Ketotifen
| Evidence Level: L3 | Predicted Indications: 10 |
Table of Contents
Ketotifen: From Atopic Conjunctivitis to Allergic Urticaria
One-Sentence Summary
Ketotifen is an H1-antihistamine and mast cell stabilizer, originally used for allergic eye conditions such as atopic, papillary and vernal conjunctivitis. The TxGNN model predicts it may be effective for allergic urticaria (top-ranked prediction), supported by 0 registered clinical trials and 20 publications, most of which are general reviews. The strongest ketotifen-specific signal is in the closely related cold urticaria (the third-ranked prediction), which has 14 publications, several of them small clinical studies.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Atopic conjunctivitis, papillary conjunctivitis, vernal conjunctivitis (the Singapore licence records contain no approved indication text) |
| Predicted New Indication | Allergic urticaria |
| TxGNN Prediction Score | 98.60% |
| Evidence Level | L3 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 6 |
| Recommended Decision | Proceed with Guardrails |
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available in the data compiled for this report. Based on the literature, ketotifen is an H1-antihistamine and mast cell stabilizer. Its efficacy in allergic conjunctivitis has been established, and mechanistically it may be applicable to urticaria.
Urticaria is driven by mast cell degranulation and histamine release. Allergic conjunctivitis is also a mast cell and histamine-mediated condition, so a drug that blocks histamine receptors and stabilizes mast cells fits both diseases. Older studies report that ketotifen reduces histamine release in physical urticarias (for example PMID 2420246).
Other predicted indications are less well supported. Atopic dermatitis is plausible mechanistically (mast cells and histamine contribute to itch), but there is no trial or literature support. Infectious conjunctivitis types (viral, parasitic, pseudomembranous, follicular), rosacea conjunctivitis and nasopharyngitis have weak mechanistic links and no clinical evidence.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
The table lists the most relevant publications for allergic urticaria and its closest subtype, cold urticaria. Most reports are small, older studies.
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 3907425 | 1985 | Double-blind crossover trial | Annals of Allergy | In 11 patients with cold-induced urticaria, ketotifen 1 mg twice daily delayed reaction time to a cold stimulus in 10 of 11; placebo had no effect |
| 6209972 | 1984 | Clinical study | Allergologia et Immunopathologia | Ketotifen was compared with clemastine (double-blind crossover) in 87 patients with idiopathic cold urticaria |
| 7488341 | 1995 | Comparative study | Asian Pac J Allergy Immunol | Double-blind crossover comparison of cyproheptadine and ketotifen in 6 Thai children with cold urticaria |
| 2420246 | 1986 | Clinical study | Annals of Internal Medicine | Ketotifen was associated with marked reductions in plasma histamine after provocation in physical urticarias |
| 6198811 | 1983 | Clinical/mechanistic study | Z Hautkr | Ketotifen and oxatomide inhibited cold-induced histamine release in 4 patients; the effect was stronger with oxatomide |
| 1364168 | 1992 | Randomized crossover study | J Investig Allergol Clin Immunol | Loratadine, cetirizine, cyproheptadine and ketotifen were compared in 7 patients with acquired cold urticaria |
| 2899435 | 1986 | Clinical study | Allergie et Immunologie | In 36 patients with chronic urticaria given ketotifen 2 mg/day, 12 healed, 11 had good results and 12 failed; best results were in cold and food-related urticaria |
| 19753736 | 2002 | Comparative study | J Dermatol Treat | Levothyroxine versus ketotifen in chronic urticaria with thyroid autoimmunity |
| 2226222 | 1990 | Review | Drugs | Pharmacology and therapeutic use of ketotifen in asthma and allergic disorders |
| 9487221 | 1998 | Clinical report | Arch Dermatol | Report on ketotifen in chronic urticaria |
Singapore Market Information
All six registrations are valid single-ingredient products. The licence records contain no approved indication text.
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN07601P | DHATIFEN TABLET 1 mg | Tablet | Not stated |
| SIN08054P | SUNTOTIFEN TABLET 1 mg | Tablet | Not stated |
| SIN08053P | SUNTOTIFEN SYRUP 1 mg/5 ml | Syrup | Not stated |
| SIN09651P | TOFEN TABLET 1 mg | Tablet | Not stated |
| SIN10107P | ASUMALIFE SYRUP 1 mg/5 ml | Syrup | Not stated |
A sixth licence, SIN08766P (KETOTIFEN SYRUP 1 mg/5 ml, Hovid), is also valid. Available forms are oral tablets and syrup.
Safety Considerations
- Drug Interactions: The interaction screen identified 86 potentially interacting drugs, but none has a severity level assigned. Examples include doxycycline, pantoprazole, metformin, omeprazole, simvastatin, prednisolone, dexamethasone, clopidogrel, acetylsalicylic acid and cromoglicic acid.
Please refer to the package insert for warnings and contraindications.
Conclusion and Next Steps
Decision: Proceed with Guardrails
Rationale: Ketotifen is already marketed in Singapore as oral tablets and syrup, and the mechanism fits urticaria. Ketotifen-specific clinical studies exist, mainly for cold urticaria, including several double-blind crossover studies. However, they are old, small and of variable quality, there are no registered trials, and the overall evidence level is L3. Proceeding should be limited to a research question rather than a clinical claim.
To proceed, the following is needed:
- Package insert warnings and contraindications from HSA, which are currently missing and block safety screening
- Detailed mechanism of action data (for example from DrugBank)
- Modern, adequately powered randomized trials of ketotifen in allergic or chronic urticaria, with comparison against current second-generation antihistamines
- Review of the approved indications for the Singapore products, as the licence records do not state them
- Severity grading and clinical review of the 86 flagged drug interactions
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.