ANalgesic Efficacy and Safety of MOrphiNe Versus Methoxyflurane in Patients With Acute Myocardial Infarction

Platelet activation plays a pivotal role in the pathophysiology of acute coronary syndromes (ACS). Pharmacological platelet inhibition with P2Y12 receptor antagonists and aspirin, together with percutaneous coronary intervention (PCI) are the cornerstone of treatment of ACS patients.

Chest pain and anxiety are both associated with sympathetic activation, which increases workload of the heart. Relieving of these symptoms in acute myocardial infarction (AMI) is expected to improve the balance between the demand for oxygen and its supply. Morphine, apart from its analgesic effects, also alleviates the work of breathing and reduces anxiety. However, despite its favourable analgesic and sedative actions, morphine also exerts adverse effects, which include vomiting and reduction of gastrointestinal motility. These side effects affect the intestinal absorption of oral drugs co-administered with morphine. Previously performed randomized studies revealed unfavourable influence of morphine on the pharmacokinetics of ticagrelor resulting in weaker and retarded antiplatelet effect.

Methoxyflurane was shown to be effective and well tolerated for the management of acute traumatic pain with a rapid onset of analgesia. As it does not affect the μ-opioid receptors, which inhibit propulsive motility and secretion of the gastro-intestinal tract, methoxyflurane is not expected to decrease or delay absorption or effects of orally administered drugs, including P2Y12 inhibitors, as well as to exert any other negative impact in patients with ACS.

Before PCI for the index ACS, after obtaining informed consent patients will be enrolled and randomly assigned with a secure on-line system in 1:1 ratio to one of two study arms. Patients in the intervention arm will receive methoxyphlurane administered by inhalation, whereas patients in the control arm will obtain morphine administered intravenously.