High-dose atomoxetine treatment of ADHD in youths with limited response to standard doses

Personalizing atomoxetine dosing in children with ADHD: what can we learn from current supporting evidence

PURPOSE

There is marked heterogeneity in treatment response of atomoxetine in patients with attention deficit/hyperactivity disorder (ADHD), especially for the pediatric population. This review aims to evaluate current evidence to characterize the dose-exposure relationship, establish clinically relevant metrics for systemic exposure to atomoxetine, define a therapeutic exposure range, and to provide a dose-adaptation strategy before implementing personalized dosing for atomoxetine in children with ADHD.

METHODS

A comprehensive search was performed across electronic databases (PubMed and Embase) covering the period of January 1, 1985 to July 10, 2022, to summarize recent advances in the pharmacokinetics, pharmacogenomics/pharmacogenetics (PGx), therapeutic drug monitoring (TDM), physiologically based pharmacokinetics (PBPK), and population pharmacokinetics (PPK) of atomoxetine in children with ADHD.

RESULTS

Some factors affecting the pharmacokinetics of atomoxetine were summarized, including food, CYP2D6 and CYP2C19 phenotypes, and drug‒drug interactions (DDIs). The association between treatment response and genetic polymorphisms of genes encoding pharmacological targets, such as norepinephrine transporter (NET/SLC6A2) and dopamine β hydroxylase (DBH), was also discussed. Based on well-developed and validated assays for monitoring plasma concentrations of atomoxetine, the therapeutic reference range in pediatric patients with ADHD proposed by several studies was summarized. However, supporting evidence on the relationship between systemic atomoxetine exposure levels and clinical response was far from sufficient.

CONCLUSION

Personalizing atomoxetine dosage may be even more complex than anticipated thus far, but elucidating the best way to tailor the non-stimulant to a patient's individual need will be achieved by combining two strategies: detailed research in linking the pharmacokinetics and pharmacodynamics in pediatric patients, and better understanding in nature and causes of ADHD, as well as environmental stressors.

Therapeutic drug monitoring of atomoxetine in children and adolescents with attention-deficit/ hyperactivity disorder: a naturalistic study

The selective norepinephrine reuptake inhibitor atomoxetine is potentially among the first-line pharmacotherapy options for ADHD. Therapeutic drug monitoring (TDM) with the quantification and interpretation of atomoxetine serum concentrations is used to determine an individual dose followed by an optimal effectiveness and minimal side effects. The aim of this retrospective pharmacokinetic–pharmacodynamic analysis was to derive age-appropriate recommendations for the implementation of TDM to improve the efficacy and tolerability of atomoxetine in children and adolescents. Using the analytical method of high-performance liquid chromatography with UV detection, 94 serum concentrations of 74 patients between 6 and 21 years of age were determined. Therapeutic effectiveness and side effects were evaluated according to the categories “low”, “moderate”, and “significant”. As part of TDM, a time interval with maximum concentrations of 1–3 h after the administration of atomoxetine was determined for blood sampling. In this time interval, a significant correlation between the weight-normalized dose and the serum concentrations was found. The efficacy as well as the tolerability proved to be mainly moderate or significant. A preliminary therapeutic reference range was between 100 and 400 ng/ml. Naturalistic studies have limitations. Therefore, and due to a limited study population, the results have to be regarded as preliminary observations that must be confirmed in further studies. The preliminary therapeutic reference range for children and adolescents proved to be narrower than the reference range for adult patients. However, due to good efficacy and tolerability an exact reference range remained difficult to determine.

The Mechanism, Clinical Efficacy, Safety, and Dosage Regimen of Atomoxetine for ADHD Therapy in Children: A Narrative Review

Atomoxetine, a selective norepinephrine (NE) reuptake inhibitor, was approved for attention deficit/hyperactivity disorder (ADHD) treatment in children, adolescents and adults. We searched the database PubMed/MEDLINE (2000 to October 1, 2021). Only publications in English were considered. Atomoxetine inhibits the presynaptic norepinephrine transporter (NET), preventing the reuptake of NE throughout the brain along with inhibiting the reuptake of dopamine in specific brain regions such as the prefrontal cortex (PFC). The novel mechanism of atomoxetine also includes several new brain imaging studies and animal model studies. It is mainly metabolized by the highly polymorphic drug metabolizing enzyme cytochrome P450 2D6 (CYP2D6). Atomoxetine is effective and generally well tolerated. ADHD is often accompanied by multiple comorbidities. A series of studies have been published suggesting that atomoxetine is effective in the treatment of ADHD symptoms for children with various types of comorbidity. In some cases, it is possible that atomoxetine may have a positive influence on the symptoms of comorbidities. Atomoxetine can be administered either as a single daily dose or split into two evenly divided doses, and has a negligible risk of abuse or misuse. The latest guideline updated that clinical dose selection of atomoxetine was recommended based on both CYP2D6 genotype and the peak concentration. To have a more comprehensive understanding of atomoxetine, this review sets the focus on the mechanism, clinical efficacy and dosage regimen in detail, and also touches on those studies regarding adverse reactions of atomoxetine.

A proof of principle study of atomoxetine for the prevention of vasovagal syncope: the Prevention of Syncope Trial VI

Aims

There are few effective therapies for vasovagal syncope (VVS). Pharmacological norepinephrine transporter (NET) inhibition increases sympathetic tone and decreases tilt-induced syncope in healthy subjects. Atomoxetine is a potent and highly selective NET inhibitor. We tested the hypothesis that atomoxetine prevents tilt-induced syncope.

Methods and results

Vasovagal syncope patients were given two doses of study drug [randomized to atomoxetine 40 mg (n = 27) or matched placebo (n = 29)] 12 h apart, followed by a 60-min drug-free head-up tilt table test. Beat-to-beat heart rate (HR), blood pressure (BP), and cardiac haemodynamics were recorded using non-invasive techniques and stroke volume modelling. Patients were 35 ± 14 years (73% female) with medians of 12 lifetime and 3 prior year faints. Fewer subjects fainted with atomoxetine than with placebo [10/29 vs. 19/27; P = 0.003; risk ratio 0.49 (confidence interval 0.28–0.86)], but equal numbers of patients developed presyncope or syncope (23/29 vs. 21/27). Of patients who developed only presyncope, 87% (13/15) had received atomoxetine. Patients with syncope had lower nadir mean arterial pressure than subjects with only presyncope (39 ± 18 vs. 69 ± 18 mmHg, P < 0.0001), and this was due to lower trough HRs in subjects with syncope (67 ± 30 vs. 103 ± 32 b.p.m., P = 0.006) and insignificantly lower cardiac index (2.20 ± 1.36 vs. 2.84 ± 1.05 L/min/m2, P = 0.075). There were no significant differences in stroke volume index (32 ± 6 vs. 35 ± 5 mL/m2, P = 0.29) or systemic vascular resistance index (2156 ± 602 vs. 1790 ± 793 dynes*s/cm5*m2, P = 0.72).

Conclusion

Norepinephrine transporter inhibition significantly decreased the risk of tilt-induced syncope in VVS subjects, mainly by blunting reflex bradycardia, thereby preventing final falls in cardiac index and BP.

Characterization of Atomoxetine Biotransformation and Implications for Development of PBPK Models for Dose Individualization in Children

Atomoxetine (ATX) is a second-line nonstimulant medication used to control symptoms of attention deficit hyperactivity disorder (ADHD). Inconsistent therapeutic efficacy has been reported with ATX, which may be related to variable CYP2D6-mediated drug clearance. We characterized ATX metabolism in a panel of human liver samples as a basis for a bottom-up PBPK model to aid in ATX exposure prediction and control. Km, Vmax, and Clint values in pooled human liver microsomes (HLMs) were 2.4 µM, 479 pmol/min/mg protein, and 202 µl/min/mg protein, respectively. Mean population values of kinetic parameters are not adequate to describe variability in a population, given that Km, Vmax, and Clint values from single-donor HLMs ranged from 0.93 to 79.2 µM, 20.0 to 1600 pmol/min/mg protein, and 0.3 to 936 µl/min/mg protein. All kinetic parameters were calculated from 4-hydroxyatomoxetine (4-OH-ATX) formation. CYP2E1 and CYP3A contributed to 4-OH-ATX formation in livers with CYP2D6 intermediate and poor metabolizer status. In HLMs with lower CYP2D6 activity levels, 2-hydroxymethylatomoxetine (2-CH2OH-ATX) formation became a more predominant pathway of metabolism, which appeared to be catalyzed by CYP2B6. ATX biotransformation at clinically relevant plasma concentrations was characterized in a panel of pediatric HLM (n = 116) samples by evaluating primary metabolites. Competing pathways of ATX metabolism [N-desmethylatomoxetine (NDM-ATX) and 2-CH2OH-ATX formation] had increasing importance in livers with lesser CYP2D6 activity, but, overall ATX clearance was still compromised. Modeling ATX exposure to individualize therapy would require comprehensive knowledge of factors that affect CYP2D6 activity as well as an understanding of competing pathways, particularly for individuals with lower CYP2D6 activity.

A critical appraisal of atomoxetine in the management of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder beginning in childhood and often continuing into adulthood. A wealth of data shows that ADHD symptoms respond well to pharmacological treatment. Stimulant medications, including amphetamine and methylphenidate, are most commonly used to treat ADHD. However, with the approval of atomoxetine (Strattera^®, [ATX]) by the US Food and Drug Administration in late 2002, an effective non-stimulant option became available. The US Food and Drug Administration approved ATX for the treatment of ADHD in children, adolescents, and adults. Although the effect size of ATX is generally lower than that of stimulants, the American Academy of Child and Adolescent Psychiatry Practice Parameter for the treatment of ADHD lists ATX as a first-line treatment option. ATX is widely prescribed and accounted for 6% of the prescriptions of ADHD visits in the US in 2010. Numerous trials have found that ATX improves quality of life and emotional lability in addition to core ADHD symptoms. Although some improvement may be seen in a patient as early as one week after the initiation of treatment, ATX generally takes longer to have a full effect. The median time to response using 25% improvement in ADHD symptoms in pooled trials was 3.7 weeks. Data from these trials indicate that the probability of symptom improvement may continue to increase up to 52 weeks after treatment is initiated. ATX has been shown to be safe and effective in combination with stimulants. It has also been studied systematically in subjects with ADHD and comorbid oppositional defiant disorder, anxiety, depression, and substance use disorders. The mechanism of action of ATX, its efficacy, and adverse events reported in trials is reviewed.

The efficacy of atomoxetine for the treatment of children and adolescents with attention-deficit/hyperactivity disorder: a comprehensive review of over a decade of clinical research

Atomoxetine was first licensed to treat attention-deficit/hyperactivity disorder (ADHD) in children and adolescents in the US in 2002. The aim of this paper is to comprehensively review subsequent publications addressing the efficacy of atomoxetine in 6- to 18-year-olds with ADHD. We identified 125 eligible papers using a predefined search strategy. Overall, these papers demonstrate that atomoxetine is an effective treatment for the core ADHD symptoms (effect sizes 0.6-1.3, vs. placebo, at 6-18 weeks), and improves functional outcomes and quality of life, in various pediatric populations with ADHD (i.e., males/females, patients with co-morbidities, children/adolescents, and with/without prior exposure to other ADHD medications). Initial responses to atomoxetine may be apparent within 1 week of treatment, but can take longer (median 23 days in a 6-week study; n=72). Responses often build gradually over time, and may not be robust until after 3 months. A pooled analysis of six randomized placebo-controlled trials (n=618) indicated that responses at 4 weeks may predict response at 6-9 weeks, although another pooled analysis of open-label data (n=338) suggests that the probability of a robust response to atomoxetine [≥40% decrease in ADHD-Rating Scale (ADHD-RS) scores] may continue to increase beyond 6-9 weeks. Atomoxetine may demonstrate similar efficacy to methylphenidate, particularly immediate-release methylphenidate, although randomized controlled trials are generally limited by short durations (3-12 weeks). In conclusion, notwithstanding these positive findings, before initiating treatment with atomoxetine, it is important that the clinician sets appropriate expectations for the patient and their family with regard to the likelihood of a gradual response, which often builds over time.

Toward quality care in ADHD: defining the goals of treatment

OBJECTIVE

Therapeutic goals for chronic mental disorders like major depressive disorder (MDD) and schizophrenia have evolved in parallel with the growing medical knowledge about the course and treatment of these disorders. Although the knowledge base regarding the clinical course of ADHD, a chronic psychiatric disorder, has evolved beyond symptomatic improvement and short-term treatment response, long-term goals, such as functional remission, have not yet been clearly defined.

METHOD

A PubMed literature search was conducted to investigate the therapeutic goals of pharmacologic treatment referenced in the published literature from January 1998 through February 2010 using the following commonly used ADHD treatments as keywords: amphetamine, methylphenidate, atomoxetine, lisdexamfetamine, guanfacine, and clonidine. This search was then combined with an additional search that included the following outcome keywords: remission, relapse, remit, response, normal, normalization, recovery, and effectiveness.

RESULTS

Our search identified 102 publications. The majority (88.2% [90/102]) of these contained predefined criteria for treatment response. Predefined criteria for normalization and remission and/or relapse were presented in 4.9% (5/102), 12.7% (13/102), and 3.9% (4/102) of publications, respectively. There was a lack of consistency between the instruments used to measure outcomes as well as the criteria used to define treatment response, normalization, and remission as well as relapse.

CONCLUSION

The therapeutic goals in treating ADHD should address optimal treatment outcomes that go beyond modest reductions of ADHD symptoms to include syndromatic, symptomatic, and functional remission. Future work should focus on reliable and valid tools to measure these outcomes in the clinical trial setting.

Differences in reporting serious adverse events in industry sponsored clinical trial registries and journal articles on antidepressant and antipsychotic drugs: a cross-sectional study

OBJECTIVE

To examine the degree of concordance in reporting serious adverse events (SAEs) from antidepressant and antipsychotic drug trials among journal articles and clinical trial summaries, and to categorise types of discrepancies.

DESIGN

Cross-sectional study of summaries of all antidepressant and antipsychotic trials included in an online trial registry and their first associated stand-alone journal articles.

SETTING

Clinicalstudyresults.org, sponsored by Pharmaceutical Research and Manufacturers of America; clinicaltrials.gov, administered by the US National Institutes of Health.

MAIN OUTCOME MEASURE

3 coders extracted data on the numbers and types of SAEs.

RESULTS

244 trial summaries for six antidepressant and antipsychotic drugs were retrieved, 142 (58.2%) listing an associated article. Of 1608 SAEs in drug-treated participants according to trial summaries, 694 (43.2%) did not appear in associated articles. Nearly 60% of SAEs counted in articles and 41% in trial summaries had no description. Most cases of death (62.3%) and suicide (53.3%) were not reported in articles. Half or more of the 142 pairs were discordant in reporting the number (49.3%) or description (67.6%) of SAEs. These discrepancies resulted from journal articles' (1) omission of complete SAE data, (2) reporting acute phase study results only and (3) more restrictive reporting criteria. Trial summaries with zero SAE were 2.35 (95% CI, 1.58 to 3.49; p<0.001) times more likely to be published with no discrepancy in their associated journal article. Since clinicalstudyresults.org was removed from the Internet in 2011, only 7.8% of retrieved trial summaries appear with results on clinicaltrials.gov.

CONCLUSIONS

Substantial discrepancies exist in SAE data found in journal articles and registered summaries of antidepressant and antipsychotic drug trials. Two main scientific sources accessible to clinicians and researchers are limited by incomplete, ambiguous and inconsistent reporting. Access to complete and accurate data from clinical trials of drugs currently in use remains a pressing concern.

Pharmacological treatment of attention deficit hyperactivity disorder in children and adolescents: clinical strategies

Attention deficit hyperactivity disorder (ADHD) is a common neurobehavioral disorder of childhood that can result in significant functional impairment, and if not adequately treated can lead to impaired quality of life. Pharmacotherapy is considered the first-line treatment for ADHD in children and adolescents. We review both recent literature and seminal studies regarding the pharmacological treatment of ADHD in children and adolescents. There is ample evidence for the efficacy and safety of both stimulants and non-stimulants in the treatment of ADHD. We review important aspects of evaluation and assessment and discuss first-line pharmacological treatments and as well as when to consider using alternative pharmacological agents. Treatment approaches to manage frequently seen comorbid disorders with ADHD are also covered.

A randomized, open-label assessment of response to various doses of atomoxetine in korean pediatric outpatients with attention-deficit/hyperactivity disorder

OBJECTIVE

This multicenter, randomized, open-label, parallel trial aimed to provide a detailed dose-response profile for atomoxetine in Korean pediatric outpatients with attention-deficit/hyperactivity disorder (ADHD).

METHODS

Male and female outpatients aged 6-18 years with ADHD meeting symptom severity criteria of 1.5 standard deviations above age and gender norms on the ADHD Rating Scale-IV-Parent: Investigator-Administered and Scored (ADHDRS-IV-Parent: Inv), and a Clinical Global Impression-ADHD-Severity score ≥4 were randomized to atomoxetine (mg/kg/day) 0.2 fixed, 0.5 fixed or 0.5 (7 days), 0.8 (7 days) then 1.2 for 28 days. The primary efficacy measure was change in ADHDRS-IV-Parent: Inv total score after 6 weeks of atomoxetine treatment.

RESULTS

Of 153 randomized patients, 83.7% were male and mean age was 9.8 (SD±2.4) years. The completion rate was 86.9%. A graded dose response was apparent with mean change in ADHDRS-IV-Parent: Inv total scores of -9.6, -12.3 and -14.5 with atomoxetine 0.2, 0.5 and 1.2 mg/kg/day, respectively (p=0.024 - F-test). Moreover, a greater reduction in ADHD symptoms, as assessed by mean change from baseline to endpoint CGI-S and mean CGI-ADHD-Improvement at endpoint, was also observed with increasing atomoxetine dose. More patients receiving atomoxetine 1.2 mg/kg/day reported ≥1 treatment-emergent adverse event/s (58.3%) compared with 0.5 (40.7%; p=0.11) or 0.2 mg/kg/day (29.4%; p=0.005). These were generally mild to moderate.

CONCLUSION

Atomoxetine was found to be safe and well tolerated at all doses administered in Korean pediatric ADHD patients, and 1.2 mg/kg/day was an efficacious dose in this population.

A comparison of atomoxetine administered as once versus twice daily dosing on the school and home functioning of children with attention-deficit/hyperactivity disorder

OBJECTIVE

This secondary analysis examined the efficacy and tolerability of atomoxetine (ATX) dosed once (QD) versus twice (BID) daily in 55 children aged 6-12 with attention-deficit/hyperactivity disorder (ADHD).

METHODS

The original 8-week trial was designed to assess the benefits of adding behavioral therapy to ATX. In it, all subjects were treated openly with ATX, with 50% randomly assigned to additional behavioral treatments. Every subject was started on QD dosing with a target dose of 1.2 mg/kg per day. A switch to BID dosing was allowed at study midpoint to improve tolerability and efficacy. Subjects not responding to ATX at midpoint were also given the option of 0.6 mg/kg dose increase. ADHD and oppositional defiant disorder (ODD) symptoms, global functioning, side effects, and classroom performance were measured weekly.

RESULTS

There were 22 subjects (40%) who switched to BID dosing at midpoint (mean dose = 1.56 mg/kg per day) with the other 33 remaining on QD dosing (mean dose = 1.33 mg/kg per day). The BID group did not display any improvement in parent-rated ODD symptoms during the first 4 weeks of the study on QD dosing, but there was a significant improvement seen after the addition of the second ATX dose (p < 0.05). However, BID dosing was not associated with differential rates of change for parent-rated ADHD symptoms or impairment, teacher ratings, or other measures of classroom functioning. BID dosing was associated with decreased rates of stomachaches (p < 0.05) but more persistent appetite loss than QD dosing. The degree of improvement observed during the first half of the study in ratings of global impairment and ODD but not ADHD symptoms predicted a switch to BID dosing at midpoint (p < 0.05).

CONCLUSIONS

The addition of an afternoon dose of ATX was associated with improved control of ODD symptoms at home, with no change in school functioning.

The occurrence of adverse drug reactions reported for attention deficit hyperactivity disorder (ADHD) medications in the pediatric population: a qualitative review of empirical studies

BACKGROUND

To review empirical studies of adverse drug reactions (ADRs) reported to be associated with the use of medications generally licensed for treatment of attention deficit hyperactivity disorder (ADHD) symptoms in the pediatric population.

METHODS

PubMed, Embase, and PsycINFO(®) databases were searched from origin until June 2011. Studies reporting ADRs from amphetamine derivates, atomoxetine, methylphenidate, and modafinil in children from birth to age 17 were included. Information about ADR reporting rates, age and gender of the child, type, and seriousness of ADRs, setting, study design, ADR assessors, authors, and funding sources were extracted.

RESULTS

The review identified 43 studies reporting ADRs associated with medicines for treatment of ADHD in clinical studies covering approximately 7000 children, the majority of 6- to 12-year-old boys, and particularly in the United States of America (USA). The most frequently reported ADRs were decrease in appetite, gastrointestinal pain, and headache. There were wide variations in reported ADR occurrence between studies of similar design, setting, included population, and type of medication. Reported ADRs were primarily assessed by the children/their parents, and very few ADRs were rated as being serious. A large number of children dropped out of studies due to serious ADRs, and therefore, the actual number of serious ADRs from use of psychostimulants is probably higher. A large number of studies were conducted by the same groups of authors and sponsored by the pharmaceutical companies manufacturing the respective medications.

CONCLUSION

Reported ADRs from use of psychostimulants in children were found in clinical trials of short duration. Since ADHD medications are prescribed for long-term treatment, there is a need for long-term safety studies. The pharmaceutical companies should make all information about ADRs reported for these medications accessible to the public, and further studies are needed on the impact of the link between researchers and the manufacturers of the respective products.

Atomoxetine and neuropsychological function in children with attention-deficit/hyperactivity disorder: results of a pilot study

This pilot longitudinal study using measures from parents and teachers evaluated the effects of flexible doses of atomoxetine (ATX) on neuropsychological and functional outcomes in 21 children with attention-deficit/hyperactivity disorder (ADHD) (mean age, 8.0 +/- 1.3 years; inattentive subtype, 71.4%; combined subtype, 28.6%). Among 16 children completing 6 months of ATX treatment, neuropsychological function measured by the NEPSY instrument found significant improvement from baseline in the memory and learning domain (p = 0.01); this change was also seen in an age- and sex-matched healthy control group (p = 0.011). The patient group showed significant improvement on the Test of Everyday Attention (TEA-Ch) and parent and teacher versions of the Behavior Rating Inventory of Executive Function (BRIEF), which assess attentional and executive processes, respectively. Functional improvement was also observed on the Weiss Functional Impairment Rating Scale-Parent Report (WFIRS-P) and parent and teacher versions of the ADHD Rating Scale (ADHDRS-IV), and the investigator-rated Clinical Global Impressions-Severity (CGI-S) scale evidenced reductions in ADHD symptoms. These findings suggest that potential benefits of ATX treatment may extend beyond reduction of core ADHD symptoms to amelioration of some neuropsychological and functional deficits.

Relationship between atomoxetine plasma concentration, treatment response and tolerability in attention-deficit/hyperactivity disorder and comorbid oppositional defiant disorder

The purpose of this study was to examine whether atomoxetine plasma concentration predicts attention-deficit/hyperactivity disorder (ADHD) or oppositional defiant disorder (ODD) response. This post-hoc analysis assessed the relationship between atomoxetine plasma concentration and ADHD and ODD symptoms in patients (with ADHD and comorbid ODD) aged 6–12 years. Patients were randomly assigned to atomoxetine 1.2 mg/kg/day (n = 156) or placebo (n = 70) for 8 weeks (Study Period II). At the end of 8 weeks, ODD non-remitters (score >9 on the SNAP-IV ODD subscale and CGI-I > 2) with atomoxetine plasma concentration <800 ng/ml at 2 weeks were re-randomized to either atomoxetine 1.2 mg/kg/day or 2.4 mg/kg/day for an additional 4 weeks (Study Period III). ODD remitters and non-remitters with plasma atomoxetine ≥800 ng/ml remained on 1.2 mg/kg/day atomoxetine for 4 weeks. Patients who received atomoxetine, completed Study Period II, and entered Study Period III were included in these analyses. All the groups demonstrated improvement on the SNAP-IV ODD and ADHD-combined subscales (P < .001). At the end of Study Periods II and III, ODD and ADHD improvement was significantly greater in the remitter group compared with the non-remitter groups. Symptom improvement was numerically greater in the non-remitter (2.4 mg/kg/day compared with the non-remitter 1.2 mg/kg/day) group. Atomoxetine plasma concentration was not indicative of ODD and ADHD improvement after 12 weeks of treatment. ADHD and ODD symptoms improved in all the groups with longer duration on atomoxetine. Results suggest atomoxetine plasma concentration does not predict ODD and ADHD symptom improvement. However, a higher atomoxetine dose may benefit some patients.

Atomoxetine: a review of its use in attention-deficit hyperactivity disorder in children and adolescents

Atomoxetine (Strattera(R)) is a selective norepinephrine (noradrenaline) reuptake inhibitor that is not classified as a stimulant, and is indicated for use in patients with attention-deficit hyperactivity disorder (ADHD). Atomoxetine is effective and generally well tolerated. It is significantly more effective than placebo and standard current therapy and does not differ significantly from or is noninferior to immediate-release methylphenidate; however, it is significantly less effective than the extended-release methylphenidate formulation OROS(R) methylphenidate (hereafter referred to as osmotically released methylphenidate) and extended-release mixed amfetamine salts. Atomoxetine can be administered either as a single daily dose or split into two evenly divided doses, has a negligible risk of abuse or misuse, and is not a controlled substance in the US. Atomoxetine is particularly useful for patients at risk of substance abuse, as well as those who have co-morbid anxiety or tics, or who do not wish to take a controlled substance. Thus, atomoxetine is a useful option in the treatment of ADHD in children and adolescents. The mechanism of action of atomoxetine is unclear, but is thought to be related to its selective inhibition of presynaptic norepinephrine reuptake in the prefrontal cortex. Atomoxetine has a high affinity and selectivity for norepinephrine transporters, but little or no affinity for various neurotransmitter receptors. Atomoxetine has a demonstrated ability to selectively inhibit norepinephrine uptake in humans and animals, and studies have shown that it preferentially binds to areas of known high distribution of noradrenergic neurons, such as the fronto-cortical subsystem. Atomoxetine was generally associated with statistically, but not clinically, significant increases in both heart rate and blood pressure in pediatric patients with ADHD. While there was an initial loss in expected height and weight among atomoxetine recipients, this eventually returned to normal in the longer term. Data suggest that atomoxetine is unlikely to have any abuse potential. Atomoxetine appeared less likely than methylphenidate to exacerbate disordered sleep in pediatric patients with ADHD. Atomoxetine is rapidly absorbed, and demonstrates dose-proportional increases in plasma exposure. It undergoes extensive biotransformation, which is affected by poor metabolism by cytochrome P450 (CYP) 2D6 in a small percentage of the population; these patients have greater exposure to and slower elimination of atomoxetine than extensive metabolizers. Patients with hepatic insufficiency show an increase in atomoxetine exposure. CYP2D6 inhibitors, such as paroxetine, are associated with changes in atomoxetine pharmacokinetics similar to those observed among poor CYP2D6 metabolizers. Once- or twice-daily atomoxetine was effective in the short-term treatment of ADHD in children and adolescents, as observed in several well designed placebo-controlled trials. Atomoxetine also demonstrated efficacy in the longer term treatment of these patients. A single morning dose was shown to be effective into the evening, and discontinuation of atomoxetine was not associated with symptom rebound. Atomoxetine efficacy did not appear to differ between children and adolescents. Stimulant-naive patients also responded well to atomoxetine treatment. Atomoxetine did not differ significantly from or was noninferior to immediate-release methylphenidate in children and adolescents with ADHD with regard to efficacy, and was significantly more effective than standard current therapy (any combination of medicines [excluding atomoxetine] and/or behavioral counseling, or no treatment). However, atomoxetine was significantly less effective than osmotically released methylphenidate and extended-release mixed amfetamine salts. The efficacy of atomoxetine did not appear to be affected by the presence of co-morbid disorders, and symptoms of the co-morbid disorders were not affected or were improved by atomoxetine administration. Health-related quality of life (HR-QOL) appeared to be positively affected by atomoxetine in both short- and long-term studies; atomoxetine also improved HR-QOL to a greater extent than standard current therapy. Atomoxetine was generally well tolerated in children and adolescents with ADHD. Common adverse events included headache, abdominal pain, decreased appetite, vomiting, somnolence, and nausea. The majority of adverse events were mild or moderate; there was a very low incidence of serious adverse events. Few patients discontinued atomoxetine treatment because of adverse events. Atomoxetine discontinuation appeared to be well tolerated, with a low incidence of discontinuation-emergent adverse events. Atomoxetine appeared better tolerated among extensive CYP2D6 metabolizers than among poor metabolizers. Slight differences were evident in the adverse event profiles of atomoxetine and stimulants, both immediate- and extended-release. Somnolence appeared more common among atomoxetine recipients and insomnia appeared more common among stimulant recipients. A black-box warning for suicidal ideation has been published in the US prescribing information, based on findings from a meta-analysis showing that atomoxetine is associated with a significantly higher incidence of suicidal ideation than placebo. Rarely, atomoxetine may also be associated with serious liver injury; postmarketing data show that three patients have had liver-related adverse events deemed probably related to atomoxetine treatment. Treatment algorithms involving the initial use of atomoxetine appear cost effective versus algorithms involving initial methylphenidate (immediate- or extended-release), dexamfetamine, tricyclic antidepressants, or no treatment in stimulant-naive, -failed, and -contraindicated children and adolescents with ADHD. The incremental cost per quality-adjusted life-year is below commonly accepted cost-effectiveness thresholds, as shown in several Markov model analyses conducted from the perspective of various European countries, with a time horizon of 1 year.

Attention-deficit-hyperactivity disorder: an update

Attention-deficit-hyperactivity disorder (ADHD) is a common neuropsychiatric disorder that impairs social, academic, and occupational functioning in children, adolescents, and adults. In patients with ADHD, neurobiologic research has shown a lack of connectivity in key brain regions, inhibitory control deficits, delayed brain maturation, and noradrenergic and dopaminergic dysfunction in multiple brain regions. The prevalence of this disorder in the United States is 6-9% in youth (i.e., children and adolescents) and 3-5% in adults. Prevalence rates for youth are similar worldwide. Children with ADHD are at greater risk than children without ADHD for substance abuse and delinquency whether or not they receive drug therapy; however, early treatment with psychoeducation as well as drug therapy and/or behavioral intervention may decrease negative outcomes of ADHD, including the rate of conduct disorder and adult antisocial personality disorder. Drug therapy is effective for all age groups, even preschoolers, and for late-onset ADHD in adults. Stimulants, such as methylphenidate and amphetamine, are the most effective therapy and have a good safety profile; although recent concerns of sudden unexplained death, psychiatric adverse effects, and growth effects have prompted the introduction of other therapies. Atomoxetine, a nonstimulant, has no abuse potential, causes less insomnia than stimulants, and poses minimal risk of growth effects. Other drug options include clonidine and guanfacine, but both can cause bradycardia and sedation. Polyunsaturated fatty acids (fish oil), acetyl-L-carnitine, and iron supplements (for youth with low ferritin levels) show promise in improving ADHD symptoms. As long-term studies show that at least 50% of youth are nonadherent with their drug therapy as prescribed over a 1-year period, long-acting formulations (administered once/day) may improve adherence. Comorbid conditions are common in patients with ADHD, but this patient population can be treated effectively with individualized treatment regimens of stimulants, atomoxetine, or bupropion, along with close monitoring.

Atomoxetine for the treatment of attention-deficit/hyperactivity disorder in children and adolescents: a review

OBJECTIVE

This review examines and summarizes the pharmacodynamic and pharmacokinetic properties, short- and longer-term efficacy, the moderating effect of comorbid disorders, as well as short- and long-term safety and tolerability of atomoxetine for the treatment of pediatric attention-deficit/hyperactivity disorder (ADHD).

METHODS

A systematic literature search was performed to review the extant literature on articles pertaining to the pharmacological treatment with atomoxetine in pediatric and/or adolescent ADHD.

RESULTS

There is an extensive literature on atomoxetine; over 4000 children have participated in clinical trials of atomoxetine, demonstrating its short- and longer-term efficacy. In addition, studies have examined the moderating effect of comorbid disorders on atomoxetine response, as well as atomoxetine's therapeutic potential for other psychiatric conditions. Short- and longer-term safety and tolerability continue to be reported.

CONCLUSIONS

Atomoxetine is indicated for both acute and maintenance/extended treatment of pediatric ADHD. Clinicians and families must be familiar with atomoxetine's evidence base, including its profile of clinical response and its possible effectiveness in the presence of comorbidity.

Validity and clinical feasibility of the ADHD rating scale (ADHD-RS) A Danish Nationwide Multicenter Study

AIM

To establish the validity of a Danish version of the Attention Deficit Hyperactivity Disorder Rating Scale (ADHD-RS), secondly to present national norm scores compared to that of United States and other European data and thirdly to evaluate ADHD-RS when used for monitoring treatment effectiveness.

METHODS

A Danish translation of the ADHD-RS was used on a normative sample of 837 children. Two clinical samples, 138 hyperkinetic disorder (HKD) cases and 110 clinical controls were recruited from eleven Danish Child and Adolescent Mental Health (CAMH) centres and assessed according to usual clinical standards. The HKD children were rated by parents and teachers at baseline and at follow-up 3 months later.

RESULTS

Internal validity of ADHD-RS was high and the factor structure supported the diagnostic classification system ICD-10. The questionnaire discriminated HKD patients in a mixed clinical sample, and was sensitive to change in symptom load as measured before and after commencing of the treatment.

CONCLUSION

The Danish version of ADHD-RS is valid and clinically feasible when measuring HKD symptom load in a CAMH-setting. The questionnaire provides useful data in patient management, quality improvement and service planning as well as in effectiveness studies of different interventions for patients with HKD and related disorders in routine clinical settings.