Validation of a behavioral economic purchase task for assessing drug abuse liability.

Behavioral economic purchase tasks quantify drug demand (i.e. reinforcing value of a drug) and have been used extensively to assess the value of various drugs among current users. However, purchase tasks have been rarely used with unfamiliar drugs to address a compound's abuse liability, and the current study sought to validate the paradigm in this capacity. Using a double-blind placebo-controlled within-subjects drug challenge design, the study evaluated differential drug demand on an experimental drug purchase task for a 20 mg dose of oral D-amphetamine (versus placebo), a prototypic psychostimulant, in 98 stimulant-naïve participants. Compared with placebo, amphetamine significantly increased intensity, breakpoint and Omax , and significantly decreased elasticity. Mechanistic analyses revealed that Omax and breakpoint mediated the relationship between subjective drug effects and 'willingness to take again', a putative indicator of liability via motivation for future drug-seeking behavior. These findings validate the purchase task paradigm for quantifying the reinforcing value and, in turn, abuse liability of unfamiliar compounds, providing a foundation for a variety of future applications.

Comparison of therapy augmentation and deviation rates from the recommended once-daily dosing regimen between LDX and commonly prescribed long-acting stimulants for the treatment of ADHD in youth and adults.

OBJECTIVE: To compare therapy augmentation and deviation rates from the recommended once-daily dosing regimen in Attention Deficit Hyperactivity Disorder (ADHD) patients initiated on lisdexamfetamine (LDX) vs other once-daily Food and Drug Administration (FDA) approved stimulants. METHODS: ADHD patients initiated on a long-acting ADHD stimulant medication (index medication) in/after 2007 were selected from a large U.S. administrative claims database. Patients were required to be persistent for ≥90 days and continuously enrolled in their healthcare plan for ≥12 months following treatment initiation date. Based on age and previous treatment status, patients were classified into treatment-naïve children and adolescents (6-17 years old), previously treated children and adolescents, treatment-naïve adults (≥18 years old), and previously treated adults. Furthermore, patients were classified into four mutually exclusive treatment groups, based on index medication: lisdexamfetamine (LDX), osmotic release methylphenidate hydrochloride long-acting (OROS MPH), other methylphenidate/dexmethylphenidate long-acting (MPH LA), and amphetamine/dextroamphetamine long-acting (AMPH LA). The average daily consumption was measured as the quantity of index medication supplied in the 12-month study period divided by the total number of days of supply. Therapy augmentation was defined as the use of another ADHD medication concomitantly with the index medication for ≥28 consecutive days. Therapy augmentation and deviation rates from the recommended once-daily dosing regimen were compared between treatment groups using multivariate logistic regression models. RESULTS: Compared to the other treatment groups, LDX patients were less likely to augment with another ADHD medication (range odds ratios [OR]; 1.28-3.30) and to deviate from the recommended once-daily dosing regimen (range OR; 1.73-4.55), except for previously treated adult patients, where therapy augmentation differences were not statistically significant when compared to OROS MPH and MPH LA patients. LIMITATION: This study did not control for ADHD severity. CONCLUSION: Overall, compared to LDX-treated patients, patients initiated on other ADHD medications were equally or more likely to have a therapy augmentation and more likely to deviate from the recommended once-daily dosing regimen.

Psychostimulants for managing unipolar and bipolar treatment-resistant melancholic depression: a medium-term evaluation of cost benefits.

BACKGROUND: We earlier reported an open study of 50 unipolar and bipolar treatment resistant depressed patients indicating that psychostimulants may have differential superiority for the melancholic depressive sub-type. We designed an extension study to examine cost benefits of psychostimulants more closely for those only with melancholic depression. METHOD: The sample comprised patients clinically diagnosed with melancholic depression who had failed to respond to and/or experienced significant side-effects with at least two antidepressants. Data were collected for 61 unipolar and 51 bipolar II patients receiving a psyschostimulant for a mean interval of 69 weeks. Benefits and side-effects were assessed. RESULTS: Effectiveness ratings were similar across unipolar and bipolar sub-sets. Psychostimulants were judged as 'very' effective for 20% of patients and 'somewhat' effective for 50%. Forty percent judged the psychostimulant as being 'as effective' or as 'superior' to previously prescribed antidepressants, and worthy of being maintained. Significant side-effects were experienced by 40% of patients, requiring medication to be ceased in 12%. Twenty percent of the bipolar patients experienced a worsening of highs. LIMITATIONS: The study was uncontrolled and retrospective, no formal rater-completed or patient-completed interval measures of severity were completed, while diagnostic judgments about melancholic depression and bipolar disorder were clinically judged. CONCLUSIONS: This open study suggests that psychostimulants may be efficacious antidepressant options for managing unipolar and bipolar melancholia, often seemingly having very rapid onset and generally requiring only low doses, and arguing the need for controlled studies in melancholic patients.

Identifying patient subgroups who benefit most from a treatment: using administrative claims data to uncover treatment heterogeneity.

OBJECTIVES: To illustrate how claims data can be used to (1) develop outcome scores that predict response to a traditional treatment and (2) estimate the economic impact of individualized assignment to a newer treatment based on the outcome score. An example application is based on two treatments for attention deficit hyperactivity disorder (ADHD): osmotic-release oral system methylphenidate (OROS-MPH) and lisdexamfetamine dimesylate (LDX). METHODS: Adolescents with ADHD initiating OROS-MPH (n=6320) or LDX (n=6394) were selected from the MarketScan claims database. A model was developed for predicting risk of switching/augmentation with OROS-MPH using multiple baseline characteristics. The model was applied to an independent sample to stratify patients by their predicted risk and, within each stratum, risk of switching/augmentation and ADHD-related total costs were compared between OROS-MPH and LDX patients using inverse probability of treatment weighting. RESULTS: The prediction model resulted in substantial stratification, showing risk of switching/augmentation with OROS-MPH ranging from 11.3-42.1%. In the two strata where OROS-MPH had highest risk of switching/augmentation, LDX had significantly lower risk of switching/augmentation than OROS-MPH (by 7.0-8.2%) and lower ADHD-related annual total costs (by $264-$625 per patient). LIMITATIONS: The current study has used the risk of switching/augmentation as a proxy measure for treatment efficacy to establish the prediction model. Future research using a clinical measure for ADHD symptoms is warranted to verify the findings. CONCLUSIONS: Combining multiple patient characteristics into a predicted score for treatment outcomes with a traditional treatment can help identify subgroups of patients who benefit most from a new treatment. In this analysis, ADHD patients with a high predicted score for switching/augmentation with OROS-MPH had a lower rate of switching/augmentation with LDX. Assigning OROS-MPH and LDX treatments based on the predicted scores that are heterogeneous in a patient population may help improve clinical outcomes and the cost-effectiveness of care.

Update on drugs for hyperactivity in childhood.

In 2001, we concluded that methylphenidate or dexamfetamine can be useful adjunctive therapy for children with severe hyperactivity in whom non-drug approaches alone have been inadequate. Since then, atomoxetine (pronounced a-toe-moks-e-teen; Strattera - Lilly) and three modified-release formulations of methylphenidate have been launched for attention deficit hyperactivity disorder (ADHD). Here we reconsider drugs for ADHD in childhood, focusing on the newer products.

Cost-effectiveness of dexamphetamine and methylphenidate for the treatment of childhood attention deficit hyperactivity disorder.

OBJECTIVE: To analyze from a health sector perspective the cost-effectiveness of dexamphetamine (DEX) and methylphenidate (MPH) interventions to treat childhood attention deficit hyperactivity disorder (ADHD), compared to current practice. METHOD: Children eligible for the interventions are those aged between 4 and 17 years in 2000, who had ADHD and were seeking care for emotional or behavioural problems, but were not receiving stimulant medication. To determine health benefit, a meta-analysis of randomized controlled trials was performed for DEX and MPH, and the effect sizes were translated into utility values. An assessment on second stage filter criteria ("equity", "strength of evidence", "feasibility" and "acceptability to stakeholders") is also undertaken to incorporate additional factors that impact on resource allocation decisions. Simulation modelling techniques are used to present a 95% uncertainty interval (UI) around the incremental cost-effectiveness ratio (ICER), which is calculated in cost (in A$) per DALY averted. RESULTS: The ICER for DEX is A$4100/DALY saved (95% UI: negative to A$14 000) and for MPH is A$15 000/DALY saved (95% UI: A$9100-22 000). DEX is more costly than MPH for the government, but much less costly for the patient. CONCLUSIONS: MPH and DEX are cost-effective interventions for childhood ADHD. DEX is more cost-effective than MPH, although if MPH were listed at a lower price on the Pharmaceutical Benefits Scheme it would become more cost-effective. Increased uptake of stimulants for ADHD would require policy change. However, the medication of children and wider availability of stimulants may concern parents and the community.