Six RCTs (n=329, range 24 to 126) were included in the review. The duration of follow-up ranged from one week to over four years. Study quality was grade B in four studies and grade C in two. Funnel plots suggested possible publication bias.
Compared with placebo aplha-adrenoceptor agonists were significantly more effective in treating vasovagal syncope (OR 0.21, 95% CI 0.06 to 0.77, p=0.02); significant heterogeneity was present (p<0.0001). The weighted mean percentage of responders for midodrine was significantly greater than that for etilefrine (76.3% ± 7.7% versus 65.5% ± 15.4%; p < 0.001).