Effects of surfactants on the absorption of salicylic acid from hamster cheek pouch as a model of keratinized oral mucosa

The effect of surfactants on the absorption of salicylic acid from keratinized oral mucosa was investigated by hamster cheek pouch method in vivo at pHs 3.0, 4.0 and 7.0. Four surfactants, sodium laurylsulfate (SLS), cetylpyridinium chloride (CPC), polysorbate 80 (PS-80) and sodium taurocholate (STC), were examined as adjuvants. The interaction between salicylic acid and each surfactant was determined by the molecular sieve method using Sephadex G-25. Decreased absorption of salicylic acid by the presence of PS-80 was observed in the lower pH conditions and this phenomenon was explained by the decrease in the free fraction of salicylic acid. The absorption of salicylic acid in the presence of ionic surfactants, SLS or CPC, was much larger than that predicted by the loss of activities which was caused by the interaction between the surfactant and the drug molecule. Pretreatment with SLC or CPC brought the salicylic acid absorption to increase in all pH conditions examined and the effects were dependent on the surfactant concentration. STC and no effect on the absorption. The mechanisms of the effects of ionic surfactants on the permeability of keratinized oral mucosa were discussed.