Dipyridamole
| Evidence Level: L4 | Predicted Indications: 10 |
Table of Contents
Dipyridamole: From Antiplatelet Therapy to Prinzmetal Angina
One-Sentence Summary
Dipyridamole is an antiplatelet and coronary vasodilator agent. The registered South African product, Asasantin 200/25 Retard, is a dipyridamole-aspirin capsule; the registration data in the Evidence Pack does not state its approved indication. The TxGNN model predicts it may be effective for Prinzmetal angina, but the evidence is weak: 0 clinical trials and 15 publications, mostly diagnostic or descriptive, with one reporting a possible safety signal.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the SAHPRA registration data (see the note under “Why is This Prediction Reasonable?”) |
| Predicted New Indication | Prinzmetal angina |
| TxGNN Prediction Score | 99.99% |
| Evidence Level | L4 |
| South Africa Market Status | Marketed |
| Number of SAHPRA Registrations | 1 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available. Dipyridamole is known to raise extracellular adenosine and act as a coronary vasodilator. In theory, this could relieve coronary spasm.
The retrieved literature does not support this at present. Most papers use dipyridamole as a diagnostic stress agent for imaging, not as a treatment. One paper reports that coronary vasospasm was triggered when dipyridamole-induced vasodilation was reversed with aminophylline in patients with variant angina. That is a possible safety signal, not therapeutic support. Coronary steal (diverting blood away from narrowed vessels) is also a recognised concern. The high model score therefore looks more like a knowledge-graph association than a clinical signal.
The registration data lists no approved indication. Dipyridamole-aspirin combinations are generally used for secondary stroke prevention, but this should be confirmed against the SAHPRA-approved Professional Information (PI). The same Evidence Pack also predicts transient ischaemic attack (TIA) and stroke, where large trials such as ESPRIT and JASAP exist. That is likely an established use rather than true repurposing, and it should be assessed separately from this Prinzmetal angina prediction.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
No therapeutic RCTs were found. The list below covers 10 of the 15 retrieved publications.
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 633593 | 1978 | Small clinical series | Jpn Circ J | 26 patients with rest angina (13 with Prinzmetal’s variant) were given several drugs including dipyridamole. Propranolol did not suppress attacks and tended to aggravate them. The dipyridamole result is not shown in the available abstract. |
| 3421166 | 1988 | Small series | Am J Cardiol | Tested whether rapid withdrawal of dipyridamole-induced vasodilation with aminophylline can trigger coronary vasospasm in variant angina (36 in-hospital patients). This is a safety signal, not evidence of benefit. |
| 3190956 | 1988 | Cohort | Br Heart J | 25 patients with exercise-induced ST elevation, grouped by dipyridamole echo response. Assessed reproducibility of exercise testing. Diagnostic, not therapeutic. |
| 16630456 | 2006 | Cohort | Zhonghua Xin Xue Guan Bing Za Zhi | Compared clinical features of typical and atypical coronary artery spasm. The abstract does not describe dipyridamole treatment results. |
| 6779029 | 1981 | Diagnostic study | Jpn Circ J | Dipyridamole-loading thallium-201 imaging in 38 patients had 66% diagnostic accuracy. Combined with exercise imaging, sensitivity rose from 71% to 87%. |
| 8417062 | 1993 | Diagnostic study | J Am Coll Cardiol | Studied increased echodensity in transiently asynergic myocardium as an echocardiographic sign of ischaemia. |
| 8634169 | 1996 | Cohort | Rev Port Cardiol | 3-year prognosis of patients with suspected coronary disease and a normal dipyridamole-thallium scan. Diagnostic and prognostic. |
| 2022043 | 1991 | Review | Circulation | Pathophysiological basis for noninvasive functional evaluation of coronary stenosis, including dipyridamole testing. |
| 7628141 | 1995 | Case report | Clin Nucl Med | Single patient with migraine, asthma and documented variant angina, examining whether “cardiac migraine” is a clinical entity. Not a treatment study. |
| 2221701 | 1990 | Review | Ann N Y Acad Sci | ECG diagnosis of transient myocardial ischaemia. Not a treatment study. |
South Africa Market Information
| Registration Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| Reg. No. 31/8/0641 | Asasantin 200/25 Retard | Capsule (oral) | Not stated in the registration data |
The Evidence Pack contains no Essential Medicines List (EML) information for this product.
Safety Considerations
- Literature-derived signal: Coronary vasospasm was reported after aminophylline reversal of dipyridamole-induced vasodilation in variant angina patients (PMID 3421166).
- Theoretical concerns: Coronary steal, and possible aggravation of sinus or AV node suppression through adenosine potentiation.
The SAHPRA package insert warnings, contraindications and interaction data were not available. Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction has no supporting therapeutic trials, and the literature is diagnostic or descriptive. One paper suggests dipyridamole-related vasodilation changes may trigger vasospasm in this very condition. The model score alone is not enough to justify clinical development.
To proceed, the following is needed:
- The SAHPRA package insert (warnings, contraindications, approved indication), which is currently a blocking gap
- Mechanism of action data from DrugBank
- Evidence of therapeutic benefit, such as controlled studies in Prinzmetal angina, and a review of the vasospasm and coronary steal safety signals
- Separate assessment of the TIA/stroke prediction, which has far stronger trial and meta-analysis support but may simply be an existing indication
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.