Dimenhydrinate
| Evidence Level: L4 | Predicted Indications: 2 |
Table of Contents
Dimenhydrinate: From Motion Sickness to Allergic Urticaria
One-Sentence Summary
Dimenhydrinate is an over-the-counter antihistamine sold in the US mainly as a motion sickness remedy (Dramamine, Gravol). The TxGNN model predicts it may be effective for allergic urticaria, but 0 clinical trials and 1 publication (a canine pharmacokinetic pilot study) currently support this direction. The evidence is very early-stage.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Motion sickness (inferred from product names; approved indication text was not supplied) |
| Predicted New Indication | Allergic urticaria |
| TxGNN Prediction Score | 99.74% |
| Evidence Level | L4 |
| US Market Status | ✓ Marketed |
| Number of NDAs | 20 licenses (the listed products carry authorization number M009) |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the Evidence Pack. Dimenhydrinate is a salt of diphenhydramine and 8-chlorotheophylline. Diphenhydramine is a first-generation H1 receptor antagonist, and dimenhydrinate is already marketed in the US for motion sickness.
H1 blockade is the established way to control histamine-driven wheals and itching in allergic urticaria. This class-level mechanism likely explains the very high TxGNN score. The same reasoning applies to the model’s second prediction, cold urticaria (score 99.24%). It is a physical urticaria driven by mast cell histamine release, but it has no trial or literature evidence and sits at L5 (model prediction only).
The mechanistic link is a class and moiety effect of diphenhydramine. No dimenhydrinate-specific efficacy data in urticaria were supplied. First-generation antihistamines are also sedating and anticholinergic. Current guidance generally prefers second-generation H1 antihistamines, which limits the practical value of this repurposing.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 30779257 | 2019 | Pharmacokinetic pilot study (dogs) | Veterinary Dermatology | Compared diphenhydramine levels after oral and IV diphenhydramine and oral dimenhydrinate in healthy dogs. It also looked at the effect on histamine-induced wheal formation. Dimenhydrinate has been reported to give better oral absorption of diphenhydramine. This is an animal study, not human evidence. |
US Market Information
Approved indication text was not provided for these listings. The table shows five of the 20 licenses.
| Authorization Number | Product Name | Dosage Form | Manufacturer |
|---|---|---|---|
| M009 | Motion Sickness Relief | Tablet | Cardinal Health 110, LLC. DBA Leader |
| M009 | Dramamine | Chewable tablet | Lil’ Drug Store Products, Inc. |
| M009 | Gravol | Syrup | Church & Dwight Co., Inc. |
| M009 | Motion Sickness Relief | Tablet | Allegiant Health |
| M009 | Dimenhydrinate | Tablet | CVS Pharmacy, Inc. |
Other dosage forms on the market include solution for injection, liquid-filled capsules and coated tablets.
Safety Considerations
- Class profile: As a first-generation H1 antihistamine, it has a sedating and anticholinergic profile. This is a practical limitation for chronic urticaria treatment.
- Drug Interactions: The DDI query returned no results.
Please refer to the package insert for warnings and contraindications.
Conclusion and Next Steps
Decision: Hold
Rationale: The mechanistic rationale is sound, and the TxGNN score is very high. However, the only supporting literature is one canine pharmacokinetic pilot study, with no clinical trials. Second-generation antihistamines are already preferred for urticaria, and the safety review cannot proceed without package insert data.
To proceed, the following is needed:
- Package insert warnings and contraindications, to complete the safety screen
- Detailed mechanism of action data (MOA)
- Human clinical evidence for dimenhydrinate specifically in urticaria, or a rationale for choosing it over second-generation antihistamines
- Route and dosage compatibility assessment for the urticaria indication
This report is for research reference only and does not constitute medical advice. Repurposing candidates require clinical validation before any application.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.