BOSTON - The combination of the antidepressant drug Prozac and the illegal "club drug" Ecstasy increases the risk of acute toxic effects of Ecstasy, and may explain the increasing number of Ecstasy-related deaths, according to research presented at the annual meeting of the American College of Clinical Pharmacology, held here this week.

In presenting the research, Dr. Vijay V. Upreti, of the University of Maryland, Baltimore, said an increasing number of Ecstasy abusers are combining the drug with Prozac in an effort to counteract the depression that occurs after the drug's high wears off. Ecstasy, also known as MDMA, helps the body relax, reduces inhibitions and increases energy and brings feelings of euphoria.

Upreti and colleagues measured brain and blood levels of MDMA in mice after a 5 mg/kg-dose of MDMA. Levels were also measured after pretreatment with Prozac followed by 10 mg/kg MDMA.

They found that pretreatment with Prozac increased brain and plasma MDMA levels by 40 percent in the animals.

The "half-life" of MDMA, meaning how long the drug is present, increased from 2 hours to 5 hours with Prozac pretreatment. There was also a 26 percent reduction in MDMA clearance when the drugs were combined.

Upreti concludes that Prozac co-administered with MDMA decreases the disposition of MDMA and its metabolite, "and may lead to increased risk of MDMA acute toxic effects."