Phosphoric Acid
| Evidence Level: L4 | Predicted Indications: 10 |
Table of Contents
Phosphoric Acid: From Pharmaceutical Excipient Use to Osteoarthritis
One-Sentence Summary
Phosphoric acid has no stated therapeutic indication in the available data. It appears in South African registered injectable products, most likely as an acidulant or pH adjuster. The TxGNN model predicts it may be effective for osteoarthritis, but there are 0 relevant clinical trials (2 registered trials, both unrelated) and 18 publications (21 retrieved), all describing disease biology rather than any treatment effect. The prediction is best read as a knowledge-graph artifact.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the SAHPRA registration data or DrugBank |
| Predicted New Indication | Osteoarthritis |
| TxGNN Prediction Score | 98.21% |
| Evidence Level | L4 |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 3 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available. DrugBank lists no original indication or mechanism for phosphoric acid. Based on known information, it is mainly used as an acidulant or excipient rather than an active therapeutic. There is no established efficacy in any disease from which to extrapolate to osteoarthritis.
The literature does link phosphate-containing crystals to osteoarthritis. Basic calcium phosphate (BCP) and calcium pyrophosphate (CPP) crystals are found in a large share of osteoarthritic joints. They are associated with cartilage calcification, NLRP3 inflammasome activation and eicosanoid production. However, this makes phosphate a possible contributor to disease, not a treatment. The direction of effect is opposite to a repurposing benefit.
The very high TxGNN score most likely reflects a generic phosphate node in the knowledge graph. The other nine predictions for this drug (rheumatoid arthritis, gout, several rare liver conditions and others) are also rated L5 and Hold, several with identical scores. This supports the artifact interpretation.
Clinical Trial Evidence
Two registered trials matched the osteoarthritis search. Neither tests phosphoric acid and neither is about osteoarthritis treatment.
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT07049731 | N/A | Not yet recruiting | 224 | Protein nutrition powder plus resistance exercise in sarcopenia. Not osteoarthritis, not phosphoric acid, no results. |
| NCT06921720 | N/A | Not yet recruiting | 65 | Phosphorus-31 spectroscopy of ATP in phosphate diabetes. Phosphate is a measurement target, not an intervention. |
No SANCTR or PACTR registrations were identified.
Literature Evidence
All items are reviews or preclinical or genetic studies of osteoarthritis pathogenesis. None evaluates phosphoric acid as a treatment.
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 39089298 | 2024 | Review | Lancet Rheumatol | CPPD disease is strongly associated with cartilage degradation and osteoarthritis. The direction of causality is unclear. |
| 36509917 | 2023 | Review | Nat Rev Rheumatol | Cartilage calcification (BCP and CPP crystals) is a hallmark of osteoarthritis. Mechanisms and clinical relevance are reviewed. |
| 34732285 | 2021 | Review | Best Pract Res Clin Rheumatol | Calcium-crystal-related endotypes are present in about 60% of osteoarthritis patients. |
| 29516278 | 2018 | Review | Curr Rheumatol Rep | BCP and CPP crystals can induce inflammation and may play a pathogenic role in osteoarthritis. |
| 26720903 | 2016 | Review | Curr Opin Rheumatol | BCP crystals are implicated in osteoarthritis pathogenesis. Potential targeted therapies would aim to block their effects. |
| 21169842 | 2011 | Review | Curr Opin Rheumatol | CPPD and BCP crystals are common in osteoarthritic joint fluid. How they contribute to joint damage remains unclear. |
| 20425024 | 2010 | Review | Curr Rheumatol Rep | Evidence for an independent link between crystals (CPP, uric acid) and osteoarthritis is sparse. |
| 16716886 | 2006 | Review | Rheum Dis Clin North Am | Calcium crystals may cause or worsen osteoarthritis, and osteoarthritis may promote crystal formation. |
| 37105395 | 2023 | Genetic study | Osteoarthritis Cartilage | Functional genomics of BCP crystal-induced inflammation, which acts through the NLRP3 inflammasome. |
| 38877353 | 2024 | Preclinical | Adv Mater | Hydroxyapatite-based hydrogel scaffold for osteoarthritis subchondral bone repair. This is a biomaterial, not phosphoric acid. |
South Africa Market Information
The registration data contain no approved indication text or manufacturer for any entry. Registration N/24/83 appears twice in the record. Essential Medicines List (EML) status is not available in the data.
| Registration Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| N/24/83 | Sabax Neonatalyte 10% Gluc 200ml AFB2718 | Infusion | Not stated |
| B/2.9/1251 | Sabax Pethidine Ampoule 1ml | Injection | Not stated |
These are injectable products in which phosphoric acid is likely an excipient. No oral, topical or intra-articular product containing it as an active ingredient was identified.
Safety Considerations
Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
No drug-drug interaction records were found in DrugBank.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction is supported only by pathogenesis literature in which phosphate-containing crystals are a possible cause of osteoarthritis, so the direction of effect is unfavourable. No trial tests phosphoric acid for this condition. The drug has no established therapeutic role or mechanism, and safety data for South Africa are missing. This evidence level is L4, and the candidate should not advance to safety screening.
To proceed, the following is needed:
- SAHPRA Professional Information (PI) for the registered products (warnings and contraindications, currently blocking)
- Mechanism of action data from DrugBank
- Confirmation that phosphoric acid is only an excipient in the registered products
- Any evidence that phosphoric acid, rather than a crystal-modulating agent, has a therapeutic effect in osteoarthritis, together with a plausible route of administration
This report is for research reference only and does not constitute medical advice. Repurposing candidates require clinical validation before any clinical use.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.