REVIEW OF: Huang J et al, Schizophr Bull 2022;48(4):850–859

STUDY TYPE: Randomized open-label single-blinded controlled trial

Olanzapine is one of the most effective treatments for schizophrenia, but weight gain on this drug is problematic. Changes in the gut microbiome are one of several mechanisms that might explain this metabolic side effect. With this in mind, investigators looked at whether probiotics could reduce weight gain on olanzapine.

The investigators conducted two 12-week open-label single-blinded randomized controlled trials. Both trials enrolled patients with first-episode schizophrenia who had recently started olanzapine. In the first study, 90 subjects were randomized to a probiotic vs placebo. In the second study, 60 subjects were randomized to a probiotic supplemented with daily fiber vs placebo. Probiotics are thought to work better when taken with a “prebiotic” such as dietary fiber. The mean age was 24 years, and the mean olanzapine dose was 18–19 mg/day. The probiotic was Bifico, which contains Bifidobacterium, Lactobacillus, and Enterococcus. The primary outcome was a change in body weight and BMI, with insulin resistance index a secondary outcome.

After 12 weeks, the subjects on probiotics had significant improvements in insulin resistance compared to placebo, but only the probiotic + fiber group had improvements in weight and BMI. Specifically, they gained 5.14 kg compared to 9.2 kg for those on placebo with olanzapine.

The main limitations of these studies were their small size and lack of double blinding. Subjects knew which treatment they were getting, but investigators did not.

CARLAT TAKE

Given the paucity of options in preventing olanzapine-induced weight gain, probiotics plus dietary fiber supplementation may be a viable preventative strategy.