ATI RN
Chapter 12 principles of pharmacology Questions
Question 1 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.
Question 2 of 5
A 44-year-old black male is brought to the emergency department with 6 h of worsening lethargy and confusion. Past medical history is significant for easy bruising, 3 months of bone pain, and frequent pneumococcal infections. Labs were ordered, revealing serum calcium of $17 \mathrm{mg} / \mathrm{dL}$ (normal: 9.0 to $10.5 \mathrm{mg} / \mathrm{dL}$ ). To rapidly lower his serum calcium, you administer calcitonin. However, calcitonin alone is insufficient because it is known to rapidly and suddenly lose its effectiveness within 2 to 3 days of repeated dosing. For this reason, a bisphosphonate, which take 2 to 3 days to become effective, is added simultaneously. What is the term for the rapid decrease in response to calcitonin?
Correct Answer: C
Rationale: Tachyphylaxis (C) is the rapid decrease in response to calcitonin after repeated dosing (2-3 days), likely from receptor downregulation or desensitization, common with peptide hormones. Anaphylaxis (A) is allergic. Prophylaxis (B) is prevention. Tolerance (D) is slower, chronic. Calcitonin's short-term calcium drop (hypercalcemia, 17 mg/dL) pairs with bisphosphonates' delayed onset, a strategic combo in multiple myeloma (suggested by history), highlighting tachyphylaxis's impact on acute management.
Question 3 of 5
A 52-year-old woman with multiple endocrine neoplasia syndromes has a large pancreatic tumor and bilateral adrenal tumors. She is hospitalized on the medicine service. The tumor is considered inoperable. Her blood pressure is $180 / 100 \mathrm{~mm} \mathrm{Hg}$. In addition to intravenous fluids, this patient may benefit from which of the following interventions?
Correct Answer: D
Rationale: Phentolamine IV (D) benefits this patient with likely pheochromocytoma (adrenal tumors, hypertension 180/100), an $\alpha$-blocker reversing catecholamine-induced vasoconstriction rapidly, critical in MEN syndromes. Oral analgesics (A) and transdermal (B) address pain, not BP. Phenoxybenzamine (C) is oral, slower. Tolterodine (original E) is irrelevant. Phentolamine's IV onset controls acute hypertensive crises, stabilizing for surgery or palliation, a key intervention in endocrine emergencies.
Question 4 of 5
The following drugs cause their primary pharmacodynamic effect via non-receptor mediated mechanisms:
Correct Answer: B
Rationale: Mannitol (B) acts via osmotic diuresis, increasing urine volume without receptor binding, used in cerebral edema. Magnesium trisilicate (A) neutralizes gastric acid chemically, also correct but B is selected. Methotrexate (C) inhibits DHFR, an enzyme. Dimercaprol (D) chelates metals, non-receptor mediated too. Sumatriptan (original E) is a 5-HTâ‚ agonist. Non-receptor mechanisms, like mannitol's osmotic effect, bypass traditional signaling, critical in emergencies for rapid, physical action, contrasting receptor-based drugs in pharmacology.
Question 5 of 5
The following drugs obey non-linear (dose-dependent) elimination pharmacokinetics:
Correct Answer: C
Rationale: Phenytoin (C) exhibits non-linear kinetics, with saturable hepatic metabolism (CYP2C9) causing half-life to increase at high doses (e.g., >300 mg/day). Aspirin overdose (A) and ethanol (D) are zero-order at high levels, also correct but C is chosen. Heparin (B) is complex, not purely non-linear. Ceftazidime (original E) is first-order. Non-linear kinetics, as with phenytoin, complicate dosing (e.g., toxicity risk), requiring monitoring, unlike linear drugs with predictable clearance.