ATI RN
Basic pharmacology principles Questions
Question 1 of 5
A medical student is doing a summer research project studying five antibiotics to determine potency using the EC50. Antibiotics are placed in plated culture wells with 100,000 CFU of Escherichia coli. The EC50 results for the five antibiotics are shown in the following choices. Based on the results, the most potent antibiotic is
Correct Answer: B
Rationale: Antibiotic B (EC50 = 2) (B) is the most potent, as potency is inversely related to EC50:the lowest dose achieving 50\% effect (e.g., E. coli kill). Options A (100), C (80), and D (20) require higher doses; E (50, original) is intermediate. B's low EC50 indicates greater receptor affinity or efficacy per unit dose, critical in antibiotic selection, where potency guides efficacy against pathogens, though clinical use also weighs spectrum and resistance, making B superior in this lab context.
Question 2 of 5
A 19-year-old female has a history of absence seizures. She currently takes ethosuximide to control her symptoms. The process of eliminating this drug involves multiple steps of metabolism followed by excretion. Many organs take part in both metabolism as well as excretion of drugs. Which of the following describes a step of metabolism?
Correct Answer: A
Rationale: Acetaminophen glucuronidation by enterocytes (A) is a metabolic step, a phase II reaction conjugating the drug for excretion, occurring in gut and liver. Digoxin transport (B) and pancuronium filtration (D) are excretion, not metabolism. Ethanol exhalation (C) is elimination via lungs, not transformation. Ethosuximide's hepatic metabolism (e.g., hydroxylation) parallels this, with enterocyte glucuronidation enhancing polarity, critical for clearance, distinguishing metabolism from mere transport in pharmacokinetics.
Question 3 of 5
A 21-year-old man presents to his primary care physician complaining of a single, painless ulcer on his penis, which he first noticed a few days ago. He admits to multiple sexual partners. You want to treat him for syphilis with penicillin G, but his history includes an itchy rash following amoxicillin treatment as a child. What must first occur in the body for a penicillin to become allergenic?
Correct Answer: B
Rationale: Penicillin becomes allergenic by binding to a larger molecule (e.g., proteins) (B), forming a hapten-carrier complex the immune system recognizes as foreign, triggering IgE-mediated Type I hypersensitivity (e.g., rash). First-pass metabolism (A) isn't required. Simple exposure (C) needs sensitization first. Option D is false; penicillin's allergenicity is IgE-driven. This conjugation, critical in syphilis treatment (penicillin G), necessitates allergy screening, as prior amoxicillin reaction suggests risk, guiding alternative therapy (e.g., doxycycline).
Question 4 of 5
The following drugs exert their effects by binding to receptors and mimicking the effects of the endogenous ligand (i.e. are agonists):
Correct Answer: B
Rationale: Salbutamol (B) is an agonist, binding $\beta_2$-adrenergic receptors to mimic adrenaline, causing bronchodilation in asthma. Tamoxifen (A) is an estrogen receptor antagonist/partial agonist, not fully mimicking estrogen. Morphine (C) is an opioid agonist, mimicking endorphins for analgesia, also correct but B is selected. Cetirizine (D) is an Hâ‚ antihistamine antagonist, blocking histamine. Lisinopril (original E) inhibits ACE, not a receptor agonist. Agonists like salbutamol activate receptors to produce effects akin to endogenous ligands, critical in pharmacodynamics for therapeutic outcomes, distinguishing them from antagonists or enzyme inhibitors.
Question 5 of 5
For a drug that obeys first-order (linear) kinetics and fits a one-compartment model for elimination:
Correct Answer: A
Rationale: For first-order kinetics (A), elimination rate is proportional to plasma concentration (rate = k × Cp), as with most drugs (e.g., ibuprofen). Option B is true (exponential decline). Option C is false; half-life is constant. Option D is incorrect; GFR affects renally cleared drugs. Option E (original) about excretion composition is true but less central. This proportionality ensures predictable clearance (e.g., tâ‚/â‚‚ = 0.693/k), critical in dosing regimens, distinguishing first-order from zero-order saturation.