TOBRAMYCIN SULFATE
Clinical safety rating: avoid
Other nephrotoxic or ototoxic drugs increase risk of toxicity Monitor peak and trough levels to minimize risk of nephrotoxicity and ototoxicity.
Aminoglycoside antibiotic; binds to 30S ribosomal subunit, causing misreading of mRNA and inhibiting bacterial protein synthesis.
| Metabolism | Not metabolized; eliminated renally by glomerular filtration (90% unchanged in urine). |
| Excretion | Primarily renal (glomerular filtration) with 90-95% excreted unchanged in urine within 24 hours; biliary/fecal <1%. |
| Half-life | Terminal elimination half-life is 2-3 hours in patients with normal renal function; extends to 24-100 hours in severe renal impairment (CrCl <10 mL/min), requiring dose adjustment. |
| Protein binding | <5% bound to serum proteins (primarily albumin). |
| Volume of Distribution | 0.2-0.3 L/kg, approximating extracellular fluid volume; increased in edema, ascites, or burn patients. |
| Bioavailability | Intravenous: 100%; intramuscular: >90%; inhaled: <10% systemic (local action); oral: <1% (not used systemically). |
| Onset of Action | Intravenous: within 30-60 minutes after infusion; intramuscular: 30-60 minutes; inhaled: within 15-30 minutes (peak sputum levels). |
| Duration of Action | Serum concentrations above MIC persist for 6-8 hours after IV/IM; dosing interval typically every 8 hours. Inhaled: bronchoalveolar levels maintained for 12-24 hours. |
Adults: Tobramycin 3-5 mg/kg/day IV divided every 8 hours, or 5-7 mg/kg/day IV once daily. For inhalation: 300 mg nebulized twice daily.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-59 mL/min: 3-5 mg/kg IV every 12-24 hours. CrCl 10-29 mL/min: 3-5 mg/kg IV every 24-48 hours. CrCl <10 mL/min: 3-5 mg/kg IV every 48-72 hours. Hemodialysis: 1.5-2 mg/kg after dialysis. |
| Liver impairment | No specific adjustment required. Monitor serum levels if severe hepatic impairment. |
| Pediatric use | Infants and children: 2.5 mg/kg IV/IM every 8 hours (total 7.5 mg/kg/day) or 4-7 mg/kg IV once daily; adjust per therapeutic drug monitoring. |
| Geriatric use | Initial dose based on ideal body weight and renal function. Reduce dose and/or extend interval due to age-related decreased GFR; monitor serum levels. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other nephrotoxic or ototoxic drugs increase risk of toxicity Monitor peak and trough levels to minimize risk of nephrotoxicity and ototoxicity.
| FDA category | Positive |
| Breastfeeding | Excreted into breast milk in low concentrations (M/P ratio not well established, estimated ~0.1-0.5). Oral bioavailability in infants is low due to poor gastrointestinal absorption, but may alter gut flora. Risk of ototoxicity and nephrotoxicity from milk is negligible. Use with caution; monitor infant for diarrhea, rash, or fungal overgrowth. |
| Teratogenic Risk |
■ FDA Black Box Warning
Boxed warning for neurotoxicity (including ototoxicity and nephrotoxicity) and neuromuscular blockade. Risk of fetal harm if used in pregnancy.
| Common Effects | Nephrotoxicity |
| Serious Effects |
Hypersensitivity to tobramycin or other aminoglycosides. Myasthenia gravis (relative).
| Precautions | Monitor renal function, audiometry, and serum trough/peak levels. Risk of ototoxicity (irreversible), nephrotoxicity, and neuromuscular blockade. Avoid concurrent use of other nephrotoxic/ototoxic drugs. Use with caution in renal impairment, myasthenia gravis, or parkinsonism. |
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| Aminoglycosides cross the placenta. First trimester: Limited data, but no consistent evidence of major malformations. Second/third trimester: Risk of fetal ototoxicity (cranial nerve VIII damage) and nephrotoxicity, especially with prolonged or high-dose exposure. Theoretical risk of neuromuscular blockade. Use only for strong maternal indications. |
| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN) and serum drug levels (trough and peak) to avoid toxicity. Assess fetal well-being with ultrasound for growth, and consider auditory screening (neonatal otoacoustic emissions) if prolonged exposure. Check for signs of fetal distress if used for maternal sepsis. |
| Fertility Effects | No known direct effects on fertility. Animal studies show no impairment. In males, aminoglycosides may rarely cause reversible infertility due to effects on sperm motility; clinical significance unclear. |