Clindamycin is a powerful antibiotic usually reserved for very serious bacterial infections. It wouldn't be a first choice for a urinary tract infection, but you didn't say whether your wife's infection failed to respond to other treatment before the Clindamycin was prescribed. I would hope that her physician had a good reason for choosing it. This antibiotic should be used with care, because it can disrupt normal flora in the intestinal tract and cause a “severe (rarely fatal) intestinal condition (pseudomembranous colitis) due to a resistant bacteria.” This adverse effect can occur during treatment or up to two months after. The symptoms to watch out for are abdominal pain, nausea, vomiting, and diarrhea. If any of these symptoms occur following treatment, be sure to contact your physician immediately.
You should be aware, however, that all drugs are capable of causing side effects. Nearly all antibiotics can cause the same intestinal problems as Clindamycin. As a savvy patient, it is important to ask about the potential risks of any drug you are prescribed and to make sure that the physician knows about any other drugs you're taking and is fully aware of your medical history. If you forget to ask the physician during your visit, follow up with a phone call. Your pharmacist can also tell you about potential side effects or drug interactions. Inform yourself before you use any prescription.
Because of the anatomy of the urethra, urinary tract infections are very common in women. To help prevent them, I recommend practicing prudent and practical hygiene (such as wiping front to back and urinating after intercourse), as well as drinking unsweetened cranberry juice concentrate diluted with water, or taking powdered cranberry extract in capsules. Cranberries contain a substance that helps prevent bacteria from sticking to the bladder walls. Drink lots of water in order to urinate more frequently and avoid alcohol and coffee, which are bladder irritants.
Andrew Weil, M.D.
Here is more information about the prevention and treatment of urinary tract infections.