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    Zyprexa (olanzapine) causes rapid weight gain in 15% of patients

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    Monday, May 09, 2005 4:15 am Email this article
    Approximately 15 percent of people gain weight rapidly when taking taking Zyprexa (olanzapine): an average of 4 percent of their body weight -- an average of 7 pounds -- in the first two weeks, and 7 percent or more of their body weight -- an average of 15.9 pounds -- during the first six weeks according to a new paper. Weight gain after six weeks: 15.9 lbs vs 2.7 lbs

    After six weeks, patients in the rapid weight gain group had gained an average of 15.9 pounds compared to 2.7 pounds in the non-rapid weight gain group.

    Weight gain plateaued after 9 months

    Weight gain plateaued after about 9 months on the drug.

    Weight gain after nine months: 26.7 lbs vs 8.1 lbs

    After roughly nine months, patients in the rapid weight gain group had gained an average of 26.7 pounds compared to 8.1 pounds in the non-rapid weight gain group.

    Rapid weight gainers: younger, lower starting BMI, increase in appetite, more robust effect on schizophrenia

    Those who gain weight rapidly tend to be younger (35.6-years-old versus 39.3-years-old), have a lower starting body mass index (BMI) (23.9 vs 26.4), were more likely to report an increase in appetite (44 percent of patients versus 25 percent), and reported a better clinical response to their schizophrenia or schizoaffective disorder than patients who did not gain weight as rapidly.

    After six weeks, BMI in the rapid weight gain group was similar to those in the non-rapid weight gain group: 26.8 versus 26.3.

    Rapid weight gain means more weight gain: 26 lbs vs 11 lbs

    Those who gained weight most rapidly, ended up gaining more weight in the long run also.

    Patients who gained weight rapidly gained on average about 26.4 pounds compared to roughly 11 pounds for those who did not gain weight rapidly.

    Comment: This is similar to what happens with diet drugs also; those who lose the most in the first month, ultimately lose the most weight.

    Subjects: 1191 people

    The analysis was from data on 1191 patients with schizophrenia or schizoaffective disorder who were treated with Zyprexa (olanzapine) for up to one year.

    Zyprexa increases appetite by blocking serotonin and histamine receptors

    The most likely cause of Zyprexa (olanzapine)-induced weight gain is from an increase in appetite due the fact that the drug blocks both serotonin and histamine receptors (specifically, serotonin 2C receptors and histamine H1 receptors).


    This study defines rapid weight gain as gaining 7 percent or more of your body weight in six weeks, and non-rapid weight gain as anyone gaining less than this.

    Can you imagine gaining 6.5 percent of your body weight in six weeks—8.5 pounds for a 130 pound person, or 10.4 pounds for a 160 pound person, or 12.4 pounds for a 190 pound person—and having your doctor tell you, “That’s good. At least you’re not one of those rapid weight gainers.”


    Study done by makers of Zyprexa

    The reason for this loose definition of rapid weight gain, is that the study was conducted by researchers at Eli Lilly and Company, the makers of Zyprexa (olanzapine).

    Defining rapid weight gain this loosely allows them to claim that 85 percent of patients taking Zyprexa (olanzapine) do not gain weight rapidly on the drug.


    Kinon B, Kaiser C, Ahmed S, Rotelli M, Kollack-Walker S. Association between early and rapid weight gain and change in weight over one year of olanzapine therapy in patients with schizophrenia and related disorders. J Clin Psychopharmacol. 2005 Jun, 25(3):255-58.


    Bruce J. Kinon, MD
    Lilly Research Laboratories
    Eli Lilly and Company
    Lilly Corporate Center
    Drop Code 6154
    Indianapolis, IN 46285 USA

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