DEAR DOCTOR K:

I have chronic knee pain. Ibuprofen pills upset my stomach. Would pain relief creams be easier on my gut? And do they work?

DEAR READER:

We often reach for pain relief pills when something hurts. Non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin, ibuprofen or naproxen are popular and effective pain relievers. However, they can cause stomach upset, ulcers and bleeding.

So-called "topical" pain relievers can be applied directly to the skin. There are dozens of these creams, ointments and oils. In theory, medication applied to just a small, painful area should mean fewer side effects than taking a pill. And this does seem to be true. But it's not certain these remedies really work.

So what's out there?

-- Topical NSAIDs include several ibuprofen creams and a gel for osteoarthritis.

Topical NSAIDs produce lower NSAID blood levels than NSAID pills. This translates into fewer stomach-related side effects. However, studies of large numbers of people have not convincingly showed that they effectively relieve pain.

-- Menthol is an active ingredient in most traditional rub-in products, such as Absorbine Jr. and Bengay.

Menthol creates a cooling sensation that diverts our attention from our pain. It's harmless, but it doesn't actually treat pain or inflammation. Nevertheless, that diversion of your attention to the cool sensation may make it feel like you have less pain.

-- Methyl salicylate is related to aspirin. It's an active ingredient in many over-the-counter pain-relief ointments, including some varieties of Bengay. Products that contain methyl salicylate do provide some pain relief.

But there's an important caution: If you are allergic to aspirin or take blood thinners, you should consult a doctor before regularly using topical salicylates.

-- Capsaicin gives chili peppers their spiciness. It's also the active ingredient in several over-the-counter products, including Capzasin HP and Sloan's Liniment.

Capsaicin is supposed to work by numbing your nerve cells so you no longer feel pain. However, the low concentrations of capsaicin in most over-the-counter products make this effect unlikely.

Plus, topical capsaicin stings and burns. People often stop using it because of the unpleasantness of the treatment itself. Still, for some people, the slight burning sensation caused by the capsaicin may divert attention from pain.

One comment about "unproven" pain-relieving creams: They're unproven because scientific studies have not shown that the average patient in a study had improved pain relief. However, there may be some patients in the study who do get pain relief -- who are somehow different from the average patient in the study. So when a patient tells me that she gets relief from a pain-relieving cream, I advise her to keep using it, even if it is "unproven."

Given the effect of NSAID pills on your stomach, I think you should give topical pain relievers a try. They should be easier on your gut. And if you're lucky, they'll relieve your knee pain.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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