Table 1

Extent of urine toxicology detection for different classes of drugs.3 7

Drug classWhat is detected?What is not detected?Other considerations
AmphetaminesMost EIA detect D-amphetamine and D-methamphetamine.Lack of sensitivity to 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyamphetamine (MDMA, ‘ecstasy’).Sensitivity for MDMA is about 50% less than for D-amphetamine and D-methamphetamine.
When screening neonates, maternal labetalol use may give a positive result as labetalol metabolites have been reported to cause amphetamine positive screens.
BenzodiazepinesMost EIAs detect the diazepam metabolites nordiazepam and/or oxazepam.Lorazepam, clonazepam and other benzodiazepines do not share these metabolites so are often undetected.Some benzodiazepines (particularly clonazepam) at therapeutic or even above therapeutic doses may not exceed detection levels in the urine.
CocaineEIA detects benzoylecgonine (inactive metabolite excreted in the urine) with good sensitivity and specificity.
Coca tea and some other preparations of the plant common in the Hispanic population may produce positive results.
Passive inhalation (unless prolonged and heavy exposure) will not produce a positive result.
Acute massive overdose may take longer to metabolise and so time for metabolite to show up in the urine may be longer.
OpiatesEIAs target natural alkaloids including morphine and codeine. As heroin (diacetylmorphine) is directly synthesised from morphine, this is often also picked up.Synthetic opioids such as methadone, oxycodone, fentanyl and tramadol are frequently undetected. They may require adjunct immunoassays, which also have cross reactivity.This may be the least sensitive and specific urinary drug screen.
MarijuanaEIAs detect 11-nor-9-carboxy-delta-9-tetrahydrocannabinol, which is the major metabolite of marijuana excreted in the urine. Generally good sensitivity and specificity for this.Synthetic cannabinoids like ‘spice’ and ‘K2’ not detected with most EIAs.
Lysergic acid diethylamide (LSD)High sensitivity but low specificity due to the fact that only a small amount of the parent molecule appears in the urine.New generation immunoassays are becoming available which targets the metabolite 2-oxo-3-hydroxy-LSD, which appears in greater concentrations in the urine, so this may improve detectability.
Tricyclic antidepressants (TCAs)There is a high overlap in structure between TCAs and other agents such as muscle relaxants, antipsychotics, anticonvulsants and antihistamines, so there is a high prevalence of inappropriate results. Not recommended as the test used if TCA toxicity is suspected.
  • EIAs, enzymatic immunoassays; TCA, tricyclic antidepressants.