DEAR DR. DONOHUE: I suffer from sciatica. Do steroid injections for it work? Could you overdose? Any additional information on this painful condition will be appreciated. – F.G.

Somewhere between 50 percent and 80 percent of the population will visit a doctor at least once in their life because of back pain. And much of that pain can be pinned on sciatica, an irritation of the sciatic nerve.

The sciatic nerve is the body’s longest nerve. It begins in the lower back where nerve roots – springing from the spinal cord – intertwine to form the nerve. It runs all the way down to the foot. Pressure on the nerve, at any place, causes pain. Usually, the pressure is in the back, and often the pain is felt not only in the back but also down the leg or legs.

Disks are soft shock absorbers inserted between backbones. A protruding disk, one whose gelatin core sticks through its rim, can impinge on sciatic nerve roots and irritate the nerve. Often that condition comes with aging. Bone spurs and thick ligaments also can compress the sciatic nerve and produce pain.

Steroid (cortisone) injections can quiet the inflammation that comes from nerve irritation and can lessen pain. An injection three or four times a year is safe, and the effects generally last that long.

Simple medicines like Aleve, Motrin or Advil can also ease inflammation and pain. Hot packs or cold packs to the back might work. You have to see which gives you greater relief. They’re left on for 20 minutes and applied three times a day.

Physical therapists can devise exercises to strengthen your back and stretch it to give the nerve breathing room. Stay as active as you can. Sitting is harder on the back than is standing, so take some “standing or walking” breaks if you’re sitting for any length of time.

The back booklet deals with the many causes of back pain and their treatments. Readers can obtain a copy by writing: Dr. Donohue – No. 303, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: This is my third letter! I take Atacand, Norvasc and hydrochlorothiazide every day. I also take vitamins, and now I have been taking Advanced Artery Solution. Am I creating a problem by combining the vitamins with these medicines? – L.L.

ANSWER: Your three medicines are blood pressure medicines. All work on blood pressure in different ways. Atacand counters the action of a body-produced, artery-constricting substance called renin. Norvasc stops calcium from constricting arteries. Hydrochlorothiazide is a water pill that takes excess fluid and salt from the body.

Vitamins don’t work against any of these medicines.

I searched long and hard on the Internet to find what’s in Advanced Artery Solution and couldn’t find the information. I can’t answer that part of your question. If you want to send me a label that lists its ingredients, I’ll give you an answer. Staple the label to your letter.

DEAR DR. DONOHUE: Through an e-mail from a friend, I have become aware of a test for women that is comparable to the PSA test for men’s prostate cancer. It is called CA-125. Will you provide information on this test and when women should have it done on a regular basis? – D.G.

When it first came into use, CA-125 was hoped to be a reliable test for screening women for ovarian cancer. It has turned out not to be such a reliable test. Too many other conditions return a positive result. Even healthy women can have a positive test.

It is useful for following a woman who is being treated for ovarian cancer to detect any recurrence. And it is useful for screening women at high risk for ovarian cancer. It is not suggested for general screening, however.

DEAR DR. DONOHUE: I received the results of my DEXA bone density test, and it shows that my results are 6 percent worse than they were two years ago. What can I do to prevent further loss of bone density? My 82-year-old mother has osteoporosis.

I work out at a gym three times a week, doing both aerobics and weight training. I have been taking calcium citrate and vitamin D for at least five years. Three years ago, I was treated for breast cancer and am now on a regimen of Tamoxifen. Could that have anything to do with my bone loss? – E.H.

You’re following the experts’ advice in doing all the things to keep bones from developing osteoporosis. By all rights, you should have strong bones.

What’s your T-score? It’s on the report. If the T-score is less than -2.5 (minus 2.5), you have osteoporosis. If it’s between -1 and -2.5, you have osteopenia – bones that are not exactly normal, but they don’t qualify as being osteoporotic. I can’t tell if that 6 percent change throws you into the osteoporosis category.

Perhaps your doctor will put you on medicines to keep calcium in your bones. The bisphosphonates are the most successful medicines for doing that. Some names are Fosamax, Actonel and Boniva.

Your Tamoxifen, a medicine that prevents breast cancer recurrence, doesn’t accelerate osteoporosis. It provides protection from it.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from