DHA Pharmacist Pharmacokinetics and Pharmacodynamics 2

Question 1

A patient requires a loading dose of gentamicin. The target plasma concentration is 8 mg/L and the volume of distribution is 0.25 L/kg. For a 60 kg patient, what is the loading dose?

Accepted Answer

120 mg

Answer

30 mg

Answer

60 mg

Answer

240 mg

Question 2

Phenytoin exhibits zero-order (saturation) kinetics at therapeutic doses. What clinical implication does this have?

Accepted Answer

Small dose increases can cause disproportionately large rises in plasma concentration

Answer

Small dose increases produce proportionally small increases in plasma levels

Answer

Half-life is constant regardless of dose

Answer

Steady-state is reached faster than with first-order drugs

Question 3

A drug is 95% bound to plasma proteins. Which statement best describes the pharmacokinetic consequence?

Accepted Answer

Only the 5% unbound fraction is pharmacologically active

Answer

A large fraction is available for renal filtration

Answer

The drug will have a very large volume of distribution

Answer

The drug cannot be displaced by other highly bound drugs

Question 4

Creatinine clearance (CrCl) is used in clinical practice primarily to:

Accepted Answer

Adjust doses of renally eliminated drugs

Answer

Estimate hepatic metabolic capacity

Answer

Predict protein binding changes

Answer

Calculate the volume of distribution

Question 5

CYP3A4 is the most abundant hepatic CYP450 enzyme. A drug that strongly inhibits CYP3A4 (e.g., ketoconazole) will most likely:

Accepted Answer

Increase plasma levels of CYP3A4 substrates

Answer

Increase the metabolism of CYP3A4 substrates

Answer

Decrease plasma levels of CYP3A4 substrates

Answer

Have no effect on drugs administered simultaneously

Question 6

In therapeutic drug monitoring (TDM), which of the following drugs has a narrow therapeutic index making TDM essential?

Accepted Answer

Lithium

Answer

Amoxicillin

Answer

Metformin

Answer

Ibuprofen

Question 7

Which pharmacokinetic change is most commonly observed in elderly patients that necessitates dose adjustments?

Accepted Answer

Decreased renal clearance

Answer

Increased hepatic blood flow

Answer

Increased gastric acid secretion

Answer

Increased volume of distribution for water-soluble drugs