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# IV Gentamicin
## Overview
Gentamicin is an aminoglycoside antibiotic that inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. It exhibits concentration-dependent bactericidal activity and a significant post-antibiotic effect.
## Primary Indications
Serious infections caused by susceptible Gram-negative bacilli (e.g., *Pseudomonas aeruginosa*, *Enterobacteriaceae*), severe staphylococcal or enterococcal infections (usually in synergy with beta-lactams), and empiric therapy for sepsis or febrile neutropenia.
## Adult Dosing
* **Traditional Dosing:** 1.5–2.5 mg/kg IV every 8–12 hours.
* **Extended-Interval (Once-Daily) Dosing:** 5–7 mg/kg IV every 24 hours.
* *Note: Dosing must be tailored to renal function and local institutional protocols, which often utilize specific nomograms (e.g., Hartford nomogram).*
## Pediatric Dosing
* **Neonates (0–7 days):** 4–5 mg/kg IV every 24–48 hours (based on weight/gestational age).
* **Neonates (>7 days):** 2.5 mg/kg IV every 12–24 hours.
* **Infants/Children:** 2.5 mg/kg IV every 8 hours.
* *Note: Highly dependent on local neonatal/pediatric unit protocols/nomograms.*
## Dose Adjustments
* **Renal Impairment:** Reduce frequency or dose based on serum creatinine, creatinine clearance (CrCl), or bedside drug monitoring. Avoid if possible in severe renal failure.
* **Obesity:** Use adjusted body weight (or pharmacy-calculated dosing weight) if actual body weight is significantly above ideal body weight.
## Contraindications
Hypersensitivity to gentamicin or other aminoglycosides. Use caution in patients with myasthenia gravis or neuromuscular disorders.
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with prolonged high trough levels.
* **Ototoxicity:** Irreversible vestibular or auditory damage; associated with prolonged high peak/trough levels.
* **Neuromuscular blockade:** Potential for respiratory paralysis, especially with concurrent neuromuscular blocking agents.
## Key Drug Interactions
* **Nephrotoxic agents:** Increased risk of renal injury (e.g., NSAIDs, vancomycin, amphotericin B, cisplatin, cyclosporine).
* **Ototoxic agents:** Increased risk of hearing loss (e.g., loop diuretics like furosemide).
* **Neuromuscular blockers:** Potentiates blockade effects.
## Monitoring
* **Serum Concentrations:** Required for most patients. Draw random levels for extended-interval dosing (nomogram-dependent) or peak/trough levels for traditional dosing (Peak: 30 minutes post-dose; Trough: 30 minutes pre-dose).
* **Renal:** Monitor serum creatinine and urine output daily.
* **Auditory:** Monitor for tinnitus, vertigo, or hearing loss.
## Clinical Pearls
* **Synergy:** When used for synergy (e.g., endocarditis), lower doses are typically used (1 mg/kg IV every 8 hours).
* **Hydration:** Maintain adequate fluid intake to mitigate nephrotoxicity risk.
* **Variability:** Gentamicin pharmacokinetics are highly unpredictable; pharmacy-led consults for therapeutic drug monitoring are standard practice.
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*Educational Disclaimer: This information is for educational purposes only. Dosing protocols vary significantly by institution, patient population, and clinical indication. Always verify current prescribing information, institutional guidelines, and clinical pharmacology databases before prescribing or administering medication.*
