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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZADITOR (ZADITOR).
| Breastfeeding | Not known if ketotifen (ophthalmic) is excreted in human milk. Systemic absorption is minimal after ocular administration, but caution is advised. M/P ratio not established. Consider developmental and health benefits of breastfeeding along with mother's clinical need for ZADITOR. |
| 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. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to any component of the product"]
| 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"] |
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| 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. |