Excretion Route Characterisation

Excretion route characterisation identifies primary and secondary pathways eliminating drugs and metabolites from the body. Renal excretion dominates for small hydrophilic molecules; hepatic metabolism and biliary excretion predominate for lipophilic compounds. Metabolism-independent pathways including pulmonary and transdermal excretion account for volatile or dermally permeable compounds. Radiolabelled drug studies track excretion routes quantitating percentages.

Excretion route knowledge informs dose adjustments in patients with renal or hepatic impairment. Individual excretion rate variation from genetic polymorphisms explains interindividual pharmacokinetic differences. Drug-drug interactions involving excretion pathway competition cause accumulation and toxicity risk. Regulatory submissions incorporate excretion characterisation supporting dose recommendations. Environmental release of drugs through excretion requires monitoring in aquatic systems.