Tuesday, November 27, 2007

The Acetaminophen Blues

Nearly everyone I talk to has a favorite pain-reliever. It isn't always a branded product, and I'd love to conduct an informal survey or track customer buying habits in my store as I couldn't find any data I wanted online, but right now all I have are informal observations. Most of the people I talk to take either ibuprofen or acetaminophen for everyday aches and pains, with a few opting for Aleve or combination products like Excedrin. And they quickly become annoyed if they can't find their favorite product; Excedrin PM and Tylenol PM are identical except for the packaging, and one customer I spoke with yesterday was very certain that there was some other product called Excedrin Migraine PM that was nowhere to be found on our shelves.

Then there are the oddball homeopathy fans who spray diluted capsaicin into their noses when they have a headache. Apparently they even have a formula for prostate trouble. I am having an incredibly difficult time wrapping my brain around the idea of spraying hyperdiluted pepper oil and saw palmetto into your nose because it's stuffy and you're coincidentally having trouble urinating.

I could probably go on about what's wrong with the aforementioned products all day, but that would be silly when I can bring up something that's actually useful.

A lot of patients are a little confused on the whole anti-inflammatory issue. Most of them assume that NSAIDs, the most common OTC anti-inflammatory drugs for oral administration, are automatically better at relieving pain than acetaminophen (or paracetamol if you're on the other side of the pond). And that simply isn't true.

Acetaminophen, hereafter referred to as APAP, is a real miracle drug in a lot of ways. In fact, its mechanism of action is not perfectly understood. It provides pain relief via a slightly different mechanism than NSAIDs; like NSAIDs, it blocks the effect of substances called prostaglandins. Prostaglandins have various short-duration effects on tissues, one of which is to sensitive nerve endings to pain stimuli; in essence, prostaglandins lower the threshold required to make the neurons associated with pain fire. NSAIDs prevent prostaglandins from being formed entirely by blocking the effect of an enzyme called cyclooxygenase, or COX. APAP appears to block prostaglandin synthesis, but not in peripheral tissues; at least one theory suggests that APAP has an effect on the same receptors that the THC in marijuana. I say APAP is a miracle drug because it does this without the side-effects that NSAIDs have, asprin included, and it provides equal pain relief to aspirin milligram for milligram. APAP does not damage the stomach, thin the blood, or affect kidney function. It's very safe at appropriate doses, non-addictive, and it's even okay to use in pregnancy!

Because NSAIDs block the formation of prostaglandins by COX at the site of injury, they provide both relief of inflammation and pain. But for many minor causes of pain, an anti-inflammatory component is unnecessary. At least one study in the American Journal of Sports Medicine suggested that anti-inflammatory effects were not necessarily especially valuable in muscle injuries. In fact, the study compared simple APAP with Merck blockbuster Vioxx and found APAP to be just as effective without causing the poor atheletes to keel over from strokes! (Just kidding about the strokes. Sorta.) And for patients with mild-to-moderate pain due to osteoarthritis, the American College of Rheumatology, recommends APAP as first-line treatment unless significant inflammation is present.

NSAIDs are commonly cited by patients as being better for pain relief, and even a lot of pharmacists will immediately reach for the ibuprofen when it comes to recommending a painkiller, but the pain-relieving component is ultimately more important in many cases than the anti-inflammatory component. And for that, APAP is often just fine. APAP isn't necessarily the best drug for all pain relief; that's something to discuss with your personal healthcare provider. But it's often a good first choice for mild pain, especially since the inflammatory response is a part of wound healing. It's cheap, too, even compared to other pain-relievers, perhaps aside from uncoated aspirin tablets.

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