Olanzapine and Weight Gain in Anorexia Nervosa

Patients treated with olanzapine (Zypyrexa), an atypical antipsychotic agent, often complain about excessive weight gain. Thus, it has been hypothesized that the drug could be useful in the treatment of anorexia nervosa. Indeed, in one study of two patients with chronic anorexia nervosa, use of olanzapine resulted in improved weight gain and maintenance of weight, as well as decreased anxiety and agitation in both (Int J Eat Disord 2000;27:363).

A more recent study of 41 female inpatients diagnosed with either restricting (26) or purging (15) anorexia nervosa showed very different results. Jill A. Gaskill, MSN, CRNP and colleagues at Western Psychiatric Institute and Clinic, Pittsburgh, reported that use of olanzapine was not associated with a greater weight gain among the 41 inpatients with AN. The study results were presented at a poster session at the Academy for Eating Disorders Meeting in May in Vancouver.

Higher doses did not make a difference

Twenty-one of the patients received a daily dose of 1.25 mg of olanzapine, unless they were on a higher dosage at admission. The dosage was increased by 1.25 mg every 2-4 days, to reach a target dose of 5.9 mg/day unless patients complained of excessive sedation or orthostasis. At discharge, the average dose was 5.77 mg/day. The patients gained a an average of 1.21 kg/week and the percent ideal body weight increased significantly over the course of treatment, from nearly 73% at admission to 84% at discharge.

Just as in the earlier study, patients receiving olanzapine were less anxious and agitated than the other patients during refeeding. Higher doses of olanzapine, such as more than 5 mg/day, did not lead to greater weight gain than lower doses, such as those below 5 mg/day.

The authors note that the result is not surprising in an inpatient setting, where caloric intake is maximized and fully monitored. They would like to see another study, one designed to see if use of olanzapine is associated with greater weight gain among AN patients in an outpatient setting, when caloric intake is less tightly controlled and restoring optimal body weight is an ongoing challenge.