4 - Pharmacokinetics

Question 1

Systemic or Local?

a) Salbutamol - asthma
b) Aspirin
c) Betnovate - hydrocortisone cream
d) Cannabis
e) Antacids
f) Nicotine patch

Answer 1

a) Salbutamol - asthma
- local but has systemic effects as taken through lungs
b) Aspirin
- systemic
c) Betnovate - hydrocortisone cream
- local
d) Cannabis
- systemic, needs to travel through blood to have effect on brain
e) Antacids
- local, in GI tract
f) Nicotine patch
- systemic, effect on brain

Question 2

Drugs have to traverse both aqueous and lipid environments. How can drugs cross these barriers?
A: Diffusing through lipid
B: Diffusing through aqueous pores in lipid
C: Carrier molecules
D: Pinocytosis

Answer 2

A: Diffuse through lipid
C: Carrier molecules

can also diifuse through pores but only if drug is soluble in an aqueous environment - not v efficient way of getting drug into body

Pinocytosis can also work but v limited

Question 3

Why might treatment with IV sodium bicarbonate increase aspirin excretion?

Answer 3

IV sodium bicarb will increase urine pH - ionises aspirin making it less lipid soluble, so less is reabsorbed from proximal and distal tubules, therefore increased rate of excretion.

Question 4

Which of the following drugs would be least likely to penetrate lipid membranes?

A: ionised drug
B: non-ionised drug 
C: protein bound drug
D: lipophilic drug
E: hydrophilic drug

Answer 4

A: ionised drug - least likely, cannot cross membranes so not absorbed

B: non-ionised drug - likely, can cross lipid membrane
C: protein bound drug - less likely, bound not available for absorption
D: lipophilic drug - likely
E: hydrophilic drug - less likely, water soluble cant cross lipid membrane