Methods for quantifying intrafollicular drug delivery: a critical appraisal

The document critically appraises various methods for quantifying intrafollicular drug delivery, highlighting the complexity of accurately measuring drug transport within hair follicles. It discusses several techniques, including comparative methods, the skin sandwich approach, differential stripping, and optical imaging technologies, each with its own advantages and disadvantages. The study of human skin sandwich on hydrocortisone revealed that formulation viscosity and topical pretreatment with chemical enhancers can influence follicular absorption. The role of sebum in drug penetration is debated, with the development of artificial sebum for research and mathematical models to describe drug delivery. The document concludes that the field lacks a consensus on the most effective method, with selective follicle blocking being the most accurate, but still requiring validation. It calls for larger scale studies using multiple techniques and drugs to improve understanding of follicular drug transport and suggests that further research, including in vivo data, is necessary to validate these methods.