DEAR DR. ROACH: Do Trimix injections work for erectile dysfunction, and are they safe? — M.B.

ANSWER: Erectile dysfunction is a common problem in men, especially as they get older. It may be a clue to serious disease of blood vessels, but also can represent low testosterone or other abnormal hormone levels, neurological issues or problems with relationships or mental health. If no particular cause is identified, most men are treated with medications like sildenafil (Viagra), which work by improving the blood flow to the penis.

However, these drugs are effective in only about 60 percent of men who use them. For men who do not get a satisfactory result (and it is imperative to take the drugs correctly — for example, Viagra should be taken on an empty stomach one or two hours before planned sexual activity), then it is time to consider second-line treatments, such as vacuum pumps and medicines that men self-inject directly into the penis. Alprostadil is the only Food and Drug Administration-approved injection drug for ED, and it is successful 90 percent of the time.

Trimix is a compounded mixture of alprostadil along with phentolamine and papaverine. I do not prescribe it because of the increased risk of infection with a compounded product, and because it is not clear to me that it is more effective than alprostadil alone.