"For women on antidepressants with orgasm problems, this may provide some wonderful relief," said psychologist Stanley Althof, director of the Center for Marital and Sexual Health of South Florida, who was not involved in the study. "But it will not improve their desire or arousal."

Pfizer Inc., which makes [Viagra], has no plans to pursue U.S. Food and Drug Administration approval for using the drug as a treatment for female sexual dysfunction. The company ended its internal research on Viagra for women in 2004, spokesperson Sally Beatty said in an e-mail. While Viagra was found to be safe, the results were inconclusive.

Althof said it's "worrisome" that 43 per cent of the women on Viagra experienced headaches, compared to 27 per cent of the women on dummy pills. Indigestion and reddening of skin (flushing) also were reported more often by the women taking Viagra.