Excretion- Pharmacokinetics

Question 1

Drug clearance

Answer 1

Synergy of all drug eliminating processes
- Mainly controlled by hepatic metabolism and renal excretion

Theoretical volume of fluid which drug is remove from in a given time.

Question 2

Kidneys in drug clearance

Answer 2

Main organ that excretes drugs- in the urine.

Question 3

Non-renal excretory methods

Answer 3

Bile—> Feaces

Sweat

Expiration

Saliva

Breast milk

Question 4

Causes of low drug clearance

Answer 4

Normal variation

Old age

Impaired kidneys and liver

Enzyme inhibition

Genetically poor metaboliser

Neonates

Question 5

Causes of high drug clerance

Answer 5

Normal variation

Genetic hypermetabolism

Enzyme induction

Increased renal blood flow

Question 6

Half life

Answer 6

Time taken for the concentration of drug in plasma to half.

Provides information for:

• Drug elimination time course
• Time course for drug accumulation
• Choice of dose interval: Volume of distribution/ clearance

Plasma concentration is negligible after 5 half lives.

Question 7

Steady state

Answer 7

An equilibrium between drug clearance and giving doses to give desired therapeutic effect.
- Additional doses replace what has been cleared.

Requires at least 5 half lives.

Question 8

Dosing of drugs

Answer 8

Can be determined by half life

Vd/ clearance

Vd determines loading dose whilst clearance determines maintenance dose.