indication

Indicated in combination with acetylsalicylic acid (ASA) to prevent atherothrombotic events in patients with acute coronary syndrome (ACS) who are to be managed with percutaneous coronary intervention (PCI). May be used in patients with unstable angina (UA), non-ST elevation myocardial infarction (NSTEMI), ST-elevation myocardial infarction (STEMI) who are to be managed with PCI. Prasugrel is not recommended in patients 75 years of age or greater due to increased risk of fatal and intracranial bleeding.

pharmacology

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.

mechanism of action

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.

toxicity

LD50 (rat) 1,000 - 2,000 mg/kg; LD50 (rabbit) > 1,000 mg/kg

biotransformation

Prasugrel is not detected in plasma following oral administration. It is rapidly hydrolyzed in the intestine to thiolactone, which is further metabolized to its active metabolite 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.

absorption

79% or greater of the dose is absorbed after oral administration. Absorption and metabolism occur rapidly and peak plasma concentrations (C_max) are reached approximately 30 minutes following oral administration. Administration with a high fat, high calorie meal did not affect the AUC of the active metabolite in healthy individuals, but the C_max was decreased by ~49% and the T_max was increased to 0.5 to 1.5 hours. Prasugrel may be administered with or without food.

half life

The active metabolite has an elimination half-life of about 7.4 hours (range 2-15 hours).

route of elimination

Approximately 68% of the orally administered dose is excreted in urine and 27% in the feces, as inactive metabolites. The active metabolite is not expected to be removed by dialysis.