Prasugrel is an thienopyridine which inhibits ADP receptors by irreversibly acting on the P2Y12 receptor on platelets. The active metabolite of prasugrel prevents binding of adenosine diphosphate (ADP) to its platelet receptor, impairing the ADP-mediated activation of the glycoprotein GPIIb/IIIa complex. Prasugrel is proposed to have a similar mechanism of action to clopidogrel.
Prasugrel is a member of the thienopyridine class of ADP receptor inhibitors, like ticlopidine (trade name Ticlid) and clopidogrel (trade name Plavix). These agents reduce the aggregation ("clumping") of platelets by irreversibly binding to P2Y12 receptors. Compared to clopidogrel, prasugrel inhibits adenosine diphosphate–induced platelet aggregation more rapidly, more consistently, and to a greater extent than do standard and higher doses of clopidogrel in healthy volunteers and in patients with coronary artery disease, including those undergoing PCI. The increased potency of prasugrel appears to be due to more efficient conversion to its active metabolite. However, it carries a higher risk of bleed compared to clopidogrel, which may be a result of its higher potency.
Prasugrel is not detected in plasma following oral administration. It is rapidly hydrolyzed in the intestine to thiolactone by human carboxylesterase (hCE) 2. This intermediate is further metabolized to its active metabolite, R-138727, in a single step by cytochrome P450 enzymes in the liver (primarily CYP3A4 and CYP2B6 and to a lesser extent by CYP2C9 and CYP2C19). The active metabolite is further metabolized by S-methylation or cysteine conjugation to two inactive metabolites. Unlike clopidogrel, transformation of prasugrel to its active metabolite does not appear to be affected by cytochrome P450 polymorphisms.
LD50 (rat) 1, 000 - 2, 000 mg/kg; LD50 (rabbit) > 1, 000 mg/kg