Excretion Of Drugs

Question 1

Excretion

Answer 1

Process of drugs and metabolites being irreversibly transferred out from internal to the external environment

Question 2

Glomerular filtration

Answer 2

Non specific and unidirectional process

Low molecular weight (small) compounds , ionized and unionized are filtered. except those bound to plasma protein.

Reduced: reduce dose, increase dose interval

Question 3

Tubular reabsorption

Answer 3

Increase half life of the drug, membrane transporters at distal renal tubule will have active reabsorption of drug from the tubular lumen back to the blood stream.

Question 4

Half life of drug is increased

Answer 4

• Diminished renal plasma flow or hepatic blood flow, for example, in cardiogenic shock, heart failure, or haemorrhage
• Decreased metabolism for example, when another drug inhibits its biotransformation or in hepatic insufficiency, as with cirrhosis.

Question 5

Factors affecting excretion of drugs

Answer 5

1. Plasma concentration of drug
   • Increase in plasma concentration of the drug
   increases the rate of elimination
2. Distribution and binding
   characteristics of the drug
   • Drug extensively bound to plasma proteins will
   have less rate of renal clearance
3. Blood flow to the kidneys
   • Increase in renal blood flow to the kidney
   increases the rate of filtration
4. Biological factor
5. Disease state
6. Drug interactions