title: What is bioavailability? Philosophy of bioavailability testing.
abstract: Bioavailability is viewed by many as a criterion of clinical effectiveness. FDA regulations recognize measurements of pharmacologic responses and clinical effectiveness as sufficing bioavailability. However, most or practically all bioavailability studies are based on blood level or urinary excretion data. Unless explicitly correlated, blood level and urinary excretion data do not per se reflect clinical effectiveness. Clinical effectiveness is so complex (disease states, nutritional status) and the factors influencing absorption so numerous (food intake, circadian rhythm, age, etc.) that a test in a small sample size can only be regarded as a biologic quality control test under specified conditions. The problem of evaluation of raw data by various pharmacokinetic methods is also addressed in this paper.
mesh_terms: D000042:Absorption; D001682:Biological Availability; D002940:Circadian Rhythm; D004194:Disease / Q000378:metabolism; D004341:Drug Evaluation / Q000379:methods; D005502:Food; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D004364:Pharmaceutical Preparations / Q000378:metabolism; D011786:Quality Control
chemical_list: D004364:Pharmaceutical Preparations