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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
Treatment of serious infections caused by susceptible gram-negative aerobic bacilli, including *Pseudomonas aeruginosa*, *Escherichia coli*, *Proteus* species, *Klebsiella*, *Enterobacter*, and *Serratia*. It is often used adjunctively with beta-lactams for synergistic coverage in endocarditis or severe sepsis.
## Adult Dosing
* **Conventional Dosing:** 1.5–2.5 mg/kg IV every 8–12 hours.
* **Extended-Interval (Once-Daily) Dosing:** 5–7 mg/kg IV once every 24 hours (based on nomograms like Hartford or Sawchuk-Zaske).
* **Endocarditis Synergy:** 1 mg/kg IV every 8 hours.
* **Note:** Dosing is highly institution-specific and must be based on ideal body weight or adjusted body weight in obese patients.
## Pediatric Dosing
* **Neonates (0-7 days):** 2.5–5 mg/kg/dose every 12–24 hours, depending on gestational/postnatal age.
* **Infants and Children:** 2.5 mg/kg/dose every 8 hours (conventional) or 5–7 mg/kg/dose every 24 hours (extended-interval), strictly dependent on renal function and local institutional protocols.
## Dose Adjustments
* **Renal Impairment:** Required. Calculate CrCl (Cockcroft-Gault). Adjust interval or dose based on serum trough/peak concentrations. Avoid if CrCl < 10–20 mL/min unless on dialysis.
* **Obesity:** Use adjusted body weight for patients with BMI > 30 kg/m².
## Contraindications
Hypersensitivity to gentamicin or other aminoglycosides; history of severe reactions to aminoglycosides.
## Adverse Effects
* **Nephrotoxicity:** Typically reversible; presents as rising serum creatinine.
* **Ototoxicity:** Vestibular (vertigo, ataxia) and auditory (high-frequency hearing loss); often irreversible.
* **Neuromuscular Blockade:** Risk increased with rapid infusion or concurrent neuromuscular blocking agents.
## Key Drug Interactions
* **Nephrotoxic Agents:** Increased risk with vancomycin, amphotericin B, cisplatin, NSAIDs, and IV contrast.
* **Ototoxic Agents:** Increased risk with loop diuretics (e.g., furosemide).
* **Neuromuscular Blockade:** Potentiation of effects when combined with succinylcholine or general anesthetics.
## Monitoring
* **Renal Function:** Monitor SCr and urine output daily.
* **Serum Concentrations:**
* **Conventional:** Trough drawn 30 minutes before 3rd or 4th dose; Peak drawn 30 minutes after completion of 30-minute infusion.
* **Extended-Interval:** Random level (usually 6–14 hours post-dose) plotted on a nomogram.
* **Auditory/Vestibular:** Monitor for hearing changes or complaints of imbalance.
## Clinical Pearls
* **Hydration:** Ensure adequate patient hydration to minimize risk of acute tubular necrosis.
* **Infusion Rate:** Always infuse over at least 30 minutes to prevent neuromuscular blockade and peak-trough variability.
* **Dialysis:** Gentamicin is cleared by hemodialysis; supplemental dosing is usually required post-dialysis.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult your institution's specific antimicrobial stewardship protocols, the latest Summary of Product Characteristics (SmPC), or the Package Insert for the most current and accurate prescribing information.
