PHARMACOKINETICS-4
EXCRETION
The process by which a drug or its metabolite is eliminated from the body. It is the final and last part of the phenomenon of pharmacokinetics.
Excretion and Secretions are two different entirely opposite actions of the body on a drug. Excretion is a passive movement of the drug according to the concentration and pressure gradient towards its port of elimination.
Secretion needs special oxidation-reduction energy which the body gets from some oxidation-reduction process to move the drug against its concentration and pressure gradient from one compartment to another compartment. The best example is the tubular secretions of some reabsorbed blood contents like sodium, potassium, and chloride ions back into the renal tubules.
The major routes of excretions are,
1.The Kidneys by urine
2.Fecal or stools by colon and rectum
3.Lungs by respiration
4.Breast Milk
5.Skin by sweat.
