Isoniazid

Evidence Level: L5

Predicted Indications: 1

Isoniazid

Pharmacist Assessment Report

Isoniazid: From Pulmonary Tuberculosis to Conjunctivitis

One-Sentence Summary

Isoniazid is an anti-tuberculosis drug, originally used to treat pulmonary tuberculosis. The TxGNN model predicts it may be effective for conjunctivitis, but the support is weak: there are no registered clinical trials and only 12 publications, mostly case reports, reviews and older studies, many of which concern tuberculosis-related eye disease or drug side effects rather than a new treatment effect.

Quick Overview

Item	Content
Original Indication	Pulmonary tuberculosis
Predicted New Indication	Conjunctivitis
TxGNN Prediction Score	0.9936
Evidence Level	L5
Canada Market Status	Marketed (marketed DINs: 3 of 3)
Number of DINs	3 (marketed: 3)
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available. Based on known information, isoniazid is an anti-mycobacterial agent whose efficacy in pulmonary tuberculosis is established, and mechanistically it may be applicable only to a narrow form of conjunctivitis.

The plausible link is limited to conjunctivitis or phlyctenular keratoconjunctivitis of tuberculous origin. In these cases, treating the underlying Mycobacterium tuberculosis infection, or the hypersensitivity reaction to tubercular antigens, may settle the eye inflammation. Isoniazid has no established activity against common bacterial, viral or allergic conjunctivitis.

Several retrieved records describe ocular or skin and mucosal adverse effects linked to systemic drugs, including isoniazid-related cases. This argues against a general anti-conjunctivitis role. The very high TxGNN score is a computational prediction and probably reflects the tuberculosis-associated ocular disease link rather than a genuinely new indication.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
14253168	1965	Cohort / field prophylaxis study	Am Rev Respir Dis	Isoniazid prophylaxis of phlyctenular keratoconjunctivitis among Eskimos in southwestern Alaska
33607832	2021	Case report	Medicine	Pediatric phlyctenular keratoconjunctivitis associated with primary sinonasal tuberculosis; tuberculosis is a common cause in high-endemic areas
10641112	1999	Case series	Oftalmologia	28 cases of tuberculous keratoconjunctivitis, 13 of them in children with primary tuberculosis
14089390	1964	Case report	Arch Ophthalmol	Primary tuberculosis of the conjunctiva
5103251	1971	Not classified	Ann Oculist	Local use of isoniazid in ocular tuberculosis (no abstract available)
1363080	1992	Review	Optom Clin	Ocular side effects of systemic drugs, including drug-associated conjunctivitis
10084171	1999	Case report	Rev Rhum (Engl Ed)	Refractory arthropathy after intravesical BCG; isoniazid was useful
10084173	1999	Case report / review	Rev Rhum (Engl Ed)	Polyarthritis after intravesical BCG immunotherapy; case plus review of 26 cases
12226788	2002	Case report	Dtsch Med Wochenschr	Chronic reactive arthritis with conjunctivitis after BCG instillation
8136810	1993	Case series	Rev Rhum (Ed Fr)	Polyarthritis in 4 patients after intravesical BCG therapy
14195962	1964	Review / case report	South Med J	Toxic epidermal necrolysis (no abstract available)
7505555	1993	Case series	Ann Trop Paediatr	Munchausen syndrome by proxy in a child; only indirectly relevant

Note: none of these is a randomized trial. Only the 1965 Alaska study directly examines isoniazid in a conjunctivitis-related condition, and that condition is tuberculosis-associated.

Canada Market Information

DIN	Product Name	Dosage Form	Approved Indication
00577812	PDP-ISONIAZID	Not specified	Not specified
00577790	PDP-ISONIAZID	Not specified	Not specified
00577804	PDP-ISONIAZID	Not specified	Not specified

Safety Considerations

Contraindications / conditions of concern (from the drug-disease knowledge graph, not label text): liver failure, acute liver failure, liver disease, hepatitis, gallbladder disease, porphyria (including inherited porphyria and porphyrin metabolism disease), diabetes mellitus, diabetic ketoacidosis, gout, peripheral neuropathy and other peripheral nervous system disease, substance abuse/dependence, and slow acetylator status.

Drug Interactions: 100 interactions were identified. Examples:

Moderate: acarbose, albiglutide, alogliptin, metformin, pioglitazone, canagliflozin, dapagliflozin, chlorpropamide (mainly antidiabetic agents, which fits the caution in diabetes), metronidazole, budesonide, alosetron, calcitriol, calcifediol, cholecalciferol, picosulfuric acid
Minor: hydrocortisone, triamcinolone, dexamethasone, betamethasone

Package insert warnings and contraindications were not available for this report. Please refer to the Health Canada package insert.

Conclusion and Next Steps

Decision: Hold

Rationale: The prediction has no registered clinical trials and no randomized evidence. The literature is mostly old case reports and reviews about tuberculosis-related eye disease or drug adverse effects. Isoniazid has no established role in common conjunctivitis, so the high model score likely reflects the known tuberculosis link rather than a new indication.

To proceed, the following is needed:

Clarify whether the target is tuberculous or phlyctenular conjunctivitis only, which is already part of tuberculosis management, rather than conjunctivitis in general
Obtain the mechanism of action data (MOA)
Obtain the Health Canada package insert warnings and contraindications, as well as dosage form and approved indication details for each DIN
Review the 1965 prophylaxis study and the ocular tuberculosis literature in full text
Assess route compatibility (for example, whether any topical ocular use is realistic), as this has not been evaluated
Review hepatotoxicity, neuropathy and the interaction profile before any new use is considered
Disclaimer

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