We evaluated frequency and type of adverse events (AE) and measures adopted in outpatients attending a hospital hypertension unit in a two-part study: ( I ) a retrospective review of the charts of the 412 patients seen in 1991 with at least one follow-up visit and (2) a prospective study of the 491 patients seen in 1993 with at least one follow-up visit for whom physicians were asked to fill out an AE form. In 1991 18.6% of patients spontaneously reported an AE; those with an AE were older ( p < 0.001) than those without and included a greater proportion of females ( p < 0.002). This retrospective analysis of AE is reproducible as demonstrated by a blind review of 30 randomly selected charts undertaken by two independent observers (McNemar's test: p = ns).
In 1993 AE were reported by 24.4% of patients who had more follow-up visits ( p < 0.001) and included a higher proportion of females ( p = 0.016) than the subgroup without AE. AE were different in the two studies ( p < 0.001), more specific and drug-related in 1993. AE were usually considered as mild or moderate (87.4%), the drugs most often involved were calcium antagonists and ACE-inhibitors and the measure adopted was switching to another substance (44%). The frequency of AE reporting varied widely between different physicians.