15-keto Latanoprost

Latanoprost is an F-series prostaglandin (PG) analog which has been approved for use as an ocular hypotensive drug. Oxidation of the C-15 hydroxyl group without isopropyl ester hydrolysis produces 15-keto latanoprost. 15-keto Latanoprost is a potential metabolite of latanoprost when administered to animals. 15-keto Latanoprost is also one of the common minor impurities found in commercial preparations of the bulk drug compound. Although much less potent that the parent compound latanoprost, 15-keto latanoprost still retains the ability to produce a small but measurable decrease (1 mm Hg) in the intraocular pressure of normal cynomolgus monkeys when administered at a dose of 1 µg/eye. 15-keto Latanoprost is also a miotic in the normal cat eye, causing an 8 mm reduction in pupillary diameter at 5 µg/eye. Again, this is not as potent as many other F-type PGs; for example, PGF2α will produce this degree of miosis at a dose of less than 1 µg/eye. Products of β-oxidation account for most of the metabolites of latanoprost recovered in plasma and urine. However, 15-keto latanoprost is a minor metabolite, and one which could be enhanced in situations where β-oxidation is reduced.