In vitro permeation and irritation of benzoyl peroxide-containing products

Two in vitro models to measure release of benzoyl peroxide (BPO) from formulations were presented. Franz-type diffusion cells and acetonitrile/water receptor mediums were used in both models. The barrier in one model was silicone sheeting and in the other was cultured human epidermis. The similarity in release profiles, rates of permeation and diffusion coefficients obtained provided enough evidence to demonstrate that the two models were comparable. An in vitro model to study the irritation of formulations containing BPO was also presented. The model used cell viability as a measure of irritation. Tissue viability was assessed using the MTT test after 5, 19 and 27 h exposure. The effective time where 75% of the keratinocytes remain viable in the skin model (ET(75)) was used as a measure to compare formulations. ET(75) decreased as the concentration of BPO increased in the formulations. Values of ET(75) were lower in vanishing formulations than in tinted formulations with the same level of BPO. Cell viability was linearly related to the rate of release of BPO. The higher the release rate, the lesser was the time needed to reach the ET(75). This indicated that the amount of BPO delivered from the vehicle was the primary cause of irritation.