BLACK BOX WARNING
- nephrotoxicity
- ototoxicity
- neuromuscular blockade
- fetal harm
tobramycin
Brand: Nebcin, TOBI
⚠ BBW TDM Required Prototype: gentamicin
Drug Class: aminoglycoside antibiotic
Drug Family: antibiotic
Subclass: anti-pseudomonal aminoglycoside
Organ Systems: infectious-diseaserespiratory
Mechanism of Action
Binds irreversibly to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting translocation; bactericidal with concentration-dependent killing; particularly active against Pseudomonas aeruginosa.
30S ribosomal subunit
Indications
- Pseudomonas aeruginosa infections (systemic)
- gram-negative septicemia
- urinary tract infections (serious)
- cystic fibrosis — inhaled tobramycin for chronic Pseudomonas suppression
Contraindications
- aminoglycoside hypersensitivity
- pregnancy (teratogenic — auditory toxicity in fetus)
Adverse Effects
Common
- nephrotoxicity (dose-related)
- ototoxicity (cochlear > vestibular)
- elevated BUN/creatinine
Serious
- irreversible sensorineural hearing loss
- acute tubular necrosis
- neuromuscular blockade (especially with anesthetics)
- auditory toxicity in fetus
Pharmacokinetics (ADME)
| Absorption | IV/IM systemic; inhaled for pulmonary delivery in CF (minimal systemic absorption from inhalation) |
| Distribution | poor CNS penetration; distributes into extracellular fluids |
| Metabolism | not metabolized |
| Excretion | renal (unchanged); accumulates in renal cortex and inner ear |
| Half-life | 2–3 hours (normal renal function); prolonged in CKD |
| Onset | immediate (IV) |
| Peak | 30 min post-infusion |
| Duration | 8–24 hours depending on dosing strategy |
| Protein Binding | <10% |
| Vd | low (0.2–0.3 L/kg) |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| loop diuretics (furosemide) | additive ototoxicity | major |
| vancomycin | additive nephrotoxicity | major |
| neuromuscular blocking agents | enhanced neuromuscular blockade | major |
Nursing Considerations
- Monitor serum tobramycin peaks (goal 5–10 mcg/mL traditional; 20–30 mcg/mL extended-interval) and troughs (<2 mcg/mL traditional; undetectable with extended-interval) before and after scheduled doses.
- Assess baseline and serial audiometric and renal function; hold dose and notify prescriber if SCr rises >25% from baseline.
- Extended-interval dosing (high-dose once-daily) is preferred in most patients to maximize peak-dependent killing and reduce nephrotoxicity.
- Inhaled tobramycin for CF: use the TOBI Podhaler or TOBI nebulizer on alternate months; teach proper inhalation technique and airway clearance before inhalation.
Clinical Pearls
- Tobramycin has superior anti-pseudomonal activity compared to gentamicin, making it the preferred aminoglycoside for Pseudomonas aeruginosa infections, including in cystic fibrosis patients.
- The outer hair cells of the cochlea accumulate aminoglycosides to concentrations far exceeding plasma; toxicity is irreversible once inner ear damage occurs, underscoring the need for monitoring.
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.