• Thirty-five patients participated in a clinical trial of pilocarpine hydrochloride gel applied once daily at 10 pm. Patients tolerated the medication well and there were no untoward side effects. Significant lowering of intraocular pressure was found for 24 hours after administration. The effect 12 hours after administration was greater than 24 hours after administration. Therefore, pilocarpine gel can be endorsed as an effective medication for 24 hours in the vast majority of patients. However, it is incumbent on the prescribing ophthalmologist to measure the IOP at 10 pm at least once after prescribing pilocarpine gel to ensure adequate control of IOP at that time.