Process of the @UT06806@ of potentially toxic substances by the body, the @B00667@ they undergo, the distribution of the substances and their metabolites in the tissues, and the @E02038@ 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 @PT06835@, but the latter term should be restricted to the study of pharmaceutical substances.