ZYLET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZYLET (ZYLET).
Loteprednol etabonate is a corticosteroid that inhibits phospholipase A2 activity, reducing prostaglandin and leukotriene synthesis. Tobramycin is an aminoglycoside antibiotic that binds to the 30S ribosomal subunit, inhibiting bacterial protein synthesis.
| Metabolism | Loteprednol etabonate is hydrolyzed to inactive metabolites by esterases in the eye and systemically. Tobramycin is primarily excreted unchanged in urine. |
| Excretion | Renal (30% unchanged), biliary/fecal (70% as metabolites) |
| Half-life | ZYLET: not applicable (fixed-dose combination); Loteprednol: 2-3 hours; Tobramycin: 2-3 hours. Clinical context: no accumulation with qid dosing. |
| Protein binding | Loteprednol: ~70% bound to albumin; Tobramycin: negligible (<10%) protein binding. |
| Volume of Distribution | Loteprednol: ~2.5 L/kg (systemic); Tobramycin: ~0.26 L/kg (systemic). Clinical meaning: loteprednol widely distributed, tobramycin mainly extracellular. |
| Bioavailability | Ocular suspension: systemic bioavailability is low (<1% for both components) due to local administration and metabolism. |
| Onset of Action | Ocular: anti-inflammatory effect within 24-48 hours; antibacterial effect within 1-2 hours after instillation. |
| Duration of Action | Ocular: anti-inflammatory and antibacterial effects persist for duration of therapy; clinical improvement typically within 3-5 days. |
| Molecular Weight | Loteprednol etabonate: 467.5 Da; Tobramycin: 467.5 Da (free base) |
One to two drops into the conjunctival sac of the affected eye(s) every 4 to 6 hours. In severe cases, every 1 to 2 hours for the first 24 to 48 hours.
| Dosage form | SUSPENSION/DROPS |
| Renal impairment | No dose adjustment required based on GFR as systemic absorption is minimal. |
| Liver impairment | No dose adjustment required based on Child-Pugh class as systemic absorption is minimal. |
| Pediatric use | Children ≥2 years: same as adult dosing. Safety and efficacy in children <2 years not established. |
| Geriatric use | No specific dose adjustment recommended; use with caution due to increased risk of ocular adverse effects from chronic corticosteroid use. |
| 1st trimester | Avoid use during first trimester unless potential benefit outweighs risk; based on animal studies showing teratogenicity with topical corticosteroids at high doses. |
| 2nd trimester | Use only if clearly needed; potential for fetal harm due to corticosteroid and antibiotic components. |
| 3rd trimester | Use only if clearly needed; risk of fetal adverse effects, especially with prolonged use. |
Clinical note
Comprehensive clinical and safety monograph for ZYLET (ZYLET).
| Placental transfer | Minimal systemic absorption after ophthalmic application; systemic levels are low, reducing likelihood of significant placental transfer. Animal studies show no direct evidence of transfer, but corticosteroids can cross placenta at higher systemic doses. |
| Breastfeeding | Topical ophthalmic use results in negligible systemic absorption; however, caution is advised due to potential for infant effects from corticosteroid or antibiotic exposure. Use only if clearly indicated. |
■ FDA Black Box Warning
None
| Common Effects | Skin rash Diarrhea Nausea |
| Serious Effects |
Hypersensitivity to any componentViral diseases of the cornea (including herpes simplex keratitis, vaccinia, varicella)Mycobacterial infection of the eyeFungal diseases of ocular structuresUntreated ocular infections
| Precautions | Prolonged use may lead to ocular hypertension/glaucoma, cataract formation, secondary infections, and delayed wound healing, Risk of bacterial resistance with prolonged use, Not for injection, Use with caution in patients with herpes simplex keratitis |
| Food/Dietary | None known. No dietary restrictions required. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category C. No adequate well-controlled studies in pregnant women. In animal studies, systemic corticosteroids and fluoroquinolones (including loteprednol and tobramycin) have shown adverse effects on fetal development at high doses. Avoid use during pregnancy unless potential benefit outweighs risk; use only if clearly needed. |
| Fetal Monitoring | Monitor for signs of maternal hypersensitivity reactions or ocular adverse effects. No specific fetal monitoring required beyond routine prenatal care unless prolonged systemic exposure occurs. |
| Fertility Effects | No known adverse effects on fertility in human studies. Animal studies with fluoroquinolones have shown no impairment of fertility at clinically relevant doses. |
| Clinical Pearls | ZYLET (loteprednol etabonate 0.5% / tobramycin 0.3%) is a corticosteroid-antibiotic combination ophthalmic suspension. Use caution in patients with glaucoma; monitor IOP. Do not use for viral or fungal infections. Shake well before use. Prescribe only for inflammatory ocular conditions where bacterial infection is present or risk is high. |
| Patient Advice | Shake the bottle well before each use. · Wash hands before instilling drops. · Do not touch the dropper tip to any surface to avoid contamination. · Remove contact lenses before use and wait at least 10 minutes before reinserting. · Use exactly as prescribed; do not stop early even if symptoms improve. · Report any eye pain, redness, or vision changes to your doctor immediately. · Prolonged use may increase intraocular pressure or cause cataracts. |