Medical treatment of autism spectrum disorder in children: Current evidence, controversies, and clinical challenges

Table 4 Comparison of methylphenidate vs atomoxetine in children with autism spectrum disorder and attention-deficit/hyperactivity disorder symptoms

Feature	Methylphenidate	Atomoxetine
Evidence base	5 placebo-controlled crossover RCTs (total n = 146)	2 placebo-controlled RCTs included in pooled analysis (total n = 113)
Effect on hyperactivity	Significant improvement (teacher-rated SMD approximately -0.78, P < 0.001)	Significant improvement (pooled SMD approximately -0.68, P = 0.0004)
Effect on inattention	Small but significant reduction (P = 0.04); not clinically large	Significant reduction on ADHD-RS in parallel trial (MD: -6.7, P < 0.001)
Effect on core ASD symptoms	No primary benefit; secondary signals for joint attention/self-regulation	No primary benefit; possible improvement only when combined with risperidone
Tolerability profile	Higher risk of irritability, emotional lability, decrease appetite (RR: 8.28)	Generally well tolerated; nausea, decrease appetite, fatigue most common
Risk of behavioral activation	Higher (especially at higher doses)	Lower
Trial duration	Very short: 1 week per dose	6-8 weeks
Clinical role	Often first-line if tolerated	Alternative when stimulants are not tolerated or contraindicated

This table compares the two most common pharmacological treatments for attention-deficit/hyperactivity disorder symptoms, primarily hyperactivity and inattention, when they co-occur in children with autism spectrum disorder: Methylphenidate, a stimulant, and atomoxetine, a non-stimulant. Both drugs demonstrate significant and comparable efficacy in reducing hyperactivity, which is the primary behavioral target. Methylphenidate, while often chosen as the first-line agent for attention-deficit/hyperactivity disorder in the general population, has been shown to have a higher risk of behavioral activation (increased irritability, emotional lability) in children with autism spectrum disorder compared to neurotypical peers, potentially leading to discontinuation. Atomoxetine, a selective norepinephrine reuptake inhibitor, offers a generally well-tolerated alternative with a lower risk of behavioral side effects, though side effects like nausea and decreased appetite are still common. Crucially, neither drug shows a primary benefit on core autism spectrum disorder symptoms (social or communication deficits). The choice between them balances potent efficacy (methylphenidate) against a better tolerability profile (atomoxetine). Atomoxetine is often preferred when methylphenidate is not tolerated or contraindicated, or as a co-treatment when combined with atypical antipsychotics like risperidone. RCTs: Randomized controlled trials; SMD: Standardized mean difference (a measure of effect size); ADHD-RS: Attention-Deficit/Hyperactivity Disorder Rating Scale; MD: Mean difference; ASD: Autism spectrum disorder; RR: Relative risk (ratio of probability of an event occurring in an exposed group vs unexposed group).