IV Gentamicin

# IV gentamicin ## Overview - **Classification**: Aminoglycoside antibiotic - **Mechanism**: Binds irreversibly to bacterial 30S ribosomal subunit, inhibiting protein synthesis. Bactericidal. ## Primary Indications 1. **Serious Gram-negative Infections**: Including *Pseudomonas aeruginosa*, *E. coli*, *Klebsiella spp.* 2. **Synergistic Therapy**: With beta-lactams for serious Gram-positive infections (e.g., infective endocarditis caused by *Enterococcus spp.*, *Streptococcus spp.*, *Staphylococcus aureus*). 3. **Empiric Therapy**: For febrile neutropenia in combination with other antibiotics. ## Adult Dosing ### Standard Dosing (Traditional Multiple Daily Dosing - MDD) **Serious Gram-negative Infections (e.g., Pneumonia, UTI, Sepsis)** - **Dose**: **1-1.7 mg/kg** (ideal body weight) - **Frequency**: Every 8 hours (q8h) - **Route**: IV infusion over 30-60 minutes - **Maximum**: **5-6 mg/kg/day** **Synergistic Dosing (e.g., Infective Endocarditis)** - **Dose**: **1 mg/kg** (ideal body weight) - **Frequency**: Every 8 hours (q8h) - **Route**: IV infusion over 30-60 minutes - **Maximum**: **80 mg/dose** - **Special considerations**: Often used for 2-4 weeks. ### Extended Interval Dosing (EID / Once Daily Dosing - ODD) **Selected Serious Gram-negative Infections (NOT endocarditis, osteomyelitis, or significant renal dysfunction)** - **Dose**: **4-7 mg/kg** (ideal body weight) - **Frequency**: Every 24 hours (q24h), or longer based on renal function - **Route**: IV infusion over 30-60 minutes - **Maximum**: **7 mg/kg/dose**, not to exceed **400 mg/day** - **Special considerations**: Lower risk of nephrotoxicity than MDD. Requires specific monitoring. ### Dose Adjustments - **Renal Impairment**: CRITICAL. Adjust dose or frequency based on CrCl and therapeutic drug monitoring (TDM). - CrCl 60-90 mL/min: MDD q8-12h or EID q24h with caution. - CrCl 30-60 mL/min: MDD q12-24h or EID q36h with caution. - CrCl <30 mL/min / Dialysis: Significant adjustment needed. Dose often given post-dialysis for HD patients. - **Hepatic Impairment**: No specific adjustment; primarily renally cleared. - **Elderly Patients**: Often have reduced renal function; use ideal body weight and monitor closely. ## Pediatric Dosing ### Neonates (0-28 days) **Serious Gram-negative Infections** - **Dose**: - <28 weeks GA & <7 days postnatal age: **5 mg/kg/dose** - <28 weeks GA & >7 days postnatal age: **4 mg/kg/dose** - 28-34 weeks GA: **4.5 mg/kg/dose** - ≥35 weeks GA: **4 mg/kg/dose** - **Frequency**: - <28 weeks GA: q48h - 28-34 weeks GA: q36h - ≥35 weeks GA: q24h - **Route**: IV infusion over 30-60 minutes - **Special Notes**: Dosing is complex based on gestational age (GA) and postnatal age. TDM is essential. ### Infants (1-12 months) **Serious Gram-negative Infections** - **Dose**: **2.5 mg/kg/dose** - **Frequency**: Every 8 hours (q8h) - **OR (Extended Interval)**: **5-7.5 mg/kg/dose** - **Frequency (Extended Interval)**: Every 24 hours (q24h) - **Route**: IV infusion over 30-60 minutes - **Maximum**: Not to exceed adult daily dose or **7.5 mg/kg/dose** (EID). ### Children (1-12 years) **Serious Gram-negative Infections** - **Dose**: **2-2.5 mg/kg/dose** - **Frequency**: Every 8 hours (q8h) - **OR (Extended Interval)**: **5-7.5 mg/kg/dose** - **Frequency (Extended Interval)**: Every 24 hours (q24h) - **Route**: IV infusion over 30-60 minutes - **Maximum**: Not to exceed adult daily dose or **7.5 mg/kg/dose** (EID). ### Adolescents (13-18 years) - **Dose**: Follow **adult dosing guidelines** (e.g., **5-7 mg/kg/dose** IV q24h for EID, or **1-1.7 mg/kg/dose** IV q8h for MDD). - **Maximum**: Adult maximum daily dose or **400 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to gentamicin or other aminoglycosides. - **Relative**: Myasthenia gravis or Parkinsonism (may exacerbate muscle weakness). Pre-existing hearing loss. ### Common Adverse Effects - **Very Common (>10%)**: - Nephrotoxicity (elevated SCr, BUN) – usually reversible. - Ototoxicity (vestibular: vertigo, ataxia; cochlear: hearing loss, tinnitus) – often irreversible. - **Common (1-10%)**: Headache, nausea, vomiting, rash. - **Serious but Rare**: Neuromuscular blockade (respiratory depression), anaphylaxis. ### Key Drug Interactions - **Nephrotoxic drugs**: NSAIDs, vancomycin, cyclosporine, amphotericin B, loop diuretics. Increased risk of kidney damage. - **Ototoxic drugs**: Loop diuretics (furosemide), cisplatin, vancomycin. Increased risk of hearing/balance issues. - **Neuromuscular blockers**: Enhanced and prolonged blockade. Monitor respiratory function. - **Penicillins/Beta-lactams**: Inactivation in vitro if mixed directly. Administer separately. ## Monitoring & Follow-up - **Before Treatment**: Baseline serum creatinine (SCr), BUN, urine output, culture and sensitivity. Consider audiometry for high-risk patients. - **During Treatment**: - **Renal function**: SCr, BUN daily or every 2-3 days. - **Drug levels**: Trough levels (MDD), peak/random (EID) for TDM. - **Clinical Signs**: Watch for signs of ototoxicity (tinnitus, hearing changes, vertigo), nephrotoxicity (decreased urine output, rising SCr). - **Clinical Signs**: Monitor for muscle weakness or respiratory difficulty. ## Clinical Pearls - 💡 **Therapeutic Drug Monitoring (TDM) is crucial** for balancing efficacy and minimizing toxicity, especially for MDD and in patients with changing renal function. - 💡 **Extended Interval Dosing (EID)** is often preferred in appropriate patients due to comparable efficacy, potentially less nephrotoxicity, and simplified administration. - 💡 **Administer IV infusions slowly** over 30-60 minutes to prevent acute toxicity. - 💡 **Ensure adequate hydration** throughout treatment to help prevent nephrotoxicity. - 💡 **Avoid concomitant use with other nephrotoxic or ototoxic agents** when possible, or monitor aggressively if unavoidable. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.