Antipsychotic medications and extreme weight gain in two health systems

We conducted this study to investigate the rate of clinically important, extreme weight gain (EWG; ≥7% body weight gain) among all second generation antipsychotic (SGA) users in two large health care systems in the United States.

Retrospective observational cohort study.

We used electronic medical record databases of two health systems to identify adults aged 18-79 years who from 1 January 2004 to 31 December 2011 had initiated a SGA medication. All patients had to have a minimum of two weight measures in the medical record: (1) one or more weights in the 180-day pre-treatment (baseline) period; and (2) one or more weights in the first year after initiating SGA treatment.

We found that EWG occurred in 7.7-17.0% of SGA users. At one year, the average weight gain was nearly 10kg among SGA users who experienced EWG. Olanzapine was the SGA most commonly associated with EWG with a rate of 17.0 per 100 users [95% confidence interval (CI): 14.2-20.5], while ziprasidone was least commonly associated with EWG (7.7 per 100 users; 95% CI: 4.6-13.0).

We found that clinically-important weight gain was common after the initiation of SGA treatment, and the EWG phenotype was easily identifiable within electronic medical records. There was significant heterogeneity in the rate of EWG across SGA medications. Weight gains of this magnitude are likely to have adverse health consequences and there is a significant unmet opportunity for physicians to identify these events and mitigate the harms of SGA use.