A 55-year-old man with nosocomial gram-negative sepsis is started on once-daily high-dose gentamicin rather than conventional thrice-daily divided dosing. The pharmacodynamic principle that justifies extended-interval aminoglycoside dosing is:

• A Time above MIC is the parameter that correlates with killing, so continuous infusion is ideal
• B Extended dosing prevents accumulation of the drug in the proximal tubule entirely
• C Aminoglycosides exhibit purely time-dependent killing with no post-antibiotic effect
• D Concentration-dependent killing combined with a significant post-antibiotic effect allows high peak doses with long intervals ✓

Explanation

Aminoglycosides show concentration-dependent bactericidal activity, meaning higher peak concentrations produce faster and greater kill, and they also produce a post-antibiotic effect, which is persistent suppression of bacterial growth after serum levels fall below the MIC. Together these allow large once-daily doses. Option A describes beta-lactams, which are time-dependent killers. Extended dosing reduces but does not abolish nephrotoxicity risk, so B is incorrect.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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