The Effect of Dorzolamide on Intraocular Pressure and Ocular Pulse Amplitude: Adjunctive Therapy to Beta-Blockers as a Substitite for Pilocarpine or as a Second-Line Therapeutic Agent in Patients with Open-Angle Glaucoma

To evaluate the effect of dorzolamide on the intraocular pressure (IOP), ocular pulse amplitude (OPA), systemic blood pressure and pulse rate in openangle glaucoma patients using a beta-blocker and 2% pilocarpine combination and beta-blocker monotherapy. The secondary aim was to find out the effect of dorzolamide on IOP and OPA in patients using selective versus nonselective beta-blocker. Methods:Thirteen patients who had beta-blocker and pilocarpine combination (Group 1) and 15 patients who had beta-blocker monotherapy (Group 2) were enrollled. A randomly selected eye of bilaterally affected patients was included in the observer-blinded and parallel-group study. Baseline data consisted of 4 day-time IOP, OPA, systemic blood pressure and pulse rate measurements. Patients in Group 1 discontinued pilocarpine and used beta-blocker-dorzolamide combination and patients in Group 2 used dorzolamide as a second-line therapeutic agent with a beta-blocker. The same measurements were performed after 4 weeks and after 6 months in both groups. Results: In Group 1 the baseline IOP was 18.9±2.2 mmHg; after 4 weeks and 6 months no statistically significant change was observed (17.6±2.3 and 17.8±3.2 mmHg respectively, p>0.05). However in Group 2, a statistically significant IOP decrease from 22.5 ± 3.3 mmHg to 18.0 ± 2.0 mmHg after 4 weeks (p<0.05) and to 18.4 ± 1.8 mmHg after 6 months (p<0.05) occurred. There were no changes in OPA, systemic blood pressure and pulse rate in either groups during the follow-up period. The additive effect of dorzolamide with selective and nonselective beta-blockers was analyzed using a cross-sectional study design of the data obtained from 28 eyes. Twelve patients who used selective beta-blocker and dorzolamide showed an increase in IOP (from 18.4±2.3 to 19.3±1.9 mmHg, p>0.05) and a decrease in OPA (from 3.7±1.2 to 3.2±0.9 mmHg, p>0.05) after 5 months, although these changes were not statistically significant. The IOP was stable during the same period (17.3±2.0 and 17.2±2.6 mmHg, p>0.05) but the OPA showed a slight, but not significant increase (2.7±1.1 and 3.1± 1.5 mmHg, p>0.05) in sixteen patients using nonselective beta-blocker and dorzolamide. Conclusion: Dorzolamide is safe and effective when used with beta-blockers but its interaction with selective and nonselective beta-blockers needs further investigation.