Module 6: how drugs work: learner's workbook

5.3 Elimination of drugs from the body and drug half-life

Page last updated: 2004

Once drugs enter the body, the process of leaving the body or elimination begins. In order for drugs to leave the body, most drugs need to be metabolised. This is a chemical process in which the liver transforms the drug into a substance called a metabolite that can be passed out of the body.

While drugs and their metabolites are mostly excreted by the kidneys into urine, drugs can also leave the body in other methods, such as breath and sweat, hence the noticeable smell of alcohol on someone who has been drinking very heavily. Drugs can also leave the body in very small quantities via saliva and breast milk.

Drug testing often detects the metabolites of specific drugs in the urine of a person, rather than the drug itself.


  • Various methods of drug administration including:
    • Injecting
    • Smoking
    • Inhaling
    • Snorting
    • Swallowing
  • Intravenous drug use and inhaling the fumes of a substance are the two fastest methods of achieving psycho-active drug effect.

Distance learners

(A good point for student to contact facilitator.)

Distance learners should take time now to reflect on their learning, check in with their facilitator and determine their progress.