MAXITROL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MAXITROL (MAXITROL).
Maxitrol is a combination of dexamethasone (corticosteroid), neomycin (aminoglycoside antibiotic), and polymyxin B (polymyxin antibiotic). Dexamethasone suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis. Neomycin binds to bacterial 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis. Polymyxin B disrupts bacterial cell membrane integrity by binding to lipopolysaccharides.
| Metabolism | Dexamethasone undergoes hepatic metabolism primarily via CYP3A4. Neomycin is not metabolized; excreted unchanged in urine. Polymyxin B is not significantly metabolized; mainly renally excreted. |
| Excretion | Renal: neomycin 30–50%; polymyxin B <1%; dexamethasone <1%. Fecal: neomycin >50% (unabsorbed); polymyxin B >99% (unabsorbed); dexamethasone <5%. Biliary: negligible for all components. |
| Half-life | Neomycin: 2–3 h (topical) but prolonged in renal impairment. Polymyxin B: 6–7 h (topical). Dexamethasone: 3–4 h (topical). Clinical: systemic absorption minimal with intact epithelium; half-life may be prolonged with corneal abrasion or inflammation. |
| Protein binding | Neomycin: <30% bound to serum proteins. Polymyxin B: ~80% bound (primarily to albumin). Dexamethasone: ~77% bound (to albumin and corticosteroid-binding globulin). |
| Volume of Distribution | Neomycin: 0.25–0.4 L/kg (topical, minimal systemic). Polymyxin B: ~0.1–0.2 L/kg (topical). Dexamethasone: ~0.8–1.0 L/kg (topical). Clinical: Vd reflects negligible systemic distribution; drug remains primarily in ocular tissues. |
| Bioavailability | Ophthalmic: <5% systemic absorption via corneal and conjunctival routes. Intact epithelium limits absorption; inflamed or abraded cornea may increase systemic absorption modestly. Oral/IM: not applicable for ophthalmic formulation. |
| Onset of Action | Ophthalmic: anti-inflammatory and antibacterial effects typically within 30–60 min after instillation. Clinical improvement in signs/symptoms often within 24–48 h. |
| Duration of Action | Antibacterial: duration of bactericidal effect on ocular surface approximately 4–6 h after a single dose. Anti-inflammatory: dexamethasone duration of action 4–8 h; requires q4–6h dosing for sustained effect. |
| Molecular Weight | 740.8 |
1-2 drops or 0.5-1 inch strip of ointment into the conjunctival sac every 4-6 hours; in severe cases, every 2-4 hours. Frequency may be reduced after improvement.
| Dosage form | OINTMENT |
| Renal impairment | No systemic absorption expected with topical ophthalmic use; no dose adjustment required. |
| Liver impairment | No systemic absorption expected with topical ophthalmic use; no dose adjustment required. |
| Pediatric use | Safety and efficacy not established in pediatric patients; use only if clearly needed. |
| Geriatric use | Same as adult dosing; monitor intraocular pressure and cataract formation closely. |
| 1st trimester | Avoid systemic use; topical use only if clearly needed. Limited human data; animal studies show risk. |
| 2nd trimester | Avoid systemic use; topical use only if clearly needed. Corticosteroids may increase risk of premature rupture of membranes. |
| 3rd trimester | Avoid systemic use; topical use only if clearly needed. Prolonged use may lead to neonatal adrenal suppression. |
Clinical note
Comprehensive clinical and safety monograph for MAXITROL (MAXITROL).
| Placental transfer | Corticosteroids and aminoglycosides cross the placenta; extent varies with dose and route. Systemic absorption after ophthalmic use is low but possible. |
| Breastfeeding | Systemic absorption is minimal with topical ophthalmic use; however, corticosteroids and neomycin may be excreted in breast milk. Use with caution, especially with prolonged or high-dose therapy. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to any componentHerpes simplex keratitis (dendritic keratitis)Viral diseases of the cornea and conjunctiva (except herpes simplex)Mycobacterial infections of the eyeFungal diseases of ocular structuresAfter uncomplicated removal of a corneal foreign body
| Precautions | Prolonged use may lead to ocular hypertension/glaucoma, cataract formation, secondary infections, and delayed wound healing., Neomycin may cause dose-related nephrotoxicity and ototoxicity, especially in patients with renal impairment or prolonged use., Polymyxin B can cause neurotoxicity and nephrotoxicity., Avoid prolonged use in children due to risk of adrenal suppression. |
| Food/Dietary | No significant food interactions. Avoid alcohol if using with other corticosteroids systemically (not typical for ophthalmic use). |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Maxitrol (neomycin, polymyxin B, dexamethasone) ophthalmic: Topical use has minimal systemic absorption. Dexamethasone is a corticosteroid; systemic corticosteroids in first trimester are associated with cleft palate (risk increase ~0.1-0.3%). No specific human data for ophthalmic route. Neomycin and polymyxin B are not absorbed systemically in significant amounts. Overall, risk is low with ophthalmic use, but avoid during pregnancy if possible. |
| Fetal Monitoring | No specific monitoring required for ophthalmic use. For prolonged or high-dose use, monitor maternal intraocular pressure and fetal growth if systemic effects concern. Evaluate for signs of adrenal suppression in newborn if used near term with high doses. |
| Fertility Effects | No known adverse effects on fertility with ophthalmic use. Topical corticosteroids, aminoglycosides, and polymyxins have not been associated with impaired fertility in humans. |
| Clinical Pearls | Maxitrol contains neomycin, polymyxin B, and dexamethasone. Avoid prolonged use (>2 weeks) due to risk of elevated intraocular pressure, cataract formation, and secondary infections. Use cautiously in patients with corneal epithelial defects, as neomycin can cause epithelial toxicity. Shake well before use to ensure uniform suspension. |
| Patient Advice | Shake the bottle vigorously before each use. · Do not touch the dropper tip to any surface to avoid contamination. · Remove contact lenses before instillation; wait at least 15 minutes before reinserting. · Do not use for longer than prescribed; overuse can lead to eye pressure problems or infections. · Report any worsening of symptoms, eye pain, or vision changes immediately. |