Risperdal (risperidone) plus Paxil (paroxetine) causes weight gain of 30-31 lbs in 4-5 months

Posted by .(JavaScript must be enabled to view this email address)
Tuesday, April 05, 2011 12:51 pm Email this article
Two patients given the antipsychotic drug Risperdal (risperidone) plus the antidepressant Paxil (paroxetine) gained a large amount of weight in a short period of time according to an article from Japan.

One person gained 31 pounds in four months, while the second person gained 30 pounds in five months. What Caused This?

Drug interaction possible cause

“Regarding the mechanism of severe weight gain in these two patients, we speculate a drug-drug interaction involving inhibition of the cytochrome P450 enzyme 2D6 (CYP4502D6) by paroxetine [Paxil],” the researchers noted.

Cytochrome P450 enzymes metabolize drugs in the liver.

Drug interactions are often the result of one drug reducing the amount of one of these Cytochrome P450 enzymes necessary to metabolize the other drug, thus leading to much higher levels of the drug in the body which can cause problems.

Here is the description of this from Wikipedia.

“Many drugs may increase or decrease the activity of various CYP isozymes either by inducing the biosynthesis of an isozyme (enzyme induction) or by directly inhibiting the activity of the CYP (enzyme inhibition).

“This is a major source of adverse drug interactions, since changes in CYP enzyme activity may affect the metabolism and clearance of various drugs.

“For example, if one drug inhibits the CYP-mediated metabolism of another drug, the second drug may accumulate within the body to toxic levels.

“Hence, these drug interactions may necessitate dosage adjustments or choosing drugs that do not interact with the CYP system.

“Such drug interactions are especially important to take into account when using drugs of vital importance to the patient, drugs with important side-effects and drugs with small therapeutic windows, but any drug may be subject to an altered plasma concentration due to altered drug metabolism.”

REFERENCE

Fukui H, Murai T. Severe weight gain induced by combination treatment with risperidone and paroxetine. Clin Neuropharmacol. 2002 Sep-Oct, 25(5):269-71.

AUTHOR’S CONTACT INFORMATION

Department of Psychiatry
Obama Public Hospital
Obama, Fukui, Japan
.(JavaScript must be enabled to view this email address)

Articles on the same subject can be found here:

• Antidepressants

• Paroxetine (antidepressant Paxil)

• Risperdal (risperidone)

• Weight-gaining drugs