May 6, 2004 — If your doctor has you on aspirin therapy to prevent heart problems, read this: For heart protection, plain aspirin may work better than enteric-coated aspirin. Coated aspirin may be less potent than plain aspirin, a new study shows.
Doctors have long advised heart patients about aspirin therapy – telling them to take a daily baby aspirin to cut heart attack or stroke risk. A small dose of daily aspirin can reduce the blood’s ability to clot and cause these events. But studies have also shown that up to 30% of people don’t get that benefit.
This study may help explain why, says researcher Dermot Cox, BSc, PhD, a pharmacology professor at the Royal College of Surgeons in Dublin, Ireland, in a news release.
Cox presented his findings at the American Heart Association’s 5th Annual Conference on Arteriosclerosis, Thrombosis, and Vascular Biology being held in San Francisco this week.
Enteric-coated aspirin is becoming easier to find than regular aspirin on store shelves notes Cox. The enteric coating is an acid-resistant coating that doesn’t aggravate stomach ulcers. With the coating, the aspirin is absorbed in the colon rather than in the stomach, he explains.
However, while the protective coating helps ulcer sufferers, it dilutes the aspirin’s effects for everyone else, his study shows. For most people, it’s not a good option for aspirin therapy.
Plain Aspirin vs. Other Aspirin Formulations
In his study, 75 healthy volunteers were randomly assigned to take five different aspirin preparations: a 75-milligram uncoated aspirin, a 75-milligram dose of three different enteric-coated aspirins, and Asasantin (a clot-busting drug that contains 25 milligrams of aspirin) twice a day. Baby aspirin the U.S. comes in 81-milligram pills.
It was a series of mini-studies: All volunteers took one type of aspirin for 14 days. Then they had 14 days without aspirin, to clear the aspirin from their systems. Then they took a different aspirin preparation for 14 days.
Blood samples were taken at the start and end of each aspirin mini-study to measure levels of blood clotting factors. The researchers found that plain aspirin had the best clot-preventing effect, explains Cox. The enteric-coated brands had the worst.