DHA Pharmacist Pharmacokinetics and Pharmacodynamics 3

Question 1

On a dose-response curve, potency refers to:

Accepted Answer

The dose required to produce 50% of the maximum effect (ED50)

Answer

The maximum effect a drug can produce

Answer

The slope of the dose-response curve

Answer

The difference between ED50 and LD50

Question 2

A full agonist differs from a partial agonist in that a full agonist:

Accepted Answer

Produces maximal receptor activation (efficacy = 1)

Answer

Binds to a different receptor subtype

Answer

Has a lower affinity for the receptor

Answer

Blocks receptor activation by antagonists

Question 3

The therapeutic index (TI) of a drug is calculated as:

Accepted Answer

LD50 / ED50

Answer

ED50 / LD50

Answer

Cmax / MEC

Answer

Vd / CL

Question 4

A competitive antagonist differs from a non-competitive antagonist because a competitive antagonist:

Accepted Answer

Can be displaced by increasing agonist concentration, shifting the curve right

Answer

Cannot be overcome by increasing agonist concentration

Answer

Permanently binds to the receptor

Answer

Decreases the maximum effect of the agonist

Question 5

Drug tolerance is best described as:

Accepted Answer

A decreased response to a drug after repeated administration requiring higher doses for the same effect

Answer

An immune-mediated hypersensitivity reaction to a drug

Answer

An increased sensitivity to a drug after initial exposure

Answer

The inability to metabolize a drug due to genetic polymorphism

Question 6

Which of the following best describes the Emax model in pharmacodynamics?

Accepted Answer

Drug effect follows a sigmoidal curve and reaches a maximum ceiling effect

Answer

Drug effect increases linearly with dose without a maximum

Answer

Drug effect is proportional only to free drug concentration

Answer

Drug effect depends solely on the route of administration

Question 7

A patient on warfarin is started on rifampicin. Rifampicin is a potent CYP2C9 inducer. What pharmacokinetic change is expected and what clinical action is required?

Accepted Answer

Warfarin metabolism increases; increase warfarin dose to maintain anticoagulation

Answer

Warfarin levels increase; reduce warfarin dose

Answer

Warfarin absorption decreases; switch to parenteral warfarin

Answer

Rifampicin inhibits warfarin; monitor for bleeding and reduce dose