Effect of topical prostaglandin PGA2, PGA2 isopropyl ester, and PGF2 alpha isopropyl ester on intraocular pressure in normotensive and glaucomatous canine eyes.

Topical instillations of 1.0, 10, and 20 micrograms/50 microliters of prostaglandin PGA2, 0.5 and 1.0 microgram/50 microliters of PGA2 isopropyl ester, and 0.5, 1.0, 5.0 and 10.0 micrograms/50 microliters of PGF2 alpha isopropyl ester were evaluated in the normal dogs and glaucomatous beagles eyes. Each concentration of drug was evaluated for a seven day period. On Day 1 baseline values were obtained, days 2-4, the drug was instilled (once a day) and on days 5-7 post-treatment values were measured. All concentrations of PGA2 failed to lower intraocular pressure (IOP) in the normal and the glaucomatous (P greater than 0.72) dogs. PGA2 isopropyl ester decreased IOP in the normal dogs and in the glaucomatous beagles (P less than 0.01). The declines in IOP were significant at 1/2 to 1 hour and continued for up to 5 hours. No significant change in IOP occurred in the non-treated fellow eye of the normotensive dog (P less than 0.54) and the glaucomatous beagle (P less than 0.29). All concentrations of PGF2 alpha isopropyl ester significantly decreased IOP in the treated eyes of the normotensive dog (P less than 0.05) and the glaucomatous beagle (P less than 0.01). The significant change in IOP occurred within one hour after the instillation of PGF2 alpha isopropyl ester. The IOP remained lower than the baseline pressures 24 hours post-treatment for both the normotensive and glaucomatous dogs. Maximal change in IOP for normal dogs was a decrease of 9 mm Hg while the glaucomatous beagle had a decrease of 19 mm Hg. No significant change in IOP occurred in the non-treated fellow eye of the normotensive animal (P less than 0.16) and the glaucomatous beagle (P less than 0.40). The side effects of PGF2 alpha isopropyl ester were miosis and mild conjunctival irritation.