Bioavailability for oral dosage forms is defined as the percentage of an administered dose that enters the systemic circulation. The bioavailability of drugs injected into the bloodstream is 100%. Drugs with poor oral bioavailability present challenges at every stage of development, as well as post-marketing. In the clinic, these compounds show widely variable inter- and intra-patient responses, which may add months – and potentially avoidable costs – to development programs. Once approved, a poorly-bioavailability drug can potentially negatively affect cost of goods per dose as a consequence of the API loading required to achieve effective systemic levels.
Because bioavailability is a function of a drug’s chemical and physical structure and interaction with or behavior within the digestive tract, optimizing these factors can help transform a poorly-bioavailable drug product into one with acceptable pharmacokinetics. This website outlines the most significant such strategies for accomplishing this. These include altering the chemical structure of the drug substance through backbone or salt modifications, formulation with solubility or absorption enhancers, and increasing the effective surface area of the drug or it’s solubility as an amorphous form through solid dispersions in suitable polymers. Taken singly or in combination, these techniques provide the means of favorably altering the pharmacokinetics of development-stage drugs, while presenting even greater opportunities for patient-centered value and lifecycle management.