Take Two Aspirin . . . Or Is It Just One?

Aspirin comes in many dosages and they have varied a lot over time

What’s the best dose of aspirin to take in order to prevent a heart attack? Which dose do you use to prevent a stroke? What if you’re on low-dose aspirin already and suffer a heart attack? Do you switch to the higher dose? What about after a stent? Or coronary bypass surgery?

Most of you know already that aspirin comes in several doses (according to my PDA-based prescription drug reference it’s available in 5 doses between 81 and 650 milligrams) but in the cardiology world we mainly use the “baby” aspirin at 81mg or the “full-strength” at 325mg.

Years ago aspirin was the mainstay for treatment of arthritis. This was of course before better painkillers and anti-inflammatory drugs came along, like ibuprofen, naproxen and acetaminophen (Tylenol). The doses used back in the day were quite high by today’s standards. It was not uncommon for someone to be on 3000mg a day or more, doses high enough to induce the classic toxic effects of ringing in the ears, hyperventilation and acidosis. The most problematic complication was gastrointestinal bleeding. Aspirin exerts several effects on the protective lining of the stomach that can lead to local erosion, ulceration and even life-threatening perforation.

These days such side effects are far less common, but even when taking lower doses patients are still at higher risk of developing an ulcer on aspirin than they would be otherwise. It is for this reason that physicians and patients frequently try to use the lowest dose of aspirin that is effective.

We use aspirin to inhibit the formation of clots where we don’t want them to occur. Heart attacks and strokes happen when a clot—composed of platelet cells and glue-like proteins—either travels to and lodges in a critical vessel or arises there spontaneously. Blocking platelet function can decrease the chance that a vessel becomes suddenly obstructed.

Lick two aspirin and call me in the morning

I have found that many cardiologists, neurologists, internists and family doctors have strong opinions regarding which dose of aspirin a patient should be taking. In order to provide a bit of expert context for this subject I consulted with an old friend of mine, Dr. Steven R. Steinhubl, who just happens to be one of the world’s foremost experts on the subject of arterial clot formation and medications used to block platelets. I reached him in Switzerland and he was kind enough to provide the briefest tutorial on the subject I’ve ever heard:

“Aspirin, the most commonly used drug worldwide for the prevention and treatment of heart disease today, was first shown to be beneficial as a blood thinner less than 30 years ago. However it was 100 years ago when Bayer first introduced a 5-grain (approximately 325 milligrams—today considered an adult dose of aspirin) aspirin pill in response to counterfeiters of aspirin powder. Twenty years later the 81mg “baby” aspirin was developed to be one-quarter the size of the adult strength. It wasn’t until almost fifty years later, following the Nobel Prize-worthy discovery identifying how aspirin inhibited platelets, that it was eventually found that only 30mg to 50mg of aspirin per day is required to fully inhibit platelets. In fact, Sir John Vane, the Nobel Prize-winning scientist, is often credited with saying that it is necessary to only lick an aspirin every day to achieve its full benefit. Despite this, 325mg remains commonly recommended, especially by cardiologists. This appears to be mainly out of habit, as clinical trial data have consistently found no benefit but a higher incidence of stomach problems in patients receiving higher doses of aspirin. Today, for patients in whom it is recommended to take a daily aspirin, an 81mg “baby” aspirin is all that’s needed.”

Dr. Steinhubl also referenced a review article he co-authored in JAMA that expands on his thesis and summarizes all the research data on the subject.

So there you have it from the experts. From now on I guess I can simply say “Lick two aspirin and call me in the morning.”