TUESDAY, Sept. 1, 2009 (HealthDay News) -- Antacids don't interfere with anti-clotting drugs such as Plavix and Effient in patients who have suffered a heart attack or unstable angina, a new study finds.
The results counter other studies that concluded that a class of antacids known as proton pump inhibitors (PPIs) could block the effect of anti-clotting drugs. Doctors often prescribe PPIs along with anti-clotting drugs to reduce the risk of gastrointestinal bleeding.
"The current findings provide some reassurance to clinicians that PPIs and clopidogrel [Plavix] can be safely combined in patients in whom there is a strong indication to use both drugs," said lead researcher Dr. Michelle O'Donoghue, an investigator in the TIMI Study Group at Brigham and Women's Hospital in Boston.
As to why the findings differ from earlier results, O'Donoghue said the answer may lie in the patients themselves and in the type of data analyzed.
"Patients who are treated with a PPI may differ quite markedly from other patients," she said. "In particular, there is concern that PPIs are often administered to sicker patients and that this may help to explain why patients on a PPI seem to do more poorly than other patients."
In the current study, the researchers adjusted for these differences, O'Donoghue said.
"Another advantage of the current study is that it was done within the confines of a clinical trial," she said. "In a clinical trial, all endpoints are strictly defined and adjudicated so there may be less of a risk for bias."
The report is published in the Sept. 1 online edition of The Lancet, to coincide with the presentation of the results Monday at the European Society of Cardiology Congress in Barcelona.
For the study, O'Donoghue's group looked at the effects of PPIs like Prilosec in two trials, the TRITON-TIMI 38 trial and a smaller trial. In the TRITON-TIMI 38 trial, researchers randomly assigned 13,608 patients to clopidogrel (Plavix) or prasugrel (Effient) after having a heart attack or unstable angina.
Giving the PPIs in combination with anti-clotting drugs did not increase the risk of death, heart attack, or stroke, the researchers concluded.
"We did not find use of a PPI to be associated with a higher risk of cardiovascular events for patients taking either clopidogrel or prasugrel," O'Donoghue said.
Dr. Dirk Sibbing, from the Technische Universitat Munchen in Germany and co-author of an accompanying commentary, said this study shows that PPIs affect the anti-clotting drugs, but not patient outcomes.
"It seems that patients who carry a risk profile comparable to that of patients enrolled in TRITON-TIMI 38 can be safe on PPI treatment as long as compliance to regular anti-platelet drug intake is well-controlled," Sibbing said.
However, cautions should remain for high-risk patients and those who are less responsive to Plavix, Sibbing said. Also, he said he believes that for some patients taking Effient and PPIs, the combination may be harmful, he said.
"In any case, monitoring of compliance to anti-platelet treatment is mandatory in all patients, but specifically in the group of patients under concomitant PPI treatment," Sibbing said.
"Specific studies, however, are warranted in this group of patients to clarify this issue," he said.
O'Donoghue doesn't disagree. "In the end, only a randomized clinical trial can definitively demonstrate the safety of combining these two classes of drugs," she said.
For more information on heart attacks, visit the U.S. National Heart, Lung, and Blood Institute.