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Chapter 26 principles of pharmacology Questions
Question 1 of 5
Precipitation may occur when mixing aqueous solutions of meperidine hydrochloride with which of the following solutions?
Correct Answer: A
Rationale: Precipitation occurs with meperidine hydrochloride and sodium bicarbonate (A), as meperidine's protonated amine (acidic) reacts with bicarbonate's base, forming insoluble free base at pH > pKa (~8). Atropine sulfate (B) and sodium chloride (C) remain soluble. No option D or original E. This incompatibility, common with pH shifts, requires separate administration in IV therapy, ensuring drug stability and efficacy, a practical concern in clinical pharmacology.
Question 2 of 5
A 27-year-old man with HIV disease and hepatic insufficiency presents to his primary care physician complaining of rectal pain and bleeding with bowel movements. Physical examination reveals several internal and external hemorrhoids. The patient would like to avoid surgical therapy for this condition. Which of the following routes of drug administration would be preferred in this patient?
Correct Answer: D
Rationale: Rectal (D) administration is preferred for this patient with hemorrhoids, hepatic insufficiency, and HIV, delivering drugs (e.g., hydrocortisone suppositories) directly to the site, minimizing systemic exposure and hepatic metabolism. Enteral (A) risks first-pass metabolism, worsened by liver dysfunction. Intramuscular (B) and intravenous (C) are systemic, unnecessary for local relief. Transdermal (original E) is impractical for rectal tissue. Rectal's local action reduces systemic load, critical in hepatic compromise, offering rapid relief, patient comfort, and avoiding surgical risks in an immunocompromised state.
Question 3 of 5
The therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces an efficacious response. By this definition, which of the following medications has the largest therapeutic index?
Correct Answer: A
Rationale: Diazepam (A) has the largest therapeutic index (TI = TD50/ED50), often >100, as its toxic dose (e.g., respiratory depression) far exceeds its anxiolytic dose, making it relatively safe. Digoxin (B), gentamicin (C), lithium (D), and theophylline (original E) have narrow TIs (<10), with toxicity (e.g., arrhythmias, ototoxicity, tremors, bronchospasm) near therapeutic doses. Diazepam's wide TI reflects its forgiving dose-response, critical in anxiolytics vs. drugs requiring tight monitoring, a key safety metric in pharmacology.
Question 4 of 5
A 22-year-old woman who is afraid of running into her former boyfriend actually meets him unexpectedly in a shopping mall. Her fears are because their former relationship was marked by physical and mental abuse. Memories of him are met with increased anxiety and fear. Which of the following physiologic responses would this woman be expected to exhibit at this time of seeing this man?
Correct Answer: C
Rationale: Hypertension (C) is expected due to sympathetic activation from fear and anxiety, releasing catecholamines (e.g., epinephrine), increasing heart rate and vasoconstriction. Bradycardia (A) opposes this fight-or-flight response. Diarrhea (B) may occur later but isn't immediate. Sweating (D) accompanies but is secondary. Tracheal deviation (original E) is unrelated. This acute stress response, mediated by the HPA axis and sympathetics, elevates BP, a physiologic adaptation to perceived threat, relevant in anxiety pharmacology.
Question 5 of 5
Researchers interested in studying a certain cytochrome P450 enzyme wish to isolate the enzyme of interest from the many other proteins in the cells. One of their initial steps is to lyse the cells and isolate the organelle which carries the enzyme they want to study. Which organelle will they isolate to find CYP enzymes?
Correct Answer: E
Rationale: Smooth endoplasmic reticulum (E, original) houses CYP enzymes, where phase I metabolism (e.g., oxidation) occurs in hepatocytes. Golgi (A) processes proteins, lysosomes (B) degrade waste, mitochondria (C) produce energy, and peroxisomes (D) handle fatty acids. SER's microsomal fraction, rich in CYPs (e.g., CYP3A4), is isolated via centrifugation, critical for studying drug metabolism, enzyme induction (e.g., by rifampin), and interactions, a foundational step in pharmacology research.