Doxycycline
| Evidence Level: L5 | Predicted Indications: 10 |
Table of Contents
Doxycycline: Punctate epithelial keratoconjunctivitis
One-Sentence Summary
Doxycycline is a tetracycline antibiotic used for bacterial infections such as bronchitis, bacterial pneumonia, gonorrhoea, anthrax and acne. The TxGNN model predicts it may be useful for punctate epithelial keratoconjunctivitis, but there are no registered clinical trials and only 1 publication (a 1992 case report), so the evidence is weak and indirect.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not recorded in the local data |
| Predicted New Indication | Punctate epithelial keratoconjunctivitis |
| TxGNN Prediction Score | 0.9994 |
| Evidence Level | L5 |
| Australia Market Status | Listed on the PBS Schedule (1 of 1 items) – TGA (ARTG) registration status is not included in this data |
| Number of PBS Items | 1 (valid: 1) |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available. Based on known information, doxycycline is a broad-spectrum tetracycline antibiotic with proven efficacy in several bacterial infections, including Chlamydia trachomatis. Mechanistically it may be applicable to ocular surface disease.
The prediction rests on two plausible links:
- Antimicrobial activity: Chlamydial conjunctivitis can be followed by punctate epithelial keratitis. Doxycycline is an established treatment for the chlamydial infection that often precedes it.
- Anti-inflammatory activity: Doxycycline is known to inhibit matrix metalloproteinases (MMPs) and reduce inflammation, which could help with ocular surface inflammation.
This is indirect reasoning. The one available paper relates to treating the preceding infection, not to a repurposing signal for the keratitis itself. Notably, in that report the keratitis persisted after the infection was treated.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 1424659 | 1992 | Case report | Cornea | Two patients with chlamydial follicular conjunctivitis were treated with oral tetracycline or doxycycline, and their follicles resolved. Both then developed recurrent, bilateral punctate corneal epithelial lesions. This describes persistent keratitis after treatment, not a benefit from doxycycline. |
Australia Market Information
| Licence Number | Product Name | Dosage Form |
|---|---|---|
| 10176N | Doxylin 100 | Tablet 100 mg (as hyclate), oral |
The approved indication text was not available in the licence data compiled for this report. Only oral tablets are listed, and no ocular or topical formulation was identified.
Safety Considerations
Contraindications flagged by the knowledge graph (these are drug-disease links, not product label text):
- Clostridium difficile colitis
- Perinatal necrotizing enterocolitis
- Dyskinesia of the oesophagus
Drug interactions: 100 interactions were identified. The 20 reviewed include:
- Major: isotretinoin, acitretin, aminolevulinic acid
- Moderate: aluminium hydroxide, aminophylline, amoxicillin, ampicillin, bedaquiline and others
- Minor: acetazolamide, amiloride, bendroflumethiazide
Please refer to the TGA-approved Product Information (PI) for full warnings, contraindications and interaction management.
Conclusion and Next Steps
Decision: Hold
Rationale: The model score is very high, but the supporting evidence is a single 1992 case report that does not show a benefit from doxycycline. There are no clinical trials, and no mechanism of action data is available for this assessment.
To proceed, the following is needed:
- Controlled clinical studies of doxycycline (oral or topical ocular) in punctate epithelial keratoconjunctivitis
- Detailed mechanism of action data
- Approved indication text and PI safety information for the Australian product
- Ophthalmic formulation and route feasibility, since only an oral tablet is currently registered
Note: Among the other predictions for this drug, chronic gingivitis/periodontitis has substantially stronger support (L2, with multiple clinical studies of subantimicrobial-dose and locally delivered doxycycline). It may be a better candidate to prioritise.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.