Effect of oral clonidine on acute intraocular pressure rise after phacoemulsification: a prospective double-blind, randomized, clinical trial.

OBJECTIVE: To determine the efficacy and safety of oral clonidine in decreasing the prevalence and intensity of postoperative intraocular pressure (IOP) rise in those undergoing phacoemulsification. METHODS: This was a prospective randomized, double-blind, placebo-controlled, clinical trial including 62 patients (each with 1 affected aye) with senile cataract scheduled for phacoemulsification who were randomly assigned to receive preoperative oral clonidine (5 µg/kg, 31 patients) or placebo (1 tablet, 31 patients). The IOP was measured preoperatively and at 6, 12, and 24 h postoperatively. The prevalence and intensity of the acute postoperative IOP rise was compared between and within the groups. RESULTS: There was no significant difference between the 2 study groups regarding the baseline characteristics and the baseline IOP (P=0.628). Patients who received placebo as premedication had significantly higher IOP at 6 (17.96±5.49 vs. 13.61±4.09; P<0.001) and 12 (16.90±4.11 vs. 13.96±3.25; P=0.003) h postoperatively compared with those who received oral clonidine. However, there was no significant difference between the 2 groups regarding the IOP at 24 h after operation (15.41±3.96 vs. 16.01±3.41; P=0.0539). The prevalence of acute IOP rise (>21 mmHg) was significantly higher in placebo group compared with clonidine group (25.8% vs. 9.6%; P=0.091). CONCLUSION: Administering preoperative oral clonidine in a dosage of 5 µg/kg, 2 h before phacoemulsification, significantly decreases the prevalence and intensity of acute postoperative IOP rise in those undergoing general anesthesia. Oral clonidine is safe, cheap, and easily accessible and, thus, it is recommended for controlling the IOP after phacoemulsification, especially in high-risk patients.