Dipyridamole
| Evidence Level: L4 | Predicted Indications: 10 |
Table of Contents
Dipyridamole: From Antiplatelet/Coronary Vasodilator Therapy to Prinzmetal Angina
One-Sentence Summary
Dipyridamole is a phosphodiesterase inhibitor and antiplatelet agent (detailed original indication and MOA are not yet confirmed in UK regulatory data). The TxGNN model assigns it a very high score (99.99%) for Prinzmetal Angina, but the underlying evidence actually describes dipyridamole provoking coronary vasospasm during diagnostic stress testing rather than treating it — no clinical trials and only mechanistic/case-level literature (15 publications) support this direction.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not on record — no UK marketing authorisation; evidence pack literature describes the drug generically as an antiplatelet / coronary vasodilator agent |
| Predicted New Indication | Prinzmetal angina |
| TxGNN Prediction Score | 99.99% |
| Evidence Level | L4 |
| UK Market Status | Not marketed |
| Number of Marketing Authorisations | 0 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism-of-action data for dipyridamole is not available in this evidence pack (flagged as data gap DG002). Based on the literature retrieved, dipyridamole is known as a phosphodiesterase inhibitor and adenosine-reuptake blocker with antiplatelet and coronary vasodilator properties, and it is widely used as a pharmacologic “stress agent” for myocardial perfusion imaging.
This is precisely where the mechanistic link to Prinzmetal (variant) angina breaks down. Prinzmetal angina is caused by focal coronary artery vasospasm. The retrieved literature does not show dipyridamole being used therapeutically to prevent or treat this spasm — instead, multiple papers (e.g. PMID 3421166, 16630456) describe dipyridamole-induced coronary vasodilation triggering or unmasking vasospastic episodes during diagnostic testing, which is closer to an adverse pharmacological interaction than a therapeutic effect.
In other words, the TxGNN model’s very high similarity score appears to be driven by dipyridamole’s strong association with the general “coronary/angina” disease neighbourhood in the knowledge graph, rather than by a genuine treatment signal for this specific vasospastic condition. No completed or ongoing clinical trial in this evidence pack tests dipyridamole as therapy for Prinzmetal angina.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 633593 | 1978 | Review | Japanese Circulation Journal | In patients with rest angina (including Prinzmetal’s variant), dipyridamole 50 mg was among several agents tested for effect on attacks; propranolol worsened attacks in Prinzmetal cases. |
| 3421166 | 1988 | Case report/Mechanistic | American Journal of Cardiology | Aminophylline-terminated dipyridamole stress can trigger coronary vasospasm in variant angina — an adverse provocation, not a treatment effect. |
| 16630456 | 2006 | Case series | Zhonghua xin xue guan bing za zhi | Compared clinical features of typical vs. atypical coronary artery spasm; dipyridamole testing used diagnostically. |
| 8417062 | 1993 | Observational | Journal of the American College of Cardiology | Echocardiographic changes in transiently asynergic myocardium during ischaemic episodes induced by various pharmacologic mechanisms, including dipyridamole. |
| 3190956 | 1988 | Study (unclassified) | British Heart Journal | Reproducibility of exercise testing in patients with different responses to the dipyridamole test; diagnostic, not therapeutic, use. |
| 6779029 | 1981 | Study (unclassified) | Japanese Circulation Journal | Dipyridamole-loading thallium myocardial imaging increased diagnostic sensitivity for coronary artery disease when combined with exercise testing. |
| 8634169 | 1996 | Study (unclassified) | Revista Portuguesa de Cardiologia | 3-year prognosis of patients with suspected CAD and normal thallium-dipyridamole scintigraphy. |
| 2022043 | 1991 | Study (unclassified) | Circulation | Reviews pathophysiological basis of noninvasive functional stress testing methods, including dipyridamole, for coronary stenosis. |
| 7628141 | 1995 | Study (unclassified) | Clinical Nuclear Medicine | Case report on “cardiac migraine,” noting documented variant angina and vasoactive disorders in the differential. |
| 2221701 | 1990 | Study (unclassified) | Annals of the New York Academy of Sciences | Discusses ECG diagnosis of transient myocardial ischaemia, sensitivity/specificity relevant to pharmacologic provocation testing. |
UK Market Information
No UK marketing authorisation is currently on record for dipyridamole in this evidence pack (market status: Not marketed, 0 licences). Collection of the TFDA/MHRA-equivalent product label (warnings, contraindications) is flagged as a blocking data gap (DG001) and must be resolved before any safety review can proceed.
Safety Considerations
Please refer to the SmPC and BNF for safety information. Report suspected adverse reactions via the Yellow Card Scheme.
(Key warnings, contraindications, and DDI data were not available in this evidence pack — see DG001.)
Conclusion and Next Steps
Decision: Hold
Rationale: Despite the very high TxGNN similarity score, the actual literature evidence for Prinzmetal angina consists entirely of diagnostic-context, mechanistic, and case-level reports (L4) describing dipyridamole inducing coronary vasospasm during stress testing — not treating it. There are zero registered clinical trials testing dipyridamole as a therapy for this condition, and the proposed mechanism may be directly contrary to the pathology it would need to treat.
To proceed, the following is needed:
- TFDA/MHRA product label (warnings, contraindications) — currently blocking (DG001)
- Confirmed mechanism of action (DG002)
- A preclinical or mechanistic study specifically distinguishing dipyridamole’s provocative (diagnostic) vs. any potential protective (therapeutic) effect on coronary vasospasm, before this candidate can move beyond S1
Note on other candidates in this evidence pack: This report evaluates only the top-ranked TxGNN prediction (Prinzmetal angina). The same evidence pack contains substantially stronger candidates for dipyridamole — notably stroke and transient ischaemic attack (both L1, “Proceed with Guardrails,” supported by large Phase 3/4 RCTs including ESPRIT (n=4,500) and PRoFESS (n=20,332), and Cochrane meta-analyses) — reflecting dipyridamole’s established combination use with aspirin for secondary stroke prevention. These may warrant a separate, dedicated evaluation report.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.