Pharmacodynamics II

Question 1

Describe competitive antagonists

Answer 1

High enough conc of agonist displaces a competitive antagonist at receptor site, results in activation

Question 2

Describe the affinity and efficacy of competitive antagonists

Answer 2

Has affinity but 0 efficacy, binds to receptor but no response induced > Inc conc of agonist can overcome effect of competitive antagonist and displace it hence activation still occurs

Question 3

Describe non-competitive antagonists

Answer 3

Binds permanently to receptor with high affinity leaving it unable to be activated by agonist despite conc of agonist present

Question 4

Describe the affinity and efficacy of non-competitive antagonists

Answer 4

Has affinity but 0 efficacy, binds to receptor but no response induced so prevents agonist binding and permanently bound to receptor

Question 5

What is dose ratio (DR)?

Answer 5

Add all the agonist conc together divide by one without agonist

Question 6

What is pA2 and what does it change or not change with?

Answer 6

Measure of affinity of competitive antagonists for its receptor
Doesn’t change with agonist used/tissue location for same receptor/Does with diff receptor/antagonist

Question 7

What are clinically relevant competitive antagonists used for?

Answer 7

Used to block endogenous agonists

Question 8

Name some examples of clinical competitive antagonists

Answer 8

Carvediol, Cimetidine, Nalonxone

Question 9

Describe Carvedilol

Answer 9

Beta1 selective adrenoceptor reversible comp ant used for hypertension treatment (BB)

Question 10

Describe Cimetidine

Answer 10

Histamine H2 receptor reversible comp ant reduced gastric acid secretion used to heal gastric/duodenal ulcers

Question 11

Describe Naloxone

Answer 11

Opioid receptor reversible comp ant used to reverse opioid-induced respiratory depression and opioid overdose

Question 12

Name some examples of non-competitive antagonists

Answer 12

Prasugrel, Ketamine, Dextromethorphan

Question 13

Describe prasugrel

Answer 13

Purinoceptor irrevers comp ant blocks platelet aggregation used as antithrombotic agent

Question 14

Describe Ketamine

Answer 14

Glutamate receptor channel blocker, IV anaesthetic

Question 15

Describe Dextromethrophan

Answer 15

Glutamate receptor channel blocker, new use in treatment of cancer pain

Question 16

What are the differences between non/competitive antagonists?

Answer 16

Competitive antagonist dec potency without changing efficacy (takes more agonist to have effect but same maximum is possible vs Non-competitive antagonist dec potency and efficacy

Question 17

Describe competitive assays using the receptor binding technique

Answer 17

Single conc of radioligand used > Level of specific binding of radioligand determined with range of conc of other competing non-radioligands (potency which they compete for radioligand binding measured)

Question 18

What is IC50?

Answer 18

Conc of competing ligand which displaces 50% of specific binding of radioligand

Question 19

What is Ki?

Answer 19

Inhibition constant for drug, conc of competing ligand that occupies 50% of receptors if no radioligand were present (IC50 value vary btw experiments depending on RD conc, Ki absolute)