Aspirin 150 mg, Clopidogrel 75 mg Tablets

Clopidogrel is an inhibitor of platelet activation and aggregation through the irreversible binding of its active metabolite to the P2Y12 class of ADP receptors on platelets.

Clopidogrel is a prodrug and is metabolized to a pharmacologically active metabolite and inactive metabolites.

Absorption — After single and repeated oral doses of 75 mg per day, clopidogrel is rapidly absorbed. Absorption is at least 50%, based on urinary excretion of clopidogrel metabolites.

Effect of food — Clopidogrel can be administered with or without food. In a study in healthy male subjects when clopidogrel 75 mg per day was given with a standard breakfast, mean inhibition of ADP-induced platelet aggregation was reduced by less than 9%. The active metabolite AUC0-24 was unchanged in the presence of food, while there was a 57% decrease in active metabolite Cmax. Similar results were observed when a clopidogrel 300 mg loading dose was administered with a high-fat breakfast.

Metabolism — Clopidogrel is extensively metabolized by two main metabolic pathways: one mediated by esterases and leading to hydrolysis into an inactive carboxylic acid derivative (85% of circulating metabolites) and one mediated by multiple cytochrome P450 enzymes. Cytochromes first oxidize clopidogrel to a 2-oxo-clopidogrel intermediate metabolite. Subsequent metabolism of the 2-oxo-clopidogrel intermediate metabolite results in formation of the active metabolite, a thiol derivative of clopidogrel. The active metabolite is formed mostly by CYP2C19 with contributions from several other CYP enzymes, including CYP1A2, CYP2B6 and CYP3A. The active thiol metabolite binds rapidly and irreversibly to platelet receptors, thus inhibiting platelet aggregation for the lifespan of the platelet.

The Cmax of the active metabolite is twice as high following a single 300 mg clopidogrel loading dose as it is after four days of 75 mg maintenance dose. Cmax occurs approximately 30 minutes to 60 minutes after dosing. In the 75 mg to 300 mg dose range, the pharmacokinetics of the active metabolite deviates from dose proportionality: 4-fold the dose results in 2.0-fold and 2.7-fold the Cmax and AUC, respectively.

Elimination — Following an oral dose of 14C-labeled clopidogrel in humans, approximately 50% of total radioactivity was excreted in urine and approximately 46% in feces over the 5 days post-dosing. After a single, oral dose of 75 mg, clopidogrel has a half-life of approximately 6 hours. The half-life of the active metabolite is about 30 minutes.

Effect of other drugs on clopidogrel — Clopidogrel is metabolized to its active metabolite in part by CYP2C19.

CYP2C19 inducers — Concomitant use of strong inducers of CYP2C19 results in increased plasma concentration of the active metabolite of clopidogrel and an increase in platelet inhibition.

Rifampin: Co-administration of rifampin 300 mg twice daily for 7 days with 600 mg loading dose of clopidogrel in healthy adults increased the mean AUC and Cmax of clopidogrel’s thiol metabolites by 3.8-fold. Mean inhibition of platelet aggregation at 4 hours post-dose was 34% higher in the presence of rifampin compared to clopidogrel administered alone.

CYP2C19 inhibitors — Concomitant use of certain inhibitors of this enzyme results in reduced plasma concentrations of the active metabolite of clopidogrel and a reduction in platelet inhibition.

Proton pump inhibitors (PPI) — The effect of proton pump inhibitors (PPI) on the systemic exposure to the clopidogrel active metabolite following multiple doses of clopidogrel 75 mg evaluated in dedicated drug interaction studies is presented in Figure 1.

Pharmacodynamic and pharmacokinetic parameters measured in these studies showed that the interaction was highest with omeprazole and least with dexlansoprazole.

Opioids — Co-administration of 5 mg intravenous morphine with 600 mg loading dose of clopidogrel in healthy adults decreased the AUC and Cmax of clopidogrel’s thiol metabolites by 34%. Mean platelet aggregation was higher up to 2 to 4 hours with morphine co-administration.

Aspirin inhibits cyclooxygenase and reduces prostaglandin production. The cited product information links this pathway to analgesic, antipyretic, anti-inflammatory and platelet effects.

For the cited dispersible-tablet reference, plasma peaks occur about 20–30 minutes after dissolution and overall bioavailability is approximately 70%. Aspirin is converted to salicylic acid, then to further metabolites that are eliminated through the kidneys. Reported half-lives are about 15–20 minutes for aspirin and 2–3 hours for salicylic acid. These estimates do not describe enteric-coated absorption or salicylate overdose.