Citric Acid

證據等級: L5

預測適應症: 10 個

Citric Acid: From Food Additive & Diagnostic Adjunct to Stomach Disease

One-Sentence Summary

Citric acid (DrugBank DB04272) has no formal approved pharmaceutical indication; it is widely recognised as a food additive (E330), a natural intermediate of the tricarboxylic acid (TCA) cycle, a standardised test-meal component for the ¹³C-urea breath test (H. pylori detection), and an anticoagulant agent (as citrate) in dialysis and catheter-lock solutions. The TxGNN model predicts it may be therapeutically relevant for Stomach Disease based on its deep biochemical integration with the gastric environment, with 0 directly relevant clinical trials and a small number of mechanistic and observational publications providing supporting context. Overall, the evidence base for active therapeutic repurposing in stomach disease remains at Level 4 (preclinical/mechanistic studies), and a Hold decision is recommended pending a clearly defined therapeutic hypothesis and further investigation.

Quick Overview

Item	Content
Original Indication	No formal approved indication; known clinical roles include diagnostic adjunct (¹³C-UBT test meal), regional anticoagulant (as citrate, in dialysis and catheter-lock solutions), and food additive
Predicted New Indication	Stomach Disease
TxGNN Prediction Score	99.74%
Evidence Level	L4
South Africa Market Status	Not marketed
Number of SAHPRA Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data for citric acid as a pharmaceutical agent is not available from this evidence pack. Based on known biochemical and clinical information, citric acid is a naturally occurring tricarboxylic acid that serves as both a food additive and a central intermediate of cellular energy metabolism. It is a natural component of human gastric juice — its gastric concentrations were quantified as early as 1967 — and this intrinsic presence in the gastric milieu provides the structural basis for the TxGNN model to associate it with stomach disease.

The most established clinical role of citric acid in stomach disease management is as a standardised test-meal component for the ¹³C-urea breath test (¹³C-UBT). By acidifying the intragastric environment, citric acid prevents H. pylori — which possesses urease activity — from relocating to non-antral, acid-protected regions of the stomach during the test. This improves the sensitivity and specificity of H. pylori detection, a critical step in managing H. pylori-related stomach diseases including gastritis, peptic ulcer disease, and gastric cancer prevention. A 2019 clinical study specifically investigated whether a citric acid meal enhances ¹³C-UBT accuracy in Asian populations, directly linking citric acid to the stomach disease diagnostic pathway.

From a metabolomics perspective, two additional mechanistic connections have been identified. First, elevated serum citric acid levels have been detected in Korean subjects before gastric cancer onset, suggesting a potential role as a pre-diagnostic metabolic biomarker and indicating that citric acid metabolism is perturbed in gastric carcinogenesis. Second, gastric cancer metabolomic research consistently identifies dysregulation of the TCA cycle — of which citric acid is a key node — as a defining feature of tumour subtypes with distinct clinical outcomes. Additionally, MX1, a compound combining a roxatidine metabolite with a bismuth-citrate complex (containing citric acid), demonstrated gastroprotective effects against stress-induced gastric ulcers in rat models. These converging lines of evidence explain the model’s high prediction score, but it is important to recognise that they reflect a physiological and diagnostic role rather than an established pharmacological treatment effect.

Clinical Trial Evidence

No clinical trials directly evaluate citric acid as a therapeutic intervention for stomach disease. Trials retrieved are testing other active agents for H. pylori eradication or stomach-adjacent conditions (Grade B relevance at the disease level only), or contain citrate as a salt/excipient component. The most contextually relevant trials are listed below:

Trial Number	Phase	Status	Enrollment	Key Findings
NCT05196945	Phase 4	Unknown	316	Vonoprazan fumarate + Amoxicillin dual therapy vs. bismuth quadruple regimen for first-line H. pylori eradication; multicenter RCT in gastritis/peptic ulcer context. Citric acid not an active agent.
NCT06760065	Phase 3	Not Yet Recruiting	316	Keverprazan + Amoxicillin dual therapy vs. susceptibility-guided quadruple therapy for rescue H. pylori eradication after prior failure; addresses antibiotic resistance challenge. Citric acid not an active agent.
NCT03812380	Phase 3	Terminated	62	Effervescent Calcium Magnesium Citrate to avert PPI-associated complications (osteoporosis, hypomagnesaemia, CKD) in patients on long-term proton pump inhibitors for gastric conditions. Contains citrate component; terminated early.
NCT03342456	Phase 4	Completed	184	Ilaprazole/Doxycycline-based bismuth quadruple therapy for H. pylori-infected duodenal ulcers; multicenter RCT addressing antibiotic resistance. Citric acid not an active agent.
NCT03320538	N/A	Completed	360	Jiangzhong Hou Gu® Mi Xi™ (TCM preparation) for peptic ulcer disease with spleen qi deficiency; double-blind RCT assessing symptom improvement. Not related to citric acid.

Note: Trials graded C (unrelated chemotherapy, orthopaedic, or other non-stomach indications) have been excluded from this table. None of the above trials test standalone citric acid as a treatment for stomach disease.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
31505905	2019	Clinical Study	Gut and Liver	Directly evaluates whether a citric acid test meal improves accuracy of the ¹³C-UBT for H. pylori detection in Asian populations — the most clinically direct evidence of citric acid’s role in stomach disease diagnostics
35900644	2022	Cohort	Metabolomics	High serum citric acid levels (and L-carnitine), inversely correlated with alkaline phosphatase, detected in Korean subjects prior to gastric cancer onset; supports citric acid as a potential pre-diagnostic biomarker of gastric carcinogenesis risk
6027230	1967	Observational	Gastroenterology	Foundational biochemical study quantifying citric acid concentration in human gastric juice alongside lactic, pyruvic, and uric acids; establishes citric acid as a natural constituent of the gastric environment
9379358	1997	Preclinical	J Pharmacy & Pharmacology	Gastroprotective effect of MX1 — a novel compound combining roxatidine’s active metabolite with a bismuth-citrate (citric acid) complex — against restraint stress-induced gastric ulcers in rats; indirect evidence involving a citrate-containing compound
38959111	2024	Molecular/Cohort	Cell Reports	Metabolic signature clustering of gastric cancer identifies TCA cycle upregulation (MSC1 subtype, with better prognosis) alongside TP53/RHOA mutations; contextualises citric acid’s metabolic role in gastric tumour biology
26088916	2015	Metabolomics	Applied Biochemistry & Biotechnology	LC/MS metabolomics analysis in gastric cancer identifies dysregulated metabolic pathways as biomarker candidates; TCA cycle intermediates including citric acid implicated in gastric cancer metabolic reprogramming

South Africa Market Information

Citric acid (DrugBank ID: DB04272) is not currently registered with SAHPRA as a standalone pharmaceutical product, and there are no approved medicinal products listed under this identity on the South African market.

Important context: Citric acid is ubiquitous as an excipient and salt-forming agent in numerous registered pharmaceutical products available in South Africa (e.g., effervescent formulations, calcium citrate supplements, oral electrolyte solutions, anticoagulant blood collection tubes [3.2% sodium citrate]). It also holds GRAS (Generally Recognised As Safe) status as a food additive (E330). However, no standalone therapeutic registration exists under SAHPRA for any medicinal indication. Inclusion on the Essential Medicines List (EML) as a standalone therapeutic agent has not been identified.

Safety Considerations

Please refer to the SAHPRA-approved Professional Information (PI) for any registered products containing citric acid as an active or excipient component. Report adverse drug reactions to SAHPRA via the MedSafety reporting system.

General safety note: At food-grade concentrations, citric acid is well-tolerated in the general population with an excellent safety profile. At higher pharmaceutical concentrations or via parenteral routes (e.g., intravenous regional citrate anticoagulation [RCA] in dialysis), careful monitoring of serum ionised calcium is essential, as citrate chelates calcium and can cause clinically significant hypocalcaemia if citrate elimination is impaired (e.g., in hepatic failure). Specific pharmaceutical-grade safety data for standalone oral or systemic citric acid use in stomach disease indications is not available from this evidence pack.

Conclusion and Next Steps

Decision: Hold

Rationale: The TxGNN model assigns a high prediction score (99.74%) to citric acid for stomach disease, reflecting its deep physiological integration with the gastric environment as a natural juice component and TCA cycle intermediate. However, no clinical trials test citric acid as an active therapeutic agent for stomach disease, and the mechanistic evidence reflects a well-established diagnostic and physiological role rather than a pharmacological treatment effect. With evidence at Level 4, a Hold decision is appropriate until a credible therapeutic hypothesis and corresponding evidence are developed.

To proceed, the following is needed:

Define the therapeutic hypothesis: Clearly distinguish whether the proposed repurposing targets citric acid as a treatment (e.g., bacteriostatic effect on H. pylori via intragastric pH reduction, mucosal cytoprotection) or an enhanced diagnostic tool (¹³C-UBT test meal — already in clinical practice and not requiring regulatory repurposing)
Safety consideration for acid-peptic disease: Citric acid’s intragastric acidification properties may be counter-therapeutic in acid-peptic disorders (e.g., gastritis, peptic ulcer disease, GORD) where reducing gastric acidity is the therapeutic goal; this pharmacological paradox must be addressed in any repurposing strategy
Systematic review: Commission a systematic review of citric acid’s gastric pharmacology, including any in vitro evidence for direct activity against H. pylori or gastric mucosal protection
MOA data retrieval: Obtain detailed mechanism-of-action data from DrugBank API and published pharmacology literature (Data Gap DG002)
Regulatory consultation: Given zero SAHPRA registrations and no original indication, any therapeutic repurposing would require a de novo registration pathway

Secondary Indication Alert — Higher Priority Finding: Among all ten TxGNN-predicted indications for citric acid, Thrombotic Disease (Rank 9) presents the strongest and most actionable evidence (Evidence Level L3, Recommendation: Proceed with Guardrails). The CLiCK trial (NCT04548713, N=1,449, Completed, Grade A) directly tested a KiteLock formulation containing citric acid as a central venous catheter lock solution for preventing catheter-related thrombosis and bloodstream infections in ICU patients. The mechanism is well-established — citrate chelates ionised calcium (Ca²⁺), interrupting the coagulation cascade — and is already routinely applied in regional citrate anticoagulation (RCA) for continuous renal replacement therapy (CRRT). A separate evaluation report specifically addressing the Thrombotic Disease indication is strongly recommended as the highest-priority repurposing candidate for citric acid.

This report is generated for research purposes only and does not constitute medical advice. Drug repurposing candidates require clinical validation before therapeutic application. All content is subject to the YMYL disclaimer: results are for research reference only and should not be applied clinically without appropriate regulatory approval and clinical evidence.

Disclaimer

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