Pirenzepine ophthalmic gel 2% effectively slows myopic progression in children between the ages of eight and 12, a study in the August issue of the Journal of the American Association for Pediatric Ophthalmology and Strabismus found.

Researchers enrolled 174 patients in a one-year study, and of the 145 that completed it, 84 volunteered for a second year. Patients were randomized into two groups that received either the pirenzepine or placebo twice daily. Of the second-year study cohort, 12 patients did not complete the trial due to adverse events, poor compliance or medical complications.

At the beginning of the study, mean refraction was -2.25 + 0.96D for the pirenzepine group and -1.83 + 0.82D for the control group. At two years, there was a mean increase in myopia of only 0.58D in the pirenzepine group vs. 0.99D in the placebo group. More than 68% of the placebo group progressed by at least 0.75D, while only 37% of the pirenzepine group progressed likewise.

Researchers note that this study was limited by lack of formal accommodation testing and phoria quantification. They note that the drug has potential, but suggest further study to answer several questionsnamely, the optimal age at which to begin treatment, since this study showed better potential in the younger patients within the cohort, while other studies have shown that older myopic patients still retain good uncorrected visual acuity.

Researchers also believe that determining the optimal duration of such a regimen could aid in succesful treatment, noting that the success rates during the first year of the study were more drastic than those recorded during the second year.

Siatkowski RM, Cotter SA, Crockett RS, et al. The U.S. Pirenzepine Study Group. Two-year multicenter, randomized, double-masked, placebo-controlled, parallel safety and efficacy study of 2% pirenzepine ophthalmic gel in children with myopia. J AAPOS 2008 Aug;12(4): 332-9.