Eicosanoids as a new class of ocular hypotensive agents. 1. The apparent therapeutic advantages of derived prostaglandins of the A and B type as compared with primary prostaglandins of the E, F and D type.

The classic primary prostaglandins (PGs), as well as some of their analogs and derivatives, are potent ocular hypotensive agents. The present studies show that A and B PGs, which are derived from PGs of the E type by dehydration and isomerization, have a much greater ocular hypotensive potency than the primary PGs of the E, F or D type. A single application of 5 micrograms of PGA2 to the cat eye in a 25-microliters volume of aqueous vehicle solution yielded a greater and more prolonged ocular hypotensive effect than as much as 100 micrograms of topically applied PGF2 alpha. As little as 1 microgram of PGA2 had a significant ocular hypotensive effect that was enhanced by three or more consecutive daily applications of the same dose. This IOP reduction, which remained significant for several days after the last of 10 daily treatments, was not associated with biomicroscopically detectable flare or invasion of the anterior chamber by cells. Although PGF2 alpha and, to a much lesser extent, PGE2 have a miotic effect in cats, PGs of the A and B type did not cause significant miosis even at doses 50- to 100-fold greater than the minimum dose required to yield significant ocular hypotension. PGA2 retained its ocular hypotensive potency when stored in an aqueous solution at room temperature for four months. The conjunctival hyperemia caused by 5 micrograms or 10 micrograms of A or B type PGs on rabbit eyes was milder and shorter in duration than that caused by the same doses of PGE2 or PGF2 alpha. These findings suggest that derived PGs, especially PGs of the A type, may have a therapeutic advantage over primary PGs for the treatment of ocular hypertension and glaucoma.