My husband and I love grapefruit and eat lots of it in season. We have a tree in our back yard that produces delicious fruit, and we squeeze our own fresh juice.

We both take cholesterol-lowering medication. He’s on Lipitor, and I take Zocor. He also takes Sular to control blood pressure.

We’ve received conflicting information regarding consumption of grapefruit and grapefruit juice while on these medications. One pharmacist said to avoid grapefruit and grapefruit juice. A doctor said just don’t drink more than a liter of grapefruit juice a day. We have been told that waiting several hours eliminates any interaction.

Can you send me any information that will clarify which drugs are affected by grapefruit so I’ll know if we can enjoy our fruit without risking our health?

Before you harvest any more grapefruit, schedule a visit with your doctor. Both Zocor and Lipitor are affected by grapefruit, with blood levels of the medications rising higher than if they were taken with water. This can lead to unanticipated effects, such as muscle pain or weakness.

One glass of grapefruit juice can produce a measurable effect, and it can last for more than 24 hours.

Sular levels are also higher if grapefruit or grapefruit juice is consumed during the same day. Dizziness or flushing could result.

Ask your physician if a noninteracting alternative such as Pravachol or Lescol might be appropriate for lowering cholesterol. Many blood pressure pills are not affected by grapefruit, so perhaps the doctor would be willing to prescribe a different pill. That way you could enjoy grapefruit safely.

We’re sending you our newly revised “Guide to Grapefruit Interactions,” with more information on medications known to be incompatible with grapefruit and solutions for people like you and your husband. Others who would like a copy should send $2 in check or money order with a long (No. 10), stamped, self-addressed envelope to: Graedons’ People’s Pharmacy, No. J-91, P.O. Box 52027, Durham, N.C. 27717-2027.

A couple of years ago vaginal dryness was causing me a lot of discomfort. I am prone to blood clots, so my doctor won’t prescribe oral estrogen.

My new doctor offered Estring, an estradiol vaginal ring that is inserted every three months. It has only 2 milligrams of estrogen and has solved my problem. Please tell others about this approach.

Estring has been available in Sweden since 1993 and in the United States since 1996. The 2-milligram dose of estrogen is very low, and it is released gradually over three months. This approach might solve the problem of vaginal dryness with fewer side effects than oral estrogens.

I get cold sores and was told to take L-lysine daily to help prevent them. I take one pill per day and have not had a cold sore in five months. Is L-lysine dangerous?

L-lysine is an amino acid, a building block for protein. Several studies have shown that it prevents cold sores. It appears quite safe except for those with kidney or liver disease.

Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Write to them in care of King Features Syndicate, 235 E. 45th St., New York, N.Y. 10017, or e-mail them via their Web site, www.peoplespharmacy.com.