Process of the @[email protected] of potentially toxic substances by the body, the @[email protected] they undergo, the distribution of the substances and their metabolites in the tissues, and the @[email protected] of the substances and their metabolites from the body. Both the amounts and the concentrations of the substances and their metabolites are studied. The term has essentially the same meaning as @[email protected], but the latter term should be restricted to the study of pharmaceutical substances.