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Chapter 11 principles of pharmacology Questions
Question 1 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 2 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 3 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.
Question 4 of 5
The following drugs are partial agonists:
Correct Answer: D
Rationale: Buprenorphine (D) is a partial agonist at μ-opioid receptors, producing submaximal analgesia with a ceiling effect, useful in addiction treatment. Isoprenaline (A) is a full $\beta$-agonist. Morphine (B) is a full opioid agonist. Flumazenil (C) is a benzodiazepine antagonist. Oxprenolol (original E) is a partial $\beta$-agonist, also correct but D is chosen. Partial agonists like buprenorphine balance efficacy and safety, limiting maximal response despite receptor occupancy, a key feature in opioid pharmacodynamics, contrasting full agonists in potency and overdose risk.
Question 5 of 5
In repeated (chronic or multiple) dosing:
Correct Answer: A
Rationale: If the dosing interval exceeds the half-life (A), minimal accumulation occurs (e.g., penicillin G, tâ‚/â‚‚ ~30 min, dosed q6h), as drug clears before the next dose. Option B is false; 50\% is ~1 half-life, 97\% is ~5. Option C is true (peak = 2 × trough at tâ‚/â‚‚ dosing). Option D is correct (loading speeds steady state). Option E (original) about gentamicin is true but specific. This principle, critical in chronic therapy, prevents toxicity, guiding interval selection.