In the management of acute coronary syndromes with ST-segment elevation (STEMI), early analgesia reduces the effects of hyperadrenalism which increases the size of myocardial infarction. In order to reduce pain intensity, the recommendations advocate emergency use of morphine. In STEMI patients, other analgesic treatments could provide analgesia that is at least as effective as morphine. The equimolar oxygen/nitrous oxide mixture (MEOPA) is widely used in emergency medicine and has minor secondary effects that are very rapidly reversible when inhalation is discontinued. Used in association with paracetamol, it could be an at least equally effective alternative to the use of morphine.