Intraocular pressure effects of multiple doses of drugs applied to glaucomatous monkey eyes

The effects of multiple dosing with 0.5% timolol maleate, 2% epinephrine hydrochloride, 4% pilocarpine hydrochloride, 1% vanadate, 1% forskolin (nonproprietary name, colforsin), or 0.5% prostaglandin F2 alpha on intraocular pressure (IOP) were each tested on eight cynomolgus monkey eyes in which glaucoma was induced by photocoagulating the trabecular meshwork with the argon laser. The week prior to drug therapy, baseline IOP measurements were carried out at hourly intervals from 9:30 am to 3:30 pm on three days. One to two days later, therapy was initiated. Each drug was applied topically to both eyes of each monkey twice daily for at least four days. The IOP was measured with a calibrated pneumatonometer at the same hourly intervals on treatment days as on the baseline days. The IOP at each time of day on treatment days was compared with the average baseline IOP measured at the corresponding time of day. Topical application of timolol, epinephrine, pilocarpine, vanadate, and prostaglandin F2 alpha significantly reduced IOP without evidence of tolerance or tachyphylaxis during the course of therapy. Forskolin did not significantly decrease IOP after the second day of treatment.