Repatha and Clopidogrel Interaction: What Clinicians and Patients Should Know

The direct answer

Evolocumab is a PCSK9 inhibitor injected subcutaneously at 140 mg every 2 weeks or 420 mg once monthly [1]. Clopidogrel is an oral P2Y12 platelet inhibitor; its label covers acute coronary syndrome with aspirin and recent myocardial infarction, recent stroke or established peripheral arterial disease [2].

The Repatha label has no drug-interactions section [1]. The interactions named for clopidogrel involve omeprazole and esomeprazole, strong CYP2C19 inducers, opioid agonists, CYP2C8 substrates such as repaglinide, and drugs that add bleeding risk (warfarin, NSAIDs, SSRIs and SNRIs, other antiplatelets) [2].

What the Repatha label does cover

There is no boxed warning. The single Warning and Precaution is hypersensitivity reactions including angioedema, and a history of serious hypersensitivity reaction to evolocumab or any excipient is a contraindication [1]. No dose adjustment is needed for renal impairment or for mild to moderate hepatic impairment [1].

Evolocumab is eliminated by target binding and proteolysis. Absolute bioavailability is about 72% and the effective half-life 11 to 17 days; age, sex, race and creatinine clearance did not affect its pharmacokinetics [1]. The one exposure note is a drug effect: adults on a high-intensity statin had about 20% lower evolocumab Cmax and AUC, which the label calls not clinically meaningful [1].

Where clopidogrel's interactions actually sit

Clopidogrel is a prodrug switched on in the liver, mostly by CYP2C19 with contributions from CYP1A2, CYP2B6 and CYP3A, into a thiol metabolite that binds platelet receptors irreversibly, so platelets stay inhibited for their 7- to 10-day life span [2]. Clopidogrel's half-life is about 6 hours and the active metabolite's about 30 minutes [2].

The boxed warning is about genetics, not about other drugs. Patients with two loss-of-function CYP2C19 alleles form less active metabolite at recommended doses and have a reduced platelet effect, and the label says to consider another P2Y12 inhibitor in patients identified as poor metabolizers [2].

The named drug interaction is omeprazole and esomeprazole: the label says to avoid them because both significantly reduce clopidogrel's antiplatelet activity. In the label's studies omeprazole did this whether the two were given together or 12 hours apart, and a similar reduction occurred with esomeprazole. Dexlansoprazole, lansoprazole and pantoprazole had less effect [2]. The label says to avoid strong CYP2C19 inducers as a precaution; opioid agonists delay and reduce clopidogrel absorption; and repaglinide exposure rises 3.9- to 5.1-fold because clopidogrel's glucuronide metabolite strongly inhibits CYP2C8 [2].

Bleeding

Bleeding is the adverse reaction the clopidogrel label emphasizes, including life-threatening and fatal bleeding, and active pathological bleeding is a contraindication, as is hypersensitivity to clopidogrel or any component [2]. The label names the combinations that add bleeding risk: warfarin, NSAIDs, SSRIs and SNRIs, and other antiplatelet agents [2].

On the evolocumab side, the label's only Warning and Precaution is hypersensitivity reactions including angioedema, and bleeding is not among its warnings [1].

CYP2C19 poor metabolizers and clopidogrel

About 2% of White patients, 4% of Black patients and 14% of Chinese patients carry two nonfunctional CYP2C19 alleles [2]. In a 40-subject crossover study, active-metabolite Cmax on 75 mg daily at day 5 was 4 ng/mL in poor metabolizers versus 13 in normal and 12 in ultrarapid metabolizers, with lower platelet inhibition [2]. The 2022 CPIC update concluded that intermediate and poor metabolizers on clopidogrel have reduced platelet inhibition and a higher risk of major adverse cardiovascular and cerebrovascular events, and it strengthened its recommendation for intermediate metabolizers [4].