DEAR DR. ROACH: I am an 88-year-old male who has been taking tamsulosin twice daily for several years because of benign prostatic hyperplasia (BPH). In October 2023, my urologist added finasteride once daily. One year later, in October 2024, I developed extreme tenderness on my left breast that wrapped around my left side.

I had a routine visit with my cardiologist who told me it was a side effect of finasteride. The cardiologist told me to stop taking it immediately and advise my urologist about my decision. I advised his nurse, who advised him, but I heard nothing further from him.

My cardiologist advised me that the tenderness would be gone in a week or so. It abated but still hasn’t gone away completely. I spoke with my primary care physician several weeks after the side effects lingered. She emphatically said that the side effects would go away but didn’t say when.

What is your opinion about these lingering side effects? — W.R.

ANSWER: Finasteride works by blocking the enzyme that converts regular testosterone to dihydrotestosterone (DHT). DHT is active in enlarging the prostate and affecting hair follicles, which leads to male pattern baldness. Thus, finasteride is used for these two conditions.

Most men don’t get side effects, but enlargement of breast tissue (gynecomastia) is a known side effect of finasteride. About 3% of men will develop gynecomastia with the usual 5-mg dose of finasteride that is used for prostate enlargement, compared to 1.8% of men on a placebo. The breast tissue can be affected on one or both sides and is sometimes painful. It usually goes away after stopping the medicine.

Unfortunately, there are cases where the breast enlargement does not go away, even after months have passed. Medications such as tamoxifen or raloxifene have been successful, but some men have had to get the breast tissue removed. A combination of surgical excision and liposuction is the standard way of removing unwanted breast tissue in men.

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