Q: For some time now, the nails on my big toes have been yellow, rough and thickened. My doctor told me this was due to a fungus and that I should apply an antifungal cream after bathing. But when I read the directions on all the over-the-counter antifungal products, they say they aren't effective for curing nail fungus infections. Do you know of any medicine that will cure toenail fungus?

A: The reason those antifungal creams don't claim to be effective for nail fungus infections is that this condition can be very difficult to get rid of.

Fungal nail infections are a stubborn but painless nail disorder. They occur more frequently in people with lowered resistance to infection, such as people with diabetes or those taking steroid medicines for long periods. But they often occur in otherwise healthy people. Having your hands in water a lot of the time can make you prone to this problem.

The infection discolors the nail and makes it thick, misshapen and brittle. Sometimes jagged edges dig into the surrounding skin, causing a red, painful bacterial infection known as a paronychia (meaning adjacent to the nail). Although a fungal nail infection can usually be diagnosed by the way it looks, a small scraping of material from under the nail is used to confirm the diagnosis and make sure it will respond to treatment.

Topical creams applied to the nail usually don't clear the infection. The most effective treatment is taking griseofulvin, an oral antifungal medicine, usually for many months, while the new nail grows out. For fingernails this takes four to six months, and toenails up to 12 months or longer. (Nails grow faster in the summer than in the winter.)

Your doctor may remove part of the nail, either by minor nail surgery or by applying urea, a nail-dissolving ointment, to speed treatment and allow you to use topical antifungal creams.

Because oral treatment is sometimes unsuccessful and has potential side effects, doctors will often advise not treating the condition, especially if it involves just the toenails, unless you are really bothered by it.

Q: I've been diagnosed as having a benign heart problem known as premature ventricular contractions (PVCs). My doctor assures me that my condition is not serious, but when attacks occur I become panicky and lightheaded. What does this condition mean in terms of my health? Will I eventually need a pacemaker? Why do these attacks occur at rest, when I'm under no stress?

A: PVCs are an extremely common irregularity of your heartbeat. Practically everyone has them from time to time, although most people don't know that they're having them. Their most common sympton is sensation of a skipped heartbeat or a fluttering feeling in your chest.

PVC stands for premature ventricular contraction, meaning a heartbeat that occurs sooner than it should. In most people they're harmless, but in some people they cause distressing symptoms, such as you're having, and in a minority of people they're a sign of a serious heart problem.

Depending on your symptoms and other medical conditions, your doctor may want to use one or more tests to decide how serious your PVCs are:

*An electrocardiogram (EKG), a tracing of your heartbeat.

A Holter monitor, which is a long recording, usually for 24 hours, of your heartbeat.

*A stress test, which is basically an EKG taken while you are exercising. If your PVCs become worse during this test, that could point to an underlying heart condition like hardening of the arteries (atherosclerosis).

*An echocardiogram, which takes a picture of your heart using sound waves, and looks for abnormalities that could produce PVCs.

*A coronary angiogram, an X-ray of your heart's circulation looking for blockages in the arteries that feed the heart.

*Heart pacing studies, which examine the electrical circuits of your heart using a catheter inserted through an artery and positioned in the heart.

If tests show that your PVCs are the kind that are likely to worsen into serious irregularities of your heartbeat, you should probably have treatment for them. I say probably because it's uncertain whether treating everyone with PVCs due to heart disease actually prevents fatal arrhythmias -- heart rhythm disruptions that make the heart unable to pump enough blood.

Heart pacemakers are not used to treat ordinary PVCs, so I don't think you'll need one for your present condition. Pacemakers are most often used for problems with a heartbeat that's too slow or one that momentarily stops beating.

Although stress can provoke PVCs, they can also occur when you're relaxed. Stress, smoking, alcohol and caffeine all can increase the amount of PVCs you're having, so cutting down or avoiding these triggering factors may help.

Because you're having symptoms of frequent PVCs, it's important to see if there's anything serious causing them, and to try one of several medications used to treat them.