Abstract
Within the scope OF evaluating transparent oil-water gels as dermatological vehicles, the percutaneous absorption of both a hydrophilic drug, tetracaine hydrochloride, and a lipophilic drug, benzyl nicotinate, is studied using excised human epidermis. From a comparison of the results with those of release experiments, it appears that in most cases the penetration of both drugs through the epidermis occurs at a much lower rate than their release from the vehicles. This indicates that the penetration process constitutes the rate limiting step.
For both drugs the penetration rate from the transparent oil-water gel through human epidermis is comparable to those from other commonly used vehicles. Due to the higher lipophilicity of benzyl nicotinate, however, its penetration occurs faster than for tetracaine hydrochloride. As to the influence OF drug concentration in the vehicle on penetration rate, the results do not provide a decisive answer.