Percutaneous diffusion of cefalexin, sulfamethoxazole and diphenhydramine from ointments

The effects of ointment base, drug concentration, and the presence of surfactant on the diffusion of cefalexin, sulfamethoxazole and diphenhydramine through excised mouse skin were studied. The total amount of diffused drug per ml against time and against the square root of time as plotted for the evaluation of results. As was expected from theory, a linear relationship was obtained for each drug when the square root of time was employed. The effect of the vehicle on the release of cefalexin was in the following decreasing order: o/w emulsion greater than water-soluble greater than hydrophilic greater than oleaginous greater than w/o emulsion base. That on the release of sulfamethoxazole was in the order: water-soluble greater than o/w emulsion greater than w/o emulsion = oleaginous = hydrophilic. The order in case of diphenhydramine was as follows: o/w emulsion greater than water-soluble greater than hydrophilic greater than oleaginous = w/o emulsion. The increase in drug concentration or the addition of a surfactant has caused an increase in the diffusion rate of each of the drugs.