Influence of ion pairing salts on the transcorneal permeability of ionized sulfonamides.

The effects of cationic ammonium, phosphonium, and arsonium ion pairing salts as well as anionic organic and inorganic salts on the transcorneal permeability of ionized sulfonamide carbonic anhydrase inhibitors have been studied in the excised rabbit cornea. Benzolamide, trichloromethazolamide (TCM), MK-927, and quaternary ammonium sulfonamide (QAS) were examined. The enhancement in the first-order rate constants (k(in)) for the first compound in the presence of pairing salts was as much as 15 times the basal rate, with smaller increases seen with the remaining three drugs. Ion pairing salts may represent a means for enhancing the transcorneal permeability of highly ionized drugs.