Relative to placebo, the olanzapine group experienced a significant increase of 0.165 BMI points, which is approximately 1 pound per month over the 16 weeks. Relative to placebo, the olanzapine group did not see a benefit in obsessionality or cognitive symptoms of anorexia, and had significantly more concerns about body weight. Lab abnormalities and hospitalization rates did not differ between the groups.
This study’s strengths include the large sample size and enrollment of diverse patients with various comorbidities that are more reflective of outpatient practice. The sample size is almost as large as all the past atypical antipsychotic studies of anorexia combined. The study’s main weaknesses include the large dropout rate (45%) and a duration that was probably not long enough to detect lab abnormality differences. On the other hand, the dropout rate was similar for olanzapine and placebo, and the data was analyzed on an intent-to-treat basis.
Despite a positive result, these modest gains in weight do not inspire a ringing endorsement of olanzapine for anorexia. The study can’t tell us whether that weight gain was due to a therapeutic effect on anorexia or to olanzapine’s known metabolic effects, but the lack of improvement in other anorexia symptoms gives us pause. Reserve olanzapine for severe, treatment-resistant patients where weight restoration is essential, or for patients with anorexia who have comorbidities—like mood disorders—where olanzapine is indicated.
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