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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
* Complicated intra-abdominal infections (in combination with anaerobic coverage).
* Complicated urinary tract infections (UTIs) and pyelonephritis.
* Bacteremia and sepsis.
* Endocarditis (synergistic dosing).
* Respiratory tract infections (in cystic fibrosis or hospital-acquired pneumonia).
## Adult Dosing
* **Conventional Dosing (Extended Interval):** 5–7 mg/kg IV every 24 hours (based on ideal body weight).
* **Traditional Dosing (TID):** 1–2 mg/kg IV every 8 hours.
* **Synergy for Endocarditis:** 1 mg/kg every 8 hours (monitored closely with trough levels).
* *Note: Dosing is highly dependent on institutional protocols regarding pharmacokinetic monitoring (peak/trough vs. random level nomograms).*
## Pediatric Dosing
* **Neonates (Post-menstrual age dependent):** Typically 4–5 mg/kg every 24–48 hours; dosing intervals increase with decreasing gestational age.
* **Children and Adolescents:** 2.5 mg/kg every 8 hours or 7.5 mg/kg once daily (depending on institutional protocol and infection site).
## Dose Adjustments
* **Renal Impairment:** Requires significant dose or interval adjustment based on creatinine clearance (CrCl). If CrCl < 60 mL/min, use extended intervals or reduce doses per nomogram.
* **Obesity:** Use Adjusted Body Weight (AdjBW) if actual body weight is >20% above ideal body weight.
* **Dialysis:** Requires post-hemodialysis supplemental doses.
## Contraindications
* Hypersensitivity to gentamicin or other aminoglycosides.
* Myasthenia gravis (may exacerbate muscle weakness).
## Adverse Effects
* **Nephrotoxicity:** Usually reversible; associated with prolonged high trough levels.
* **Ototoxicity:** Auditory (hearing loss) or vestibular (vertigo/ataxia); often irreversible.
* **Neuromuscular Blockade:** Rare; primarily risk in patients with underlying neuromuscular disorders or rapidly infused doses.
## Key Drug Interactions
* **Nephrotoxic Agents:** Increased risk of kidney injury when combined with vancomycin, amphotericin B, cisplatin, or NSAIDs.
* **Neuromuscular Blocking Agents:** Potential for enhanced paralytic effects.
* **Loop Diuretics:** Increased risk of ototoxicity (e.g., furosemide).
## Monitoring
* **Serum Concentrations:** Obtain random levels for extended-interval dosing or peak/trough levels for traditional dosing 30 minutes after the third dose.
* **Renal Function:** Monitor Serum Creatinine and BUN at baseline and throughout therapy.
* **Symptoms:** Monitor for tinnitus, dizziness, or decreased urine output.
## Clinical Pearls
* **Weight-based dosing:** Always clarify whether your institution uses Total, Ideal, or Adjusted Body Weight.
* **"Peak" levels:** Correlate with efficacy; "Trough" levels are the primary indicator of toxicity risk.
* **Incompatibility:** Gentamicin is physically incompatible with beta-lactam antibiotics (e.g., piperacillin/tazobactam) in the same IV line; flush lines thoroughly between doses.
* **Duration:** Limit total duration of therapy whenever possible to minimize risk of cumulative ototoxicity and nephrotoxicity.
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*Disclaimer: This information is for educational purposes and does not replace professional clinical judgment. Always verify dosages, contraindications, and drug-drug interactions with your institution’s current antimicrobial stewardship guidelines, pharmacy department, and official prescribing information (package insert) before administration.*
