Dextromethorphan

Evidence Level: L5

Predicted Indications: 5

Dextromethorphan

Pharmacist Assessment Report

Dextromethorphan: NMDA receptor antagonist and sigma-1 agonist (centrally acting antitussive) → nasal cavity disease

One-Sentence Summary

Dextromethorphan is a centrally acting cough suppressant that is marketed in Canada in many single-ingredient products. The TxGNN model predicts it may be relevant for nasal cavity disease, but no clinical trials and no publications were found to support this direction, so the evidence rests on the model prediction alone.

Quick Overview

Item	Content
Original Indication	Not recorded in the local data
Predicted New Indication	nasal cavity disease
TxGNN Prediction Score	0.9998
Evidence Level	L5
Canada Market Status	Marketed (marketed DINs on record: at least 20)
Number of DINs	at least 20
Recommended Decision	Hold

Why is This Prediction Reasonable?

Dextromethorphan acts in the central nervous system as an NMDA receptor antagonist and sigma-1 receptor agonist. Detailed mechanism of action data is not available in the data compiled for this report, so this description reflects general pharmacological knowledge rather than the supplied data.

The high score for nasal cavity disease most likely reflects how close this condition sits to upper respiratory conditions already linked to the drug, such as rhinitis and the common cold. It looks like a broad parent-category prediction that overlaps with those existing uses rather than a new repurposing signal. Nothing in the supplied data gives an independent mechanistic reason why a centrally acting antitussive would treat a disease of the nasal cavity itself. At most, it may relieve symptoms such as cough that accompany these conditions.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

Currently no related literature available.

Canada Market Information

At least 20 valid single-ingredient licences were found, and the list may be partial. Approved indication text is not recorded in the local data. Five representative products:

DIN	Product Name	Dosage Form	Approved Indication
01944738	BENYLIN EXTRA STRENGTH DRY COUGH	Not recorded	Not recorded
02511320	BUCKLEY’S DRY COUGH EXTRA STRENGTH	Not recorded	Not recorded
02534754	DRY COUGH RELIEF EXTRA STRENGTH	Not recorded	Not recorded
01928775	BALMINIL DM (3MG/ML SUCROSE FREE)	Not recorded	Not recorded
02549360	DAYQUIL KIDS HONEY	Not recorded	Not recorded

Safety Considerations

Drug Interactions: 100 interactions are recorded. Major-level interactions include:
- Serotonergic agents: dexfenfluramine, fenfluramine, lorcaserin, sibutramine
- 5-HT3 antagonist antiemetics: dolasetron, granisetron, ondansetron, palonosetron
Moderate-level examples: bupropion, cimetidine, morphine, metoclopramide, opium, phentermine, dronabinol, nabilone, eliglustat, mazindol, glycerol phenylbutyrate.
Other considerations: Dextromethorphan depends on CYP2D6 metabolism, so CYP2D6 inhibitors (such as bupropion) deserve particular attention.

Please refer to the package insert for warnings and contraindications.

Conclusion and Next Steps

Decision: Hold

Rationale: The score is very high, but there is no clinical or published evidence for nasal cavity disease, and the prediction likely overlaps with conditions the drug is already associated with. No independent mechanistic rationale is supported.

To proceed, the following is needed:

Direct clinical or preclinical studies in nasal cavity disease
Detailed mechanism of action data
Package insert warnings and contraindications from Health Canada
A clear definition of how the predicted condition differs from the existing upper respiratory uses
A review of the interaction profile (serotonergic agents, CYP2D6 inhibitors) for any new use
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.