Clarithromycin is preferred over erythromycin for H. pylori eradication. The pharmacokinetic advantage of clarithromycin over erythromycin is:
- A Clarithromycin achieves higher serum peaks due to IV formulation only
- B Clarithromycin is acid-stable, has higher oral bioavailability, twice-daily dosing, and its active metabolite (14-hydroxyclarithromycin) has synergistic activity ✓
- C Clarithromycin lacks 3-keto lactone metabolites that cause GI prokinetic adverse effects
- D Clarithromycin has broader gram-positive spectrum due to 15-membered lactone ring
Correct answer: B. Clarithromycin is acid-stable, has higher oral bioavailability, twice-daily dosing, and its active metabolite (14-hydroxyclarithromycin) has synergistic activity
Explanation
Clarithromycin is a 6-O-methyl derivative of erythromycin with superior acid stability (unlike erythromycin which degrades in gastric acid reducing bioavailability), is well-absorbed orally with ~50% bioavailability, requires only twice-daily dosing, and produces the active 14-hydroxy metabolite that provides additive or synergistic antibacterial activity particularly against H. influenzae. Erythromycin causes significant GI side effects due to motilin receptor agonism — clarithromycin also has this property but to a lesser extent.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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