02.04.1 Introduction

The most common way from administration of drug to elimination is by liver metabolism and kidney excretion (Figure 2.7). After oral administration, drugs are taken from the gastrointestinal tract in the circulation for metabolism in the liver.

Figure 2.7 Drug Elimination (Copyright QUT, Sheila Doggrell)

Drugs administered by other routes (e.g. sublingual, via injection) also end up in the circulation being carried to the liver for metabolism. After metabolism in the liver, the metabolites are carried in the circulation to the kidney for excretion in the urine. A few drugs are excreted without metabolism. Some drug metabolites are transported in the bile to the gastrointestinal tract, where they may be recycled or eliminated in the faeces.