ATI RN
Chapter 12 principles of pharmacology Questions
Question 1 of 5
Which class of antibody has the longest serum half-life and opsonizes antigens for phagocytosis through two different pathways?
Correct Answer: A
Rationale: IgG (A) has the longest serum half-life (~21 days) and opsonizes antigens via Fc receptors and complement activation, enhancing phagocytosis (e.g., bacterial clearance). IgM (B) is short-lived, pentameric. IgA (C) protects mucosae. IgE (D) drives allergies. No original E. IgG's persistence and dual opsonization (FcγR and C3b) make it key in immunity and monoclonal antibody drugs (e.g., rituximab), impacting pharmacokinetics and therapeutic longevity.
Question 2 of 5
Which of the following radionuclides is most commonly used in nuclear pharmacy practice?
Correct Answer: C
Rationale: â¹â¹áµTc (C) is most commonly used in nuclear pharmacy, a gamma-emitter (tâ‚/â‚‚ 6h) ideal for imaging (e.g., bone scans), produced via generators. â¶â·Ga (A) is for infection. ²â°Â¹Tl (B) is cardiac-specific. ¹²³I (D) and ¹³³Xe (original E) are less versatile. Tc-99m's short half-life and gamma emission suit diagnostics, dominating nuclear medicine for its availability and imaging clarity, a staple in radiopharmaceuticals.
Question 3 of 5
A 29-year-old man presents to his primary care physician complaining of dysuria, urgency, and painful ejaculation. The patient has a past medical history of allergic rhinitis. Physical examination reveals a tender prostate. The patient is given a prescription of sulfamethoxazole to be taken daily (q 12 h) for 30 days. The half-life is 12 h. How long will it take for the medication to reach $90 \%$ of its final steady state level?
Correct Answer: D
Rationale: It takes 40 h (D) for sulfamethoxazole (tâ‚/â‚‚ = 12 h) to reach $90\%$ steady state. Steady state is ~4-5 half-lives; $90\%$ occurs at ~3.3 half-lives (derived from 1 - 1/2^n = 0.9, n ≈ 3.32). Thus, 3.32 × 12 h ≈ 39.84 h, rounding to 40 h. Options A (10 h), B (20 h), and C (30 h) are too short; E (50 h) overshoots. This first-order kinetic principle ensures therapeutic levels for prostatitis, with q12h dosing matching tâ‚/â‚‚, optimizing efficacy while minimizing resistance in chronic infections.
Question 4 of 5
A 40-year-old man is brought to the emergency department after suffering a cardiac arrest while in a shopping mall. His blood pressure is $70 / 40 \mathrm{~mm} \mathrm{Hg}$ and his pulse is 40 beats/minute. He is given a dose of intravenous epinephrine. Which of the following reactions is necessary to induce a biologic response of increased heart rate?
Correct Answer: B
Rationale: Drug-receptor complex formation (B) is necessary for epinephrine to increase heart rate. Epinephrine binds $\beta_1$-adrenergic receptors on cardiac myocytes, activating Gs proteins, increasing cAMP, and enhancing contractility/chronotropy. Detrusor contraction (A) is bladder-related. Hepatic oxidation (C) is metabolism, not action. Renal contraction (D) or splanchnic stimulation (original E) are unrelated. This receptor interaction, critical in cardiac arrest, drives rapid hemodynamic response, a pharmacodynamic cornerstone for catecholamines in emergencies.
Question 5 of 5
A 67-year-old hospitalized patient with a deep venous thrombosis of the left calf and pulmonary embolism is currently on intravenous heparin on an hourly drip. Unfortunately, because of a calculation error, the heparin drip is running at 100 times the rate it should be running at. Protamine sulfate is immediately given intravenously. This agent works by which of the following mechanisms of action?
Correct Answer: B
Rationale: Protamine sulfate acts as a chemical antagonist (B), binding heparin (a negatively charged anticoagulant) via ionic interactions, neutralizing it without receptor involvement, reversing overdose effects (e.g., bleeding). Agonist (A) activates receptors. Functional agonist (C) mimics via different pathways. Partial agonist (D) or antagonist (original E) involve receptors. Protamine's direct chemical neutralization, critical in emergencies, restores clotting rapidly, a unique non-receptor mechanism in pharmacology, essential for managing heparin toxicity.