Tobradex vs Maxitrol for Eye Infections
For bacterial eye infections, Tobradex (tobramycin-dexamethasone) is the preferred choice over Maxitrol (neomycin-polymyxin B-dexamethasone) due to superior gram-negative coverage, lower toxicity risk, and better tissue penetration—particularly the newer TobraDex ST formulation. 1, 2
Key Differences in Antibiotic Coverage
Tobramycin provides superior coverage against Pseudomonas aeruginosa and other gram-negative organisms, which are critical pathogens in bacterial keratitis and contact lens-related infections. 1 The newer TobraDex ST formulation demonstrates an 8.3-fold increase in tear film concentration and up to 12.5-fold greater tissue penetration compared to standard formulations. 2
Maxitrol's neomycin component carries significant toxicity concerns with chronic use, which is a well-documented limitation that must be considered in treatment planning. 3 While Maxitrol does provide broad-spectrum coverage through its combination of neomycin and polymyxin B, the neomycin toxicity risk makes it less suitable for prolonged therapy.
Clinical Efficacy Data
TobraDex ST demonstrated superior bactericidal activity against resistant organisms, achieving >99.9% kill of methicillin-resistant Staphylococcus aureus in 90 minutes and 3-log reduction of Streptococcus pneumoniae in just 5 minutes. 2
In experimental Pseudomonas keratitis, TobraDex ST showed statistically superior anti-inflammatory and bactericidal properties compared to standard TobraDex formulation. 1
Maxitrol achieved 90% bacterial count reduction and 50% bacterial eradication in chronic blepharitis/conjunctivitis, compared to only 34% and 17% with steroid alone. 3
When to Use Each Medication
Use Tobradex (preferably ST formulation) for:
- Contact lens-related infections (Pseudomonas risk) 1
- Bacterial keratitis requiring aggressive gram-negative coverage 4, 1
- Post-surgical inflammation prophylaxis 5
- Cases requiring prolonged therapy (lower toxicity profile) 2
Consider Maxitrol only for:
- Chronic blepharitis or conjunctivitis when short-term therapy is planned 3
- Situations where broader gram-positive coverage is specifically needed and neomycin allergy is absent 3
Critical Timing and Steroid Considerations
Corticosteroids should only be added after 2-3 days of antibiotic therapy once the organism is identified and the epithelial defect is healing. 4 Adding corticosteroids within 2-3 days (rather than after 4+ days) results in 1-line better visual acuity at 3 months. 4
Never use combination steroid-antibiotic drops as initial monotherapy for suspected bacterial keratitis—start with antibiotic-only therapy, then add steroids once infection is controlled. 4
Important Caveats
Fungal keratitis must be ruled out before initiating corticosteroids, as steroid use is a risk factor for requiring penetrating keratoplasty in fungal infections. 4
Monitor intraocular pressure within 1-2 days after initiating any topical corticosteroid therapy. 4
Do not taper antibiotics below subtherapeutic dosing, as this increases antibiotic resistance risk. 4
If no improvement occurs within 48 hours, modify therapy and consider reculture. 4
Prolonged antibiotic use causes toxicity and should be tapered as infection improves. 4