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Metformin for APS Weight Gain — MRCPsych Paper B MCQ

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ModerateSchizophrenia & PsychosisMetformin for APS Weight GainMRCPsych Paper B

A 29-year-old man with schizophrenia has gained 8 kg during 4 months of olanzapine treatment. His psychosis is well controlled, and continuing olanzapine is currently preferred after reviewing its benefits and adverse effects. He is participating in a healthy-eating and physical-activity programme. If off-label metformin is added specifically for antipsychotic-induced weight gain, which outcome is most consistent with the evidence?

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Correct answer: A — Approximately 3 kg lower body weight than with placebo, as an adjunct to lifestyle measures

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

B is correct. Placebo-controlled evidence indicates that adjunctive metformin produces a modest effect on antipsychotic-induced weight gain, averaging approximately 3 kg lower body weight than placebo over short-term treatment. It may also improve BMI and insulin resistance. Metformin should be viewed as an adjunct to, rather than a replacement for, healthy-eating and physical-activity interventions. It does not cure established diabetes, and metabolic risk still requires appropriate monitoring and treatment. It also does not remove the need to review whether the benefits of the current antipsychotic outweigh its adverse effects. Although some lipid measures may improve, complete normalisation is not a reliable or expected outcome. Therefore A, C, D and E substantially misstate the magnitude or role of metformin.

Reference: NICE. 2023 exceptional surveillance of psychosis and schizophrenia in children, young people and adults (NICE guidelines CG155 and CG178), 2023. https://www.nice.org.uk/guidance/cg178/evidence/2023-exceptional-surveillance-of-psychosis-and-schizophrenia-in-children-young-people-and-adults-nice-guidelines-cg155-and-cg178-13244105197