Tissue binding affects the kinetics of theophylline diffusion through the stratum corneum barrier layer of skin.
Frasch-HF; Barbero-AM; Hettick-JM; Nitsche-JM
J Pharm Sci 2011 Jul; 100(7):2989-2995
New data sets on both (i) equilibrium theophylline (TH) partitioning/binding in stratum corneum and (ii) transient TH diffusion through human epidermis are explained by an extended partition-diffusion model with reversible binding. Data conform to a linear binding isotherm within the tested concentration range (0-2000 :g/mL) with an equilibrium ratio of bound-to-free solute of approximately 1.4. The permeability coefficient for TH is 4.86 × 10-5 cm/h, and the lag time is 20.1 h. Binding occurs as a slow process, significantly affecting the kinetics of dermal penetration.
Skin-exposure; Skin-absorption; Dermatology; Exposure-assessment; Cell-function; Cellular-transport-mechanism;
Author Keywords: transdermal; passive diffusion/transport; kinetics; protein binding; transient diffusion; lag time; reversible binding; permeable corneocytes; theophylline; keratin
H. Frederick Frasch, Health Effects Laboratory, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505
Journal of Pharmaceutical Sciences