Another factor in the selection of an in vivo versus in vitro test system or a combination of the two may be the preference of the national regulatory authority. Diffusion back to the surface with evaporation of chemical from the skin is an essential addition to a dermal absorption model for these compounds. Because skin is a membrane, membrane models of the skin appear more realistic Scheuplein, but can be mathematically cumbersome. Because the skin in various regions of the body has different physiological properties Scheuplein, , the rate and extent of dermal absorption may be different for different regions of skin. The regulatory authorities in the European Union now extensively utilize the in vitro human skin method as a stand-alone method as part of the approval process for the registration of new pesticide products. The biological factors affecting absorption include the site of the body, the integrity of the stratum corneum and thickness of the epidermis in addition to other physiologic determinants such as temperature and local blood flow OECD, a ; b ; WHO, PubMed Commons home PubMed Commons.
(PDF) QSAR Models for the Dermal Penetration of Polycyclic Aromatic Hydrocarbons
The comparison with heuristic method and support vector machines approaches reveals a good prediction of GEP. Two properties, in vitro percutaneous absorption in rat skin and discrete levels of carcinogenic activity, are examined using molecular quantum similarity measures MQSM. Series on Testing and Assessment. Many publications were emerging as to the value of the alternative approach in this area of toxicology Scott and Ramsey, ; Ramsey et al. Recommended values for these dermal factors are not provided in the Handbook because data are limited; however, data from relevant studies are described.
Improved Drug Efficacy using Nanomaterials In addition to the safety area, the introduction of nanotechnology has been shown to have advantages in the dermal delivery of pharmaceutical actives. It is shown that the GEP predicted results are in good agreement with experimental ones. The main contributions to the. The McKone and Howd model and the Robinson model have the advantage, that they predict more precisely the skin permeation of highly hydrophilic and highly lipophilic chemicals compared to the Guy and Potts model. A sub-set of hydrocortisone derivatives within the steroid group had measured permeability coefficients which were around 1.
Here, we present a compartment model describing the dermal absorption of D 4 and D 5 that includes the storage capacity of the skin and evaporation either from the neat chemical on the skin or from chemical absorbed in skin that has diffused back to the skin surface. PubMed US National Library of Medicine National Institutes of Health. Model estimates of the peak D 4 blood concentration may be inaccurate because there were no data available in the critical time region. Two aspects of the model presented here capture the ability of the skin to store chemical. Although both whole blood and plasma concentrations of D 4 and D 5 were determined, parameter estimation was done using plasma concentrations to be consistent with the earlier inhalation models that were also developed using plasma data. In Vitro 8 4 ,