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Local application of hydralazine has been found to alter intraocular pressure in animal eyes. This study was undertaken to determine, in normotensive humans, the effects of topically-applied hydralazine on systemic cardiovascular parameters, blood-aqueous barrier, and aqueous humor flow. Two different concentrations of hydralazine were used: 0.03%, and 0.1%. Twenty healthy normotensive subjects were studied. Blood pressure, pulse rate, and intraocular pressure were measured every hour for six hours after hydralazine or placebo was instilled into the conjunctival sac in a double-masked, randomized fashion. With either hydralazine dose, there was no significant change in systemic blood pressure or pulse. In addition, spectrophotometrically-measured polarization of fluorescence and flare failed to show any significant breakdown of the blood-aqueous barrier. In most individuals, application of hydralazine was followed by a brief, mild to moderate, conjunctival hyperemic response. Compared to placebo at the same time of day, a small increase in intraocular pressure was observed with 0.03% hydralazine (p < .05). At 0.1%, this increase tended to be less. There was no statistically significant difference in aqueous humor flow between hydralazine-treated and placebo-treated eyes at the lower concentration (3.20 +/- 0.63 vs. 3.05 +/- 0.61 microL/min (mean +/- S.D.) or at the higher concentration (3.37 +/- 0.53 vs. 3.28 +/- 0.60 microL/min) of hydralazine. These results suggest that acute topical application of 0.1% hydralazine to the eyes of normal humans does not cause clinically significant cardiovascular effects or significant ocular toxicity.

To measure and compare the effect of apraclonidine hydrochloride and brimonidine tartrate on the rate of aqueous humor flow in human subjects.Subjects and Methods: Forty normal human subjects were given apraclonidine or brimonidine by topical instillation. Aqueous humor flow was measured by the rate of disappearance of topically applied fluorescein. Intraocular pressure was measured by applanation tonometry.Results: Apraclonidine suppressed aqueous humor flow between 39% and 44% and lowered intraocular pressure between 20% and 23%. Brimonidine suppressed aqueous humor flow between 44% and 48% and lowered intraocular pressure between 19% and 22%. Conclusion:No statistically significant differences were found between the effects of the 2 drugs on aqueous humor dynamics in normal subjects.