Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (825 page)

   This drug is an ester of benzoic acid and amino alcohol. Other names: benzoylmethylecgonine, ecgonine methyl ester benzoate. A therapeutic range has not been established when cocaine is used clinically as a local anesthetic in ophthalmic and otolaryngologic procedures. Cocaine is considered to be a drug of abuse and is controlled in schedule II of the U.S. Controlled Substances Act of 1970.

   Use

   Local anesthetic due to blockade of sodium channel conductance

   CNS stimulant: blocks reuptake of neurotransmitters norepinephrine, serotonin, dopamine

   Interpretation

   Cocaine is metabolized primarily to benzoylecgonine and ecgonine methyl ester. Further metabolism produces ecgonine and additional compounds. Coingestion of ethanol results in the formation of cocaethylene. Presence of these compounds is indicative of exposure but does not provide guidance as to the degree of intoxication or impairment. Clinical signs and symptoms must be used.

   The clinician should be aware of testing performed in the laboratory, especially the target analyte and whether the test is a screen or confirmation. The analyte present or absent may provide guidance to the time of exposure.

   Limitations

   Screening assays are commonly immunoassay based

   ELISA for blood, serum, plasma

   Target analyte: cocaine

   Cutoff concentration: variable—20–50 ng/mL

   Significant cross-reactivity with cocaethylene