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It has come to our attention that it is common practice within our health authority for paramedics to routinely administer to all patients with suspected cardiac chest pain, a 50 mg intravenous dose of cyclizine, as an antiemetic, in conjunction with the intravenous analgesic nalbuphine. This is the protocol in our area.
We are concerned at the use of a drug likely to increase heart rate and thus myocardial oxygen demand, in patients with an already critically ischaemic myocardium. The vagolytic effects of cyclizine are well known often with a substantial increase in heart rate.1 Several studies have shown a direct link between myocardial ischaemia and heart rate (hence the beneficial effects of β block on high risk cardiac patients).2 Indeed the avoidance of tachycardia and hypertension is the principal therapeutic aim of anaesthesia in patients with significant myocardial ischaemia.3
In guidelines published by various health authorities on the treatment of acute myocardial infarction, cyclizine is recommended as a first line drug, although a note of caution is suggested in at least one publication if the patient is thought to have left ventricular failure. It would seem to us to be more pertinent to avoid its use in patients at risk of further myocardial damage regardless of their left ventricular function.
The BNF reports that cyclizine counteracts haemodynamic effects provided by opioid administration and goes further to state that a common side effect is palpitations and arrythmias, surely neither being beneficial to the patient with chest pain.4
In our view the logical antiemetic of choice would be ondansetron, which is effective, if expensive, and devoid of serious common side effects unlike cyclizine and indeed metoclopramide.
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