KETOTIFEN FUMARATE
Clinical safety rating: safe
Animal studies have demonstrated safety
Antihistamine and mast cell stabilizer; inhibits release of histamine and other mediators from mast cells; also blocks histamine H1 receptors.
| Metabolism | Hepatic; undergoes glucuronidation and O-demethylation; CYP3A4 minor involvement. |
| Excretion | Renal (50-70% as conjugates, <2% unchanged), fecal (<10%), with enterohepatic circulation. |
| Half-life | Terminal half-life 12-24 hours (mean 18 hours); requires twice-daily dosing after initial titration. |
| Protein binding | ~75%, primarily to albumin. |
| Volume of Distribution | 2.4-3.6 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: ~50% (due to first-pass metabolism); Ophthalmic: minimal systemic absorption (<5%). |
| Onset of Action | Oral: 2-4 weeks for prophylactic effect in asthma; Ophthalmic: 5-15 minutes for histamine-induced effects. |
| Duration of Action | Oral: 8-12 hours (symptom control), requires continuous dosing; Ophthalmic: up to 8 hours for itch relief. |
| Molecular Weight | 425.5 |
| Action Class | Antihistamine (H1-receptor antagonist) / Mast Cell Stabilizer |
1 mg orally twice daily; ophthalmic: 1 drop in each eye every 8-12 hours.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment; GFR <30 mL/min: use caution, no specific guidelines. |
| Liver impairment | Child-Pugh Class A and B: no adjustment; Class C: use caution, consider dose reduction due to increased exposure. |
| Pediatric use | Children ≥3 years: 1 mg orally twice daily; <3 years: 0.5 mg twice daily; ophthalmic: 1 drop in each eye every 8-12 hours for children ≥3 years. |
| Geriatric use | Initiate at 0.5 mg twice daily; increase to 1 mg twice daily if tolerated due to increased risk of sedation and dizziness. |
| 1st trimester | Limited human data; animal studies show no teratogenicity at clinically relevant doses. Use only if clearly needed. |
| 2nd trimester | No known harm; caution due to potential anticholinergic effects. |
| 3rd trimester | Avoid near term due to possible sedative effects on neonate. |
Clinical note
CNS depressants may enhance sedative effects For ophthalmic use only may cause transient stinging.
| Placental transfer | Crosses placenta in animal studies; molecular weight suggests likely transfer. |
| Breastfeeding | Small amounts excreted into breast milk; risk of infant sedation and anticholinergic effects. Consider benefit vs risk. |
| Lactation Rating |
■ FDA Black Box Warning
None.
| Common Effects | Drowsiness |
| Serious Effects | Anaphylaxis, Severe hypersensitivity reactions, Seizures, Extrapyramidal symptoms (dystonia, dyskinesia), Severe sedation or CNS depression, Hepatotoxicity (rare), Thrombocytopenia (rare) |
Hypersensitivity to ketotifen or any excipient
| Precautions | Not for treatment of acute symptoms or contact lens-related irritation., May cause transient stinging or burning upon instillation., Soft contact lenses should be removed before use and may be reinserted after 10 minutes. |
| Food/Dietary | None significant. Ketotifen absorption is not affected by food. Avoid alcohol as it may increase sedation. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | Ketotifen fumarate is classified as Pregnancy Category C. In animal studies, ketotifen has been shown to be teratogenic at high doses, causing increased fetal resorption and skeletal abnormalities. However, adequate well-controlled studies in pregnant women are lacking. First trimester exposure: potential risk of fetal harm based on animal data, but human data insufficient; second and third trimester: risk cannot be excluded. Should be used during pregnancy only if the potential benefit outweighs the risk. |
| Fetal Monitoring | Monitor for signs of sedation, dizziness, and anticholinergic effects in the mother. Fetal monitoring: consider periodic ultrasound if used long-term in pregnancy to assess fetal growth and development. No specific fetal monitoring is routinely required, but observe for neonatal adverse effects such as sedation if used near term. |
| Fertility Effects | In animal reproduction studies, ketotifen did not impair fertility at therapeutic doses. However, high doses caused reduced fertility and increased preimplantation loss. Human data on fertility effects are lacking; theoretical risk of hormonal or gamete effects exists due to antihistamine and mast cell stabilizing properties, but no specific studies have been conducted. |
| Clinical Pearls | Ketotifen fumarate is a mast cell stabilizer with antihistamine properties, used primarily for prophylaxis of asthma and for allergic conditions. It may cause sedation, especially early in therapy; dose titration is recommended. Onset of therapeutic effect in asthma prophylaxis may take several weeks. For allergic conjunctivitis, topical ophthalmic solution is used. Do not use for acute asthma attacks. |
| Patient Advice | Take ketotifen exactly as prescribed; do not exceed the recommended dose. · For asthma prophylaxis, effects may not be noticeable for several weeks; continue treatment regularly. · Avoid activities requiring mental alertness until you know how ketotifen affects you, as it may cause drowsiness. · Do not stop taking ketotifen abruptly without consulting your doctor, as asthma symptoms may worsen. · If using ophthalmic solution, do not touch the dropper tip to any surface to avoid contamination. · Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding. |