New studies indicate the three drugs used to treat male impotence also appear to work in females, albeit a little differently, and should give the scientific community pause to take a second look at their potential in the 40 percent of women who report sexual dysfunction, researchers say.

Certain anti-angina drugs, blood pressure medicines, grapefruit juice and the herbal supplement St. John's wort are among the substances that could negatively interact with popular erectile dysfunction (E.D.) drugs, the consumer group Public Citizen said Monday in releasing a list of 56 such substances.

Viagra and other impotence drugs' usage may result in sudden hearing loss. It is not clear that the drugs truly trigger hearing loss, but the U.S. Food and Drug Administration decided Thursday to add a warning about the possible risk after counting 29 reports of the problem since 1996 among users of this family of medicines.