FACEM Pharmacology Fundamentals 4

Question 1

A patient on warfarin develops bleeding after starting fluconazole. The most likely mechanism is:

Accepted Answer

Fluconazole inhibits CYP2C9, reducing warfarin metabolism

Answer

Fluconazole increases vitamin K production

Answer

Fluconazole induces CYP3A4, increasing warfarin production

Answer

Fluconazole displaces warfarin from renal tubule transporters

Question 2

Which statement about zero-order kinetics is correct in the context of emergency pharmacology?

Accepted Answer

Elimination rate is independent of drug concentration

Answer

A constant fraction of drug is eliminated per unit time

Answer

Half-life is constant regardless of plasma concentration

Answer

The drug follows linear pharmacokinetics

Question 3

The antidote for benzodiazepine overdose, flumazenil, acts by:

Accepted Answer

Competitively antagonizing benzodiazepines at the GABA-A receptor

Answer

Increasing GABA synthesis in the CNS

Answer

Irreversibly blocking benzodiazepine binding sites

Answer

Enhancing hepatic metabolism of benzodiazepines

Question 4

Phenytoin exhibits dose-dependent (Michaelis-Menten) kinetics at therapeutic concentrations. The clinical implication is that:

Accepted Answer

Small dose increases can cause disproportionately large plasma level increases

Answer

Small dose increases cause proportionally small plasma level increases

Answer

Phenytoin has a wide therapeutic index

Answer

Steady-state is reached within 24 hours at any dose

Question 5

Which of the following correctly describes the mechanism of action of adenosine in terminating supraventricular tachycardia?

Accepted Answer

Activates A1 adenosine receptors, increasing K+ conductance and slowing AV conduction

Answer

Blocks beta-1 adrenoceptors in the SA and AV nodes

Answer

Inhibits voltage-gated calcium channels in ventricular myocardium

Answer

Enhances vagal tone via muscarinic M2 receptors

Question 6

Activated charcoal is most effective when administered within what timeframe after ingestion, and for which drug type?

Accepted Answer

Within 1 hour; for drugs that bind well to charcoal (e.g., most organic compounds)

Answer

Within 6 hours; for drugs that undergo enterohepatic recirculation only

Answer

Within 1 hour; for drugs not well absorbed by charcoal (e.g., iron, lithium)

Answer

Within 4 hours; for all acidic drugs regardless of formulation

Question 7

The 'ion trapping' phenomenon is important in toxicology because:

Accepted Answer

Drugs accumulate in compartments where pH causes ionization, reducing back-diffusion

Answer

Ionized drugs cross cell membranes more readily than un-ionized forms

Answer

All drugs are ionized at physiological pH and cannot exit cells

Answer

Ion trapping increases renal clearance by preventing tubular reabsorption only for bases