Bioavailability testing study designs

Both bioavailability and bioequivalence focus on measuring the absorption of the drug into systemic circulation hence, similar study design approaches are used to establish bioavailability of a drug or to assess bioequivalence. Bioavailability is a comparison of the drug product to an intravenous formulation, a solution, or a suspension, whereas bioequivalence is a more formal comparative test that uses specified criteria for comparisons with predetermined bioequivalence limits for evaluation. 

The last step of the drug discovery process involves the testing of lead compounds to address issues such as efficacy, bioavailability, and safety. Testing may include in vitro assays but ultimately would require a suitable disease model and studies in animals. Many compounds may need to be designed and synthesized to identify the one compound with all the desired properties. Such a compound can be advanced to preclinical studies and eventually to the clinic. 

In 1975 an EU Directive (75/318/EEC) required each member state to ensure the submission of safety and efficacy for marketing authorisation. Good laboratory practice (GLP) became the principle of non-clinical testing on pharmaceutical products and the requirement of a GCP standard in conducting clinical trials. It stated that all phases of clinical investigation, including bioavailability and bioequivalence studies shall be designed, implemented and reported in accordance of GCP (75/318/EEC, B.1.1). 

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