Mepyramine
| Evidence Level: L4 | Predicted Indications: 4 |
Table of Contents
Mepyramine: From Antihistamine Use to Allergic Urticaria
One-Sentence Summary
Mepyramine is a first-generation histamine H1-receptor antagonist. It is marketed in South Africa, but the registered indication text was not supplied. The TxGNN model predicts it may be effective for allergic urticaria (score 99.92%). Support is thin: 0 registered clinical trials and 5 publications, all preclinical or veterinary, with no human trial data.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the supplied SAHPRA data (a first-generation H1 antihistamine, generally used for allergic conditions) |
| Predicted New Indication | Allergic urticaria |
| TxGNN Prediction Score | 99.92% |
| Evidence Level | L4 |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 9 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available. Based on known information, mepyramine is a first-generation H1-receptor antagonist. Histamine released from activated mast cells drives the wheal-and-flare reaction in allergic urticaria, so blocking H1 receptors is biologically plausible.
The high TxGNN score is consistent with this class effect. However, this is largely a class-effect indication, not a novel repurposing finding, because H1 antihistamines are already the standard drug class for urticaria. Because no original indication or mechanism data were supplied, the link cannot be confirmed from this record alone.
TxGNN also ranked three other indications for mepyramine: nasal cavity disease (99.74%), acute laryngopharyngitis (99.72%) and cold urticaria (99.70%). They have weaker or no supporting evidence and are not assessed further here.
Clinical Trial Evidence
Currently no related clinical trials registered. No ClinicalTrials.gov, ICTRP, SANCTR or PACTR records were found in the supplied data.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 21033572 | 2010 | Veterinary randomised study (dogs) | Pol J Vet Sci | 27 dogs with angioedema were randomised to mepyramine maleate (n=15) or placebo (n=12). The authors concluded it may be helpful. This is the only disease-relevant clinical signal, and it is not in humans. |
| 34758144 | 2021 | Preclinical | FASEB J | Mepyramine directly blocks nociceptor sodium channels, which explains topical pain relief. This is off-target pharmacology, not urticaria. |
| 18222495 | 2008 | Preclinical in vitro | Neuropharmacology | Mepyramine inhibits the KCNQ/M potassium channel in rat neurons, which may relate to seizure risk in overdose. |
| 34387278 | 2021 | In vitro receptor affinity assessment | Curr Opin Allergy Clin Immunol | Assessed receptor affinities of agents used in dry eye disease. It is not specific to urticaria. |
| 29371669 | 2018 | In vitro tool development | Sci Rep | Developed fluorescent H1-receptor ligands to study binding kinetics. It is a methods paper, not efficacy evidence. |
South Africa Market Information
Nine SAHPRA registrations were found; the five main ones are shown below. The approved indication text and Essential Medicines List (EML) status were not supplied. The product names suggest cough, cold and teething products, likely combinations, but ingredients and strengths were not provided.
| Registration Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| G1260 (ACT101) | Codomil new formula | Syrup | Not stated in supplied data |
| G892 (OM) | Adco-Metaxol | Suspension | Not stated in supplied data |
| C739 | Sinu-flu (was Universal cold & flu) | Tablet | Not stated in supplied data |
| G1236 | Codef Cough | Syrup | Not stated in supplied data |
| B0917 (ACT 101) | Vidol teething powders | Powder (listed as “Pwo”) | Not stated in supplied data |
Safety Considerations
Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
The supplied literature describes serious effects of first-generation antihistamine overdose, including drowsiness, seizures, convulsions and coma. These are background observations, not label warnings.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction is mechanistically plausible but is essentially a class effect. Support is limited to preclinical work and one veterinary study, with no human trials (L4). The safety review is also blocked, because the SAHPRA package insert warnings and contraindications are missing.
To proceed, the following is needed:
- Download and review the SAHPRA package inserts (warnings, contraindications, active ingredient and strength in each product). This is a blocking gap.
- Mechanism of action data from DrugBank.
- The registered indication text for each South African product.
- Human clinical evidence for mepyramine in urticaria, including a comparison with the second-generation antihistamines already used.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.