Objective: To evaluate the safety and efficacy of the relatively selective M1 antagonist pirenzepine hydrochloride in slowing the progression of myopia in school-aged children. Methods: This was a parallel-group, placebo-controlled, double-masked study in healthy children, aged 8 to 12 years, with a spherical equivalent of -0.75 to -4.00 diopters (D) and astigmatism of 1.00 D or less. Patients underwent a baseline complete eye examination and regular examinations during a 1-year period. The setting was 13 US academic clinics and private practices. Patients were randomized in a 2:1 ratio to receive 2% pirenzepine ophthalmic gel or a placebo control twice daily for 1 year. Results: At study entry, the spherical equivalent was mean±SD -2.098±0.903 D for the pirenzepine group (n=117) and -1.933±0.825 D for the placebo group (n=57, P=.22). At 1 year, there was a mean increase in myopia of 0.26 D in the pirenzepine group vs 0.53 D in the placebo group (P<.001). No patients in the placebo group and 13 (11%) of 117 patients in the pirenzepine group discontinued participation in the study because of adverse effects (5 [4%] of 117 due to excessive antimuscarinic effects). Conclusions: Pirenzepine is effective and relatively safe in slowing the progression of myopia during a 1-year treatment period.
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