Ocular Absorption of Sulfonamide Derivatives After Local Application. ∗

Abstract

It has been reported previously 1 , 2 that sulfanilamide and sulfapyridine after local application to the eyes of experimental animals are absorbed in greater amounts by ocular tissues and fluids than occurs when these agents are administered orally. 3 - 7 The ocular absorption of sulfathiazole has recently been studied by Bellows and Chinn. 8 Dogs given 0.2 g per kg of the drug, which was dissolved in HCl before administration, after 4 hours developed blood concentrations of 7.4 mg %. The amounts of sulfathiazole found in ocular tissues and fluids were: sclera 10.4, conjunctiva 8.4, chorioretinal layers 4.9, cornea 2.0, vitreous humor 0.9, aqueous humor 0.4, and lens 0 mg %. When an aqueous suspension of a similar dose of sulfathiazole was given orally the concentrations were considerably lower: blood 1.7, conjunctiva 2.9, chorioretinal layers 1.7, aqueous humor 0.3, vitreous humor 0.2 and lens and cornea 0 mg %. Similar results have been reported on cats by Scheie and Sounders, 9 who found that a very small amount of sulfathiazole diffuses into the aqueous humor as compared with the blood concentration. In addition they have observed that sulfadiazine, like sulfanilamide, penetrates into the aqueous humor when given orally. Turkell and Wilhelm 10 have shown that sulfathiazole was secreted in tears in amounts far less than in the blood after oral use.

Since sulfanilamide and related agents have been used in the therapy of ocular diseases it was believed desirable to compare the absorptive rates of 8 sulfonamide derivatives after local application to the eyes of rabbits. The technic employed has been described elsewhere. 1 For N⁴-nicotinylsulfanilamide and N^1,N^4,-dinicotinylsulfanilamide a method not previously described has been used.†