Propylene Glycol

證據等級: L5

預測適應症: 10 個

Propylene Glycol: From Pharmaceutical Excipient to Bronchitis (Prediction Under Review)

One-Sentence Summary

Propylene glycol (PG) is not marketed in Taiwan as a standalone therapeutic product and has no recorded original indication — it is conventionally used as a pharmaceutical excipient/solvent in other formulations. The TxGNN model’s top-ranked prediction is Bronchitis, but the supporting clinical trials involve a different active drug (inhaled cyclosporine) with PG only as a solvent, and the literature signal actually points toward airway irritation risk rather than therapeutic benefit. Evidence for this specific prediction is therefore weak and partly contradictory.

Quick Overview

Item	Content
Original Indication	No approved indication on record; PG is conventionally used as a pharmaceutical excipient/solvent, not marketed as a standalone active drug in Taiwan
Predicted New Indication	Bronchitis
TxGNN Prediction Score	99.90%
Evidence Level	L4
US Market Status	Not Marketed
Number of NDAs	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data for propylene glycol is not available. Based on known information, PG is not developed as a standalone therapeutic agent — it functions almost exclusively as an excipient/solvent within other drug formulations (e.g., inhalation solutions, ophthalmic preparations, oral/topical vehicles). It has no established original indication or proven clinical efficacy of its own.

The clinical trials retrieved for the “bronchitis” prediction (all Grade C relevance) are actually studies of Cyclosporine Inhalation Solution for bronchiolitis obliterans syndrome after lung/stem-cell transplant — PG appears only as a formulation solvent, not as the tested active ingredient. This means the trial evidence does not directly demonstrate any therapeutic effect of PG itself on bronchitis.

More notably, the associated literature evidence trends in the opposite direction: reviews on e-cigarette (“vaping”) liquids — which commonly contain propylene glycol as a base — discuss its potential association with airway irritation, chronic bronchitis, and COPD-like pathology, rather than any protective or therapeutic role. Taken together, the mechanistic rationale for PG as a treatment for bronchitis is not well supported and may even represent a safety signal rather than an efficacy signal.

For context, among PG’s other TxGNN-predicted indications, diabetic retinopathy (rank 3) reached a higher evidence stage (L3 / S1, “Research Question”) based on formulation-related ophthalmic literature, though it still lacks direct efficacy data for PG itself. This suggests any further exploration of PG repurposing may be better directed there than toward bronchitis.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT00755781	Phase 3	Completed	284	Tested Cyclosporine Inhalation Solution (CIS) for preventing bronchiolitis obliterans syndrome post-lung transplant; PG is a formulation solvent only, not the tested drug
NCT01273207	Phase 2	Completed	7	Extended-access CIS study in lung/stem-cell transplant recipients with bronchiolitis obliterans; PG not the active agent
NCT00938236	Phase 3	Terminated	17	Long-term follow-up of inhaled cyclosporine for chronic rejection prevention; trial terminated, PG not the active agent
NCT01287078	Phase 2	Completed	25	CIS treatment trial for bronchiolitis obliterans syndrome in transplant recipients; PG present only as excipient

Literature Evidence

PMID	Year	Type	Journal	Key Findings
26408554	2015	Review	Am J Physiol Lung Cell Mol Physiol	Discusses whether chronic e-cigarette use (liquids commonly containing PG) may cause chronic bronchitis and COPD-like lung disease
28983782	2017	Review	Curr Allergy Asthma Rep	Reviews e-cigarette constituents (including PG-based e-liquids) and potential links to asthma/airway pathology
20920189	2010	Preclinical (mouse model)	Respiratory Research	Studies quercetin (not PG) in an elastase/LPS mouse model of chronic bronchitis/COPD; PG not the study agent

US Market Information

Propylene glycol has no marketing authorization records in the current dataset (0 licenses; market status: Not Marketed).

Safety Considerations

Please refer to the package insert for safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: The top-ranked TxGNN prediction (bronchitis) has a high model score but is not supported by genuine PG-specific clinical evidence — the retrieved trials tested a different active drug (inhaled cyclosporine) with PG only as a solvent, and the associated literature raises a potential airway-irritation safety concern rather than a therapeutic signal. This does not meet the bar to advance beyond model prediction (S0).

To proceed, the following is needed:

TFDA/regulatory label data on warnings and contraindications for PG (currently blocking, DG001)
Confirmed mechanism of action data from DrugBank or other authoritative source (DG002)
If pursued, a re-scoped evidence search specifically distinguishing PG-as-active-agent studies from PG-as-excipient studies
Consider evaluating the diabetic retinopathy prediction (L3/S1) instead, given its comparatively stronger (though still indirect) evidence base
Disclaimer

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