ADME

What does ADME stand for?

Absorption, Distribution, Metabolism, Excretion

What does ADME describe?

The four pharmacokinetic stages, which occur simultaneously

What is pharmacokinetics?

The study of how the body processes a drug

What is the primary mechanism for drug absorption?

Passive diffusion

What is an example of a drug absorbed by carrier-mediated transport?

Levodopa

How can diet affect levodopa absorption?

High-protein diets may reduce absorption

What is the role of P-glycoproteins in drug absorption?

They are efflux transporters that actively pump absorbed drugs back into the gut lumen using ATP

Where are P-glycoproteins located?

In the apical membrane of intestinal epithelial cells

What is bioavailability (F)?

The fraction of an administered dose that reaches systemic circulation

How is bioavailability expressed?

As a fraction or percentage, without units (e.g., 0.8 or 80%)

What is the bioavailability of an IV drug?

1 or 100%

What are causes of incomplete oral bioavailability(4)?

1) Failure of disintegration/dissolution,

2) Chemical/enzymatic/bacterial degradation,

3) Incomplete absorption or P-gp efflux,

4) First-pass metabolism

Where does first-pass metabolism occur?

Gut wall and liver

Name 4 pharmacokinetic stages

Drug at the site of elimination

Then in plasma

drugs/metabolites in tissue

Then in urine, faeces and bile