ABSTRACT
Many guidances exist to aid in the development of pharmaceutical drugs, but very few guidances exist to aid in the formulation of drugs for nonclinical safety evaluation, or for the assessment of pharmaceutical excipient safety. Formulations used to administer potential drugs undergoing development occupy an unusual place in pharmaceutical safety assessment compared to the rest of industrial toxicology. The diffusion coefficient of the hydrated stratum corneum is larger than that of dry skin. Therefore, hydration increases the rate of passage of all substances that penetrate the skin. The physical form of a material destined for oral administration often presents unique challenges. Liquids can be administered as supplied or diluted with an appropriate vehicle, and powders or particulates can often be dissolved or suspended in an appropriate vehicle. One of the key steps in the nonclinical and clinical formulation of the drug is the selection of vehicles and of the inactive ingredients.
