Topical administration of protriptyline 0.025% and 0.05%, and a test drug, MK-940, failed to produce any significant change in the intraocular pressure when applied twice daily to human subjects. Similarly, MK-940 failed to potentiate the effect of topically applied l-norepinephrine 2%. When applied twice daily as the free base, l-norepinephrine 2% produced a significant decrease in intraocular pressure and outflow resistance in persons with ocular hypertension. The amount of pressure reduction was related to the height of the initial intraocular pressure.
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