Mechanism of Drug action

Question 1

state the types of drug antagonism (4)

Answer 1

1. Receptor blockade
2. Physiological antagonism
3. Chemical antagonism
4. Pharmacokinetic antagonism

Question 2

Describe the types of drug antagonism

Answer 2

receptor blockade = competitive, irreversible, use dependency of ion channel blocker (local anaesthetics)

physiological antagonism = DIFFERENT receptors, OPPOSITE effects in the same tissue (NA + histamine on BP)

chemical antagonism = interaction in solutions, dimercaprol => heavy metal complexes (chelating agent)

pharmacokinetic antagonism = antagonist => ↓conc of active drug at action site + ↑metabolism, ↑excretion, ↓absorption (barbiturates)

Question 3

Drug tolerance description

Answer 3

A gradual decrease in responsiveness to a drug with repeated administration (days/weeks)

Benzodiazepine

Question 4

Effects of drug tolerance (6) ppeddc

Answer 4

Pharmacokinetic factors = Increase metabolic rate (barbiturates/alcohol)

Decrease in receptors = via membrane endocytosis, receptor down regulation (b-adrenoceptors)

Denervation supersensitivity = receptor up-regulation

Change in receptors = desensitisation => conformational changes (nAChR at neuromuscular junction)

Mediator store exhaustion = Amphetamines

Physiological adaptation = homeostatic responses, tolerance to side effects of drug

Question 5

What 2 factors are the receptor families based on? (how are they distinguished)

Answer 5

Molecular structure

signal transduction systems

Question 6

Outline the 4 types of receptor families (speed and example)

Answer 6

Ion channel-linked receptors = fast (m secs), nAChR; GABAa

G protein-coupled = slower (secs), B1- adrenoreceptors (heart)

Kinase linked types = insulin/growth factors (mins)

Intracellular steroid type = steroid/thyroid hormones (hrs), DNA transcription regulation

Question 7

Outline the location, effector, coupling and examples for each receptor type

Answer 7

Question 8

Outline how the different receptors function, their timescale and examples

Answer 8

Question 9

Distinguish between the different types of receptors and their binding domains

Answer 9

Question 10

Describe how G proteins work and what they activate

Answer 10

Question 11

Use dependency

Answer 11

Increased tissue activity = blocker will be more effective (will be taken up more) = increased interaction between the drug and target