Pharmacology and Therapeutics

Question 1

What is the difference between efficacy and affinity

Answer 1

Affinity: binding strength
Efficacy: ability of a drug to produce an effect once bound

Question 2

What is potency

Answer 2

Conc of drug for a 50% tissue response

Question 3

What is the difference between EC50 and ED50

Answer 3

EC50 : concentration that produces 50% effect
ED50: dose of drug that produces desired effect in 50% of individuals

Question 4

What is bioavailability

Answer 4

fraction of the dose that gains access to the systemic circulation

Answer 5

Diffuse across lipid membranes : does this in unionised form

Carier mediated transport

Question 6

How does pKa and pH relate to whether the drug is ionised or unionised

Answer 6

If pKa of drug and pH of tissue are equal then 50% will be unionised and 50 ionised.

Question 7

How would changes to pH affect weak acid and weak bases ionisation/unionised

Answer 7

Weak acids : if pH decreases then more unionised. more acidic= more unionised
Weak bases: if pH increases then more unionised. more basic= more unionised

Question 8

What four factors affect distribution of a drug

Answer 8

Regional blood flow
Plasma protein binding
Capillary permeability
Tissue location

Question 9

Ho does regional blood flow impact drug distribution

Answer 9

depends on circumstance, e.g. exercise means more to muscles

Question 10

How does plasma protein binding impact drug distribution

Answer 10

Bind to plasma proteins like albumin
depends on :
free drug conc
affinity for the protein binding sites
plasma protein conc

if albumin conc is 0.6 and has two binding sites then 1.2mmol binding capacity

Question 11

How does capillary permeability affect drug distribution

Answer 11

Diffuse across continuous structure if lipid soluble, if not then need transporter
Discontinuous: liver, easily diffuse out
Fenestrated: kidney glomerulus,