Eight RCTs (163 participants), including 7 crossover trials (113 participants) and 1 parallel study (50 participants), were included.
Phenylephrine had a significantly greater effect on NAR than placebo in 4 studies, and no significantly different effect in 4 studies.
In the meta-analyses (7 RCTs, 113 participants, except at 180- and 240-minute time points which included 5 RCTs, 82 participants), significantly greater effects of phenylephrine over placebo were found at 30, 60 and 90 minutes after dosing using the random-effects model, and at 30, 45, 60, 90, 120 and 180 minutes after dosing using the fixed-effect model. Significant heterogeneity (p<0.10) was detected at all time points.
No adverse events were reported in 7 studies. One study reported comparable adverse events in the phenylephrine and placebo groups.