Harvard Women's Health Watch

By the way, doctor: Is it okay to take antibiotics indefinitely to prevent urinary tract infections?

Q. This year I've had four urinary tract infections. Each cleared up with antibiotic treatment. Now, my doctor is prescribing a prophylactic antibiotic, Bactrim 400/80, that I'm supposed to take every day. Are there long-term risks in this?

A. Urinary tract infections (UTIs) are common in women of all ages. They can affect any part of the urinary tract, but most occur in the bladder (cystitis), producing symptoms of frequent, urgent, and painful urination, bloody urine, and lower abdominal pressure or pain. Less often, the kidneys become infected (pyelonephritis), causing low back pain, pain between the upper abdomen and back (flank pain), nausea, vomiting, and high fever.

Most urinary infections are caused by Escherichia coli, or E. coli, which is abundant in human feces and can travel from the anus to the urethra during activities such as going to the bathroom and having sexual intercourse. After gaining a foothold in the urethra, the bacteria can move up the urinary tract to the bladder or kidneys. Some strains of E. coli have a special ability to start an infection by sticking to the cells lining the urinary tract.

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