Pharmacokinetics Flashcards
ADME
What is pharmacokinetics? [1 mark]
It is what the body does to the drug
What is pharmacokinetics [1 mark]
It is what the drug does to the body
What is absorption? [1 mark]
When an unchanged drug enters the circulation
What is distribution? [1 mark]
Dispersion of a drug among fluids and tissues of the body
What is metabolism? [1 mark]
Transformation of a drug into daughter compound(s)
What is excretion? [1 mark]
Removal of drugs/metabolites from the body
What is elimination? [2 marks]
Metabolism AND excretion
Why is ADME important? [4 marks]
- Safe use
- Designing dose regimes
- Monitoring
- Medicinal licensing
What is first pass metabolism? [2 marks]
- when the drug is funneled into the liver via the hepatic portal vein
- [drug] at systemic cirulation < [drug] absorbed
Fick’s Law equation [4 marks]
Rate of diffusion = surface area x concentration gradient x permeability
What happens to an acidic drug in acidic environments (e.g. stomach)? [1 mark]
More of it stays unionised/neutral
What happens to an basic drug in basic environments (e.g. intestines)? [1 mark]
More of it stays unionised/neutral
What is the Lipinski rule? [4 mark]
- Small molecular weight
- No more than 5 H-bond donors
- No more than 10 H-bond acceptors – related to metabolism
- Log P < 5 (partition coefficient)
What can Lipinski minimise? [1 mark]
Desirable properties for receptor binding
What is the half life and clearance for 1st order kinetics? [1 mark]
Constant
What happens if you take a big dose in zero order kinetics? [1 mark]
The bigger the dose, the longer it takes to remove it
What does the volume of distribution (Vd) show? [1 mark]
The extent of distribution
Do drugs that bind tightly to plasma proteins have a higher or lower Vd? [2 marks]
LOWER
- ‘trapped’ in the circulation
What is clearance (CL)? [2 marks]
- The volume of blood cleared of the drug per time
- Higher CL = lower half time
What does bioavailability measure? [1 mark]
The extent of absorption
What is the steady/plateu state? [1 mark]
Where:
[drug] absorbed = [drug] eliminated
How can the attainment of steady state be accelearated? [2 marks]
- By an initial loading dose
- Followed by a maintenance dose
How are drugs metabolised? [1 mark]
They are made water soluble
What are the 2 phases of drug metabolism? [2 marks]
- Introducing chemically reactive groups
- Increasing water solubility for excretion
