Opioids delay gastric emptying and the absorption of many oral drugs, including the P2Y₁₂ inhibitors clopidogrel (Plavix, and generics), prasugrel (Effient, and generics), and ticagrelor (Brilinta), which are commonly used for initial treatment of acute coronary syndrome (ACS). An article in our February 25, 2019 issue reviewed studies showing that coadministration of opioids delayed and decreased absorption of oral P2Y₁₂ inhibitors and increased platelet reactivity. Recently published clinical outcomes data may add to these concerns.

The FDA has required manufacturers of the oral P2Y₁₂ platelet inhibitors clopidogrel (Plavix, and generics), prasugrel (Effient, and generics), and ticagrelor (Brilinta) to warn in the product labels that the absorption of these drugs may be delayed or reduced when taken with an opioid agonist.

The FDA has approved cangrelor (Kengreal – The Medicines Company), an IV P2Y12 platelet inhibitor, as an adjunct to percutaneous coronary intervention (PCI) in patients who have not been pretreated with a P2Y12 inhibitor and are not being given a glycoprotein IIb/IIIa inhibitor.

Antiplatelet drugs are the drugs of choice for prevention and treatment of arterial thrombosis. Anticoagulants are the drugs of choice for prevention and treatment of venous thromboembolism and for prevention of cardioembolic events in patients with atrial fibrillation.

The FDA has approved vorapaxar (Zontivity – Merck), an oral protease-activated receptor-1 (PAR-1) antagonist, for use with aspirin and/or clopidogrel to reduce the risk of thrombotic cardiovascular events in patients with peripheral arterial disease or a history of myocardial infarction (MI). It is the first PAR-1 antagonist to be approved by the FDA.

Arterial thrombi are composed mainly of platelet aggregates held together by small amounts of fibrin. Antiplatelet drugs are the drugs of choice for prevention and treatment of arterial thrombosis, but anticoagulants are also effective, and their effects can add to those of antiplatelet drugs. Venous thrombi are composed mainly of fibrin and trapped red blood cells, with relatively few platelets. Anticoagulants are the agents of choice for prevention and treatment of venous thromboembolism and for prevention of cardioembolic events in patients with atrial fibrillation.

The FDA has approved ticagrelor (Brilinta – AstraZeneca), an oral antiplatelet drug, for use with low-dose aspirin to reduce the rate of thrombotic cardiovascular events in patients with acute coronary syndrome (ACS). It will compete with clopidogrel (Plavix) and prasugrel (Effient) for such use. Clopidogrel is expected to become available generically in the US within the next few months.

The FDA has required the manufacturer of Plavix, an antiplatelet drug used in addition to aspirin to prevent cardiovascular events in high-risk patients,1 to add a boxed warning to the package insert about the risk of a poor response to the drug in patients with genetic polymorphisms of the cytochrome P450 enzyme CYP2C19. Clopidogrel is a prodrug and CYP2C19 is mainly responsible for its bioactivation. The Medical Letter reported last year that several studies have found higher rates of cardiovascular events, including stent thrombosis, in patients with these polymorphisms taking clopidogrel.2

At least one genetic polymorphism leading to poor metabolism of clopidogrel has been reported to occur in 15% of Caucasians, 17% of African Americans and 30% of Asians.3 Since many patients take clopidogrel to protect against life-threatening events, and some continue to do so for extended periods of time, it might be worthwhile to test for these polymorphisms. Such tests, requiring small amounts of blood or saliva, are commercially available from clinical laboratories. More directly, patients who are taking clopidogrel could have platelet aggregation assays to determine whether the drug is being activated.

However, the best course of action for patients who prove to be poor metabolizers of clopidogrel is not clear. They could be treated with higher doses of clopidogrel, but the doses that would be safe and effective in such patients have not been established. Alternatively, they could be treated with prasugrel (Effient), a similar antiplatelet drug that does not require CYP2C19 for activation, instead of clopidogrel, but prasugrel has a greater effect on platelets and may cause more bleeding.4

1. Antiplatelet and anticoagulant drugs. Treat Guidel Med Lett 2008; 6:29.
2. PPI interactions with clopidogrel revisited. Med Lett Drugs Ther 2009; 51:13.
3. Z Desta et al. Clinical significance of the cytochrome P450 2C19 genetic polymorphism. Clin Pharmacokinet 2002; 41:913.
4. Prasugrel (Effient) vs. clopidogrel (Plavix). Med Lett Drugs Ther 2009; 51:69.

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The FDA has approved prasugrel (Effient - Lilly/Daiichi Sankyo), an oral antiplatelet drug, for use with aspirin to reduce the rate of thrombotic cardiovascular events in patients with acute coronary syndromes (ACS) being managed with percutaneous coronary intervention (PCI). It will compete with clopidogrel (Plavix) for such use.