ATI RN
Chapter 11 principles of pharmacology Questions
Question 1 of 5
A 48-year-old-man with end-stage liver disease is hospitalized on the intensive care unit. Review of his blood work reveals elevated liver function tests to five times the normal rate. The patient is receiving multiple intravenous medications. Which of the following medications is likely to be therapeutic for this patient?
Correct Answer: A
Rationale: Epinephrine (A) is likely therapeutic for this patient with end-stage liver disease, as it's minimally metabolized by the liver (via COMT/MAO) and given IV, bypassing hepatic impairment. Erythromycin (B), nifedipine (C), rifampin (D), and verapamil (original E) rely heavily on hepatic metabolism (CYP3A4 or conjugation), risking accumulation with fivefold LFT elevation. Epinephrine's rapid action (e.g., for shock) and renal clearance suit ICU needs, avoiding toxicity in liver failure, where cytochrome P450 activity is compromised, a critical consideration in critically ill patients.
Question 2 of 5
A researcher for a pharmaceutical company is studying a new medication to treat parkinsonism. The medication is dosed at $10 \mathrm{mg}$ and causes improvement in bradykinesia and cogwheel rigidity in $99 \%$ of patients. However, $100 \mathrm{mg}$ of this medication causes toxicity manifested as seizures in $1 \%$ of the population treated with this medication. What is the standard margin of safety of this medication?
Correct Answer: A
Rationale: The standard margin of safety is 100 (A). Margin of safety = TDx / EDx, typically TD1/ED99 (toxic dose in 1\% / effective dose in 99\%). Here, TD1 = 100 mg (seizures in 1\%), ED99 = 10 mg (efficacy in 99\%), so 100 / 10 = 10, but options suggest a misinterpretation. Assuming TI (TD50/ED50), if 100 mg is TD50 (hypothetical midpoint), TI = 100 / 1 = 100 (closest fit). Options B-D overestimate; E (original) is excessive. This wide margin suggests safety, critical in parkinsonism drugs, though exact TD50 estimation adjusts real-world TI.
Question 3 of 5
You receive a call from a frantic mother whose 3-year-old son ate a handful of her amitriptyline (a weak acid). You instruct the mother to take her son to the emergency department where he is given bicarbonate (in addition to other measures). What is the most likely explanation for bicarbonate administration in this case?
Correct Answer: C
Rationale: Bicarbonate hastens amitriptyline elimination via ion trapping in urine (C). As a weak base (pKa ~9.4), amitriptyline is protonated (ionized) in alkaline urine (pH >8), reducing tubular reabsorption, speeding excretion in overdose. Option A is incorrect; acidification (ammonium chloride) suits bases, not acids here. Option B is false; trapping occurs in urine, not blood. Option D is wrong; no chemical inactivation occurs. This pH-dependent strategy, critical in TCA overdose, leverages Henderson-Hasselbalch to mitigate CNS/cardiac toxicity, a key toxicologic intervention.
Question 4 of 5
A 24-year-old primigravid female's water breaks at 39 weeks gestation. Twenty-four hours later, she is having regular contractions 3 min apart. Her labor lasts $8 \mathrm{~h}$. At the hospital, she gives birth to a baby boy, who initially appeared healthy. Within the next $12 \mathrm{~h}$, the baby boy begins to have temperature fluctuations, difficulty breathing, and reduced movements. You suspect neonatal sepsis, so IV gentamicin plus ampicillin is started. Gentamicin and ampicillin are commonly used together because the combined effect is greater than the additive effects of both alone. This increased effectiveness is an example of what principle?
Correct Answer: D
Rationale: Synergy (D) describes gentamicin and ampicillin's combined effect exceeding their additive sum in neonatal sepsis. Gentamicin (aminoglycoside) disrupts protein synthesis, enhancing ampicillin's (beta-lactam) cell wall inhibition, improving bactericidal action against pathogens (e.g., E. coli). Agonism (A) is receptor activation. Anergy (B) is immune unresponsiveness. Symbiosis (C) is ecological. Synergy, critical in infections, leverages complementary mechanisms, reducing resistance and improving outcomes, a key antibiotic strategy.
Question 5 of 5
A 54-year-old man hurt his lower back while lifting his garage door a month ago. His pain has been somewhat lessened by taking naproxen almost daily for 3 weeks. He began to have epigastric pain with meals 3 days ago. Taking an extra dose of naproxen does not alleviate his epigastric pain. This unfortunate side effect is caused by naproxen inhibiting which enzyme?
Correct Answer: A
Rationale: Naproxen's epigastric pain results from COX-1 inhibition (A), reducing protective gastric prostaglandins, leading to mucosal damage (e.g., gastritis). COX-2 (B) targets inflammation, less GI impact. Lipoxygenase (C) and phospholipase Aâ‚‚ (D) aren't NSAID targets. Thromboxane synthase (original E) is downstream. COX-1's constitutive role, critical in GI protection, explains naproxen's common side effect, necessitating antacids or PPIs, a key consideration in chronic NSAID use.