A study evaluating the level of platelet aggregation achieved after switching from Plavix 75 mg once daily maintenance dosing (MD) plus aspirin to Effient 10 mg once daily MD in patients with acute coronary syndrome (ACS) was published in the Journal of the American College of Cardiology. In this Phase II study, ACS patients who were switched to Effient (either 10 mg maintenance dose [MD] or 60 mg loading dose [LD] followed by 10 mg MD) plus aspirin demonstrated a statistically significant greater reduction in maximum platelet aggregation (MPA) after one week when compared with patients who remained on maintenance therapy with clopidogrel.
Platelet aggregation is a critical step in the formation of blood clots, which pose a significant risk to patients following an ACS event, including heart attack and heart-related chest pain. The study provides further evidence to suggest that Effient reduces platelet aggregation to a greater extent among ACS patients compared to Plavix.
Of the 128 patients who completed the study, 100 patients were eligible to be included in the platelet function analysis. After a 10-14 day run in phase with open label clopidogrel 75 mg once daily plus aspirin, patients were randomly assigned to one of the following three treatments: remain on clopidogrel 75 mg plus aspirin for seven days (n=33); switch to prasugrel 10 mg plus aspirin for seven days (n=36); or switch to prasugrel 60 mg loading dose plus aspirin followed by prasugrel 10 mg plus aspirin daily for six days (n=31).
At day seven, MPA (as measured using 20 micromolar ADP) was statistically significantly lower in patients switched to prasugrel 10 mg plus aspirin when compared with the patients who remained on clopidogrel (41.1 percent vs. 55.0 percent, p < 0.0001) and in those patients switched to prasugrel 60 mg LD followed by prasugrel 10 mg MD vs. clopidogrel (41.0 percent vs. 55.0 percent, p < 0.0001).
“These findings are important because they provide new insights into potential differences in the levels of platelet inhibition that can be achieved with dual oral antiplatelet therapy in patients with ACS,” said Dominick J. Angiolillo. “The data showed that Effient plus aspirin may provide additional reduction in platelet aggregation in ACS patients over those taking standard-dose clopidogrel plus aspirin. However, a larger study would be needed to assess the potential impact of switching on cardiovascular outcomes.”
SWAP was a Phase II, multicenter, randomised, double-blind, double-dummy, active-controlled trial evaluating the effects on platelet function after switching patients on daily clopidogrel therapy following an ACS event to daily Effient therapy. Patients were eligible for enrollment if they were between 18 and 75 years of age, presented 30 to 330 days after an ACS event and treated with daily aspirin and clopidogrel. They were excluded if they had any of the following: a planned coronary revascularisation procedure (coronary artery bypass surgery or coronary angioplasty) during the study, high risk of bleeding, history of stroke or mini stroke, or weight of less than 60 kg. Platelet function was evaluated at two hours, 24 hours, seven days and 14 days using three different tests, including light transmittance aggregometry.
