Diclofenac-Associated Kounis Syndrome: A Systematic Review and Disproportionality Analysis of FAERS Database

Kounis syndrome, or allergic acute coronary syndrome, is a potentially underdiagnosed condition triggered by hypersensitivity reactions. Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently implicated, with diclofenac repeatedly reported as a precipitating agent. However, no systematic synthesis has specifically evaluated the clinical characteristics, management, and outcomes of diclofenac-induced Kounis syndrome.

We conducted a systematic review of case reports and case series describing diclofenac-associated Kounis syndrome, searching PubMed/MEDLINE, Scopus, and Google Scholar from inception through January 31, 2026. Eligible studies documented a temporal association between diclofenac exposure and acute coronary events with allergic manifestations. Data on demographics, clinical presentation, diagnostic findings, management, and outcomes were extracted. Methodological quality was assessed using a modified CARE checklist framework. Data were synthesized descriptively. Additionally, we carried out disproportionality analysis of reported events with Kounis syndrome and diclofenac from the United States Food and Drug Administration Adverse Event Reporting System (FAERS).

Twenty-seven patients were included. The majority were male (81.5%), and 44.4% had no cardiovascular comorbidities. Allergic manifestations included hypotension (70.4%), urticaria (66.7%), and chest pain (85.2%). Type I Kounis syndrome (vasospasm without underlying coronary disease) was most common (59.3%), followed by type II (25.9%) and type III (3.7%). ST-segment elevation was present in 66.7%, and coronary angiography was normal in 63.0%. Management consisted of antihistamines (85.2%), corticosteroids (77.8%), and epinephrine (37.0%). Percutaneous coronary intervention was performed in 11.1%. Causality was probable or definite in all cases. All patients survived discharge. Quality assessment revealed high-quality reporting in 70.4% of cases, though documentation of patient perspective and informed consent was universally absent. FAERS analysis revealed positive signals between diclofenac and Kounis syndrome from 137 reports.

Diclofenac-induced Kounis syndrome most commonly presents as type I vasospastic myocardial ischemia with prominent allergic features, ST-segment elevation, and normal coronary angiography. Outcomes are favorable with prompt recognition and combined anti-allergic and anti-ischemic therapy. Clinicians should maintain a high index of suspicion following diclofenac exposure, even in patients without cardiovascular risk factors, and strict avoidance of re-exposure is essential.