Editor,—Diamorphine has been used extensively in cardiology in the UK in the management of acute left ventricular failure, unstable angina, and for relieving pain during a myocardial infarction. Our European and American colleagues however remain firmly committed to the use of morphine for the same clinical situations. To date no studies have revealed any difference in efficacy between morphine and diamorphine.

Ischaemic preconditioning is thought to play an important role in reducing the severity of myocardial damage in acute coronary events.1 Implementation of ischaemic preconditioning however remains clinically impractical.

The recent discovery that activation of the opioid δ receptor on the myocardium can exert a protective effect to myocardial ischaemia similar in extent to classic ischaemic preconditioning may have important implications.2 Morphine is known to act predominantly via the opioid μ receptor while diamorphine acts at the δ receptor.3 4 By implication, diamorphine could offer the benefits of ischaemic preconditioning to patients who receive it compared to those who receive morphine.

Unfortunately adequate numbers and practicalities of patient stratification would make a clinical study difficult, especially for two off patent drugs; however, we may still be right.