A 62-year-old man presents to the emergency department with 1 hour of central crushing chest pain radiating to his left arm, associated with diaphoresis and nausea. ECG shows ST elevation in leads V2-V5. He received 300 mg aspirin from paramedics. Emergent percutaneous coronary intervention (PCI) has been arranged within 60 minutes. What is the most appropriate additional immediate pharmacological management?