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Can Amantadine Cause Weight Loss?

By Andy Humphrey ; Updated July 18, 2017

Although second-generation anti-psychotic drugs have proven to be effective in cases of serious mental illness, they all induce significant weight gain in the patients. In a nation that already has an obesity problem, doctors are working to find solutions to allow patients to take these medications without the health risks that come from weight gain. A recent study shows the antiviral drug amantadine may be an answer.

The Problem

Second generation anti-psychotic medications, such as olanzapine, are used to treat serious conditions, such as bipolar disorder and schizophrenia. Although they are effective, these drugs have a number of detrimental side effects, including significant weight gain. An article in the September 2005 issue of the "American Journal of Psychiatry" calls weight gain the leading issue for tolerability of this class of drugs. Recently, researchers have found evidence that the antiviral drug amantadine may be able to prevent the mechanism that causes patients to gain weight.

Amantadine History & Benefits

Amantadine was originally approved as an antiviral drug. Since then, it has been found to have other uses, such as relieving symptoms of Parkinson's disease, helping patients with sensory processing disorders and, more recently, preventing the weight gain associated with second generation anti-psychotic drugs. In a double-blind, placebo-controlled study published in the "American Journal of Psychiatry," patients who took amantadine with olanzapine not only didn't gain weight like patients who took olanzapine with a placebo, but actually lost weight.

Amantadine Side Effects

Not all doctors feel that amantadine is the right choice for combating weight gain due to anti-psychotics, including Dr. James Phelps, a board-certified psychiatrist who works at Samarian Mental Health and runs the mental health information site PsychEducation.org. He has tried this approach on three patients and, though they didn't gain weight, he later discontinued the amantadine due to side effects. His patients had problems with tremors, and one of the subjects in Graham's study was removed due to a psychotic reaction.


Phelps lists a number of alternatives to using amantadine for weight loss. He suggests that patients try other mood-stabilizing drugs rather than second-generation anti-psychotics, since they don't show association with weight gain. He says there is a form of Zyprexa, the trade name for olanzapine, called Zydis, which is absorbed directly into the tissues of the mouth so doesn't appear to trigger the increased appetite assumed to be the cause for weight gain. Plus, of course, he recommends exercise as a safe and effective method of weight loss.

General Weight Loss

Amantadine does not promote weight loss as much as it interferes with the mechanism associated with weight gain from drugs like olanzapine. Researchers do not know how it works and are quick to caution this is not a tool for weight loss. In a follow-up interview published in Psychiatric News, Graham says weight gain is caused by many factors in a patient's life, not just the medications taken. Although there is some evidence amantadine may act as a mild appetite suppressant, there is no evidence to support its use for general weight loss.

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