Metformin for weight control in patients with schizophrenia

Abstract

Introduction. People use antipsychotic medications to manage schizophrenia as well as other disorders. The most bothersome side effect, especially for women is the weight gain associated with the use of antipsychotic medications. Currently there is no first line medication for weight control with antipsychotics. The mechanism of the weight gain by antipsychotics is unclear, however, it might be due to blocking of central histamine 1 (H1) or serotonin (5HT2c) receptors. It is suspected that naltrexone, an opioid antagonist, suppresses the desire for high fat foods via acting on D2 receptors. Metformin, however, is involved in appetite suppression and slowing of gastric emptying via promoting glucagon-like peptide-1 secretion. Thus, both these mechanisms might be able to counteract or prevent weight gain associated with antipsychotics use. Aim of the study. To determine whether metformin is more effective in weight loss after the use of antipsychotic medications. Materials and methods. PubMed database was used to search meshterms “antipsychotic, weight gain, metformin,” which were combined with “and” to result in 14 articles. After the addition of the filter “published within the last 5 years” was added, 5 articles were left. The meshterms “antipsychotic, weight gain, naltrexone” were combined with “and” to result in 3 articles. There were no articles with both drugs together. Embase database was searched from 1996 till 2017 week 02. Mapped key words “antipsychotic, weight gain, naltrexone” were filtered with randomized controlled trials within the last 5 years and combined with “and” which resulted in one article. Similarly key words “antipsychotic, weight gain, metformin” resulted in 5 articles. Two articles were not on the correct topic. Results. Metformin is shown to significantly reduce weight in schizophrenic patients by about 3 kg (2 RCTs; n=148, 45 women; and n=72, 32 women). Second study shows that metformin reduced initial body weight greater than was clinically significant (>7%, p=0.003). Naltrexone showed significant weight loss of 3.4 kg (CI=-5.16, -1.65, p=0.001) (1 RCT; n=24). No studies compared metformin and naltrexone in one trial. Metformin was shown to have more additional health benefits. Conclusions. Both metformin and naltrexone show statistically significant weight reduction in patients taking antipsychotics. However, metformin appears in more studies than naltrexone and shows additional health benefits like reduction of triglycerides. Thus, metformin appears to be more effective in weight control for women with schizophrenia. Pharmacists might be able to recommend metformin as an adjunct to the antipsychotic therapy.