DEAR DR. DONOHUE: At age 17, my son still wets the bed at night. We have always kept our son in a safe environment, and I have questioned him about the possibility of abuse in his younger years. No such thing happened. He is a well-balanced, well-mannered, good student who plays football, baseball and basketball and runs track. He is well-liked by male and female peers.

We have had him examined by a pediatric urologist three times. The doctor gave him some pills, but my son does not like to take medicine. The doctor told him not to drink liquids for two hours prior to bedtime, but that is hard for a teenager to follow. He is a deep sleeper. What other steps can we take? – H.H.

Your son is an extremely well-adjusted adolescent, even in the face of a problem that must be a source of embarrassment to him.

By age 5, only 7 percent of boys and 3 percent of girls wet the bed. By age 10, the percentage drops to 3 for boys and 2 for girls. By age 18, 99 percent of boys no longer wet the bed, and close to 100 percent of girls remain dry throughout the night.

Although the ban on fluids before sleep might be hard, your son ought to try it and see what the results are. The same goes for medicines. Tofranil could be the answer to his problem. He should try it. DDAVP is another medicine that comes in a nasal spray or as a tablet and can be used on special occasions when the boy must sleep outside the home.

Even though there is not a strong connection between foods and bed-wetting, see what happens if he stops consuming milk products, chocolate and citrus fruits.

He is not too old for an alarm system that wakens a child from sound sleep when it detects the first few drops of moisture.

At this juncture, it is worthwhile to seek an opinion from a nearby medical school’s urologists. They might come up with the answer.

DEAR DR. DONOHUE: I am an 86-year-old female. I have been advised to take glucosamine and chondroitin for arthritis in my right hip. After a month, I had more pain than before, so I stopped taking the capsules. Do you believe that they can help arthritis? – M.C.

I am limiting my remarks to osteoarthritis, the common kind of arthritis and the kind frequently found in older people.

About 13 studies on the efficacy of glucosamine have shown it alleviates some people’s arthritic pain. Four studies failed to show any effectiveness for it. Glucosamine plays a role in cartilage formation and repair. In osteoarthritis, joint cartilage crumbles.

There are fewer studies done on chondroitin. It too is a component of cartilage, and it keeps cartilage elastic.

I might give the pills one more month on trial.

The definite answer to your question will soon be coming. The National Institutes of Health is conducting a study on these products, and the word should be out shortly.

DEAR DR. DONOHUE: Is it true that shrimp is a big problem for cholesterol? Some of my friends say it is OK to eat small amounts every day, but others say it is better not to eat shrimp at all. Your opinion, please. – L.L.

Ounce for ounce, shrimp has more cholesterol than meat. Shrimp lovers, don’t despair; good news is about to come.

Shrimp has a very low concentration of saturated fat. Saturated fat raises blood cholesterol higher than does cholesterol in foods. Furthermore, some investigators say shrimp cholesterol is poorly absorbed.

Shrimp also contains omega-3 fatty acids, magical stuff that protects arteries from clogging with cholesterol.

Go ahead. Munch on shrimp without fear.

DEAR DR. DONOHUE: Six months ago I saw my doctor, who pronounced me as being healthy. One month later I had a heart attack. How could I be given a clean bill of health and then have a heart attack within a few weeks of being pronounced fit? – D.A.

Medicine is not an exact science, even though we would like to believe it is. Nor does medicine have perfect tests to uncover all hidden illnesses.

A large number of people have clogged heart arteries without having any pain. Furthermore, an ECG can look normal when blood is not briskly flowing through heart arteries, but only trickling.

With no symptoms that indicate trouble is brewing, such as the chest pain of angina, doctor and patient can be misled.

Your experience shows how pain can be a blessing. It is a warning that all is not well, and then steps can be taken to address the cause of the pain.

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.

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