Follicles play an important role in percutaneous absorption

Area of Science:

• Dermatology
• Pharmacokinetics
• Skin Physiology

Background:

• The stratum corneum and follicular pathways' relative contributions to percutaneous absorption remain unclear.
• Understanding these routes is vital for optimizing topical drug delivery and efficacy.

Purpose of the Study:

• To quantitatively assess the significance of the transappendageal route in percutaneous absorption.
• To investigate the role of hair follicles in the in vitro diffusion of various compounds through rat skin.

Main Methods:

• Utilized a hairless rat model with surgically created appendage-free skin.
• Compared in vitro percutaneous absorption of [3H]hydrocortisone, niflumic acid, caffeine, and p-aminobenzoic acid using diffusion cells.
• Examined diffusion in early postnatal (follicle-devoid) versus later postnatal (follicle-developed) rat skin samples.

Main Results:

• Follicles were identified as the predominant pathway for in vitro diffusion of tested compounds in hairless rat skin.
• Steady-state flux and diffusion amounts were 2-4 times lower in appendage-free skin compared to normal skin.
• Follicle-free skin exhibited a fivefold reduction in steady-state flux and total 24-hour diffusion of [3H]hydrocortisone.

Conclusions:

• Appendageal diffusion, primarily through hair follicles, is the major route for percutaneous absorption in hairless rat skin.
• Hair follicles play a more significant role in percutaneous absorption than commonly acknowledged.
• These findings have implications for drug formulation and delivery strategies targeting skin.