KAPS Pharmacology and Therapeutics 5

Question 1

A drug has a bioavailability of 50% and a clearance of 20 L/h. What is the oral maintenance dose rate needed to achieve an average steady-state concentration of 10 mg/L?

Accepted Answer

400 mg/h

Answer

Oral dose rate = (Css × CL) / F = (10 mg/L × 20 L/h) / 0.5 = 400 mg/h; bioavailability of 50% means twice as much drug must be given orally to achieve the same systemic exposure as intravenous administration.

Question 2

Which anticoagulant mechanism of action is shared by both unfractionated heparin and low-molecular-weight heparins (LMWHs)?

Accepted Answer

Potentiation of antithrombin to inhibit factor Xa

Answer

Both UFH and LMWH bind antithrombin and enhance its inhibition of factor Xa; UFH also inhibits thrombin (factor IIa) due to its greater chain length, while LMWHs have minimal anti-IIa activity.

Question 3

A patient with Parkinson's disease taking levodopa/carbidopa develops hallucinations. Which adjunctive drug is most appropriate to manage this without worsening motor symptoms?

Accepted Answer

Quetiapine or clozapine, atypical antipsychotics with low D2 affinity

Answer

Quetiapine and clozapine have low striatal D2 affinity relative to limbic areas, allowing antipsychotic effect with minimal worsening of Parkinsonian motor symptoms.

Question 4

Oseltamivir (Tamiflu) exerts its antiviral effect against influenza through which mechanism?

Accepted Answer

Inhibiting neuraminidase to prevent new viral particle release from host cells

Answer

Neuraminidase cleaves sialic acid residues that tether new virions to the host cell surface; oseltamivir inhibits this enzyme, trapping viral particles and limiting spread.

Question 5

Which mechanism best explains tolerance that develops to nitrate vasodilators (e.g., nitroglycerin) with continuous use?

Accepted Answer

Depletion of sulfhydryl groups needed for bioactivation and oxidative stress impairing mitochondrial aldehyde dehydrogenase

Answer

Continuous nitrate exposure depletes free sulfhydryl groups and generates reactive oxygen species that impair mitochondrial aldehyde dehydrogenase-2 (ALDH2), the enzyme required for bioactivation of organic nitrates to NO.

(KAPS) Knowledge Assessment of Pharmaceutical Sciences Practice Test

(KAPS) Knowledge Assessment of Pharmaceutical Sciences Practice Test

KAPS Pharmacology and Therapeutics 5