Procaine

證據等級: L5

預測適應症: 10 個

Procaine: From Local Anaesthesia to Methemoglobinemia

One-Sentence Summary

Procaine (DrugBank DB00721) is an ester-type local anaesthetic historically used for infiltration, nerve block, and intravenous regional anaesthesia. The TxGNN model’s top prediction links it to Methemoglobinemia with a 99.50% score, but the 8 supporting publications (no clinical trials) describe procaine as a documented cause of methemoglobinemia, not a treatment — the mechanistic direction is inverted, and this candidate does not currently support a repurposing hypothesis.

Quick Overview

Item	Content
Original Indication	Local anaesthesia (ester-type local anaesthetic; no SAHPRA-registered product/indication text available)
Predicted New Indication	Methemoglobinemia
TxGNN Prediction Score	99.50%
Evidence Level	L4 (case reports/experimental data only; no controlled trials)
South Africa Market Status	Not marketed
Number of SAHPRA Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism-of-action data for procaine is not available in this evidence pack (data gap DG002, severity High). Based on the classification notes attached to the literature evidence, procaine is an ester-type local anaesthetic that blocks voltage-gated sodium channels for its anaesthetic effect; its hydrolysis produces para-aminobenzoic acid (PABA) and diethylaminoethanol, and aromatic-amine metabolites of this type are known oxidisers of haemoglobin iron (Fe²⁺ → Fe³⁺) — the mechanism underlying drug-induced methemoglobinemia.

This is the key issue with the top-ranked prediction: all 8 associated publications describe procaine as the causative agent of methemoglobinemia (including a case in a newborn after subcutaneous infiltration, and a direct experimental study on IV procaine raising methemoglobin levels), not as a therapeutic agent for the condition. The relationship between the original use (local anaesthesia) and the predicted indication is therefore an adverse-effect association, not a repurposing signal. This pattern is consistent with a known limitation of knowledge-graph-based prediction: it can learn drug–disease co-occurrence without capturing causal direction, so a strong “drug causes disease X” literature signal can surface as a high-scoring “drug treats disease X” candidate. The same inverted pattern appears in ranks 2–6 of this evidence pack (methemoglobinemia subtype, anaphylaxis, hyperthyroidism), where procaine is documented as a risk factor or diagnostic-test reagent rather than a treatment.

By contrast, two lower-ranked candidates in this pack — fibromyalgia (rank 7) and tendinitis (rank 8) — point in the correct therapeutic direction: procaine has historically been injected into myofascial trigger points (“neural therapy”) to interrupt nociceptive signalling and pain-spasm cycles, and their literature includes an RCT for supraspinatus tendinopathy (PMID 35480510). These are mechanistically more coherent, though evidence quality remains low (L3, uncontrolled/dated case series), and they are flagged as “Research Question” rather than repurposing candidates ready for further evaluation.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
5529388	1970	Case Report	Acta physiologica latino americana	Methemoglobinemia due to intravenous procaine — procaine identified as the causative agent
3691245	1987	Observational/Experimental	Zhonghua wai ke za zhi	IV procaine anaesthesia raises methemoglobin levels
6705717	1984	Review	Drugs	General review of rational local anaesthetic use; not procaine/methemoglobinemia-specific
5118947	1971	Review	Laval medical	General review of local anaesthetics
705003	1978	Case Report (newborn)	Revista espanola de anestesiologia y reanimacion	Methemoglobinemia in a newborn after subcutaneous novocaine infiltration during general anaesthesia
5644303	1968	PK study	American journal of obstetrics and gynecology	Placental transfer of procaine HCl and PABA; not a treatment study
14246695	1965	Case Report (lignocaine, not procaine)	Lancet	Methaemoglobinaemia following lignocaine — different drug, limited relevance
6745527	1984	Review (organophosphate mechanism)	Fundamental and Applied Toxicology	Organophosphate-ester toxicology interactions; not directly about procaine

All procaine-specific entries describe methemoglobinemia as an adverse reaction to procaine, not a treatment indication.

South Africa Market Information

Procaine is currently not marketed in South Africa, with 0 SAHPRA-registered products in this evidence pack. No registration numbers, product names, or approved-indication text are available for South Africa at this time.

Safety Considerations

Please refer to the SAHPRA-approved Professional Information (PI) for formal safety information; PI warnings and contraindications data are not available in this evidence pack (data gap DG001, severity Blocking). Report adverse drug reactions to SAHPRA.

Note: independent of the formal PI data gap, the literature reviewed for this repurposing signal itself documents two safety-relevant patterns for procaine — (1) drug-induced methemoglobinemia, particularly with IV/high-dose or neonatal exposure, and (2) pseudoanaphylactic/anaphylactoid reactions (Hoigné’s syndrome), most often with procaine-penicillin formulations. These should be treated as safety signals for any future clinical use of procaine, not as supporting evidence for repurposing.

Conclusion and Next Steps

Decision: Hold

Rationale: The top TxGNN-predicted indication (methemoglobinemia) is contradicted by its own supporting literature, which documents procaine as a cause of the condition rather than a treatment; no clinical trials exist for this or any of the other 9 predicted indications in this pack, and two Blocking/High-severity data gaps (PI safety data, formal MOA) remain unresolved.

To proceed, the following is needed:

SAHPRA-approved Professional Information (warnings, contraindications) — currently a Blocking data gap
Formal mechanism-of-action documentation from DrugBank or equivalent — currently a High-severity data gap
If pursuing the mechanistically plausible secondary signals (fibromyalgia, tendinitis — “neural therapy” use), contemporary controlled trials confirming efficacy against modern comparators, since existing evidence predates current diagnostic criteria and is largely uncontrolled case-series data
Re-evaluation of the methemoglobinemia, anaphylaxis, and hyperthyroidism signals as potential safety flags rather than repurposing candidates, given the directionality of the underlying evidence
Disclaimer

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