Is it safe for a woman to take Flomax to pass kidney stones?
Ask the doctor
Q. After extracorporeal lithotripsy treatment for kidney stones, I became obstructed while passing the fragments. During a visit to the ER, I was prescribed Flomax. Is this safe for women? How long should I use Flomax for this purpose?
A. Flomax (tamsulosin) is safe for women. I can easily understand your concern, since the only FDA indication for the drug is to treat men with symptoms of benign prostatic hyperplasia (BPH). However, doctors commonly prescribe tamsulosin 0.4 mg daily in both men and women for two to four weeks to help decrease pain and facilitate passage of a stuck kidney stone. In the United States, this is considered “off label.”
Tamsulosin is very different from other types of prostate medications such as finasteride (Proscar) and dutasteride (Avodart). These drugs work by blocking testosterone effects. In general, women should not take either of these drugs. However, sometimes doctors will prescribe a low dose of finasteride (also “off label”) in older women with male pattern baldness.
Flomax is an alpha blocker. It relaxes smooth muscle cells in a variety of tissues. Alpha blockers were originally developed to treat high blood pressure because they relax the smooth muscle cells in arteries. This allows blood to flow more easily, requiring less pressure inside the arteries.
Researchers discovered that alpha blockers also relax the muscles around the prostate and urethra. They tested this on men with prostate problems. Alpha blockers improved symptoms such as a slow urine stream and the frequent urge to urinate.
Flomax was designed to work more on the muscles around the prostate and urethra with less effect on blood pressure.
Years ago, doctors found another use for tamsulosin and related drugs. Alpha blockers relax the smooth muscles in the ureters, the tubes that connect the kidneys to the bladder.
There is no set number of days that Flomax should be used for this purpose. Original studies arbitrarily chose 10 to 14 days. But some people with kidney stones have stayed on much longer courses.
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About the Author
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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