Urine Toxicology Screen
Urine Toxicology Screen
|Drug||Causes False (+) Test||Duration of detectability|
|Amphetamines||Amantadine, Buproprion, Chlorpromazine, Desipramine, Fluoxetine, L-methamphetamine in nasal decongestant, Labetalol, Methylphenidate (Ritalin), Phentermine, Phenylephrine, Phenylpropanolamine, Promethazine, Pseudoephedrine, Ranitidine, Thioridazine, Trazodone||2-3 days|
|Benzodiazepines||Oxaprozin, Sertraline||3 days for short acting (e.g. lorazepam) and up to 30 days for long acting (e.g. diazepam)|
|Cocaine||Topical anesthetics which have cocaine||2-3 days (occasional user), up to 8 days (heavy user)|
|Opiates||Dextromethorphan, Diphenhydramine, Fluoroquinolones, Poppy seed, Quinine, Rifampin, Verapamil||1-3 days|
|Phenycyclidine||Dextromethorphan, Diphenhydramine, Ibuprofen, Imipramine, Ketamine, Lamotrigine, Meperidine, Thioridazine, Tramadol, Venlafaxine||7-14 days|
|Marijuana (tetrahydrocannabinol)||Dronabinol, NSAID, Pantoprazole and other proton pump inhibitors||3-5 days with 1x use, 5-7 days with 4x/wk use, 10-15 days with daily use, >30 days with long term and heavy use|
Pearl: MDMA (Ecstacy) may not be positive on amphetamine drug screen, unless specifically screen for MDMA.
Benzodiazepines are popular. In the U.S., alprazolam, clonazepam, lorazepam, and diazepam are among the most commonly prescribed medications in the outpatient setting.
Important points on benzodiazepine urine toxicology test:
- Most benzodiazepines screens look for oxazepam, because diazepam and chlordiazepoxide both are metabolized to oxazepam.
- The test does not specifically look for alprazolam, clonazepam, lorazepam (or many others). Therefore, a negative result does not necessarily rule out use of these agents.
- Benzodiazepines vary in reactivity and potency and can trigger a positive result due to cross-reactivity.
A negative result doesn't rule out benzodiazepine ingestion, and a positive result only guarantees that oxazepam, diazepam, or chlordiazepoxide is present.
Opioid vs Opiate
These two terms are often used interchangeably and really shouldn't be.
- Opioid: Broad category name which encompasses opiates, semi-synthetic, and synthetic agents
- Opiate: Refers to only naturally occurring opioids
- Oxycodone, a semi-synthetic, is similar to morphine.
- Methadone, a synthetic, has a completely unrelated structure.
- Notice the name of the urine drug screen next time you order one. It is opiates (not opioids).
- The test was designed to look for heroin (technically a semi-synthetic) via its metabolite, 6-monacetyl morphine. It also picks up morphine and codeine.
- The test does not specifically look for oxycodone, hydromorphone, hydrocodone, etc. They can trigger a positive result due to their structural similarities, but not in every case. Therefore, a negative result doesn't rule out use of these common drugs of abuse.
- Synthetics will never cross-react with the opiate urine drug screen. They are too structurally dissimilar. That's why there is a separate test for methadone.
A negative result doesn't rule out opioid ingestion, and a positive result only guarantees that heroin, morphine, or codeine is present.
- Standridge JB, Adams SM, Zotos AP. Urine drug screening: a valuable office procedure. Am Fam Physician. 2010 Mar 1;81(5):635-40. [PubMed]
- Geraci, M.J., Peele, J., McCoy, S.L. et al. Int J Emerg Med. 2010 Nov 3: 327. doi:10.1007/s12245-010-0235-3