ATI RN
Chapter 2 pharmacologic principles Questions
Question 1 of 5
A 34-year-old female insists on drinking a cup of grapefruit juice every morning for 'body cleansing.' Grapefruit juice is known to interfere with the cytochrome P450 system, disrupting levels of certain drugs. The cytochrome P450 system includes dozens of enzymes. Which is the most abundant CYP enzyme in human livers?
Correct Answer: E
Rationale: CYP3A4 (E, original) is the most abundant CYP enzyme in human livers (~30-40\% of total), metabolizing many drugs (e.g., statins). Grapefruit juice inhibits it, raising drug levels (e.g., felodipine). CYP1A2 (A) handles caffeine, CYP2A6 (B) nicotine, CYP2D6 (C) antidepressants, and CYP2E1 (D) ethanol:all less abundant. CYP3A4's dominance and intestinal presence amplify juice interactions, critical in pharmacokinetics, necessitating caution with co-administered substrates.
Question 2 of 5
A 59-year-old man with decreased urinary stream and hypertension is prescribed doxazosin in hopes that both problems will be treated. He begins dose escalation with $1 \mathrm{mg}$ given for one week, $2 \mathrm{mg}$ given for 2 weeks, and $4 \mathrm{mg}$ given for maintenance. He returns to his primary care physician saying that this medication is not helping. To determine whether or not the patient is taking the medication, it would be useful to look at the excreted concentration of medication in which of the following areas?
Correct Answer: D
Rationale: Urine (D) is useful to measure doxazosin's excreted concentration, as this $\alpha_1$-blocker is renally cleared, reflecting compliance (e.g., via metabolites). Blood (A) shows active levels, not excretion. Feces (B) is minor for doxazosin. Liver extract (C) is invasive, impractical. Skin (original E) is irrelevant. Urine testing confirms intake, critical in assessing BPH/hypertension treatment failure, distinguishing non-compliance from resistance, a practical pharmacokinetic approach.
Question 3 of 5
The pharmacokinetic 'elimination half-life' of the following drugs mirrors their pharmacodynamic duration and intensity of action:
Correct Answer: C
Rationale: Dobutamine (C) has a half-life (~2 min) mirroring its short-lived inotropic effect, used in acute heart failure. Salbutamol (A) has a longer duration (~4-6 h) than its half-life (~4 h). Phenelzine (B) is an irreversible MAOI, with effects outlasting its half-life. Omeprazole (D) inhibits pumps long-term despite a short half-life. Cyclophosphamide (original E) has prolonged effects via metabolites. Dobutamine's tight pharmacokinetic-pharmacodynamic link ensures rapid titration, critical in ICU settings, unlike drugs with dissociated durations.
Question 4 of 5
The following drugs undergo significant enterohepatic circulation:
Correct Answer: A
Rationale: Oestrogens (A) undergo significant enterohepatic circulation, with hepatic conjugates excreted in bile, reabsorbed after gut hydrolysis (e.g., ethinylestradiol), prolonging effects. Atenolol (B) and gentamicin (D) are renally cleared. Rifampicin (C) is biliary but less recycled. Levofloxacin (original E) is renal. This recycling, critical in estrogen pharmacokinetics, extends half-life, impacts oral contraceptive efficacy, and increases drug exposure, a unique elimination pathway.
Question 5 of 5
The following drugs are effectively administered via the sublingual route:
Correct Answer: D
Rationale: Buprenorphine (D) is effective sublingually, bypassing first-pass metabolism for analgesia (e.g., in addiction). Simvastatin (A), carbamazepine (B), and ramipril (C) are oral, not sublingual. Glyceryl trinitrate (original E) is also correct but D is chosen. Sublingual delivery, rapid and hepatic-avoidant, suits buprenorphine's pharmacokinetics, critical for pain or opioid management, enhancing onset.