Gentamicin is increasingly given as a single large daily dose rather than divided doses for serious Gram-negative infections. The pharmacodynamic basis for extended-interval aminoglycoside dosing is:

• A Concentration-dependent killing plus a significant post-antibiotic effect allows high peaks with long dosing gaps ✓
• B Time above MIC is the best predictor of efficacy, so continuous infusion is ideal
• C The drug undergoes extensive hepatic metabolism, so single doses saturate clearance
• D Trough levels must be kept high to prevent emergence of adaptive resistance

Explanation

Aminoglycosides show concentration-dependent killing, so a higher peak concentration gives greater bacterial kill per dose. They also have a post-antibiotic effect, meaning suppression of bacterial regrowth persists even after serum levels fall below the MIC, allowing a longer dosing interval without loss of efficacy. High peaks also help avoid adaptive resistance. Time above MIC governs beta-lactams, not aminoglycosides, which rules out option B.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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