Use of intravenous cyclizine in cardiac chest pain

May and Kumar¹ conclude that “cyclizine should be avoided in patients with acute coronary events”, although we note that the BETs online version states “there appears to be no firm evidence that cyclizine increases morbidity and mortality in patients with myocardial ischaemia”. They reviewed a single 16–year–old study, which looked at a small number of patients suffering from heart failure.

The study by Tan, et al,² which was reviewed, contained measurement data when cyclizine was given 30 min before diamorphine. Although cyclizine produced haemodynamic changes, the subsequent diamorphine tended to change those variables toward the basal values, although right atrial and pulmonary arterial pressures remained significantly above basal values. To their credit May and Kumar observe that it was a small study in a very specific group of patients. Tan et al quoted work that concluded cyclizine may be useful if avoidance or prompt reversal of the hypotensive effect of opiate is required.³ It is also relevant to observe that no data were given for simultaneous administration of cyclizine with opiate, because cyclizine is usually administered simultaneously with opiate, considerable caution is required if the conclusions of this study are to be translated into advice about clinical care.

The clinical bottom line begs the question “if not cyclizine, what should I use?” We repeated their search strategy but replaced the “cyclizine” with “metoclopramide” or “stemetil/prochlorperazine”, revealing no studies of the effects of these two commonly used drugs. A Cochrane study is being undertaken to review other anti‐emetics,⁴ we suggest that a more appropriate conclusion would be “There is the possibility of adverse haemodynamic effects of cyclizine in patients with heart failure, and of beneficial effects in patients with opiate induced hypotension; the effects of other known anti‐emetics are unknown.”