Dipyrone negates aspirin's antiplatelet effect

(HealthDay)—There is an unfavorable pharmacological drug interaction between the non-narcotic analgesic dipyrone and aspirin in patients with coronary artery disease (CAD), according to research published online Aug. 14 in the Journal of the American College of Cardiology.

Amin Polzin, M.D., from the Heinrich Heine University Medical Center in Düsseldorf, Germany, and colleagues studied three subgroups of CAD patients with optimal medical therapy according to current guidelines. Group A included 10 CAD patients in whom aspirin had been withdrawn because of scheduled cardiac surgery; group B included 20 CAD patients taking aspirin; and group C included 36 patients with a co-medication of aspirin/dipyrone. Seventy-five percent of patients in groups B and C were on dual antiplatelet therapy with clopidogrel. Platelet function was measured by arachidonic acid-induced light-transmission aggregometry and thromboxane B₂-formation by immunoassay.

The researchers found that patients not taking aspirin had effective platelet aggregation. In group B patients, thromboxane formation was nearly completely inhibited. Patients in group C restituted arachidonic acid-induced thromboxane formation to levels sufficient for complete restoration of platelet aggregation; an impaired aspirin effect was seen in half of group C's co-medicated patients.

"Dipyrone co-medication in CAD patients can completely blunt the antiplatelet effects of aspirin," the authors write.