Cocaine

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Subject: Cocaine

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Definition

  • 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

      • Low cross-reactivity with ecgonine methyl ester, norcocaine, ecgonine

    • EIA for urine

      • Target analyte: benzoylecgonine (metabolite)

      • Cutoff concentration:

        • 150 ng/mL

        • 300 ng/mL

      • Approximately 50–60% cross-reactivity with cocaine and cocaethylene

      • Low cross-reactivity with EME, ecgonine

  • Confirmation assays are commonly chromatography based regardless of the specimen.

    • GC/MS

      • Full scan mode for qualitative identification of cocaine, cocaethylene, and metabolites: limits of detection—20–50 ng/mL

      • Selected ion-monitoring mode for quantitative analysis of serum, plasma for cocaine, cocaethylene, and metabolites: limits of quantitation—5–20 ng/mL

    • LC/MSn (multiple MS)

      • Multiple reaction–monitoring mode for qualitative or quantitative analysis of cocaine, cocaethylene, and metabolites: limits of detection/quantitation—20–50 ng/mL

 
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