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Dear Dr. Roach • I am a 75-year-old male in excellent health who is sexually active. During my thirties, I was exposed to the herpes virus 2, but recurrences now are extremely rare and mild. Even so, I use a condom during sexual intercourse and also take acyclovir beforehand. How long before intercourse should acyclovir be taken so that it is at high strength? If I take two 400-mg tablets instead of one, will that improve protection? Will acyclovir by itself provide enough protection so that a condom is not necessary? Finally, if my female partner takes acyclovir, will that help increase protection? — Anon.

Answer • There are conflicting answers to your questions, but here is my summary:

People with any history of genital herpes are at risk of shedding infectious virus, which can potentially infect a partner who has never had it. Although people with lesions (such as painful blisters) are much more infectious, people with no symptoms at all can transmit the virus. Many people with genital herpes don’t even know they have it.

Acyclovir, like its more potent cousin, valacyclovir (Valtrex), suppresses viral shedding — but the suppression isn’t complete, and takes about five days for maximum effectiveness. Valacyclovir reduced overall days of shedding (and therefore potential infectivity) from 11 percent of days to 3 percent of days. The studies I found to suppress shedding used acyclovir 400 mg twice daily.

In couples where one person had genital herpes and the other didn’t, chronic suppression did not reduce the likelihood of the uninfected partner getting herpes, but this study was done in people with HIV, who likely have a higher risk of infecting their partner.

Condoms reduce transmission of genital herpes by about 30 percent.

Your partner taking medication to prevent infection (called pre-exposure prophylaxis) makes some sense; however, I could find no good data to show how effective it might be.

Because of these factors, your female partner should understand that despite you doing everything you can, she is still at risk of acquiring genital herpes, so she should be aware of that fact prior to initiating sexual activity.

Dr. Roach Writes • A recent column on nerve pain after shingles (post-herpetic neuralgia) left a lot of questions from readers about alternative ways of treating it. Some of the potentially useful advice I received included using a TENS unit, which uses electrical current to stimulate nerves. Its effectiveness is unproven, but the side effect profile is modest and may be worth a try. One reader suggested lidocaine, given topically through patch or cream. Several small studies have suggested benefit, and one reader found a lot of relief.

Alpha-lipoic acid, an antioxidant that was shown to be beneficial in some people with diabetic neuropathy, was also suggested; I could find no evidence for or against this. Several people recommended acupuncture. A review from 2018 concluded that “acupuncture is safe and might be effective in pain relieving” for people with post-herpetic neuralgia. I did mention the epilepsy drug gabapentin, but other readers wanted to bring attention to the unrelated drug carbamazepine, which has been proven to be useful.

Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.