Pharmacokinetics

Question 1

What two broad categories affect the oral bioavailability of medicines?

Answer 1

Characteristics of the medicine
Characteristics of the patient

Question 2

Give five characteristics of the medicine which may affect the oral bioavailability of a drug.

Answer 2

Molecular weight
Molecular charge (pKa)
Disintegration of the drug
Dissolution characteristics in GI fluid
Lipophilicity

Question 3

Give some characteristics of the patient which may affect the oral bioavailability of a drug (9 on the card).

Answer 3

Gastric contents
Gastric pH
Intestinal blood circulation
Gut membrane permeability
Hepatic first-pass metabolism
Enterohepatic re-circulation
Biliary excretion
Drug efflux in gut wall (active transport of drugs out of cells, causing drug resistance - common in bacterial antibiotic resistance)
GI and hepatic disease.

Question 4

What two main factors affect drug distribution?

Answer 4

Body water content
Plasma protein binding

Question 5

What group of enzymes are responsible for the majority of phase 1 metabolism reactions?

Answer 5

Cytochrome P450 group (CYP450)

Question 6

What are the three ways phase 1 enzymes metabolise drugs in order for them to combine with another molecule?

Answer 6

Oxidation
Reduction
Methylation

Question 7

What is the function of phase 2 enzymes in metabolism?

Answer 7

Conjugation - they metabolise things into more water soluble compounds, which are usually inactive and more easily excreted in the urine or bile.

Question 8

What is the most common route of medicine and metabolite excretion?

Answer 8

Glomerular filtration