The effects of prostacyclin and its stable analog on intraocular pressure.

Prostacyclin, a natural arachidonic acid derivative that has potent vasodilatory and anti-platelet aggregatory effects in vivo can effectively reduce IOP in rabbits when applied topically to the eye. However, great care has to be taken to apply this highly labile autacoid immediately after the pH of the solution is brought down from the alkaline side, where the compound is more stable, to the neutral region, where it can be applied to the eye. A stable analogue of prostacyclin, Iloprost, especially its esterified form which can be expected to penetrate the eye more rapidly, was found to be an even more potent ocular hypotensive agent in both rabbits and dogs. While in the present studies prostacyclin or its analogue was only studied for six hours, it has already been shown that some PGs can maintain IOP reduction in cats, monkeys and humans for weeks or months as long as daily PG application is continued (see Bito et al., 1989; Alm and Villumsen, 1989). Thus, the stable analogues of prostacyclin must be considered, together with the stable classical prostaglandins of the E and F type, as potential therapeutic agents for the long-term management of glaucoma.