In vivo dermal studies are conducted to evaluate the pharmacokinetics, toxicity, and/or effi cacy of test compounds and formulations. Studies may be performed in rodents or non-rodents, on intact or compromised skin, and in healthy or diseased animal models. Pharmacokinetic studies determine the local and systemic concentrations of a drug over time. While many dermal products are locally acting, assessment of systemic distribution is also important to rule out exposure to potentially toxic concentrations. This is particularly true in a diseased or wounded model since the condition of the skin may affect the absorption profile of the drug.
Transdermal delivery systems also have the potential to cause irritation at the site of administration since they are in direct contact with the patient’s skin. Dermal irritation of a test article should be evaluated against a placebo formulation and control formulations such as 0.1% sodium lauryl sulfate (SLS, high-irritancy control) and 0.9% saline (low-irritancy control). Draize scoring is the standard method used to quantify observations of the dose site.