Tobramycin
Tobramycin
Tobrex (ophthalmic), Tobi, Tobi Podhaler, Bethkis (inhaled, cystic fibrosis), generic IV
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Summary
Common uses
Gram-negative sepsis (with β-lactam, IV)0, Cystic fibrosis Pseudomonas suppression (inhaled)0, Bacterial conjunctivitis (topical ophthalmic)0, Bacterial keratitis (topical ophthalmic)0
Pharmacy
Starting dose
IV: traditional 1-1.7 mg/kg q8h or extended-interval 5-7 mg/kg q24h with target-trough monitoring; inhaled CF 300 mg BID × 28 days on / 28 days off; ophthalmic 1-2 drops in affected eye(s) q4h
Preparations
IV 10 mg/mL, 40 mg/mL; inhaled 300 mg/5 mL solution (Tobi, Bethkis); Podhaler dry powder; 0.3% ophthalmic solution and ointment
US FDA Max
IV: monitored by levels (trough <1 mg/L for extended-interval; <2 mg/L for traditional)
Pharmacology
Routes
IV, IM, inhaled, ophthalmic, intravitreal
Onset
Hours (systemic); minutes (ophthalmic)
Duration
6-12 hours systemic
Half-life
2-3 hours (normal renal function); markedly prolonged in renal impairment[1]
Bioavailability
IV/IM ~100%; inhaled: minimal systemic; oral: negligible (not used orally for systemic infection)[1]
Pregnancy
Aminoglycoside-class ototoxicity in fetal cochlea is documented; use only when alternatives have failed.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Tobramycin binds the 30S bacterial ribosomal subunit at the A site, causing translational misreading and premature termination; bactericidal activity is concentration-dependent, which is the pharmacodynamic basis of extended-interval (once-daily) IV dosing in critically ill patients.0 Class concerns: nephrotoxicity (acute tubular necrosis, usually reversible) and ototoxicity (cochlear and vestibular, often irreversible). Therapeutic drug monitoring (peaks for efficacy in traditional regimens, troughs for toxicity in both) is standard. Inhaled use bypasses systemic toxicity for CF Pseudomonas suppression[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Tobi (tobramycin) inhalation solution, Novartis, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/050753s016lbl.pdf