To the Editor: The letter by Drs. Moreira-Almeida and Pietrobon casts doubt on whether olanzapine monotherapy is efficacious for treatment of bipolar depression. The authors acknowledge that olanzapine monotherapy was associated with a statistically significant drop in the Montgomery-Asberg Depression Rating Scale score over 8 weeks compared with placebo. Most of this drug/placebo difference was due to improvement in sleep and increased appetite, which are known side effects of olanzapine. Olanzapine monotherapy was not associated with improvement in core symptoms of depression, including depressed mood.
My professional opinion is in agreement with the position that olanzapine monotherapy is of limited utility in treating bipolar depression. I believe the efficacy of olanzapine-fluoxetine combination is well established and is reflected in the fact that eight of the 10 Montgomery-Asberg Depression Rating Scale items showed improvement over placebo.
I do take issue with the assertion that the APA Guideline Watch for the Treatment of Patients with Bipolar Disorder claimed “the efficacy associated with olanzapine or olanzapine plus fluoxetine in the treatment of bipolar depression.” In the Guideline Watch, the results of the study were presented, but no claim to efficacy was made.