Doctors write millions of prescriptions annually for the class of medications called SSRIs (selective serotonin reuptake inhibitors). These drugs-Prozac, Paxil, Celexa, Lexapro, Zoloft and Luvox-are among the best weapons available to fight depression. But for up to 60 percent of patients, there can be a debilitating side effect: a dwindling libido or difficulty with orgasm. Some researchers estimate that half of patients may throw out their pills because of sexual troubles. That's a major public-health problem because it means people with depression aren't getting the help they need. "Depression is potentially fatal," says Dr. Karen Swartz, codirector of the Mood Disorders Program at Johns Hopkins University School of Medicine. "Not taking treatment is serious."

Now, after more than 15 years of clinical experience with SSRIs, doctors have found lots of ways to help patients deal with the sexual problems caused by most antidepressants. At the same time, recent advances in understanding the nature of sexuality give doctors new tools to pinpoint trouble spots in each individual. Scientists divide human sexual response into four phases: drive (sexual desire or libido), arousal (erectile function in men and lubrication in women), orgasm and resolution (a feeling of well-being). In a study of 6,300 patients to be published next year, Dr. Anita Clayton, professor of psychiatry at the University of Virginia , found that two thirds of men who had sexual problems with SSRIs complained about desire and orgasmic function. The women were much more likely to complain of arousal problems. The simplest solution is to wait. In up to 30 percent of cases, patients develop a tolerance for the drug and their sex lives improve. But that can take up to six months. "People are willing to wait a little bit," says Swartz, "especially if they're getting good benefit for their depression, but not indefinitely."

Another strategy is scheduling "drug holidays"- over the weekend, for example. That works for patients organized enough to go back on the medication on Monday and who don't mind scheduling sex. (It's not an option if you're on Prozac, which stays in the body longer than other SSRIs.) Doctors also sometimes suggest switching to another kind of antidepressant whose side effects may be less distressing to a particular patient. Dealing with nausea, for example, might not be as bad as an inability to have orgasms. Adding the antidepressant Wellbutrin, not an SSRI, also often helps-perhaps because it increases levels of the neurotransmitter dopamine, which is believed to increase desire.

If the main issue is arousal, doctors might prescribe Viagra for men, says Dr. Michelle Riba, clinical professor of psychiatry at the University of Michigan . To improve lubrication for women, Riba suggests either a lubricant or more foreplay before sex. Even getting more sleep may help. "People with depression often can't fall asleep or stay asleep," says Riba, "so sleep can get all tied into it, along with the fact that they don't feel well."