Investigation of newborn pig skin as an in vitro animal model for transdermal drug delivery
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Ethical considerations and the limitation in availability of human skin for percutaneous absorption studies of drugs are the main reasons for the use of animal skin. Pig skin has been reported to have permeability properties resembling that of human skin. The aim of the current study was to investigate the suitability of newborn pig skin as a model in percutaneous absorption studies. The anatomical features of skin from newborn pigs have been investigated using light and electron microscopy. The use of pigs that have died of natural causes shortly after birth allows the experiments to be carried out under tissue retrieval rather than animal ethics regulations. The thickness of the stratum corneum and epidermis was found to be similar to that of human skin and considerably thinner than adult pig skin, although the hair follicle density was much greater than that in either adult pigs or humans. Assessment of integrity of full-thickness newborn pig skin was performed using water permeability and electrical resistance measurements. A resistance greater than 20 kΩcm2 was proposed as a stringent and conservative indicator of an intact barrier function. The in vitro permeation characteristics of some model compounds (tritiated water, [14C] mannitol, and propranolol hydrochloride) have also been investigated. With the exception of mannitol, newborn pig skin was found to have a similar permeation properties to human skin (factor of difference values between 1-1.5). In addition, a comparison has been made on the enhancing effect of two terpenes, carvacrol and menthol, on the permeation of propranolol hydrochloride. Permeability through newborn pig skin was approximately double that of human skin but the rank order of enhancement remained the same. The factor difference values suggest that as a human skin substitute, newborn pig skin may be a suitable model for percutaneous absorption screening studies.
|S.T.P. Pharma Sciences
|Number of pages
|Published - Mar 2003
- Anatomical features, Electrical resistance, Newborn pig skin, Percutaneous absorption, Water permeability