Monday, December 29, 2014

Circumvention

Four patients show up to your emergency department. You send standard urine drugs-of-abuse screens on all of them.

Patient A took amphetamines five days ago.
Patient B ingested 2L of water right before providing a sample; he used cocaine several hours before.
Patient C takes rifampin, finished a course of ciprofloxacin for a UTI, eats poppy seeds, drinks quinine in tonic water, and takes LSD.
Patient D says he is a chronic pain patient who ran out of methadone. You do a more specific urine drug test that is positive for methadone but not for 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine.

Challenge: What can you tell me about the tests for these patients and what they mean?

Image of opium field shown under Fair Use, from Wikipedia.

2 comments:

RaH said...

Hello
Patient A, his urine should come back clean, Amphetamines are quickly metabolised and do not stay detectable in urine for more than 2-4 days
Patient B, drinking water is good, but doesnt interfere with the urine test, the dilution 2 liters in over 42 liters of bodyfluid is not enough to lower the concentration in his urine for metabolites. his urine will stay positive for 5-8 days for benzoylecgonine.
Patient C: i do not know whether any of these substances might react and create false positive test results, LSD is positive up to 4 days
Patient D should have EDDP in his urine if he used 3-5 days ago, as he ran out he surely substituted his opoids, hence the poppy seeds. his urine should be positive for hydromorphone.
the competitive inhibition by the poppy seeds might make block the metabolism of the methadone to EDDP as both are metabolised by the CYP2D6 (next to CYP 3A4, and CYP1A2, metabolism varies from person to person)
i think Patient D is lying about his consumption, as i do not know methadone to be a metabolite of some sort, or he is just accumulating methadone in his tissue

Craig Chen said...

wow! i'm impressed
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Circumvention

Patient A will likely have a negative urine drugs of abuse screen; amphetamines are detected up to 2-3 days after last use. Patient B may have a negative screen from dilution; checking urine specific gravity is important in these situations. Patient C may test positive for opiates as rifampin, fluoroquinolones, poppy seeds, and quinine all can cause a false positive; LSD is not picked up by standard drugs of abuse screens. Patient D’s urine is consistent with him spiking his urine with methadone as EDDP is a methadone metabolite and its absence suggests he is not ingesting the methadone (this is a red flag for diversion).

Source: UpToDate.