Immunoassays for amphetamines are prone to cross-reactivity with various non-stimulant medications due to structural mimicry. Identifying these interferents is critical for accurate forensic and clinical interpretations. While several medications are known to trigger false-positive results for amphetamines, nicardipine has not been previously documented as a source of interference. This report details a case of nicardipine-induced analytical interference in a post-mortem context.

Toxicological investigation was performed following the sudden cardiac death of a 51-year-old female managed with nicardipine for hypertension. Initial screening of cardiac blood was conducted using a Viva-E® automated analyser utilizing the Enzyme Multiplied Immunoassay Technique. Results were subsequently verified via Gas Chromatography-Mass Spectrometry following liquid-liquid extraction and chemical derivatization.

The EMIT analysis of the cardiac blood yielded a presumptive positive for amphetamines at a concentration of 485 ng/mL, while all other screened substance classes remained below the limit of quantification. Subsequent confirmatory analysis using Gas Chromatography-Mass Spectrometry definitively ruled out the presence of amphetamine and its derivatives.

This case identifies nicardipine as a novel interferent in amphetamine immunoassays, expanding the known list of cardiovascular medications – such as labetalol and metoprolol – prone to analytical cross-reactivity. It underscores the necessity of a thorough anamnesis and the imperative use of gold-standard chromatography methods to ensure diagnostic and legal accuracy in forensic practice.