Abstract
IMPORTANCE: Stimulants (methylphenidate and amphetamines) are often prescribed at unlicensed doses for adults with attention-deficit/hyperactivity disorder (ADHD). Whether dose escalation beyond US Food and Drug Administration recommendations is associated with positive risk benefits is unclear. OBJECTIVE: To investigate the impact, based on averages, of stimulant doses on treatment outcomes in adults with ADHD and to determine, based on averages, whether unlicensed doses are associated with positive risk benefits compared with licensed doses. DATA SOURCES: Twelve databases, including published (PubMed, Cochrane Library, Embase, Web of Sciences) and unpublished (ClinicalTrials.gov) literature, up to February 22, 2023, without language restrictions. STUDY SELECTION: Two researchers independently screened records to identify double-blinded randomized clinical trials of stimulants against placebo in adults (18 years and older) with ADHD. DATA EXTRACTION AND SYNTHESIS: Aggregate data were extracted and synthesized in random-effects dose-response meta-analyses and network meta-analyses. MAIN OUTCOME MEASURES: Change in ADHD symptoms and discontinuations due to adverse events. RESULTS: A total of 47 randomized clinical trials (7714 participants; mean age, 35 (SD, 11) years; 4204 male [56%]) were included. For methylphenidate, dose-response curves indicated additional reductions of symptoms with increments in doses, but the gains were progressively smaller and accompanied by continued additional risk of adverse events dropouts. Network meta-analyses showed that unlicensed doses were associated with greater reductions of symptoms compared with licensed doses (standardized mean difference [SMD], -0.23; 95% CI, -0.44 to -0.02; very low certainty of evidence), but the additional gain was small and accompanied by increased risk of adverse event dropouts (odds ratio, 2.02; 95% CI, 1.19-3.43; moderate certainty of evidence). For amphetamines, the dose-response curve approached a plateau and increments in doses did not indicate additional reductions of symptoms, but there were continued increments in the risk of adverse event dropouts. Network meta-analysis did not identify differences between unlicensed and licensed doses for reductions of symptoms (SMD, -0.08; 95% CI, -0.24 to 0.08; very low certainty of evidence). CONCLUSIONS AND RELEVANCE: Based on group averages, unlicensed doses of stimulants may not have positive risk benefits compared with licensed doses for adults with ADHD. In general, practitioners should consider unlicensed doses cautiously. Practitioners may trial unlicensed doses if needed and tolerated but should be aware that there may not be large gains in the response to the medication with those further increments in dose. However, the findings are averages and will not generalize to every patient.