Sulfonamide and trimethoprim concentrations in human serum and skin blister fluid.

Various sulfonamides and trimethoprim were given orally twice a day to healthy volunteers. The drug concentrations in serum and tissue fluid from skin blisters were determined concomitantly. Maximal serum concentrations were obtained after 1 to 3 h. Absorption of sulfacarbamide and sulfadimidine was more rapid than for sulfadiazine, sulfamethoxazole, and trimethoprim. The penetration to blister fluid was delayed and maximal concentrations were usually reached after 4 to 8 h. The highest penetration to blister fluid was found for sulfacarbamide, sulfadiazine, and trimethoprim. During maintenance therapy sulfadiazine and trimethoprim gave blister fluid concentrations usually above 50% of the serum level. However, on the basis of dosage the highest sulfonamide concentration both in serum and blister fluid was obtained with sulfamethoxazole.