The pharmacology and clinical outcomes of amphetamines to treat ADHD: does composition matter?

Attention-deficit hyperactivity disorder (ADHD) treatment options include pharmacological and nonpharmacological approaches. In North America, psychostimulants (amphetamine and methylphenidate) are considered first-line pharmacological treatments for patients (children, adolescents and adults) with ADHD. However, in the UK, National Institute for Health and Clinical Excellence (NICE) guidelines have placed short-acting d-amphetamine as a third-line treatment option due to a lack of contemporary, published clinical trials on its efficacy and the concerns from clinical and patient experts regarding the potential for increased abuse and/or misuse compared with methylphenidate. These guidelines do not account for some of the more recent amphetamine products that have been developed to alleviate some of these concerns, but that are not currently approved in the UK or other European countries. The purpose of this review is to describe the pharmacology and clinical efficacy of various amphetamine compositions, as well as to explore the apparent differences in these compositions and their associated risks and benefits. A PubMed literature search was conducted to investigate amphetamine pharmacology, clinical efficacy and safety and ADHD outcomes in the published literature from 1980 through March 2011. Search terms included the keywords 'ADHD' or 'ADD' or 'hyperkinetic disorder' and any of the following keywords combined with 'or': 'amphetamine', 'dexamphetamine', 'mixed amphetamine salts', 'lisdexamfetamine' and 'methamphetamine'. The search included English-language primary research articles and review articles but excluded editorial articles and commentaries. The literature search resulted in 330 articles. Pertinent articles relating to amphetamine pharmacology, compositions, clinical efficacy and safety, effectiveness and tolerability, ADHD outcomes and abuse liability were included in this review. The different delivery profiles of amphetamine compositions result in pharmacological and pharmacokinetic differences that contribute to varying effects in the clinical treatment of ADHD, ADHD outcomes and abuse liability. The efficacy and safety of amphetamine compositions for the treatment of ADHD have been demonstrated in clinical trials and meta-analyses, and the long-acting amphetamine compositions have been widely studied and found efficacious without increased adverse effects. Long-acting amphetamine compositions offer the obvious advantage of enhanced duration of action over short-acting amphetamine compositions, and lisdexamfetamine has been shown to have reduced abuse liability compared with short-acting amphetamine.