Promethazine
| Evidence Level: L5 | Predicted Indications: 10 |
Table of Contents
- Promethazine
- Promethazine: From Its Established Use as an H1 Antihistamine to Rosacea Conjunctivitis
Promethazine: From Its Established Use as an H1 Antihistamine to Rosacea Conjunctivitis
One-Sentence Summary
Promethazine is a first-generation H1 antihistamine with anticholinergic and sedating activity, marketed in South Africa in several syrup and tablet products. The TxGNN model predicts it may be effective for rosacea conjunctivitis, with a very high model score. However, 0 clinical trials and 0 publications currently support this specific prediction, so it rests on the model alone.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the retrieved SAHPRA records (approved-indication text is empty) |
| Predicted New Indication | Rosacea conjunctivitis |
| TxGNN Prediction Score | 98.94% |
| Evidence Level | L5 (model prediction only) |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 17 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the source record. Based on known information, promethazine is an H1 receptor antagonist with anticholinergic activity, and its use as an antihistamine is well established. Mechanistically, it could relieve histamine-driven itch and irritation in the eye.
The link to rosacea conjunctivitis is weak, though. Ocular inflammation in rosacea is not mainly driven by histamine. At most, an antihistamine or anticholinergic could give symptomatic relief. No trials or publications were found, so the prediction should be treated as speculative. A high model score reflects similarity in the knowledge graph, not proof of benefit.
Clinical Trial Evidence
Currently no related clinical trials registered. No SANCTR or PACTR entries were identified either.
Literature Evidence
Currently no related literature available.
South Africa Market Information
Showing 5 of 17 registrations. The retrieved records do not include approved-indication text or Essential Medicines List (EML) status.
| Registration Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| B1234 | Propain | Syrup | Not listed in retrieved record |
| 27/2.8/0242 | Goldgesic | Syrup | Not listed in retrieved record |
| 27/2.8/0575 | Salterpyn | Syrup | Not listed in retrieved record |
| X/2.8/174 | Mepromol | Syrup | Not listed in retrieved record |
| X/2.8/298 | Pynmed Tablets/Tablette | Tablet | Not listed in retrieved record |
Available dosage forms are oral syrup, oral tablet and suspension. No ophthalmic formulation was identified, so route compatibility for an eye indication is unassessed.
Safety Considerations
Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
The evidence pack also notes that sedation and anticholinergic burden are recognised limitations of promethazine. No drug-interaction records were found.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction is model-only (L5), with no trials or literature. The mechanism is weak because rosacea-related eye inflammation is not primarily histamine-driven. No ophthalmic formulation is registered.
To proceed, the following is needed:
- SAHPRA Professional Information (warnings, contraindications and approved indications) for the registered products
- Detailed mechanism of action data for promethazine
- Any preclinical or clinical evidence in rosacea-related ocular disease, plus a route-compatibility assessment, since only oral forms are registered
Note on other predictions: Lower-ranked predictions have more support. These are allergic urticaria (L4), with an indirect Phase 3 antihistamine trial and a healthy-volunteer study of promethazine, and rhinitis (L3), with older case series and pharmacodynamic studies. Both may already be labelled uses, which should be confirmed against the PI. They are better candidates for follow-up than rosacea conjunctivitis.
This report is for research reference only and does not constitute medical advice. Repurposing candidates require clinical validation before use.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.