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When testing for cocaine, the lab is actually looking for its unique metabolite, benzoylecgonine. No other drug has this metabolite. If only a screening test is used, such as immunoassay, there is a possibility of Marcaine (bupivacaine) giving a false positive for cocaine. However, this can be clarified by using a confirmation test. Both a screening and confirmation test should be carried out if a person tests positive for cocaine.
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