What is the therapeutic range for gentamicin in IV therapy?

• A. 3-5 mg/L
• B. 1-3 mg/L
• C. 6-8 mg/L
• D. 8-12 mg/L

Answer: (A)

Gentamicin is an aminoglycoside whose effectiveness depends on achieving a high concentration for a short period (concentration-dependent killing). In IV therapy, the important target is the peak level (Cmax) relative to the pathogen’s MIC, while keeping trough levels low to minimize toxicity. A peak of about 3–5 mg/L is commonly used as a therapeutic target in many IV regimens, especially when using gentamicin for synergy with beta-lactams or for certain infections. Higher peaks (6–8 mg/L or more) increase the risk of nephrotoxicity and ototoxicity without a proportional gain in efficacy, while lower peaks (1–3 mg/L) can be subtherapeutic for pathogens with higher MICs. Therefore, 3–5 mg/L best represents the practical therapeutic peak range for IV gentamicin in many clinical settings.