Phenylbutazone
| Evidence Level: L2 | Predicted Indications: 10 |
Table of Contents
Phenylbutazone: Revisiting a Historical NSAID Use in Rheumatoid Arthritis
One-Sentence Summary
Phenylbutazone is a pyrazolone-class NSAID with no confirmed marketing authorisation currently on record in the UK dataset. TxGNN’s top-ranked prediction is Rheumatoid Arthritis, but the underlying evidence indicates this is largely a re-identification of the drug’s long-established historical use rather than a novel repurposing signal, supported by 20 publications (no registered clinical trials) spanning 1952–2009.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not specified in the regulatory dataset; historically used as a pyrazolone NSAID for rheumatic/inflammatory joint disease |
| Predicted New Indication | Rheumatoid Arthritis |
| TxGNN Prediction Score | 99.82% |
| Evidence Level | L2 |
| UK Market Status | Not Marketed |
| Number of Marketing Authorisations | 0 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available (original_moa is unrecorded in this dataset). Based on the supporting literature and repurposing rationale, phenylbutazone is a pyrazolone-class NSAID that inhibits COX-1/COX-2, producing anti-inflammatory and analgesic effects — a mechanism directly relevant to the joint inflammation seen in rheumatoid arthritis.
Importantly, the evidence pack itself flags that rheumatoid arthritis is not a novel predicted use for this drug, but rather a condition in which phenylbutazone already has a long clinical history (dating back to the 1950s–1980s double-blind trials). The same pattern holds for two other high-ranking predictions in this pack — gout (rank 4) and osteoarthritis (rank 7) — both supported by head-to-head trials against comparator NSAIDs (naproxen, indomethacin, flufenamic acid, aspirin). This suggests TxGNN is largely recovering the drug’s established pharmacological class effect rather than surfacing a genuinely new therapeutic hypothesis.
By contrast, several lower-tier predictions in this pack (colobomatous microphthalmia-rhizomelic dysplasia syndrome, brachydactyly-syndactyly syndrome, acromesomelic dysplasia, brachyolmia, myosclerosis) are rare congenital skeletal/connective-tissue disorders with no supporting literature or trials (L5) and no plausible mechanistic link to NSAID pharmacology. One prediction — sclerosing cholangitis — is arguably contraindicated in direction, since the RA literature includes a documented case of phenylbutazone-induced hepatitis, i.e. a hepatic risk signal rather than a therapeutic opportunity.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 4903691 | 1969 | RCT | Canadian Medical Association journal | Double-blind comparison of monobutazone vs phenylbutazone in RA; fewer side effects with monobutazone |
| 788739 | 1976 | Cohort | British Journal of Clinical Pharmacology | Double-blind dose-response study (50–300 mg/day) showing plasma concentration correlates with clinical response |
| 913873 | 1977 | Cohort | Journal of International Medical Research | Double-blind dose-response study (50–400 mg/day); plasma levels linked to effectiveness |
| 6884415 | 1983 | Dose-finding (double-blind) | European Journal of Clinical Pharmacology | Determined 300 mg/day as minimum effective dose across 8 dose levels; 7/32 patients had adverse reactions |
| 334476 | 1977 | Controlled trial | Current Medical Research and Opinion | Comparison of flurbiprofen vs phenylbutazone; rash observed in phenylbutazone arm |
| 6345427 | 1983 | Double-blind trial | International Journal of Tissue Reactions | Suxibuzone (prodrug) vs phenylbutazone; comparable efficacy, significantly fewer GI side effects with prodrug |
| 786193 | 1976 | Review | Archives of Internal Medicine | Overview of RA treatment including anti-inflammatory agents |
| 13009482 | 1952 | Clinical evaluation | California Medicine | Landmark 409-patient evaluation of phenylbutazone across rheumatic diseases including RA and gout |
| 1145012 | 1975 | Case Report | Rheumatology and Rehabilitation | Phenylbutazone-associated hepatitis; review of 41 case histories (hepatic safety signal) |
| 13126544 | 1954 | Clinical report | British Medical Journal | Early clinical experience with phenylbutazone use in RA |
UK Market Information
Phenylbutazone currently holds no marketing authorisations on record in this dataset (market status: Not Marketed; total licences: 0). No product, dosage form, or approved indication text is available to summarise.
Safety Considerations
Please refer to the SmPC and BNF for safety information. Report suspected adverse reactions via the Yellow Card Scheme.
Note: The evidence pack flags UK safety data (warnings/contraindications) as a Blocking data gap — this must be resolved before any safety review can proceed. Separately, literature evidence for this indication includes a documented case report of phenylbutazone-associated hepatitis (PMID 1145012), which should be considered when assessing hepatic risk.
Conclusion and Next Steps
Decision: Hold
Rationale:
- The safety data gap (DG001, Blocking) means an initial safety assessment (S1) cannot be completed, regardless of efficacy evidence strength.
- The top prediction (rheumatoid arthritis) largely reflects the drug’s own pre-existing historical use rather than a novel repurposing opportunity, and the drug has no current UK marketing authorisation to build on.
- The remaining higher-ranked predictions in this pack (rare skeletal dysplasias, sclerosing cholangitis) either lack any supporting evidence (L5) or point in a direction inconsistent with a known hepatotoxicity signal.
To proceed, the following is needed:
- UK SmPC/MHRA-equivalent safety data (warnings, contraindications, DDI) to resolve DG001
- Confirmed mechanism of action and formally documented original indication(s) to resolve DG002
- Clarification of UK regulatory/marketing pathway, given zero current licences
- If pursuing genuinely novel indications, independent mechanistic or preclinical validation for the L5-rated candidates, as none currently have literature or trial support
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.