Comparison of Prasugrel and Ticagrelor Loading Doses in ST-Segment Elevation Myocardial Infarction Patients: RAPID (Rapid Activity of Platelet Inhibitor Drugs) Primary PCI Study

Study Questions:

What is the comparative degree of platelet inhibition of prasugrel and ticagrelor in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PPCI)?

Methods:

Fifty patients with STEMI undergoing PPCI with bivalirudin monotherapy were randomized to receive 60 mg prasugrel loading dose (LD) (n = 25) or 180 mg ticagrelor LD (n = 25). Residual platelet reactivity (RPR) was assessed by VerifyNow at baseline and 2, 4, 8, and 12 hours after LD.

Results:

Platelet reactivity units (PRUs) 2 hours after the LD (study primary endpoint) were 217 (12-279) and 275 (88-305) in the prasugrel and ticagrelor groups, respectively (p = not significant), satisfying prespecified noninferiority criteria. High RPR (PRU ≥240) was found in 44% and 60% of patients (p = 0.258) at 2 hours. The mean time to achieve a PRU <240 was 3 ± 2 and 5 ± 4 hours in the prasugrel and ticagrelor groups, respectively. The independent predictors of high RPR at 2 hours were morphine use (odds ratio, 5.29; 95% confidence interval, 1.44-19.49; p = 0.012) and baseline PRU value (odds ratio, 1.014; 95% confidence interval, 1.00-1.03; p = 0.046).

Conclusions:

The authors concluded that in patients with STEMI, prasugrel was noninferior as compared with ticagrelor in terms of RPR 2 hours after the LD.

Perspective:

This study reported that in patients with STEMI, prasugrel was noninferior as compared with ticagrelor in terms of RPR 2 hours after the LD. Both drugs appear to provide an effective platelet inhibition 2 hours after the LD in only half of the patients, and at least 4 hours are required to achieve an effective platelet inhibition in the majority of patients. Also, morphine use is associated with a delayed activity of these agents. Despite some limitations, this pilot study provides some unique and potentially important insights in the treatment of STEMI patients by PPCI, but requires more rigorous prospective validation.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Novel Agents

Keywords: Myocardial Infarction, Platelet Aggregation Inhibitors, Biological Markers, Sulfhydryl Compounds, Percutaneous Coronary Intervention


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