Amantadine for Zyprexa's Weight Gain
(Updated 1/2008)

The following information is primarily for my own patients.  Others are welcome to view it.  This information is not intended to be used on your own.  Most doctors do know a thing or two which you don't, and can help you decide whether the risks of this medication might outweigh -- so to speak -- the benefits in your situation.   Dr. Phelps

How does it work?

The medication affects "dopamine", a nerve cell chemical messenger (neurotransmitter).  That's why it's used in Parkinson's disease, which is the main use for this medication.  Why might it decrease Zyprexa-weight-gain?  This is not known.  For a summary of the recent data (1/2008 revision) showing this treatment does appear to help some people, see the amantadine section of my page on olanzapine (Zyprexa).

What are the risks?

If you read about this medication on a standard internet medication-information site, the "Warnings, Precautions, and Adverse Effects" section will scare you pretty badly.  It's important to remember that these reports include a very large number of people who've been exposed to this medication.  Only a very small percentage have the problems reported.  For example, the only side effects which occur more often than 5% of the time are nausea, dizziness, and insomnia. 

Less than 5% of the time, this medication can cause some of the very symptoms that Zyprexa is supposed to be treating:  depression, anxiety and irritability, even psychosis.  Remember, 95 people out of  hundred do not have these reactions to amantadine.  They are listed here so that if something like this happens, you'll know it could be from the medication. 

One of the risks is stopping the medication suddenly.  We generally taper off almost all psychiatric medications, but this one has even more specific reasons for doing so.  You can get bad symptoms, resembling severe Parkinson's disease, from stopping this medication suddenly (rare, but it can happen).

Why consider taking these risks? 

Weight gain carries its own risks.  For some people, these can be very large.  Some people won't consider staying on a medication that is causing weight gain -- and may not have many alternative medications to consider. 

How do I take it?

The one study published so far, which did that people lost weight while continuing Zyprexa, used the full dose: 300 mg per day.  So for now, you should plan on going that high to see if this will work, as long as you're not having any side effects. I tell my patients to start with 100 mg once a day, and increase by one pill per week up to 3 per day:  week 1 = one; week 2 = one per am, one per pm; and week 3 = two per am, and one per pm.