Ecgonine is an important marker for cocaine use in inadequately preserved specimens.

Abstract

To the Editor: We have previously reported a method for the analysis of ecgonine together with other polar cocaine metabolites in postmortem blood (1). The findings in that manuscript and our subsequent experience (2,3) have shown that ecgonine is consistently present in postmortem blood specimens; its origins, however, are usually open to debate and discussion (4-6). Application of the method in carefully preserved whole blood specimens from cocaine addicts reporting to an emergency room have also shown ecgonine to be consistently present (3). This suggests that at least in high doses, often chronic cocaine administration, ecgonine will be present during life also. Our intent in the work that led to our original publication was to investigate the utility of ecgonine as a potentially longerlived marker than benzoylecgonine of past cocaine use. All our findings to date however have indicated that the detection windows for benzoylecgonine and ecgonine are approximately the same, at least at our limit of detection (10 ng/mL) (1-3). Other workers have documented the instability of both cocaine and its monoester metabolites, benzoylecgonine and ecgonine methyl ester, during in vitro storage of blood (4,5). It is likely that at least some of the loss of these primary metabolites is via a secondary de-esterification to ecgonine. Consequently, the true value of an assay for ecgonine may be its ability to detect what is likely the final in vitro degradation product following cocaine use. Ecgonine would thus be the analyte of choice in cases in which a specimen has been collected without an enzyme-inhibiting preservative or at temperatures known to be inadequate for the preservation of cocaine or its primary monoester metabolites (4,5). We report a case in which a defendant in a homicide case relied in part on his recent cocaine use as a component of his defense. The specimen was collected in a tube containing EDTA, a chelating agent with no significant enzyme-inhibiting properties, and was stored for approximately 18 months, some of which time included at least some period of room-temperature storage. During that time it was subjected to an analysis for a variety of drugs including cocaine, benzoylecgonine, cocaethylene, and ecgonine methyl ester, all of which proved negative. Following this lengthy storage, the specimen was submitted to us for analysis for the presence of ecgonine, according to the method described in our earlier work (1,2). The testing disclosed the presecnce of ecgoinine in the blood at a concentration of 557 ng/mL. The specimen was negative for other cocaine-related compounds and metabolites including cocaine, benzoylecgonine, ecgonine methyl ester, ecgonine ethyl ester, cocaethylene, and norcocaine. The assay used was a selected ion-monitoring assay; however, the presence of ecgonine was confirmed by full scan mass spectrometry of its derivative. To our satisfaction, this demonstrated that the subject, sometime prior to the collection of the blood specimen, had in fact ingested cocaine, which may have been corroborative of his defense. We did not attempt to estimate the dose, the time since ingestion, or the likely effects of the ingestion on the subject proximate to the time of the specimen collection. The complete absence of other cocaine metabolites suggests that the ecognine was at least partly an artifact of the inadequate preservation of the specimen. Based on this experience, we strongly suggest that ecognine analysis may be an appropriate test to demonstrate cocaine use when the provenance of the specimen is unknown, when preservation has been inadequate, or when other cocaine metabolites have been shown to be undetectable.