Tobramycin Classification
Tobramycin is an aminoglycoside antibiotic with activity against Gram-positive and Gram-negative bacteria, particularly effective against Pseudomonas aeruginosa 1.
Mechanism of Action
Tobramycin works by:
- Inhibiting protein synthesis in bacterial cells by binding to bacterial ribosomes
- Demonstrating bactericidal (killing) rather than bacteriostatic activity
- Acting synergistically with certain beta-lactam antibiotics (like penicillins) against specific organisms 1
Antimicrobial Spectrum
Tobramycin is active against:
Gram-negative bacteria (primary targets)
- Pseudomonas aeruginosa (with greater activity than gentamicin)
- Enterobacteriaceae (Escherichia coli, Klebsiella, Proteus, etc.)
- Citrobacter species
- Enterobacter species
- Morganella morganii
- Providencia species
- Serratia species 1
Gram-positive bacteria (limited activity)
- Staphylococcus aureus
- Low activity against streptococci and enterococci 1
Clinical Considerations
Tobramycin has several important clinical properties:
- Penetrates poorly into pancreatic tissue, making it suboptimal for pancreatic infections 2
- Often used in combination with beta-lactams for synergistic effects, particularly in cystic fibrosis patients with Pseudomonas infections 2
- Can be administered intravenously, intramuscularly, or via inhalation (particularly in cystic fibrosis) 2
- Requires therapeutic drug monitoring due to its narrow therapeutic window 2
Toxicity Profile
As with other aminoglycosides, tobramycin has potential toxicities:
- Nephrotoxicity (though possibly less than gentamicin) 3
- Ototoxicity affecting the vestibular-auditory system
- Neuromuscular blockade (rare)
Dosing Considerations
Dosing must be adjusted based on:
- Renal function (eliminated primarily by glomerular filtration)
- Weight/body surface area
- Monitoring of serum drug levels (peak and trough)
- Once-daily dosing may be as effective as multiple daily dosing with potentially reduced toxicity 2
Tobramycin's classification as an aminoglycoside determines its clinical applications, toxicity profile, and monitoring requirements, making this an essential consideration when selecting antimicrobial therapy.