ACE-inhibitor-induced cough, an adverse drug reaction unrecognised for several years : studies in Prescription-Event Monitoring

OBJECTIVE. This study examines cough recorded in Prescription-Event Monitoring (PEM) of four ACE-inhibitors. Particular attention was paid to the study of enalapril because the drug was monitored before the causal relationship between cough and ACE-inhibitors had been widely accepted. RESULTS. Several factors which had obscured the causal relationship in the individual cases were found to be also an obstacle in PEM. For example, cough was a common and non-serious event and was under-reported in the PEM study of enalapril and the rate was not strikingly different from that recorded for other drugs. Cough induced by ACE-inhibitors has several characteristics which reduce the chance of a recognisable "signal'. The original questionnaires returned from doctors in the PEM study of enalapril have been reexamined. The observation that the rate of cough diminished after enalapril had been stopped rather than increased after starting, provided the best evidence of causality, because this was not affected by many biases such as the publicity that had occurred prior to doctors participating in PEM completed later reports.