ZADITOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZADITOR (ZADITOR).
Selective histamine H1 receptor antagonist. Stabilizes mast cells, reducing release of histamine and other mediators of allergic response.
| Metabolism | Not extensively metabolized; small fraction undergoes hepatic metabolism via CYP450 enzymes. |
| Excretion | Primarily renal excretion as unchanged drug (approximately 30-40% of dose) and biliary/fecal elimination of metabolites (60-70%). |
| Half-life | Terminal elimination half-life is approximately 7 hours in adults, which supports twice-daily dosing for sustained ocular effects. |
| Protein binding | Approximately 90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is approximately 1.5 L/kg, indicating extensive tissue distribution beyond the vascular space. |
| Bioavailability | Systemic bioavailability after ocular administration is very low (less than 1%) due to minimal absorption and first-pass metabolism. |
| Onset of Action | Onset of action occurs within minutes after topical ocular administration; clinical relief of itching is observed as early as 3-5 minutes post-instillation. |
| Duration of Action | Duration of action is up to 8-12 hours, allowing for twice-daily dosing; clinical effect on ocular itching lasts at least 8 hours after a single dose. |
| Molecular Weight | 454.5 |
1 drop in each affected eye twice daily, approximately 6-8 hours apart.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Children 3 years and older: 1 drop in each affected eye twice daily. |
| Geriatric use | No specific dose adjustment required; use same as adult dosing. |
| 1st trimester | Insufficient human data; animal studies show no risk at clinically relevant doses. Use only if clearly needed. |
| 2nd trimester | Same as T1. |
| 3rd trimester | Same as T1. |
Clinical note
Comprehensive clinical and safety monograph for ZADITOR (ZADITOR).
| Placental transfer | Not expected after topical use due to minimal systemic absorption; no data on transfer after systemic exposure. |
| Breastfeeding | Keratolytic agent; negligible systemic absorption after topical application, but avoid application to breast area to prevent infant ingestion. |
| Lactation Rating | L3 (Moderately Safe) |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to ketorolac or any component of the formulationActive peptic ulcer diseaseRecent gastrointestinal bleeding or perforationAdvanced renal impairmentRisk of or actual bleeding diathesisConcomitant use with other NSAIDs including aspirin
| Precautions | Not for the treatment of contact lens-related irritation if lenses are being worn, Do not instill while wearing contact lenses; may contain benzalkonium chloride which can be absorbed by soft lenses, If eye pain, change in vision, continued redness or irritation occurs, discontinue use and consult a doctor |
| Food/Dietary | None known for ophthalmic route. No dietary restrictions. |
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| Teratogenic Risk | FDA Pregnancy Category C. No adequate and well-controlled studies in pregnant women. Animal studies have shown teratogenic effects at high doses. Risk cannot be ruled out. First trimester: potential for fetal harm based on animal data. Second and third trimesters: limited data, use only if potential benefit justifies potential risk. |
| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for maternal ocular adverse effects; no fetal monitoring indicated due to minimal systemic absorption. |
| Fertility Effects | No known effects on fertility in humans. Animal studies at high oral doses showed reduced fertility, but relevance to ophthalmic use is negligible due to low systemic absorption. |
| Clinical Pearls |
| Zaditor (ketotifen fumarate ophthalmic solution) is a mast cell stabilizer with antihistaminic properties for prophylaxis of allergic conjunctivitis. Onset of action may require several weeks for optimal effect; concurrent use with antihistamine eye drops may provide acute relief. Do not administer while patient wears soft contact lenses due to benzalkonium chloride preservative. Wait at least 10 minutes after instillation before inserting lenses. |
| Patient Advice | Do not use to treat contact lens-related irritation. · Remove contact lenses before applying eyedrops; wait at least 10 minutes before reinserting. · Do not touch the dropper tip to any surface, including the eye, to avoid contamination. · Close the bottle tightly after each use. · May cause mild burning or stinging upon instillation. · May cause eye redness, headache, or cold-like symptoms; inform your doctor if severe. · Continue using as prescribed even if symptoms improve, as it may take several weeks for full effect. |