Doxylamine
| Evidence Level: L5 | Predicted Indications: 4 |
Table of Contents
Doxylamine: From First-Generation Antihistamine to Allergic Urticaria
One-Sentence Summary
Doxylamine is a first-generation H1-antihistamine (ethanolamine class) that is marketed in South Africa. The TxGNN model predicts it may be effective for allergic urticaria, but currently 0 clinical trials and 0 publications support this prediction, so it rests on model output alone.
Quick Overview
| Item | Content |
|---|---|
| Predicted New Indication | Allergic urticaria |
| TxGNN Prediction Score | 99.85% |
| Evidence Level | L5 |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 12 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the Evidence Pack. Based on general pharmacology, doxylamine is a first-generation H1-receptor antagonist. In allergic urticaria, histamine released from mast cells drives wheals and itching, so blocking H1 receptors is biologically plausible.
The score is very high, but it is a model prediction only. It probably reflects a class effect of antihistamines, so this may be an already-known class use rather than a novel repurposing finding. Doxylamine-specific efficacy and dosing in urticaria are unverified. Sedation and anticholinergic burden are also relevant considerations.
The other predicted indications are weaker or less specific. All are also L5 with a Hold recommendation:
- Cold urticaria (99.26%): a physical urticaria that also involves histamine release, so H1 blockade is plausible. Second-generation antihistamines are usually preferred because they cause less sedation.
- Nasal cavity disease (99.36%): this is a broad category covering allergic rhinitis, sinusitis, polyps and more, so it is too non-specific to support a defined indication.
- Acute laryngopharyngitis (99.34%): this is mostly infectious, and antihistamine benefit is not established. Drying of secretions could plausibly worsen throat discomfort.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
Currently no related literature available.
South Africa Market Information
Twelve SAHPRA registrations are recorded. The five main ones are listed below.
| Registration Number | Product Name | Dosage Form |
|---|---|---|
| Reg. No. 33/7.1.3/0452 | Hypace | Tablet |
| Reg. No. 33/2.8/0098 | Doxy co | Tablet |
| Reg. No. H/10.1/140 | Vicks Medinite | Syrup |
| Reg. No. 36/2.8/0271 | Alpha-Dol | Tablet |
| Reg. No. 29/2.6/0182 | Azor | Tablet |
Available dosage forms are oral tablets and syrup.
Safety Considerations
Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction score is high, but there are no clinical trials or publications for any predicted indication. Safety information from the SAHPRA package insert is also missing, so the candidate cannot proceed to safety screening.
To proceed, the following is needed:
- SAHPRA package insert warnings and contraindications (download and review the PI)
- Mechanism of action data (query DrugBank)
- A literature and trial search for doxylamine in urticaria, to check whether this is already an established class use
- Clarification of the registered indications for the local products, which are not recorded in the current data
- A benefit-risk comparison against second-generation antihistamines, given sedation and anticholinergic burden
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.