Antiplatelet Prescribing After Acute Coronary Syndrome

After acute coronary syndrome, aspirin is combined with a P2Y12 inhibitor to prevent recurrent myocardial infarction and stent thrombosis. Aspirin is given immediately and continued for life. The P2Y12 inhibitor is usually continued for 12 months. Ticagrelor or prasugrel is preferred over clopidogrel when percutaneous coronary intervention is done, and clopidogrel is used when bleeding risk is high, an oral anticoagulant is needed, or the others are unavailable.

Fibrinolysis. Where primary percutaneous intervention is not available, for example in many East African settings, STEMI is often treated with fibrinolysis. Give aspirin and clopidogrel with it.

Gastric protection. Give a proton pump inhibitor to people at high gastrointestinal bleeding risk.

Aspirin. Loading 300 mg chewed (150 to 325 mg), then 75 to 100 mg orally once daily for life. With ticagrelor keep aspirin at 100 mg daily or under.

Ticagrelor. Loading 180 mg orally, then 90 mg twice daily for 12 months.

Prasugrel. Loading 60 mg orally at percutaneous intervention, then 10 mg once daily. Use 5 mg daily if weight is under 60 kg or age is 75 or over, and generally avoid at 75 or over. Contraindicated after previous stroke or transient ischaemic attack.

Clopidogrel. Loading 300 to 600 mg orally, then 75 mg once daily. With fibrinolysis, give 300 mg loading (75 mg if aged over 75 years), then 75 mg daily.

Gastric protection. Pantoprazole 40 mg orally once daily. Avoid omeprazole and esomeprazole with clopidogrel because of reduced activation.

Special groups. In creatinine clearance under 30 mL/min, no adjustment, but bleeding risk is high. In hepatic impairment, avoid ticagrelor and prasugrel in severe disease. In pregnancy, discuss with a cardiologist. In older adults, favour clopidogrel or low-dose prasugrel if bleeding risk is high. In people with thrombocytopenia under 50 x 10^9/L, specialist advice is needed.

Monitoring. Haemoglobin, platelets, creatinine, bleeding symptoms and adherence at each review. Ticagrelor causes dyspnoea in about 1 in 7 people, which is rarely dangerous, and may cause bradycardia.

Interactions. Strong CYP3A4 inhibitors and inducers (ketoconazole, ritonavir, rifampicin, carbamazepine) with ticagrelor, and oral anticoagulants, NSAIDs and SSRIs for bleeding.

Before surgery. Stop clopidogrel 5 days, ticagrelor 3 to 5 days and prasugrel 7 days before elective surgery, after discussion with a cardiologist when a stent is under 6 months old.

Switching. De-escalate from ticagrelor or prasugrel to clopidogrel 75 mg daily for bleeding, cost, or after 1 month in high bleeding risk, with a loading dose of 600 mg if the switch is from ticagrelor in the acute phase.

Stopping. Never stop early without cardiology advice, because of stent thrombosis. Stop only for life-threatening bleeding.

Common errors. Aspirin over 100 mg daily with ticagrelor, omeprazole with clopidogrel, and omitting the P2Y12 inhibitor at discharge.

Referral and escalation. Refer for recurrent chest pain, bleeding on treatment, or need for surgery.