GENTAMICIN SULFATE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER
Clinical safety rating
safeNo significant drug interactions Can cause hypernatremia and fluid overload.
Aminoglycoside antibiotic that binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis in susceptible bacteria.
| Metabolism | Gentamicin is not significantly metabolized; it is excreted primarily unchanged by glomerular filtration. |
| Excretion | Renal: >90% unchanged via glomerular filtration; biliary: <2%; fecal: negligible. |
| Half-life | Terminal elimination half-life: 2-3 hours in adults with normal renal function; prolonged to 24-48 hours in anuric patients requiring dose adjustment. |
| Protein binding | <30% bound primarily to albumin; low binding reduces displacement interactions. |
| Volume of Distribution | 0.2-0.3 L/kg; approximates extracellular fluid volume; increased in edema, ascites, or burns. |
| Bioavailability | Intramuscular: ~100%; topical: minimal systemic absorption (<1%); intravenous: 100% (by definition). |
| Onset of Action | Intravenous: peak levels achieved within 30 minutes after infusion; intramuscular: peak at 30-90 minutes; topical: variable, local effect within hours. |
| Duration of Action | Concentration-dependent; typical dosing interval 8-24 hours; prolonged in renal impairment; post-antibiotic effect up to 8 hours for gram-negative bacilli. |
| Molecular Weight | 477.6 |
1-2 mg/kg IV every 8 hours, adjusted based on serum concentrations and creatinine clearance.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 60-90 mL/min: 1.7 mg/kg every 12 hours; CrCl 40-59 mL/min: 1.7 mg/kg every 24 hours; CrCl 20-39 mL/min: 1.7 mg/kg as a single dose then adjust based on serum levels; CrCl <20 mL/min: 1.7 mg/kg as a single dose then redose based on serum levels; Hemodialysis: 1-2 mg/kg after dialysis with supplemental dosing based on serum levels. |
| Liver impairment | No dose adjustment required for hepatic impairment; gentamicin is primarily renally eliminated. |
| Pediatric use | Neonates (<7 days): 4-5 mg/kg IV every 24-36 hours; Infants >7 days: 2.5 mg/kg IV every 8 hours; Children: 2-2.5 mg/kg IV every 8 hours; adjust based on serum concentrations and renal function. |
| Geriatric use | Dose adjustment based on renal function; calculate CrCl using Cockcroft-Gault equation with ideal body weight; typical starting dose: 1-1.7 mg/kg IV every 8-12 hours, with subsequent dosing guided by serum concentrations. |
| 1st trimester | Gentamicin crosses the placenta and may cause fetal harm (ototoxicity, nephrotoxicity) if used during pregnancy. Avoid use in first trimester unless clearly needed and no alternative. |
| 2nd trimester | Use only if clearly needed and potential benefit justifies potential risk to fetus. Monitor maternal and fetal status. Risk of ototoxicity and nephrotoxicity. |
| 3rd trimester | Use only if clearly needed. Risk of fetal ototoxicity and nephrotoxicity, particularly with prolonged or high-dose therapy. |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Placental transfer | Gentamicin crosses the placenta. Fetal serum concentrations may reach 30-50% of maternal levels. Accumulation in fetal kidneys and inner ear may occur. |
| Breastfeeding | Gentamicin is excreted into breast milk in low concentrations. It is poorly absorbed orally, so risk to infant is low. However, caution is advised due to potential alteration of infant gut flora. Monitor infant for diarrhea, rash, or thrush. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Gentamicin is classified as FDA Pregnancy Category D. There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk. First trimester: Avoid unless essential due to potential for ototoxicity and nephrotoxicity. Second and third trimesters: Use only for severe infections when alternative antibiotics are not available. Risk of fetal inner ear damage and renal impairment associated with aminoglycosides. |
| Fetal Monitoring | Maternal: Serum gentamicin trough and peak concentrations, renal function (serum creatinine, BUN), urinalysis, and audiometry (baseline and periodic). Fetal/Neonatal: Ultrasound for growth and amniotic fluid volume, neonatal hearing screening at birth, and renal function post-delivery if significant maternal exposure. |
| Fertility Effects | In animal studies, gentamicin has been associated with testicular damage and impaired spermatogenesis at high doses. Human data on fertility effects are lacking. No specific studies on female fertility. Use should be limited to necessary indications in patients of reproductive potential. |
■ FDA Black Box Warning
WARNING: OTOTOXICITY AND NEPHROTOXICITY. Gentamicin can cause ototoxicity (vestibular and auditory) and nephrotoxicity. Risk increases with prolonged use, high doses, renal impairment, and advanced age. Monitor renal function and auditory function regularly.
| Common Effects | fluid replacement |
| Serious Effects |
Hypersensitivity to gentamicin or any aminoglycosideMyasthenia gravis (use caution, but not absolute; potential for neuromuscular blockade)
| Precautions | Neurotoxicity including ototoxicity and nephrotoxicity, Neuromuscular blockade leading to respiratory paralysis, Superinfection with resistant organisms, May worsen weakness in myasthenia gravis or Parkinson's disease, Use with caution in premature infants and neonates due to renal immaturity, Monitor serum drug levels to avoid toxicity |
| Food/Dietary | No significant food interactions. Avoid excessive potassium intake if renal impairment. |
| Clinical Pearls | Monitor peak (30 min after 30-min infusion) and trough (just before next dose) levels; target peak 5-10 mcg/mL, trough <2 mcg/mL. Adjust dose in renal impairment. Avoid concurrent ototoxic/nephrotoxic drugs. Consider once-daily dosing for synergy with beta-lactams. Assess for vestibular toxicity with Romberg test. |
| Patient Advice | Report any hearing loss, ringing in ears, dizziness, or balance problems immediately. · Drink plenty of fluids unless instructed otherwise by your doctor. · Inform your doctor if you have kidney disease, myasthenia gravis, or are pregnant. · This medication is given intravenously; do not mix with other drugs in the same line without pharmacy approval. |
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