ATI RN
Chapter 12 principles of pharmacology Questions
Question 1 of 5
Which equation is true for a zero-order reaction rate of drug ?
Correct Answer: A
Rationale: For a zero-order reaction, dA/dt = -k (A) is true, indicating a constant rate of drug elimination (e.g., ethanol above Km), independent of concentration. Option B (tâ‚â‚‚=0.693/k) is first-order. Option C (A=Aâ‚€eâ»áµ) is first-order decay. No options D or original E exist, but C is incorrect here. Zero-order kinetics, rare in drugs, means half-life increases with dose, complicating dosing (e.g., phenytoin overdose), contrasting with first-order's constant half-life, key in pharmacokinetics.
Question 2 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 3 of 5
Hydrolysis reaction are involved with the metabolism of following drugs, except
Correct Answer: B
Rationale: Diazepam (B) does not undergo hydrolysis; it's metabolized by CYP450 oxidation and glucuronidation (e.g., to nordazepam). Procaine (A), aspirin (C), and lidocaine (D) hydrolyze via esterases (e.g., procaine to PABA), cleaving ester bonds. No original E. Hydrolysis, a phase I reaction, increases polarity for excretion, but diazepam's oxidative path prolongs its action, impacting its use as a long-acting anxiolytic, distinct in metabolism profiles.
Question 4 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 5 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.