Influence of sodium lauryl sulphate on the in vitro percutaneous absorption of compounds with different lipophilicity

The effects of sodium lauryl sulphate (SLS) at different concentrations on the ''in vitro'' percutaneous absorption of a number of compounds (5-fluorouracil, antipyrine, pentoxifylline, salicylamide, 4-ethylaniline, 4-n-butylaniline and indomethacin) with a wide range of lipophilicity values (log P-OCT from -0.95 to 4.42) through rat skin were analysed. After pretreatment of the skin with SLS (1% and 5%, w/w) the permeability coefficients increased only for compounds having a log P-OCT < 3 (5-fluorouracil, antipyrine, pentoxifylline, salicylamide and 4-ethylaniline). The enhancement ratios show that the greater the enhancer effect observed, the lower the lipophilicity value of the penetrant. An empirical hyperbolic equation between enhancement ratios and partitioning values was established. This equation makes it possible to determine the enhancement ratio for a compound with a known P-OCT when the membrane has been pretreated with SLS (1%, w/w). In conclusion, the effect of SLS as an enhancer depends on the lipophilicity value of the penetrant and seems similar in this aspect to other enhancers such as Laurocapram.