Please check your internet connection and try again.
# IV Gentamicin
## Overview
Gentamicin is an aminoglycoside antibiotic that inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. It is bactericidal and exhibits concentration-dependent killing and a significant post-antibiotic effect.
## Primary Indications
Treatment of serious infections caused by susceptible Gram-negative organisms, including *Pseudomonas aeruginosa*, *Enterobacter*, *Klebsiella*, and *Serratia* species. Often used in synergy with beta-lactams for Gram-positive endocarditis.
## Adult Dosing
* **Traditional (Multiple Daily Dosing):** 3–5 mg/kg/day divided every 8 hours.
* **Extended-Interval Dosing (EID):** 5–7 mg/kg administered every 24 hours (use caution in patients with CrCl <60 mL/min).
* **Synergy (Gram-positive endocarditis):** 1 mg/kg/dose every 8 hours.
* *Note: Dosing must be based on ideal body weight or adjusted body weight in obese patients to avoid toxicity.*
## Pediatric Dosing
* **Neonates (0–7 days):** 2.5–4 mg/kg per dose every 12–24 hours (varies significantly by gestational age and birth weight).
* **Infants and Children:** 2.5 mg/kg per dose every 8 hours.
* *Consult local neonatal/pediatric antimicrobial stewardship protocols as dosing is highly weight and age-dependent.*
## Dose Adjustments
* **Renal Impairment:** Required for all patients with CrCl <60 mL/min. Adjust dosing interval or reduce dose based on serum creatinine and therapeutic drug monitoring (TDM).
* **Obesity:** Use adjusted body weight (IBW + 0.4[Actual - IBW]) to prevent over-dosing.
## Contraindications
Hypersensitivity to gentamicin or other aminoglycosides. Use caution in patients with myasthenia gravis or neuromuscular blockade, as aminoglycosides may exacerbate weakness.
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with prolonged high trough levels.
* **Ototoxicity:** Irreversible vestibular or auditory damage; risk increases with cumulative exposure.
* **Neuromuscular Blockade:** Rare potential for respiratory paralysis.
## Key Drug Interactions
* **Nephrotoxic agents:** Increased risk of renal failure with concomitant use of vancomycin, amphotericin B, cyclosporine, or cisplatin.
* **Neuromuscular blockers:** May potentiate the effects of paralytic agents.
* **Loop diurectics:** Increased risk of ototoxicity.
## Monitoring
* **Serum Concentrations:** Obtain levels for patients on prolonged therapy, renal impairment, or high-dose regimens.
* *Traditional:* Trough (<1–2 mcg/mL), Peak (5–10 mcg/mL depending on infection).
* *EID:* Random level 6–14 hours post-infusion; plot on a Hartford Nomogram.
* **Renal Function:** Monitor serum creatinine and urine output daily.
* **Auditory/Vestibular:** Monitor for dizziness, tinnitus, or hearing loss.
## Clinical Pearls
* **Avoid "Level-less" therapy:** Do not dose gentamicin blindly for >48 hours without checking renal function and planning for TDM.
* **Synergy:** When used for synergy (e.g., *Staphylococcus aureus* or *Enterococcus* endocarditis), serum levels are generally lower, and the duration is often limited to 1–2 weeks to prevent toxicity.
* **Site-specific protocols:** Always defer to institutional antimicrobial stewardship guidelines for specific nomograms and target ranges.
***
**Educational Disclaimer:** This information is for educational purposes only. Clinical protocols, target concentrations, and dosing adjustments vary by institution and patient variables. Always verify current prescribing information in a trusted clinical database (e.g., Lexicomp, Micromedex) or with your facility's pharmacy department before prescribing.
