Risperidone (RISP) may induce both elevated prolactin (PRL) levels and weight gain. the aim of this study was to evaluate body weight and mass index (BMI), and PRL modifications in schizophrenic patients treated for 1 year with long-acting risperidone (LAR).

Body weight and BMI (calculated as weight in kilograms divide by height in meter squared) were determined at baseline and at endpoint in 19 schizophrenic patients (9 men and 10 women; mean[SEM] age 33.4[2.9] years). PRL levels were determined at baseline, after oral risperidone treatment (mean length of treatment: 79[30] days; mean dose: 5.8[0.5] mg daily) and during a 12 month treatment with LAR (mean dose: 50[10] mg every 2 weeks; PRL levels were measured before each injection).

At endpoint, a significant weight gain (Δweight: 8,1[1,4] kg) and BMI (ΔBMI: 2,9[0,5] kg/m²) was observed (both p< 0.0002). Compared with baseline, PRL levels were significantly increased (p< 0.0007; mean ΔPRL: 33[8] ng/ml). There was an association between ΔBMI>1,5 kg/m² and ΔPRL>40 ng/ ml (p< 0.04). Moreover ΔBMI was linked to the length of treatment (rho=0.47; n=19; p< 0.05).

Our results suggest a link between weight gain and long term hyperprolactinemia in patients treated with LAR. It has been hypothesized that PRL may have a role in the regulation of food intake by increasing leptin synthesis and secretion.