ATI RN
Chapter 11 principles of pharmacology Questions
Question 1 of 5
Which of the following emissions from the decay of radionuclides is most commonly used in nuclear medicine imaging?
Correct Answer: D
Rationale: Gamma (D) emissions are most used in nuclear medicine imaging (e.g., Tc-99m in SPECT), penetrating tissue for detection without significant damage. X-rays (A) are diagnostic, not decay emissions. Beta (B) and alpha (C) are ionizing, less suitable. Positron (original E) is for PET. Gamma's high energy and low mass enable non-invasive imaging, critical for diagnosing conditions (e.g., myocardial perfusion), balancing sensitivity and safety in nuclear pharmacy.
Question 2 of 5
A researcher is studying the bioavailability of commonly used antimuscarinics to treat irritable bowel syndrome. Medication A is administered in a $100 \mathrm{mg}$ daily dose orally and $60 \mathrm{mg}$ of the drug is absorbed from the gastrointestinal tract unchanged. Thus, the bioavailability of Medication A is
Correct Answer: B
Rationale: The bioavailability of Medication A is $60\%$ (B). Bioavailability (F) = (Amount absorbed unchanged / Dose) × 100 = (60 mg / 100 mg) × 100 = $60\%$. Options A (50\%), C (70\%), D (80\%), and E (90\%, original) miscalculate. This reflects the fraction reaching systemic circulation intact (e.g., avoiding first-pass metabolism), typical for antimuscarinics (e.g., hyoscyamine), guiding dosing for IBS, where GI absorption and hepatic metabolism determine efficacy, a key pharmacokinetic metric.
Question 3 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 4 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 5 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.