Kinetic transdermal absorption

The physicochemical approach to the prediction of transdermal absorption kinetics described In this paper offers a promising stategy for the estimation of cutaneous exposure risk. The model Is conceptually straightforward yet sensitive to the biology of skin and to the chemical and physical properties of the penetrant. Human, In vivo, penetration data for a diverse array of absorbing molecules have been... 

These linear kinetic models and diffusion models of skin absorption kinetics have a number of features in common they are subject to similar constraints and have a similar theoretical basis. The kinetic models, however, are more versatile and are potentially powerful predictive tools used to simulate various aspects of percutaneous absorption. Techniques for simulating multiple-dose behavior evaporation, cutaneous metabolism, microbial degradation, and other surface-loss processes dermal risk assessment transdermal drug delivery and vehicle effects have all been described. Recently, more sophisticated approaches involving physiologically relevant perfusion-limited models for simulating skin absorption pharmacokinetics have been described. These advanced models provide the conceptual framework from which experiments may be designed to simultaneously assess the role of the cutaneous vasculature and cutaneous metabolism in percutaneous absorption. 

These studies also determined that these various exposure conditions resulted in a wide range of DEET absorption (13 to 68 pg/cm ) within 8 h of dermal exposure. It should be noted that DEET absorption ranged from 13 to 16 pg/cm irrespective of whether it is either 7.5 or 75% DEET in a binary ethanol mixture. In effect, DEET transdermal flux is a zero-order kinetic process with a flux of 2.0 pg/cm /h. This transdermal flux was also observed in human skin exposed to either neat or 15% DEET (Selim etal., 1995) and demonstrates that DEET flux is saturated... 

The pulmonary and transdermal routes are the least investigated of the alternative, nonparenteral delivery routes for insulin, and perhaps therefore they still hold some promise. The potential of pulmonary delivery for bolus therapy has been demonstrated as this route is feasible from a bioavailability standpoint, even without the addition of enhancers. However, long-term safety remains to be established. Inhalation of insulin may offer fairly reproducible absorption kinetics, but it is a major challenge from a device point of view to ensure reproducibility of the administered dose. 

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