Cocaine and Metabolite Excretion in Saliva under Stimulated and Nonstimulated Conditions

The accessibility of saliva for rapid, noninvasive sampling makes it an attractive biological fluid for detecting drug use. However, little is known about salivary excretion patterns of the major cocaine metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME). Additionally, there is a general lack of information on the effects of salivary collection conditions on cocaine excretion in saliva. This study documents the profile of cocaine and metabolites in human saliva under stimulated and nonstimulated saliva flow conditions. Saliva samples were obtained periodically from six healthy volunteers who were administered three, equally spaced, single intravenous doses of 25 mg of cocaine during a 6-h test session. On different days, whole saliva was obtained either under nonstimulated or stimulated (sour candy) conditions. The samples were analyzed for cocaine and metabolites by GC/MS. Cocaine, BE, and EME were detected and quantitated in the saliva of all subjects. Cocaine was the predominant analyte identified in all samples. Nonstimulated saliva contained substantially more drug than stimulated samples. The ratio of the area under the curve (AUC) of cocaine in nonstimulated saliva to that of stimulated saliva was variable and ranged from 3.0 to 9.5. The AUC ratios of BE and EME were similar to those observed for cocaine. The lowering of cocaine concentration in saliva in the stimulated flow condition was likely due to an increase in saliva pH associated with increased saliva flow rate; it is known that an increase in saliva pH retards cocaine partitioning into this biological fluid. Generally, the results of this study indicated that cocaine is the predominant analyte in saliva and that concentrations of cocaine and metabolites can be influenced substantially by the method of collection. These factors should be taken into account in the design of saliva tests for detection of cocaine exposure.