BCSE Pharmacology and Toxicology 3 — Questions and Answers
Question 1: A patient with major depression is started on phenelzine. Which dietary restriction is most critical to prevent a hypertensive crisis?
- Tyramine-containing foods (Correct answer)
- High-potassium foods
- Grapefruit juice
- Calcium-rich dairy products
Correct answer: Tyramine-containing foods
MAO inhibitors like phenelzine prevent the breakdown of tyramine in the gut, causing massive norepinephrine release and a potentially fatal hypertensive crisis when tyramine-rich foods are consumed.
Question 2: Heparin-induced thrombocytopenia (HIT) is caused by:
- IgG antibodies against heparin-PF4 complex activating platelets (Correct answer)
- Direct toxic suppression of megakaryocytes in bone marrow
- Complement-mediated lysis of platelet membrane
- Heparin binding to GPIIb/IIIa and blocking platelet aggregation
Correct answer: IgG antibodies against heparin-PF4 complex activating platelets
In HIT, IgG antibodies form against the heparin-platelet factor 4 (PF4) complex, activating platelets via FcγRIIA receptors and causing paradoxical thrombosis despite thrombocytopenia.
Question 3: Which drug class works by inhibiting the Na+/K+/2Cl- cotransporter (NKCC2) in the thick ascending limb of the loop of Henle?
- Loop diuretics (Correct answer)
- Thiazide diuretics
- Potassium-sparing diuretics
- Carbonic anhydrase inhibitors
Correct answer: Loop diuretics
Loop diuretics such as furosemide inhibit NKCC2 in the thick ascending limb, preventing reabsorption of sodium, potassium, and chloride, producing the most potent diuresis of any diuretic class.
Question 4: A 45-year-old patient develops rhabdomyolysis while taking a statin. Which co-administered drug most likely contributed to this toxicity?
- Gemfibrozil (Correct answer)
- Ezetimibe
- Cholestyramine
- Colesevelam
Correct answer: Gemfibrozil
Gemfibrozil inhibits OATP1B1 and CYP2C8, impairing statin hepatic uptake and increasing plasma statin concentrations, dramatically raising the risk of myopathy and rhabdomyolysis.
Question 5: The cardiotoxicity of digoxin overdose is primarily managed with:
- Digoxin-specific antibody fragments (Digibind) (Correct answer)
- Activated charcoal and dialysis
- Calcium gluconate infusion
- High-dose atropine boluses
Correct answer: Digoxin-specific antibody fragments (Digibind)
Digoxin-specific Fab antibody fragments bind free digoxin in the plasma, rapidly reversing toxicity; because digoxin has a large volume of distribution, dialysis is ineffective.
Question 6: Which mechanism underlies the teratogenicity of thalidomide?
- Inhibition of cereblon-mediated degradation of transcription factors required for limb development (Correct answer)
- Direct alkylation of embryonic DNA causing strand breaks
- Folate antagonism impairing neural tube closure
- Androgen receptor blockade disrupting genital development
Correct answer: Inhibition of cereblon-mediated degradation of transcription factors required for limb development
Thalidomide binds cereblon (CRBN), diverting its E3 ubiquitin ligase activity to degrade transcription factors such as SALL4 that are essential for limb and organ development.
Question 7: Which pharmacokinetic parameter best describes the apparent volume in which a drug is distributed throughout the body?
- Volume of distribution (Vd) (Correct answer)
- Clearance (CL)
- Half-life (t½)
- Bioavailability (F)
Correct answer: Volume of distribution (Vd)
Volume of distribution (Vd) is the theoretical volume that would be necessary to contain the total amount of drug at the same concentration as observed in plasma, reflecting tissue binding and lipophilicity.
BCSE Pharmacology and Toxicology 3
A patient with major depression is started on phenelzine.
Which dietary restriction is most critical to prevent a hypertensive crisis?