Q: I’ve never seen this subject addressed in your column, and hope it is not taboo. My husband had one problem that Viagra addressed, but now he cannot ejaculate.

I’ve read that ejaculating at least once a week keeps the prostate healthy. It’s been more than a year since this problem started, and frankly, I”m concerned. The family physician brushed it off with no explanation or referral. Is this a side effect of Viagra? Or could it be it a symptom of something else?

A: The official prescribing information for Viagra notes that “abnormal ejaculation” has been reported, although it appears to be uncommon.

Factors that affect ejaculation include diabetes, changes in hormone levels, surgery, spinal cord injury and certain medications. Some drugs that are associated with ejaculation difficulties include Celexa, Effexor, Flomax, Normodyne, Prozac, Lipitor and Proscar.

Your husband should see a urologist to rule out any medical problems. As far as we can tell, there’s no evidence that failing to ejaculate will put your husband’s prostate at risk.

Q: I have recently been prescribed Adalat for high blood pressure, and I am confused about whether I can continue drinking grapefruit juice, which I love. On the pill bottle it says not to eat grapefruit for two hours after taking the pill.

I’ve gotten the impression that I could never have grapefruit or its juice again while I am taking this medication. When I asked my pharmacist, she said don’t drink more than a liter of grapefruit juice a day. Which is right not more than a liter, not within two hours, or not at all?

I also take atenolol and Mevacor. Does grapefruit have any effect on these medicines? What does it do? I’d appreciate any information you have.

A: Two of your medications, Adalat and Mevacor, are subject to the “grapefruit effect.” You could have higher blood levels of the drugs if you drink grapefruit juice while you take these medicines. That could increase the risk of side effects.

The grapefruit effect lasts all day; the label advising against drinking grapefruit juice within two hours is misleading.

People vary in their vulnerability to the grapefruit effect, but a glass or two of grapefruit juice could trigger an interaction in a susceptible person. To help you sort out all these questions, we’re sending you our Guide to Grapefruit Interactions, which provides more details and lists many drugs that interact with grapefruit.

Q: I’m trying to locate an arthritis rub called Naprosyn Gel. I bought it in Italy last year, but it is not available in the United States.

Could you recommend something similar that might work as well as this product?

A: The Food and Drug Administration has not approved topical anti-inflammatory drugs in the United States, even though they are very popular elsewhere in the world. In many countries, Feldene Gel, Naprosyn Gel, Orudis Gel and Voltaren Emulgel are sold for sprains, tendinitis or sports injuries. If your doctor wrote you a prescription, a compounding pharmacist in the United States could make you something comparable.