I seem to suffer from persistent urinary tract infections after sex. I have heard that cranberry juice can help stave off these problems, but I can't stand the taste of cranberry juice. Could I get the same benefits from taking it in pill form?

C.R.

Urinary tract infections (UTIs) are especially common in young women, and there are some women who have very frequent UTIs related to sexual activity. I have seen patients who seem to have a UTI after every act of intercourse. Studies indicate that sexual intercourse is one of the most important risk factors for recurrent UTI. One study found that a woman who has intercourse three times a week has more than double the risk of UTI of a woman who had no intercourse that week. Daily intercourse increases the risk even more. Spermicides can actually increase the risk of infection.

One point should be remembered: Although burning on urination is a common symptom of a UTI, not all such episodes are actually due to UTIs. At some point, all women with frequent episodes should have testing to prove that infection is actually present.

What can be done for women who have UTIs after sex? Well, cranberry juice is an option, though not a very attractive one. In some studies, the juice reduced the UTI frequency by about one-third. While this is something, it will not do the trick for those with very frequent infections. The pill form of cranberry juice should provide only the same modest benefit. Urinating immediately after intercourse is effective in reducing infection, probably more so than using cranberry products.

The most effective means of preventing recurrences is prophylactic (preventive) antibiotics. As a rule, physicians do not like to prescribe antibiotics to be taken continuously for the purpose of preventing infection. This is because disease-causing microbes can develop resistance to those drugs, making it more difficult to treat the infection when it does occur. To reduce the likelihood of resistance, doctors may prescribe a single low dose of, say, ciprofloxacin (Cipro), after each act of intercourse rather than continuous antibiotics. One weekly dose is also effective. In the rare instances when these approaches do not work, then daily therapy will usually control the problem.