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Methylphenidate mechanism — MRCPsych Paper A MCQ

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HardPsychopharmacologyMethylphenidate mechanismMRCPsych Paper A

A 14-year-old boy with ADHD shows a clear improvement in sustained attention after starting methylphenidate. Which principal synaptic action best distinguishes methylphenidate from amphetamine?

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Correct answer: D — DAT and NET blockade with reduced presynaptic catecholamine reuptake

Explanation lettering: D = shown as A · A = shown as B · B = shown as D

Methylphenidate principally blocks the dopamine transporter (DAT) and noradrenaline transporter (NET), reducing presynaptic catecholamine reuptake and increasing extracellular dopamine and noradrenaline. This differs from amphetamine, which additionally enters presynaptic neurons, disrupts vesicular storage through VMAT2 and promotes reverse transport; therefore A describes amphetamine more closely. Selective NET inhibition with relatively little direct DAT activity is characteristic of atomoxetine (C). Postsynaptic alpha-2A-adrenoceptor agonism is the mechanism of guanfacine (D). Methylphenidate does not exert its therapeutic effect by inhibiting monoamine oxidase, so E is incorrect.

Reference: Ritalin 10 mg Tablets, Summary of Product Characteristics, section 5.1 Pharmacodynamic properties: Mechanism of action, revised 24 November 2025. https://www.medicines.org.uk/emc/product/15987/smpc