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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 protein synthesis. It provides excellent coverage against aerobic gram-negative bacilli, including *Pseudomonas aeruginosa*.
## Primary Indications
* Serious systemic infections caused by susceptible gram-negative organisms (e.g., sepsis, complicated UTI, pneumonia, intra-abdominal infections).
* Synergistic treatment for *Staphylococcus*, *Streptococcus*, or *Enterococcus* endocarditis (low-dose).
## Adult Dosing
* **Traditional (Multiple Daily Dose):** 1–2.5 mg/kg IV every 8–12 hours.
* **Extended Interval (Once-Daily):** 5–7 mg/kg IV every 24 hours (based on institutional nomograms, such as the Hartford Nomogram).
* **Synergy Dosing (for endocarditis):** 1 mg/kg IV every 8–12 hours.
* *Note: Dosing is heavily dependent on renal function and local institutional protocols.*
## Pediatric Dosing
* **Neonates (Post-menstrual age dependent):** 3.5–5 mg/kg IV every 12–24 hours (refer to specific NICU weight-based tables/local protocols).
* **Infants/Children:** 2.5 mg/kg IV every 8 hours.
* *Note: Pediatric dosing requires strict adherence to institutional weight/age-based nomograms due to immature renal clearance.*
## Dose Adjustments
* **Renal Impairment:** Required for CrCl < 60 mL/min. Adjust dosage interval (e.g., extend to q24h or q48h) or reduce dose based on serum levels.
* **Obesity:** Use Adjusted Body Weight (AdjBW) for dosing calculations to prevent toxicity.
## Contraindications
* Hypersensitivity to aminoglycosides.
* Use with caution in patients with underlying vestibular/auditory impairment or myasthenia gravis, as aminoglycosides may cause neuromuscular blockade.
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with trough accumulation.
* **Ototoxicity:** Often irreversible; includes vestibular (dizziness/vertigo) and auditory (tinnitus/hearing loss) damage.
* **Neuromuscular Blockade:** Rare; may occur at high doses or in sensitive patients.
## Key Drug Interactions
* **Nephrotoxic Agents:** Increased risk of kidney injury when combined with vancomycin, amphotericin B, cisplatin, or NSAIDs.
* **Ototoxic Agents:** Increased risk of hearing loss when combined with loop diuretics (e.g., furosemide).
* **Neuromuscular Blockers:** May potentiate the effects of non-depolarizing muscle relaxants.
## Monitoring
* **Serum Levels:**
* *Traditional:* Trough level (drawn 30 mins before 3rd or 4th dose) and Peak level (drawn 30 mins post-infusion).
* *Extended Interval:* Random level (8–12 hours after dose) using a nomogram.
* **Renal Function:** Monitor SCr, BUN, and urine output daily.
* **Toxicity:** Counsel patients to report hearing changes, tinnitus, or vertigo immediately.
## Clinical Pearls
* **Dosing Weight:** Ideal Body Weight (IBW) is generally used for patients of normal weight; Adjusted Body Weight (AdjBW) for obese patients (>20% over IBW).
* **Synergy:** When used for synergy (e.g., enterococcal endocarditis), serum levels are not required for efficacy but may be checked to monitor for toxicity.
* **Infusion:** Administer IV doses over 30 minutes to prevent infusion-related reactions.
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**Educational Disclaimer:** This information is intended for educational purposes only and does not constitute medical advice. Dosing for aminoglycosides is highly institution-specific and depends on local susceptibility patterns and clinical protocols. Always verify current prescribing information, institutional guidelines, and pharmacy policy before administration.
