Pharmacology- Introduction to Pharmacology

Question 1

What are the chemical forces/bonds that binds aspirin to its receptor

Answer 1

covalent- long lasting

multiple sites effect

anti-inflammatory: cyclooxygenase (COX-1/2) is inhibited irreversibly by covalent bond

Question 2

What sort of drugs usually use hydrophobic bonds?

Answer 2

local anasthetic- bind to membrane (stablises it)

Question 3

Choose 2 TRUE statements:

Activation of receptor is governed by efficacy

Activation of receptor is governed by affinity

Occupation of receptor is governed by efficacy

Occupation of receptor is governed by affinity

Answer 3

Occupation of receptor is governed by affinity

• higher affinity compounds bind more avidly to the receptors

Activation of receptor is governed by efficacy

• magnitude of functional response will depend on the capacity of a drug to produce an alteration in a target cell

Question 4

what can bioassay (organ bath) determine for a drug?

Answer 4

efficacy

potency

Question 5

What is Emax

Answer 5

measure of efficacy

Question 6

What is EC50

Answer 6

measure of potency- strength of drug interaction (how much drug is needed for a certain effect)

Question 7

If a drug has a low EC50, what does it mean

Answer 7

more potent drug

*higher potency usually mean higher affinity

Question 8

What does drug efficacy indicate?

Answer 8

tendency to activate receptor once bound

.’. antagonists = 0 efficacy

Question 9

Define efficacy

Answer 9

the ability of a drug to cause a functional response as a result of binding to its receptor

Question 10

Define potency

Answer 10

measure of drug activity, governed by both affinity and efficacy

Question 11

2 Drugs with same Emax but A has lower EC50, what does it mean

Answer 11

same efficacy but A is more potent (requires less amount to reach max response)

Question 12

What is a partial agonist

Answer 12

when 100% of the receptors are occupied but tissue response is submaximal (compared to endogenous)

Question 13

What is the idea of spare receptors

Answer 13

all receptors do not have to be occupied to produce a full response

WHY=>
1. spare receptors increase both SENSITIVITY and SPEED of a tissue’s responsiveness to a ligand

2. require less drug to produce desired effect (drug economy)

Question 14

Which drug can get better absorbed? lipid soluble or aqueous based?

Answer 14

lipid soluble

subjected to large transmembrane conc. grad. -> diffuse more rapidly

Question 15

How does being weak base/acid affect a drug’s absorption

Answer 15

pH determines drug ionisation

most drugs are either weak acids (eg. aspirin) or weak bases

conjugate form= charged
.’. gets trapped with urine and is excreted

*pH of plasma will affect the proportion of ionised/unionised molecules of drug > determine its activity level

Question 16

What is pharmacokinetics

Answer 16

Actions of body on the drug (eg. excretion, duration of action..)

Question 17

What is Pharmacodynamics?

Answer 17

Actions of drug on body

eg. drug-receptor interaction

Question 18

Formula for volume of distribution of drug

Answer 18

VD (ml) = Dose (mg) / drug plasma concentration (mg/ml)

Question 19

VD (volume of distribution) higher than total volume of water means

Answer 19

drug is highly distributed in tissue

Question 20

How does VD change in

1. Renal failure
2. Liver failure
3. dehydration

Answer 20

1. increase VD (fluid retention)
2. Increase VD (altered body fluid and plasma protein binding)
3. decrease VD

Question 21

equilibrium of drug distribution is determined by?

Answer 21

1. permeability of barrier to the drug
2. pH of compartments/chemical nature of drug
3. binding capacity within compartments

Question 22

4 major class of receptors

Answer 22

1. ligand-gated ion channels
2. GPCR
3. Kinase linked receptors
4. nuclear receptors (eg. oestrogen, thyroid hormones)