Metformin reduces 12-month change in body weight among people newly commenced on clozapine: a retrospective naturalistic cohort study
Abstract
Background: People with schizophrenia have a 15–20-year reduction in life expectancy, driven in part by the metabolic effects of antipsychotics. Clozapine is associated with the highest rates of weight gain. As clozapine remains the most effective antipsychotic for treatment-resistant schizophrenia (TRS), identifying treatments to ameliorate clozapine-induced weight gain (CIWG) is urgently needed to reduce this morality gap. Methods: We retrospectively analysed digital health records of patients with TRS aged 18–65 newly initiated on clozapine at four tertiary hospitals in south-east Queensland from 1 March 2017 to 30 June 2019. Our primary outcome was the effect of metformin on change in percentage bodyweight at 12 months after clozapine initiation, with secondary outcome being proportion with >5% or >7% bodyweight change. We also explored impact on bodyweight change of other variables including sex, tobacco smoking, type 2 diabetes (T2DM), age, clozapine level and dose and clozapine/norclozapine ratio. Results: Among 90 patients initiated on clozapine, metformin use (n = 48) was associated with a smaller increase in percentage bodyweight (1.32% versus 5.95%, p = 0.031), lower rates of >7% gain in bodyweight (37.8% versus 63.0%, p = 0.025) but not >5% gain in bodyweight. Age below the median (32.0 years) was associated with greater bodyweight gain (5.55% versus 1.22%, p = 0.046). Sex, tobacco smoking, T2DM, clozapine dose and level and clozapine/norclozapine ratio were not…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 90 participants or records.
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