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Title: Drug Abuse Screens
Author: Kishan Kapadia
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Performance Characteristics of Common Drug Abuse Screening Immunoassays
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Drug/Class
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Detection Interval (***)
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Comments
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Amphetamines
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1-2 days (2-4 days)
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Decongestants, ephedrine,l-methamphetamine, selegilene & bupropion metabolites may give False (+) results; MDA & MDMA are variably detected
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Barbiturates
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2-4 days
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Phenobarbital may be detected for up to 4 weeks
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Benzodiazepines
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1-30 days
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Benzos vary in reactivityand potency; False (+) results may be seen with oxaprozin
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Cannabinoids
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1-3 days (>1 month)
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Screening assays detect inactive and active cannabinoids; Confirmatory assays detects inactive metabolite THCA (tetrahydrocannabinoic acid)
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Cocaine
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2 days (1 week)
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Screening & confirmatory assays detect inactive metabolite BE (benzoylecgonine); False (+) results are unlikely
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Opiates
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1-2 days; 2-4 days (<1 week)
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Semisynthetic opiates derived from morphine show variable cross-reactivity; Fully synthetic opioids (e.g., fentanyl, meperidine, methadone, propoxyphene, tramadol) have minimal cross reactivity; Quinolone may cross-react
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Methadone
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1-4 days
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Doxylamine may cross-react
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Phencyclidine
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4-7 days (>1 month)
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Dextromethorphan, diphenhydramine, ketamine, & venlafaxine may cross react
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Propoxyphene
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3-10 days
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Duration of positivity depends on cross reactivity of metabolite norpropoxyphene
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(***)Values are after typical use; values in parentheses are after heavy or prolonged use.
References
Adapted from Goldfrank’s Toxicologic Emergencies, 9th ed; Table 6-10.