At a recent meeting of the American Psychiatric Association, researchers presented a study suggesting that ziprasidone (Geodon) was less effective in treating acute mania in people with obesity or hyperglycemia (very high blood sugar level). The study was funded by Pfizer, which makes Geodon, and was done by looking at pooled data from previous studies performed by Pfizer looking at this medication’s effectiveness.

The lead author of the study, Roger S. McIntyre, Associate Professor of Psychiatry and Pharmacology at the University of Toronto, indicated that while the findings could be related to a need for higher doses in people with higher body mass indexes, it could also be that these differences in body mass and blood sugar could reduce the effectiveness of the drug at any dose. While this type of study is apparently uncommon in psychiatric research, it is actually quite important in helping us understand patterns of effectiveness in various medications used to treat bipolar disorder.

Traditionally, studies have looked at groups of patients and how they respond to medicines without any kind of stratification along these lines. Research studies often look at how factors such as substance use, other diagnoses, age, and sex contribute to medication effects. But we haven’t routinely looked at obesity and hyperglycemia, which are common conditions, and how they might affect medication response – positive or negative.

Paradoxically, ziprasidone is often chosen specifically for patients who are already overweight because it doesn’t have the same problems with weight gain and changes in glucose metabolism as the other atypical antipsychotics. If this is the same population that tends to have a less complete response to ziprasidone, then this could affect the medication choices doctors make when treating acute mania.

Furthermore, while this study looked at ziprasidone, it makes sense to do similar studies with the other atypical antipsychotics. Most of them cause weight gain and increase risk of problems with blood sugar. Now we must consider the possibility that those very side effects may reduce the effectiveness of the medicines themselves. This further complicates an already complex picture of the risks and benefits of atypical antipsychotics.

Photo by Tony Alter, available under a Creative Commons attribution license.

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    Last reviewed: 28 May 2011