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# IV Gentamicin
## Overview
Gentamicin is an aminoglycoside antibiotic that exerts bactericidal activity by inhibiting bacterial protein synthesis via irreversible binding to the 30S ribosomal subunit. It exhibits concentration-dependent killing and has a significant post-antibiotic effect.
## Primary Indications
Treatment of serious infections caused by susceptible Gram-negative organisms, including *Pseudomonas aeruginosa*, *Enterobacteriaceae*, and synergy with beta-lactams/vancomycin for Gram-positive endocarditis.
## Adult Dosing
* **Traditional Dosing:** 1–2.5 mg/kg every 8–12 hours (depending on renal function).
* **Extended Interval Dosing (EID):** 5–7 mg/kg every 24 hours (subject to nomogram, e.g., Hartford Nomogram).
* **Synergy Dosing (Endocarditis):** 1 mg/kg every 8 hours.
## Pediatric Dosing
* **Neonates (0-28 days):** Dosing is highly weight- and gestational age-dependent (e.g., 3–5 mg/kg/dose). Frequency varies from every 18 to 48 hours based on postnatal age.
* **Infants/Children:** 7.5 mg/kg/day divided every 8 hours (traditional) or 5–7.5 mg/kg once daily (EID, institutional protocols vary).
## Dose Adjustments
* **Renal Impairment:** Mandatory. Dose must be adjusted based on creatinine clearance (CrCl). If CrCl <60 mL/min, the interval is typically extended rather than reducing the dose to maintain peak concentrations.
* **Obesity:** Use Adjusted Body Weight (ABW) for dosing calculations if the patient is significantly overweight to prevent toxicity.
## Contraindications
* Known hypersensitivity to aminoglycosides.
* Use caution in patients with myasthenia gravis or active vestibular/auditory impairment.
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with prolonged trough levels.
* **Ototoxicity:** Often irreversible; includes vestibular (dizziness, vertigo) and auditory (tinnitus, hearing loss) damage.
* **Neuromuscular Blockade:** Rare, but can occur, especially with rapid infusion or concomitant paralytics.
## Key Drug Interactions
* **Nephrotoxic agents:** Increased risk of renal injury (e.g., vancomycin, amphotericin B, cisplatin, NSAIDs, IV contrast).
* **Ototoxic agents:** Increased risk of hearing loss (e.g., loop diuretics such as furosemide).
* **Neuromuscular blockers:** May potentiate paralytic effects.
## Monitoring
* **Serum Peaks/Troughs:** Required for traditional dosing (target peak 5–10 mcg/mL; target trough <2 mcg/mL).
* **Random Levels:** Required for EID (check level at specific hour post-dose per nomogram).
* **Renal Function:** Monitor serum creatinine and urine output daily.
* **Auditory/Vestibular:** Monitor for signs of hearing loss or vertigo.
## Clinical Pearls
* **Local Protocol:** Always consult institutional antibiograms and dosing guidelines, as EID protocols vary significantly by hospital regarding nomograms and patient eligibility (e.g., exclusionary criteria like dialysis or pregnancy).
* **Infusion:** Administer over 30–60 minutes to ensure adequate peak levels.
* **Therapeutic Drug Monitoring (TDM):** Clinical judgment should override lab values; trends are more important than single levels.
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*Disclaimer: This information is for educational purposes only. Clinical guidelines change frequently; always verify dosages and safety parameters against current institutional protocols, the drug package insert, or a reliable clinical resource such as Lexicomp or Micromedex before prescribing or administering medication.*
