Intro to pharm

Question 1

What is potency?

Answer 1

The concentration at which a drug is effective (determined by affinity of drug for receptors, its efficacy & the receptor reserve)

n.b. this is in relation to another drug!!

Question 2

What is affinity?

Answer 2

How well a drug binds to its receptor

Question 3

What is efficacy?

Answer 3

How efficiently a drug elicits a response in cells

Question 4

Which enzyme terminates ACh action?

Answer 4

ACh esterase

Question 5

Name an anticholinesterase drug?

Answer 5

Neostigmine (prolongs presence of ACh in cleft = indirect sympathomimmetic)

Question 6

What is the action of Carbidopa?

Answer 6

inhibits the intracellular enzyme required for NA synthesis (prevents excesss NA release) = Parkinson’s

Question 7

What is Sildenafil used to treat (3)?

Answer 7

pulmonary hypertension High altitude sickness erectile dysfunction

Question 8

What type of receptors are GPCR’s?

Answer 8

Metabotrophic receptor

Question 9

What is pharmokinetics?

Answer 9

how the body deals with a drug

Question 10

What are the 4 different receptor superfamilies?

Answer 10

1. Ionotrophic
2. Metabotrophic
3. Tyrosine Kinase
4. DNA-linked

Question 11

What is specifity?

Answer 11

how selective a drug is

n.b. no drug is truly selective (higher concentrations often increases other actions)

Question 12

What does the dissociation constant show?

Answer 12

the concentration of drug that occupies 50% of receptors

Question 13

What does a lower dissociation constant show us about the efficacy of a drug?

Answer 13

Higher efficacy

(less drug is needs to be added before 50% of receptors are bound)

Question 14

How do you calculate the dissocaiation constant?

Answer 14

Question 15

How do you work out fractional receptor occupancy?

Answer 15

Question 16

In which 5 conditions is the fractional receptor occupancy equation valid?

Answer 16

• Equilibrium
• Receptor drug concentration the same as that applied to the system
• 1 drug combines to only 1 receptor
• a negligible amount of drug added is bound
• binding of 1 drug molecule doesnt influence another (no cooperativity)

Question 17

Which direction does a concentration response curve shift with a drug of lower efficacy?

Answer 17

Right

(EC50 increases and receptor reserve decreases)

Question 18

How do we calculate response?

Answer 18

Question 19

What is the EC50?

Answer 19

The concentration of drug that gives 50% of that drugs maximum response

Question 20

On a concentration response curve which side of the dissociation constant does the EC50 lie?

Answer 20

The left

(you dont occupy 50% of the receptors to get 50% the biological response -> often binding = cascade of events)

Question 21

What is partial agonism?

Answer 21

A drugs maximum response is less than the full response the tissue is capable of

(no receptor reserve)

Question 22

With partial agonists how do we need a few or lots of receptors to have an effect?

Answer 22

Lots

(e.g. salbutamol -> lots of beta 2 receptors in lungs)

Question 23

What are the 4 different types of antagonism?

Answer 23

1. Competitive
2. Non-competitive
3. Un-competitive (activation state changes -> exposes binding sites)
4. Physiological (reversal mechanisms e.g baroreceptor reflex)

Question 24

In competitive antagonism what happens to the concentration response curve?

Answer 24

It shifts parrellel to the right

(more agonist is needed to get the same response = no reduction is max response!)

Question 25

What are the 3 different ways of competititve irreversible antagoism?

Answer 25

• Allosteric modulation
• Ligand gated channel blockers
• Block later in pathway from receptor activation to response (e.g. enzyme inhibitor or Ca channel blocker)

Question 26

What is the theory of constitutive activity?

Answer 26

Some receptors have a constitutive (resting) level -> becomes active on its own can agonise to produce response but can use inverse antagonist = no response

Question 27

what is tolerance?

Answer 27

Repeated drug administration leading to adaptive downregulation of receptors to that drug

n.b. this is how some drugs (anti-depressants work -> downregulate serotonin reuptake channels)

Question 28

What happens over time follwoing desensitisation?

Answer 28

Channels recover to normal level of response