10. Pharmacodynamics

Question 1

What is therapeutic index?

Answer 1

The therapeutic index of a drug is a measure of its safety (ED50/LD50)

Question 2

The efficacy/ intrinsic activity of a drug:

Is greater for drug A if A is effective in a dose of 100 micrograms than for drug B if B is effective in a dose of 100 milligrams? T/F

Answer 2

The dose of a drug required to produce a given effect decribes its potency, not its efficacy. In the example described, drug A is more potent than drug B

Question 3

What is efficacy?

Answer 3

Efficacy, however, is a measure of the maximal effect of an agonist.

Question 4

What is rapid acetylator status vs slow acetylator status?

Answer 4

40% of the UK population and is inherited in an autosomal dominant pattern.

Slow acetylator status occurs in approximately 60% of the UK population and is inherited in an autosomal recessive pattern.

Question 5

Which of the following drugs effect acetylator status?

Hydralazine
Isoniazid
Propanolol
Amiodarone
Digoxin

Answer 5

Hydralazine, Isoniazid,

ALSO: Sulphonamides, Phenelzine, Dapsone, Procainamide.

Question 6

What is potency?

Answer 6

Potency is the dose (mg/kg) required to produce a given effect.

Question 7

The following interactions are antagonistic?

A. Nalaxone and dextropropoxyphe

B. Acetylcysteine and paracetamol

C. Atenolol and salbutamol

D. Protamine and warfarin

E. Tranexamic acid and streptokinase

Answer 7

All except Protamine and Warfarin as Protamine is used to counteract effects of Heparin.

Question 8

Non-competitive agonists:

Have an effect unrelated to the agonist plasma concentration

T/F?

Answer 8

False.

Increasing the agonist dose will increase the response, however the maximum response will never be achieved in the presence of a non-competetive antagonist

Question 9

Non-competitive agonists: Prevent a maximum agonist response?

Answer 9

TRUE

Question 10

Non-competitive agonists: Display surmount ability?

Answer 10

False.

They are non-surmountable.

No matter how high an agonist concentration exists, the peak response will not be reached.

Question 11

At the neuromuscular junction, weak competitive antagonists tend to have a faster onset? T/F

Answer 11

True - as they are given in higher dose so initially there are more molecules to occupy the receptors.

Question 12

Competitive antagonists shift the log dose-response curve down?? T/F

Answer 12

FALSE.

The same maximal response will be possible, just at higher doses.

Question 13

How are competitive antagonists compared?

Answer 13

They are compared using the Dose Ratio of 2, which indicates the degree of right shift of the log dose-response curve.

Question 14

Considering drug-receptor interactions, antagonists will have a higher receptor affinity?

Answer 14

TRUE. but no intrinsic activity.

Question 15

Protein binding of Diazepam and Midazolam?

Answer 15

98%

Question 16

The following are examples of pharmacokinetic drug interactions

Select true or false for each of the following statements.

A. Lithium and thiazide diuretics

B. Digoxin and amiodarone

C. Phenytoin and cimetidine

D. Beta blockers and verapamil

E. Ethanol and diazepam

Answer 16

A. True. Increased lithium levels are produced owing to an increase in lithium reabsorbtion

B. True. Amiodarone reduces the renal clearance of digoxin

C. True. Cimetidine inhibits cyt P450 leading to phenytoin toxicity

D. False. The interactions between beta blockers and verapamil, and ethanol and diazepam are pharmocodynamic

E. False.

Question 17

The following drugs exhibit tachyphylaxis:

Select true or false for each of the following statements.

A.	Glyceryl trinitrate		
B.	Ephedrine		
C.	Succinylcholine		
D.	Trimetaphan				
E.	Hydralazine

Answer 17

GTN, Ephedrine, Trimetaphan

Tachyphylaxis is tolerance that develops rapidly.

Question 18

The following are examples of physiological antagonism

Select true or false for each of the following statements.

A. Morphine and naloxone

B. Fentanyl and doxapram

C. Morphine and pentazocine

D. Ritodrine and syntocinon

E. Furosemide and amiloride

Answer 18

Fentanyl and Doxapram

Ritodrine and Syntocinon

Furosemide and Amiloride

Question 19

Regarding partial agonists:

If given in combination with a full agonist, they can act as an antagonist?

Answer 19

True.

If the full agonist is given at a low dose, the partial agonists effects are additive. As the full agonist dose increases, the partial agonist begins to act as a competitive antagonist.

Question 20

Regarding log-dose response curves:

A partial agonist binds to the receptor with a lower affinity than an agonist?

Answer 20

False.

Partial agonists cannot produce a maximal response, though they may bind to the receptor with the same affinity as agonists.

Question 21

How do partial agonists shift the log-dose response curve?

Answer 21

They shift the curve down and to the right.