DHA Pharmacist Pharmacokinetics and Pharmacodynamics

Question 1

A drug has a volume of distribution (Vd) of 700 L in a 70 kg patient. What does this suggest?

Accepted Answer

The drug is extensively distributed into tissues

Answer

A large Vd (much greater than total body water ~42 L) indicates the drug distributes extensively into peripheral tissues rather than remaining in plasma.

Question 2

A drug has a half-life of 8 hours. Approximately how long will it take to reach steady-state plasma concentration with regular dosing?

Accepted Answer

40 hours

Answer

Steady-state is reached after approximately 4–5 half-lives; 5 × 8 hours = 40 hours.

Question 3

Which route of administration completely bypasses first-pass hepatic metabolism?

Accepted Answer

Intravenous

Answer

Intravenous administration delivers the drug directly into systemic circulation, completely bypassing hepatic first-pass metabolism.

Question 4

The bioavailability of an oral drug is 25%. If the IV dose producing the desired effect is 20 mg, what oral dose is required to achieve the same effect?

Accepted Answer

80 mg

Answer

Oral dose = IV dose / bioavailability = 20 mg / 0.25 = 80 mg to achieve equivalent systemic exposure.

Question 5

Hepatic clearance of a high-extraction drug (extraction ratio > 0.7) is primarily dependent on:

Accepted Answer

Hepatic blood flow

Answer

High-extraction drugs are efficiently cleared by the liver on first pass, so their clearance is limited by hepatic blood flow, not enzyme capacity.

DHA Pharmacist Practice Test

DHA Pharmacist Practice Test

DHA Pharmacist Pharmacokinetics and Pharmacodynamics