ABSTRACT
Drugs are eliminated from the body by excretion of the unchanged drug from the body or by metabolism to form one or more metabolites that can then be excreted. The major excretion pathways include renal excretion of drugs in urine, biliary excretion of drugs to the gastrointestinal tract (GIT), lung excretion of volatile drugs during expiration, in addition to other minor excretion pathways such as excretion of drugs in sweat and in milk. Drug metabolism involves enzymatic modication of the drug chemical structure to form the metabolites. Most of the metabolites are pharmacologically inactive; however, few metabolites have pharmacological activity and some metabolites can cause adverse effects.
