting Reaction|
|Atomoxetine Hydrochloride (N=1597)||Placebo (N=934)|
|General Disorders and Administration Site Conditions|
|Therapeutic response unexpected||2||1|
|Metabolism and Nutritional Disorders|
|Nervous System Disorders|
|Skin and Subcutaneous Tissue Disorders|
a Reactions reported by at least 2% of patients treated with atomoxetine, and greater than placebo. The following reactions did not meet this criterion but were reported by more atomoxetine-treated patients than placebo-treated patients and are possibly related to atomoxetine treatment: blood pressure increased, early morning awakening (terminal insomnia), flushing, mydriasis, sinus tachycardia, asthenia, palpitations, mood swings, constipation and dyspepsia. The following reactions were reported by at least 2% of patients treated with atomoxetine, and equal to or less than placebo: pharyngolaryngeal pain, insomnia (insomnia includes the terms, insomnia, initial insomnia, middle insomnia). The following reaction did not meet this criterion but shows a statistically significant dose relationship: pruritus.
b Abdominal pain includes the terms: abdominal pain upper, abdominal pain, stomach discomfort, abdominal discomfort, epigastric discomfort.
c Somnolence includes the terms: sedation, somnolence.
Table 3: Common Treatment-Emergent Adverse Reactions Associated with the Use of Atomoxetine Hydrochloride in Acute (up to 18 weeks) Child and Adolescent Trials
|Adverse Reaction||Percentage of Patients Reporting Reaction from BID Trials||Percentage of Patients Reporting Reaction from QD Trials|
|Atomoxetine Hydrochloride (N=715)||Placebo (N=434)||Atomoxetine Hydrochloride (N=882)||Placebo (N=500)|
a Abdominal pain includes the terms: abdominal pain upper, abdominal pain, stomach discomfort, abdominal discomfort, epigastric discomfort.
b Constipation didn’t meet the statistical significance on Breslow-Day test but is included in the table because of pharmacologic plausibility.
c Mood swings didn’t meet the statistical significance on Breslow-Day test at 0.05 level but p-value was <0.1 (trend).
The following adverse reactions occurred in at least 2% of child and adolescent CYP2D6 PM patients and were statistically significantly more frequent in PM patients compared with CYP2D6 EM patients: insomnia (11% of PMs, 6% of EMs); weight decreased (7% of PMs, 4% of EMs); constipation (7% of PMs, 4% of EMs); depression1 (7% of PMs, 4% of EMs); tremor (5% of PMs, 1% of EMs); excoriation (4% of PMs, 2% of EMs); middle insomnia (3% of PMs, 1% of EMs); conjunctivitis (3% of PMs, 1% of EMs); syncope (3% of PMs, 1% of EMs); early morning awakening (2% of PMs, 1% of EMs); mydriasis (2% of PMs, 1% of EMs); sedation (4% of PMs, 2% of EMs).
1 Depression includes the following terms: depression, major depression, depressive symptoms, depressed mood, dysphoria.
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