Loratadine
| Evidence Level: L3 | Predicted Indications: 10 |
Table of Contents
Loratadine: From Allergic Rhinitis to Allergic Urticaria
One-Sentence Summary
Loratadine is a second-generation H1 antihistamine, originally used for allergic rhinitis, allergic conjunctivitis and idiopathic urticaria. The TxGNN model predicts it may be effective for allergic urticaria, supported by 1 post-marketing investigation (n=1,003) and 17 publications, mostly narrative reviews. Because idiopathic urticaria is already a labelled indication, this is a close extension of existing use rather than a true repurposing.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Allergic rhinitis (other listed indications: vasomotor rhinitis, pharyngitis, common cold, conjunctivitis subtypes, idiopathic urticaria) |
| Predicted New Indication | Allergic urticaria |
| TxGNN Prediction Score | 98.98% |
| Evidence Level | L3 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 17 |
| Recommended Decision | Proceed with Guardrails |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the data compiled for this report. Based on known information, loratadine is a long-acting antihistamine that selectively blocks peripheral histamine H1 receptors. Its efficacy in allergic rhinitis and idiopathic urticaria is established.
In allergic urticaria, histamine released from mast cells drives the characteristic wheal and flare, so H1 blockade directly addresses the pathway. Idiopathic urticaria is already a labelled indication, and the allergic form shares the same histamine-mediated mechanism.
Reviews in the compiled literature report that loratadine is effective in chronic urticaria and as effective as several other antihistamines in controlled comparative studies.
Clinical Trial Evidence
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT00762983 | N/A (post-marketing survey) | Completed | 1003 | Drug use investigation of Claritin tablet, RediTabs and dry syrup in children. It collected adverse reactions and symptom scores. It is observational, and its specific coverage of allergic urticaria cannot be confirmed. |
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 35396016 | 2022 | Review | Profiles of Drug Substances, Excipients, and Related Methodology | Drug profile of loratadine, noting its use in allergic rhinitis, chronic urticaria and asthma |
| 16278258 | 2005 | Review | Annals of Pharmacotherapy | Efficacy and safety of oral antihistamines in allergic rhinitis and chronic idiopathic urticaria |
| 14977391 | 2004 | Review | Drugs | Review of cetirizine in allergic disorders (a comparator antihistamine) |
| 12113226 | 2002 | Review | Clinical Allergy and Immunology | H1-antihistamines in children are effective for allergic rhinoconjunctivitis |
| 7528133 | 1994 | Review | Drugs | Loratadine beat placebo and matched several comparator antihistamines in allergic rhinitis and urticaria |
| 7530629 | 1994 | Review | Drugs | Non-sedating antihistamines are the mainstay of treatment for chronic idiopathic urticaria |
| 9951950 | 1999 | Review | Drugs | Comparative review of second-generation antihistamines, including loratadine |
| 19348661 | 2009 | Case report | Journal of Dermatology | Rare case of urticaria worsened by H1-antihistamines |
Singapore Market Information
All 17 registrations are valid single-ingredient licences. The data compiled for this report contain no approved-indication text. Five main authorizations are listed below.
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN14077P | CLARITYNE TABLET 10mg | Tablet, film coated | Not stated |
| SIN16091P | CLARITYNE SYRUP 5 MG/5 ML (GRAPE FLAVOR) | Syrup | Not stated |
| SIN12466P | LORACIN TABLET 10 mg | Tablet | Not stated |
| SIN13341P | Loradine Tablet 10 mg | Tablet | Not stated |
| SIN12246P | CLARITYN-D 24HOUR EXTENDED RELEASE TABLET | Tablet, sugar coated | Not stated |
Safety Considerations
- Contraindications (knowledge-graph associations, not label text): The drug-disease graph links loratadine with caution in these conditions:
- Hypertension
- Liver disease and liver failure
- Kidney disease and impaired renal function
- Gallbladder disease
- Diabetes mellitus and diabetic ketoacidosis
- Benign prostatic hyperplasia
- Coronary artery disease and atherosclerosis
- Angle-closure glaucoma
- Hyperthyroidism, Graves disease and thyrotoxicosis
- Drug Interactions: 100 interactions were found in total. The listed ones include:
- Moderate: glycerol phenylbutyrate, troglitazone
- Minor: clarithromycin, miconazole
- Many others are of unknown severity (for example metformin, omeprazole, morphine, doxycycline).
Please refer to the package insert for label warnings and contraindications.
Conclusion and Next Steps
Decision: Proceed with Guardrails
Rationale:
- Allergic urticaria is a histamine-mediated condition, and loratadine is already marketed in Singapore for related allergic conditions, including idiopathic urticaria.
- The supporting evidence is mainly narrative reviews and one observational survey, with no completed controlled Phase 3 trials specific to this indication.
To proceed, the following is needed:
- The Singapore package insert, to confirm approved indications, warnings and contraindications
- Detailed mechanism of action data
- Controlled efficacy data specific to allergic urticaria
- Review of interactions and graph-flagged comorbidities (renal, hepatic, cardiovascular, glaucoma) before use
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.