Multiple dosing of prostaglandin F2 alpha or epinephrine on cynomolgus monkey eyes. I. Aqueous humor dynamics

After obtaining baseline intraocular pressure (IOP) measurements for 1 week, prostaglandin (PG) F2 alpha (250 micrograms in 50 microliters saline) or epinephrine 2% solution (50 microliters) was topically applied twice daily for 2 weeks to one eye of six cynomolgus monkeys for each agent tested. Contralateral control eyes received their respective vehicles. PGF2 alpha significantly reduced IOP beginning 2 to 3 hr after the first dose, persisting thereafter. A significant (P less than 0.05) hypotensive effect remained for at least 10 hr after the first dose and at least 14 hr after the sixth dose. At 4 hr after the seventh dose, the mean reduction was 10.2 +/- 3.5 (+/- SD) mmHg below baseline (P less than 0.0025). At this time, there was also a significant (P less than 0.01) mean reduction of IOP in the contralateral vehicle-treated eyes of 6.0 +/- 3.3 (+/- SD) mmHg below baseline, which did not appear to be secondary to diurnal fluctuations, repeated tonometry, experimental manipulation, or inadvertent drug transfer. Epinephrine significantly (P less than 0.05) reduced IOP beginning 3 hr after the first dose, but this reduction was minimal and not consistent. Neither PGF2 alpha nor epinephrine altered aqueous flow as measured by fluorophotometry 2 to 6 hr after the fifth dose. Outflow facility could not be assessed by indentation tonography because IOP was often too low at the time of measurement. Whereas PGF2 alpha did not alter pupil size, epinephrine caused significant pupillary dilation.(ABSTRACT TRUNCATED AT 250 WORDS)