Flashcards in Toxicology Deck (15)
What are the various specimens you can use to evaluate for drug use?
Why do we usually do urine drug screens?
drugs and metabolites tend to be higher longer in the urine than serum
What is the basis for most of the drug screening assays?
most are immunoassay based, so use antibodies to identify drug or drug class
because of this, cross-reactivity is common and critical to recognize
In general, what is the basis for confirmatory testing?
usually gas or liquid chromatography mass spect
(the nice thing about them is they can identify drugs with certainty, but you need to know the specific drug to test for it - not good for screening)
Urine from what time of day is the most helpful for drug testing?
early morning, because that's when the drug will be at the highest concentration
What are some tip-offs that someone has falsified their urine sample?
excessive bubble formation
the pH is less than 3 or more than 11
the specific gravity is less than 1.002 (diluted) or greater than 1.020
Creatinine is less than 5 mg/cL
What does the urine drug screen look for specifically when screening for cannabinoids?
also metabolite of THC
Why not just look for THC?
it's highly soluble in lipids so has slow excretion into urine whereas the metabolites get there faster
A single use of marijuana can result in a positive urine screen for how long?
up to 1 week
Long-term use of marijuana can result in a positive screen for how long?
up to 46 days
What are three common drugs that have been shown to cross-react with cannabinoid immunoassays?
some antibiotics (quinolones)
Also hemp-containing foods and eye drops like visine!
Why can someone on methadone have a negative opiate screen?
methadone is an opioid that interacts with the opioid receptor but has no chemical similarity to opiates and won't cross-react with the reagent
What do most amphetamine screens look for?
most do amphetamine and methamphetamine, but others do MDMA and MDA
others do the stimulants more broadly
WHat are some drugs that will cause clinical false positives on amphetamine screens?
famprofazone (apparently it's an alagesic and antipyretic)