Heart Attacks are a major cause of death in this country. When patients have a heart attack, they are treated with anti-clotting drugs, one of which is a drug called Prasugrel. It is important that Prasugrel starts to work as quickly as possible following a heart attack. As many patients who have a heart attack experience excruciating pain, they are often given morphine (a strong painkiller) by the Ambulance crew. We think that morphine may affect how Prasugrel is absorbed from the stomach and may delay how quickly it starts to work. We intend to study the effect of morphine on the absorption of Prasugrel.

Inclusion Criteria:

• >18 years of age and willing and able to provide informed consent
• Admission to hospital with a STEMI >12 months prior to recruitment
• Previous prasugrel and morphine use with no adverse effect

Exclusion Criteria:

• Active respiratory disorder, resting oxygen saturation < 95% or decompensated congestive cardiac failure
• Current use of anti-platelet or anti-coagulant drugs apart from aspirin 75 mg daily, or receipt of any dose of clopidogrel, prasugrel or ticagrelor in the last 2 weeks
• Current use of opiate analgesia