Isoniazid
| Evidence Level: L4 | Predicted Indications: 10 |
Table of Contents
Isoniazid: From Tuberculosis to Conjunctivitis
One-Sentence Summary
Isoniazid is an antimycobacterial drug, used mainly to treat and prevent tuberculosis (TB). The TxGNN model predicts it may be effective for conjunctivitis, but the support is weak: 1 clinical trial (not about conjunctivitis) and 20 publications, mostly case reports and reviews of TB-related eye disease or drug side effects.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Tuberculosis (the SAHPRA record for the registered product does not list an indication) |
| Predicted New Indication | Conjunctivitis |
| TxGNN Prediction Score | 99.36% |
| Evidence Level | L4 |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 1 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in the Evidence Pack. Isoniazid is generally understood to be a prodrug activated inside mycobacteria that blocks mycolic acid synthesis. Its efficacy in TB is well established.
The link to conjunctivitis is indirect. The literature describes:
- Rare TB-related eye disease, such as tuberculous conjunctivitis and phlyctenular keratoconjunctivitis, where isoniazid treats the underlying mycobacterial infection.
- Conjunctivitis as a side effect of BCG treatment and of other systemic drugs.
There is no evidence that isoniazid helps common bacterial, viral or allergic conjunctivitis. The high score (99.36%) is not backed by clinical data.
Clinical Trial Evidence
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT04094012 | Phase 3 | Completed | 490 | Compared systemic drug reactions under 3HP (rifapentine + isoniazid, weekly) and 1HP regimens for latent TB. It does not study conjunctivitis, so it gives no efficacy evidence for this indication. |
No SANCTR or PACTR registrations were identified.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 32674602 | 2020 | Case report | Clinical Pediatrics | Adolescent with an unexpected cause of conjunctivitis (no abstract available) |
| 33607832 | 2021 | Case report | Medicine | Child with phlyctenular keratoconjunctivitis linked to primary sinonasal TB |
| 26692731 | 2015 | Case report | Middle East African J Ophthalmol | Tuberculous conjunctivitis in an anophthalmic socket, in a patient with prior miliary TB |
| 25433746 | 2014 | Not classified | Can J Ophthalmol | Conjunctival phlyctenulosis as a warning sign of impending clinical TB |
| 17133069 | 2006 | Not classified | Cornea | Case of conjunctival TB presenting as chronic red eye |
| 1363080 | 1992 | Review | Optom Clin | Ocular side effects of systemic drugs; conjunctivitis is linked to several other drug classes |
| 10641112 | 1999 | Not classified | Oftalmologia | 28 cases of tuberculous keratoconjunctivitis, 13 of them in children with primary TB |
| 14253168 | 1965 | Not classified | Am Rev Respir Dis | Isoniazid prophylaxis for phlyctenular keratoconjunctivitis among Alaskan Eskimos (no abstract available) |
| 5103251 | 1971 | Not classified | Ann Ocul | Local use of isoniazid in ocular TB (no abstract available) |
| 14089390 | 1964 | Case report | Arch Ophthalmol | Primary TB of the conjunctiva (no abstract available) |
All evidence concerns TB-related eye disease, not routine conjunctivitis. No randomised trials were found.
South Africa Market Information
| Registration Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| Reg. No. 52/20.2/0208 | Cotrizid | Tablet | Not listed in the registration record |
Route: oral only.
Safety Considerations
Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction rests on model score alone. The only trial is unrelated to conjunctivitis, and the literature consists of case reports and side-effect reviews. Isoniazid has no established role in ordinary conjunctivitis.
To proceed, the following is needed:
- SAHPRA Professional Information (warnings and contraindications), which is required before any safety screening.
- Mechanism of action data, e.g. from DrugBank.
- Evidence of benefit in conjunctivitis, beyond TB-related ocular disease. Absent that, this is not a new indication.
- Of the other predictions in this pack, only leprosy (rank 5) has a biologically plausible signal. It is historical, mostly 1950s reports, and needs comparison against current WHO multidrug therapy.
This report is for research reference only and does not constitute medical advice. Predicted indications require clinical validation before use.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.