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# IV Gentamicin
## Overview
Gentamicin is an aminoglycoside antibiotic that exerts bactericidal activity by irreversibly binding to the 30S ribosomal subunit, inhibiting bacterial protein synthesis. It provides excellent coverage against aerobic gram-negative bacilli, including *Pseudomonas aeruginosa*.
## Primary Indications
* Serious gram-negative infections (e.g., sepsis, pneumonia, intra-abdominal infections).
* Synergy with beta-lactams/glycopeptides for gram-positive endocarditis (e.g., *S. aureus*, *Enterococcus*).
* Prophylaxis/treatment of complicated UTI.
## Adult Dosing
* **Traditional/Multiple Daily Dosing:** 1.5–2.5 mg/kg IV every 8–12 hours (renal function dependent).
* **Extended Interval Dosing (EID/Once-daily):** 5–7 mg/kg IV every 24 hours. *Note: Always follow institutional nomograms (e.g., Hartford nomogram).*
* **Synergy Dosing (Endocarditis):** 1 mg/kg IV every 8 hours.
## Pediatric Dosing
* **Neonatal (0–7 days):** 2.5–5 mg/kg every 12–24 hours (based on weight/gestational age).
* **Infants/Children (≥1 month):** 2.5 mg/kg every 8 hours (traditional) or 5–7.5 mg/kg once daily (EID, institutional protocol dependent).
## Dose Adjustments
* **Renal Impairment:** Required for both interval and volume. Use CrCl (Cockcroft-Gault) to determine frequency. Avoid in severe renal failure unless benefit outweighs risk.
* **Obesity:** Use Adjusted Body Weight (AdjBW) for initial dosing calculations to minimize toxicity.
## Contraindications
* Hypersensitivity to aminoglycosides.
* Myasthenia gravis (may exacerbate muscle weakness).
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with prolonged high trough levels.
* **Ototoxicity:** Irreversible vestibular or auditory damage; associated with prolonged high peak levels.
* **Neuromuscular blockade:** Rare; risk increases with rapid infusion or underlying neuromuscular disease.
## Key Drug Interactions
* **Nephrotoxic agents:** (e.g., Cisplatin, Amphotericin B, Vancomycin, Loop diuretics, NSAIDs) increase risk of renal impairment.
* **Neuromuscular blockers:** May potentiate paralytic effects.
## Monitoring
* **Renal Function:** Monitor SCr, BUN, and urine output daily.
* **Serum Concentrations:**
* *Traditional:* Trough 30 min before 3rd dose; Peak 30 min after end of 30-min infusion.
* *EID:* Serum level 6–14 hours post-dose per institutional nomogram.
* **Audiometry:** If therapy exceeds 7–10 days.
## Clinical Pearls
* **Efficacy:** Concentration-dependent killing.
* **Administration:** Infuse over 30–60 minutes.
* **Uncertainty:** Always consult institutional antibiogram and specific dosing protocols, as aminoglycoside management varies significantly by facility.
* **Synergy:** When used for synergy, serum concentrations are typically low and target therapeutic ranges are usually not required (unless treatment is prolonged).
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**Disclaimer:** This information is for educational purposes only. Always verify drug dosages, contraindications, and monitoring requirements with the most current version of the institutional formulary, the package insert, or a clinical resource such as Lexicomp or Micromedex before prescribing or administering medication.
