Eighteen RCTs with a total of 560 patients, of whom 437 had primary RP, were included in the review.
All of the included studies were double-blind. No further details of study quality were reported.
Frequency of RP attacks.
The random-effects meta-analysis of 17 RCTs showed a reduction in the frequency of RP attacks (WMD -5.00, 95% CI: -9.02, -0.99, p=0.01). A sensitivity analysis without the 2 trials with the highest and lowest WMD point estimates did not significantly change the results of the analysis. The results of a subgroup analysis of 12 trials comparing nifedipine with placebo did not differ significantly from those of the main analysis (WMD -6.05, 95% CI: -11.19, -0.19, p=0.04). Subgroup analyses of 2 trials comparing nicardipine with placebo and nisoldipine with placebo found no significant differences in frequency of attacks between the groups.
Severity of RP attacks.
The random-effects meta-analysis of 17 RCTs showed a reduction in the severity of RP attacks measured on a 10-cm VAS (WMD -1.39, 95% CI: -2.20, -0.58, p<0.00001). There was also a reduction in the severity of RP attacks measured on a 5-point VAS (WMD -1.04, 95% CI: -1.51, -0.56, p=0.0015). The results of subgroup analyses of 12 trials comparing nifedipine with placebo did not differ significantly from those of the main analysis: the WMD was -1.81 (95% CI: -3.08, -0.54, p=0.005) on the 10-cm VAS and -1.11 (95% CI: -1.38, -0.85, p<0.00001) on the 5-point VAS. Subgroup analyses of 2 trials comparing nicardipine with placebo and nisoldipine with placebo found no significant differences in severity of attacks between the groups.