A sexual side effect of phenoxybenzamine

As the cliché goes, the best teacher of a doctor is the patient. There is nothing more true about it, especially on side effects of a drug.

Years ago, I had the opportunity of seeing a very pleasant 30-something male patient. He had been diagnosed with pheo by another doctor and saw me for a second opinion. He had been on phenoxybenzamine for the alleged specific anti-pheo effects for more than a year. His blood pressure was well controlled by phenoxybenzamine. After reviewing the numerous tests and imaging studies, I determined that he did not have pheo. I recommended using a diuretic medication for blood pressure control, instead of using the expensive phenoxybenzamine. He was so relieved once he learned that he would not absolutely need phenoxybenzamine—but not due to financial reasons. He told me that he could not have children while on the drug but his wife and he so much wanted to start a family. An inquisitive soul, I asked him to elaborate. The patient shyly told me that he had not had ejaculates after he was on phenoxybenzamine.

That was the first time I learned this very common side effect of phenoxybenzamine in men. We all know the standard common side effects such as nasal stuffiness, orthostatic hypotension, and fatigue. Ejaculatory failure happens in almost every man taking phenoxybenzamine. Most men do not complain of this side effect, probably because the treatment is usually short-term and patients have anxiety before operation so that they do not attempt sexual activity. Men may also be embarrassed to talk about this what is perceived by some as a sensitive but trivial symptom.

The mechanism of ejaculatory failure is not retrograde ejaculation, rather, patients simply do not transfer seminal fluid (the bulk of ejaculates) to be ejaculated. The good news is that this sexual side effect is completely reversible in 1-2 days after discontinuing phenoxybenzamine. And phenoxybenzamine does NOT affect libido, potency, or orgasm.

Prazosin and doxazosin usually do not cause ejaculatory problems but sometimes they do.

After I learned this side effect from that patient, I always inform my male patients of this unique side effect of phenoxybenzamine. Most of them appreciate my warning. Some would say “Doc, sex is the last thing I am thinking of now.” Hey, you never know. Sexual activity is generally not contraindicated in patients with pheo, provided that it is not particularly violent.

Dr. Pheo