A Cochrane review included 6 studies (1 of oral, 3 of transdermal clonidine) with a total of 776 subjects. There was a statistically significant effect of clonidine in one of these trials. The pooled risk ratio for success with clonidine versus placebo was 1.63 (95% CI 1.22 to 2.18; 6 studies). There was a high incidence of dose-dependent side-effects, particularly dry mouth and sedation.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and by limitations in study quality (inadequate or unclear allocation concealment and blinding).