People who take prescription medication and also smoke cigarettes now have one more reason to stop lighting up: Smoking cigarettes can interfere with how the body metabolizes drugs.

The result, according to John F. Schlegel, president of the American Pharmaceutical Association (APhA), is that smokers may need to take greater amounts of drugs or take them more frequently to get the same effect as nonsmokers.

"Nearly all people who smoke recognize the harmful effects of their habit," Schlegl noted at a press conference last week. "But they may not know that ciagette smoke interacts with some drugs to decrease their effectiveness or to multiply the health risks."

For that reason, the APhA teamed with the National Cancer Institute last week to promote a new public health campaign called "Helping Smokers Quit."

"The pharmacist probably interacts with the smoker more often than the physician, and the setting may be more informal and conducive to routine conversation and recommendation than the doctor's office ," said Joseph W. Cullen, deputy director of the National Cancer Institute's Division of Cancer Prevention and Control.

As part of the program, pharmacists will distribute pamphlets and offer help to smokers who want to quit. Among the drugs that smoking interferes with are anti-anxiety drugs including diazepam (commonly sold as Valium); painkillers such as propoxyphene (sold as Darvon); tricyclic antidepressants including amitriptyline (sold as Elavil, Amitril and others); anti-blood clotting drugs such as heparin; phenothiazines including chlorpromazine (sold as Thorazine); anti-asthmatic drugs including theophylline; and the anti-angina drugs known as beta blockers (propranolol).