Australia. Since the introduction of sildenafil (Viagra) to the Australian market more than 3 years ago, the Australian Adverse Drug Reactions Advisory Committee (ADRAC) has received 773 reports of adverse reactions associated with its use; in 741 reports, sildenafil was the sole suspected drug. The most commonly reported reactions were relatively minor in nature and consistent with those observed during clinical trials, including headache (233 reports), flushing (139), abnormal vision (65), rhinitis (42), dizziness (31), dyspepsia (28), nausea (27), abdominal pain, palpitation and priapism (16 reports each). However, ADRAC has also received 20 reports of myocardial infarction (MI) associated with sildenafil (including 4 with fatal outcomes), 26 reports of chest pain, and 10 other reports with a fatal outcome (6 unexplained deaths, 2 strokes and 2 subarachnoid haemorrhages). The committee notes that the ingestion of sildenafil was temporally associated with only 23 of these 56 adverse events. Furthermore, of the 20 cases of myocardial infarction, 9 had or were at high risk of cardiovascular disease and 1 was receiving concomitant nitrates. The committee says that the contribution of sildenafil to cardiac events is difficult to assess, but notes that a recent publication shows no evidence for an increased risk of fatal myocardial infarction or ischaemic disease among sildenafil users. ADRAC reminds prescribers that sildenafil is contraindicated in men with severe cardiovascular disease, heart failure or unstable angina pectoris and, since sildenafil can potentiate the hypotensive effects of nitrates, co-administration with nitrates is also contraindicated.
Sildenafil - three years experience. Australian Adverse Drug Reactions Bulletin 21: 6, Jun 2002.