Pharmacology and Therapeutics Flashcards
7 cards from real KAPS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacology and Therapeutics flashcards as text
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?
Answer: 400 mg/h
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.
Which anticoagulant mechanism of action is shared by both unfractionated heparin and low-molecular-weight heparins (LMWHs)?
Answer: Potentiation of antithrombin to inhibit factor Xa
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.
A patient with Parkinson's disease taking levodopa/carbidopa develops hallucinations. Which adjunctive drug is most appropriate to manage this without worsening motor symptoms?
Answer: Quetiapine or clozapine, atypical antipsychotics with low D2 affinity
Quetiapine and clozapine have low striatal D2 affinity relative to limbic areas, allowing antipsychotic effect with minimal worsening of Parkinsonian motor symptoms.
Oseltamivir (Tamiflu) exerts its antiviral effect against influenza through which mechanism?
Answer: Inhibiting neuraminidase to prevent new viral particle release from host cells
Neuraminidase cleaves sialic acid residues that tether new virions to the host cell surface; oseltamivir inhibits this enzyme, trapping viral particles and limiting spread.
Which mechanism best explains tolerance that develops to nitrate vasodilators (e.g., nitroglycerin) with continuous use?
Answer: Depletion of sulfhydryl groups needed for bioactivation and oxidative stress impairing mitochondrial aldehyde dehydrogenase
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.
A pregnant patient in her first trimester requires anticoagulation therapy for a deep vein thrombosis. Which agent is safest to use?
Answer: Unfractionated heparin or LMWH, as they do not cross the placenta
Heparins (UFH and LMWH) do not cross the placental barrier due to their large molecular size and are the anticoagulants of choice throughout pregnancy.
A patient on an MAO-B inhibitor for Parkinson's disease consumes aged cheese. What potentially dangerous interaction can occur?
Answer: Hypertensive crisis due to accumulation of tyramine
MAO normally metabolizes dietary tyramine in the gut and liver; MAO inhibition allows tyramine to enter the systemic circulation, triggering massive norepinephrine release and a potentially fatal hypertensive crisis.