UMEM Educational Pearls

Category: Toxicology

Title: Drug Abuse Screens

Keywords: Drug Screens, Drug Intervals (PubMed Search)

Posted: 2/5/2015 by Kishan Kapadia, DO
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Performance Characteristics of Common Drug Abuse Screening Immunoassays

Drug/Class

Detection Interval (***)

Comments

Amphetamines

1-2 days (2-4 days)

Decongestants, ephedrine,l-methamphetamine, selegilene & bupropion metabolites may give False (+) results; MDA & MDMA are variably detected

Barbiturates

2-4 days

Phenobarbital may be detected for up to 4 weeks

Benzodiazepines

1-30 days

Benzos vary in reactivityand potency; False (+) results may be seen with oxaprozin

Cannabinoids

1-3 days (>1 month)

Screening assays detect inactive and active cannabinoids; Confirmatory assays detects inactive metabolite THCA (tetrahydrocannabinoic acid)

Cocaine                  

2 days (1 week)

Screening & confirmatory assays detect inactive metabolite BE (benzoylecgonine); False (+) results are unlikely

Opiates

1-2 days; 2-4 days (<1 week)

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

Methadone

1-4 days

Doxylamine may cross-react

Phencyclidine

4-7 days (>1 month)

Dextromethorphan, diphenhydramine, ketamine, & venlafaxine may cross react

Propoxyphene

3-10 days

Duration of positivity depends on cross reactivity of metabolite norpropoxyphene

(***)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.