Q. I have a question about Valtrex.

September 14, 2008 at 12:00a.m.

I know this drug is prescribed to treat genital herpes. If someone is exposed to a partner with herpes, will taking Valtrex right away destroy any of the virus that may have been acquired before it has a chance to take hold and become dormant? In other words, can Valtrex be used as sort of a “day after” medication if taken soon enough?

A. We were intrigued by the idea that Valtrex might protect someone against genital herpes, so we asked the manufacturer, GlaxoSmithKline. We learned that GSK has never done a study to investigate this scenario. The company has only done studies in people known to be infected with herpes simplex virus. As a result, there aren’t any clinical data to support the use of Valtrex as a “day after” medication or as a prophylactic drug in uninfected individuals whose sexual partners have genital herpes.

Q. My nails break, crack, split, peel and grow out very slowly. They’re not strong enough to open a soda can.

I take Synthroid for my thyroid, hydrochlorothiazide for blood pressure control, simvastatin for high cholesterol and Prevacid for heartburn. Could any of these affect my nails? Is there anything natural I could take or use to help my sad nails? Nail hardeners seem to make the problem worse.

A. Many things may affect nail health. The proper balance of thyroid hormone has an impact. Cholesterol-lowering drugs such as simvastatin (Zocor) have been linked to nail changes, and so has the acid-suppressing drug lansoprazole (Prevacid).

Avoid nail hardeners, since they may aggravate the situation. Some readers report that taking a dietary supplement called MSM (methylsulfonylmethane), commonly used for arthritis, may be helpful. Others tell us that moisturizing the nails with products such as Elon, Epilyt or almond oil is the ticket.

For more details on these approaches, we are sending you our new guide to Hair and Nail Care with a discussion of nail problems and many natural approaches for improving nails. Anyone who would like a copy, please send $3 in check or money order with a long (No. 10), stamped (59 cents), self-addressed envelope to: Graedons’ People’s Pharmacy, No.H-31, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our Web site: www.peoplespharmacy.com.

Q. I’ve had an odd experience. I’m 66 and in good health, but my eyesight has deteriorated. The ophthalmologist says it’s just because of my age.

When I take Lunesta to go to sleep, the next day my eyesight is crystal-clear and needs no correction — just as if I were 18 again. Then, the following day if I don’t take the sleeping pill, my eyes are so blurry and out of focus I have a hard time even with my glasses.

I only take the Lunesta twice a week. Has anyone else reported this weird occurrence?

A. We have searched the official label information and the medical literature and could find no reference to beneficial effects of Lunesta on vision. Thank you for your fascinating report.

Have you considered the possibility that getting a good night’s sleep makes the difference? If others have noticed an improvement in vision linked to Lunesta, we invite them to report it to our Web site: www.peoplespharmacy.com.

XIn their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of The Vindicator or e-mail them via their Web site: www.PeoplesPharmacy.com. Their newest book is “Best Choices From The People’s Pharmacy” (Rodale Books).