Ticagrelor and primidone interaction masquerading as dual antiplatelet therapy noncompliance

Ticagrelor and aspirin is a common dual antiplatelet therapy regimen for patients who undergo percutaneous coronary intervention. Despite its ability to significantly reduce cardiovascular complications, ticagrelor response may be altered by other medications causing subtherapeutic effects. Traditionally, ticagrelor is thought to have fewer drug-drug interactions compared to other thienopyridine antiplatelet medications such as clopidogrel. Primidone, metabolized into phenobarbital, is a strong CYP-3A inducer that can reduce serum concentrations of ticagrelor resulting in ineffective antiplatelet therapy. We present a 67-year-old male who suffered in-stent thrombosis after percutaneous intervention possibly due to the interaction between primidone and ticagrelor.