Dexchlorpheniramine Maleate
| Evidence Level: L5 | Predicted Indications: 10 |
Table of Contents
- Dexchlorpheniramine Maleate
- Dexchlorpheniramine Maleate: From Antihistamine Use to Acute Intermittent Porphyria
Dexchlorpheniramine Maleate: From Antihistamine Use to Acute Intermittent Porphyria
One-Sentence Summary
Dexchlorpheniramine maleate is a first-generation H1 antihistamine marketed in Singapore in tablet and syrup forms. The TxGNN model's top prediction is acute intermittent porphyria, but this is a model prediction only, with no clinical trials and no publications supporting it. The approved indication text is not available in the data compiled for this report.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the licence records |
| Predicted New Indication | Acute intermittent porphyria |
| TxGNN Prediction Score | 99.12% |
| Evidence Level | L5 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 10 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available. Dexchlorpheniramine is known to be a first-generation H1 antihistamine, but the data compiled for this report contain no mechanism entry and no stated original indication.
The prediction is not mechanistically supported. Nothing connects H1 receptor blockade to heme biosynthesis or to the pathophysiology of porphyria attacks. The high score therefore reflects the model's pattern-matching alone. Safety is also a concern: some drugs are porphyrinogenic, so the drug's safety in porphyria would need to be checked before any further consideration.
Other predictions in the top 10 (all Hold unless noted):
| Rank | Predicted Indication | Score | Evidence Level | Comment |
|---|---|---|---|---|
| 2 | Nephrogenic syndrome of inappropriate antidiuresis | 98.36% | L5 | This condition arises from gain-of-function variants in the vasopressin V2 receptor, and H1 antagonism has no known action there. |
| 3 | Porphyria | 97.69% | L5 | This is a broader category that overlaps with rank 1, so the two predictions are likely correlated. |
| 4 | Schizophrenia | 97.17% | L5 | The link is speculative. The anticholinergic properties of a first-generation antihistamine could also worsen cognition. |
| 5 | Polymicrogyria, perisylvian, with cerebellar hypoplasia and arthrogryposis | 97.13% | L5 | This is a structural developmental disorder with no plausible mechanism. |
| 6 | Allergic urticaria | 96.96% | L4 | The mechanism is coherent, since H1 antihistamines are standard symptomatic therapy. This is most likely a rediscovery of existing use rather than true repurposing, and its recommendation is "Research Question". |
| 7 | Syndromic myopia | 96.83% | L5 | The antimuscarinic activity is weak and non-selective, and the syndromic forms are genetic. |
| 8 | Atypical glycine encephalopathy | 96.75% | L5 | This is an inborn error of glycine metabolism with no supported link. |
| 9 | Myopia 26, X-linked, female-limited | 96.71% | L5 | The prediction is likely correlated with the other myopia entries. |
| 10 | Myopia X-linked | 96.61% | L5 | The prediction is likely correlated with the other myopia entries. |
Allergic urticaria is the only prediction with a coherent mechanism, although it is not a true repurposing case.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
For the top prediction (acute intermittent porphyria), currently no related literature available.
The only literature item in the top 10 predictions concerns the lower-ranked prediction, allergic urticaria:
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 39803 | 1979 | Clinical/immunological study (likely case series) | Dermatologica | Describes a single case of acquired heat contact urticaria in a young woman. The title does not show that dexchlorpheniramine was evaluated, and this is not a controlled trial. |
Singapore Market Information
All 10 licences are valid single-ingredient products. Approved indication text is not recorded for any of them. The table lists five main authorisations.
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN09373P | DEXTRAMINE TABLET 2 mg | Tablet | Not recorded |
| SIN02655P | DEXCHLORAMINE TABLET 2 mg | Tablet | Not recorded |
| SIN02491P | POLARAX SYRUP 2 mg/5 ml | Syrup | Not recorded |
| SIN09916P | SOMIN TAB 2 mg | Tablet | Not recorded |
| SIN10542P | AXCEL DEXCHLORPHENIRAMINE FORTE SYRUP 2 mg/5 ml | Syrup | Not recorded |
The remaining five licences are POLARAX TABLET (SIN09125P), POLARINE TABLET (SIN07612P), POLARINE SYRUP (SIN03182P), MENDICOF SYRUP (SIN11516P) and PAEDICOF SYRUP (SIN11515P).
Safety Considerations
Please refer to the package insert for safety information.
Package insert warnings and contraindications could not be retrieved for this report. This is a blocking gap for safety screening. No drug interaction records were found, and the knowledge graph lists no contraindicated diseases for this drug.
For the top prediction, the porphyria safety question noted above must be resolved first.
Conclusion and Next Steps
Decision: Hold
Rationale: The top prediction, acute intermittent porphyria, rests on a model score alone, with no trials, no literature and no plausible mechanism. There is also a potential porphyrinogenic safety concern. The only mechanistically coherent prediction, allergic urticaria, is likely just the drug's existing antihistamine use.
To proceed, the following is needed:
- Package insert warnings and contraindications from the HSA website (blocking gap)
- Mechanism of action data from DrugBank
- A porphyria safety review (porphyrinogenic potential) before any further work on the top prediction
- Confirmation of the approved indications from the HSA licences
- A targeted literature search for dexchlorpheniramine in the predicted conditions, starting with urticaria if a rediscovery framing is acceptable
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.