Question

Discuss the role of the liver and kidney in drug metabolism and excretion. Include, at least, an analysis of two (2) relevant cellular and/or biochemical processes per organ (showing how the drug is metabolized and excreted).

Answer 1

Liver

Liver is a primary site for drug metabolism.

Mechanism

In liver drugs are converted into active metabolites or inactive form by liver enzymes. The primary mechanism for metabolism of drug in liver is by a specific group of cytochrome P-450 enzymes. The level of P-450 enzymes control the rate of metabolism. The level is less in infants and newborn. If the enzyme is less the effect of drug including side effects increases.

Elimination

Drugs are eliminated in liver through bile in unchanged form or after converting into metabolites. The bile with drug is secreted to the digestive tract from there drug eliminated in feces or reabsorbed into the blood stream and recycled.

Kidney

The role of kidney in drug metabolism is under study.

Metabolism

The recent studies shows that drug metabolism is carried out in kidney very actively. Kidney is metabolically very active in the bio transformation of drugs. The drugs such as morphine, paracetamol and p-aminobenzoic acid are metabolized in kidney. The metabolism is reduced in kidney diseases. The enzymes CYP1, CYP2, CYP3 are responsible for drug metabolism in kidney.

Elimination

Drugs that are eliminated through kidney should be water soluble and must not be bonded tightly to protein in the blood stream. The ability of the kidney to excrete drugs depends upon:

• Urine flow
• Blood flow to kidney
• The condition of kidney.