If you shop for aspirin these days, whether for pain relief or to protect your heart, you’ll find that some are "enteric coated," including virtually all low-dose aspirin (except the chewable kind). Enteric-coated aspirin is sometimes labeled "safety coated." For instance, "safety coated for added stomach protection," says the Bayer label. "Safer on the stomach—designed to dissolve safely in the small intestine, not in the stomach," boasts Ecotrin, which employs "safer" or "safely" several times on its package. From this, you may conclude that the enteric coating prevents the stomach bleeding that aspirin can cause. But it’s misleading advertising. Enteric coatings do not reduce the risk of significant stomach bleeding, and they even have some drawbacks.
What enteric does—and doesn’t do
"Enteric" comes from the Greek word for intestine, and an enteric coating does allow aspirin to pass through the stomach to the small intestine before dissolving. Many brands of full-strength aspirin are coated merely to make the tablets easier to swallow (the label will just say "coated," not "enteric coated"). The special enteric coating also does this, but its primary purpose is to prevent the stomach upset and discomfort that aspirin causes in some people. The risk of bleeding is a different issue. Along with its benefits—blocking the effect of certain substances (prostaglandins and thromboxanes) involved in producing pain and inflammation and in blood clotting—aspirin also inhibits the beneficial prostaglandins that protect the stomach lining. It’s this systemic effect, occurring no matter where the aspirin dissolves, that can lead to stomach bleeding.
If people incorrectly think the enteric coating makes aspirin safe or safer, they may take too much of it, and that could lead to additional cases of stomach bleeding, ulcers, and even death in a small percentage of users. The risk of bleeding (and stomach upset) is much smaller with low-dose aspirin, but it still exists.
Problems, known and potential
Another problem: By slowing the dissolving and absorption of aspirin, the enteric coating delays maximum pain relief by as long as three or four hours. The small print on the label of enteric-coated Bayer says this: "Because of its delayed action, this product will not provide fast relief of headaches or other symptoms needing immediate relief." But the labels on most enteric-coated generics do not say this. How many people would buy this aspirin if the ads said "slow relief" in large type?
One more concern: The enteric coating may lessen the ability of aspirin to reduce the risk of heart attacks and strokes. A study published in Circulation in 2013 suggested that those taking low-dose aspirin for heart health should avoid the enteric coating since it may reduce aspirin's ability to inhibit blood clotting. An older Irish study published in the journal Stroke found that the coating reduces the absorption and bioavailability of low-dose aspirin, and thus may be less effective in inhibiting clotting, especially in heavier people. In that study, a 75-milligram enteric tablet (the dose typically used in Europe, similar to the 81-milligram "baby" aspirin used here) was equal in effect to 50 milligrams of uncoated aspirin. Previous studies by this research team had similar findings.
But don’t throw away your enteric low-dose aspirin yet. Other studies have concluded that enteric aspirin is effective at "thinning" the blood, perhaps even as effective as uncoated. In fact, a few of the major studies that showed that low-dose aspirin helps protect the heart used enteric. The problem is, there have been few studies comparing coated and uncoated aspirin, and they don’t always measure aspirin’s effect the same way. And the enteric coatings used by different aspirin makers may act differently.
Does it really matter?
The debate about the effect of enteric coatings may not matter much in practical terms. The fact is, even after years of study, experts still do not know what the "right" dose of aspirin is for heart protection. Many factors come into play, and the optimal dose may vary from person to person. In the case of low-dose aspirin, more does not mean better. The goal is to use the lowest effective dose possible so as to reduce the risk of bleeding. All you need is about 81 milligrams (the amount in "low-dose" aspirin in the U.S., or one-quarter of a standard 325-milligram tablet) a day, though some experts advise 162 milligrams a day or 162 to 325 milligrams every other day. Even lower doses may be effective, though the evidence is limited and inconsistent.
What to do
- Don’t think that enteric-coated aspirin is safer than regular. It needs to be used with the same caution. In fact, enteric-coated aspirin is just as likely to cause stomach bleeding. If you find that aspirin upsets your stomach or gives you heartburn, check with your doctor to make sure your distress isn’t something more serious. If it's important that you continue aspirin therapy, you may be advised to take an H2 blocker or a proton-pump inhibitor (PPI). A 2012 study from Japan found that H2 blockers (such as Axid, Pepcid, Tagamet and Zantac) and PPIs (Nexium, Prevacid, Prilosec) may reduce the likelihood of gastric damage. Interestingly, other research from Japan suggested that cholesterol-lowering statins and some blood pressure medications have a protective effect against peptic ulcers in those taking enteric-coated aspirin.
- For quick pain relief, avoid enteric-coated aspirin. Those simply labeled "coated" or "lightly coated" (not "enteric coated" or "safety coated") are okay, since they do not have delayed absorption. Note: If you take full-strength aspirin or other pain relievers regularly for pain relief, get medical advice.
- Talk to your doctor about low-dose aspirin therapy. It can be a lifesaver, but it isn’t for everyone. Only about one-third of people who should be taking it are doing so, while many of those who are taking it on their own do not need to (because they are at low risk for heart disease) or should not (because they are at high risk for bleeding and/or other complications).
- If you are a candidate for low-dose aspirin, the most important thing is to take it, whatever the coating. All brands of low-dose aspirin, including generics, that we could find are enteric-coated, except for the chewable kind—usually labeled "children’s."It’s okay to take enteric aspirin. It isn’t definite that the enteric coating reduces aspirin’s beneficial effect on blood, and even if it does, the reduced effect is probably sufficient for heart protection. (As we said above, the studies showing that low-dose aspirin protects against heart attacks were done with enteric-coated tablets.) Still, uncoated low-dose aspirin should be made available so consumers have the choice. The only other options are to take chewable low-dose aspirin (preferably with a full glass of water or with food), or cut a full-dose tablet and take one quarter a day or one half every other day.
News about aspirin and ibuprofen: Several studies have suggested that if you take low-dose aspirin to protect your heart, you shouldn’t take ibuprofen (such as Motrin or Advil) or naproxen (such as Aleve) frequently, since they can block the anti-clotting effect of the aspirin. In fact, the Food and Drug Administration (FDA) issued a warning about this, saying that people should get medical advice about the timing of the two drugs. Occasional use of ibuprofen is okay, the FDA suggested, but you shouldn’t take it during the eight hours before or half hour after taking regular (uncoated) low-dose aspirin. Because enteric-coated aspirin takes longer to be absorbed, ibuprofen seems to interfere with it for at least 12 hours, so there’s no clear way to avoid the interaction, according to the FDA.
Originally published in December 2006. Updated April 2013.