Clinical Toxicology & Poisoning

Clinical Toxicology & Poisoning

1. Definitions & scope

• Toxicology is the study of the adverse effects of substances on living organisms; any substance becomes a poison when exposure produces a damaging physiological (toxic) effect (G&G 14e Ch.9, p.155).
• Clinical toxicology is the discipline that studies undesired effects of pharmaceutical therapies in humans and the effects and treatment of poisoning — distinct from environmental/ecotoxicology (G&G 14e Ch.9, p.155).
• Toxicokinetics denotes the absorption, distribution, metabolism, and excretion (ADME) of toxins, of toxic doses of therapeutic agents, and of their metabolites; toxicodynamics denotes the injurious effects of these substances on body functions (Katzung 16e Ch.58, p.1097).
• Although toxicokinetics largely parallels pharmacokinetics, important differences emerge at supratherapeutic exposure — saturation kinetics, altered protein binding, delayed/erratic absorption (G&G 14e Ch.9, p.156; Katzung 16e Ch.58, p.1097).
• Hazard = the ability of a chemical to cause injury in a given setting (depends on inherent toxicity and amount of exposure); risk = the expected frequency of an undesirable effect from exposure, estimated from dose-response data (Katzung 16e Ch.56, p.1063).
• Adverse drug effects occur with normal therapeutic use, whereas drug toxicity results from supratherapeutic concentrations (unintentional or intentional) (G&G 14e Ch.9, p.159).
• Over 1 million acute poisonings occur annually in the USA; most deaths are intentional suicidal overdoses in adolescents/adults. Even serious exposures are rarely fatal if the victim receives prompt medical attention and good supportive care (Katzung 16e Ch.58, p.1097).