Summary

Sildenafil is a phosphodiesterase-type-5 inhibitor indicated for the treat-ment of erectile dysfunction in men.  We report a case of NAION identified from a cohort of 8,893 patients (from a Prescription-Event Monitoring study) prescribed sildenafil by their primary care physician in England be-tween April and June 1999.  This 61-year-old patient had risk factors for NAION independent of drug therapy.  It was not possible to be confident about a causal association between sildenafil and NAION, though the possibility could not be ruled out.  Epidemiological data suggest that one case of NAION might be ex-pected in a cohort of 8,893 subjects.  Thus it remains important for clinicians to consider the range of risk factors for NAION; while equally, the processes of pharmacovigilance need to continue as for any recently launched drug preparation.