Urine Toxicology Screen
Urine Toxicology Screen
Amphetamines
Duration of Detectability: 2-3 days
Causes of False Positives:
- Amantadine
- Buproprion
- Chlorpromazine
- Desipramine
- Fluoxetine
- L-methamphetamine in nasal decongestant
- Labetalol
- Methylphenidate (Ritalin)
- Phentermine
- Phenylephrine
- Phenylpropanolamine
- Promethazine
- Pseudoephedrine
- Ranitidine
- Thioridazine
- Trazodone
Benzodiazepines
Duration of Detectability: 3 days for short acting (e.g. lorazepam) and up to 30 days for long acting (e.g. diazepam)
Causes of False Positives:
- Oxaprozin
- Sertraline
Cocaine
Duration of Detectability: 2-3 days (occasional user), up to 8 days (heavy user)
Causes of False Positives:
- Topical anesthetics which have cocaine
Opiates
Duration of Detectability: 1-3 days
Causes of False Positives:
- Dextromethorphan
- Diphenhydramine
- Fluoroquinolones
- Poppy seed
- Quinine
- Rifampin
- Verapamil
Phenycyclidine
Duration of Detectability: 7-14 days
Causes of False Positives:
- Dextromethorphan
- Diphenhydramine
- Ibuprofen
- Imipramine
- Ketamine
- Lamotrigine
- Meperidine
- Thioridazine
- Tramadol
- Venlafaxine
Marijuana (THC)
Duration of Detectability:
- 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 us
Causes of False Positives:
- Dronabinol
- NSAID
- Pantoprazole and other proton pump inhibitors
Pearl
MDMA (Ecstacy) may not be positive on amphetamine drug screen, unless specifically screen for MDMA.
Benzodiazepines
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.
Bottom Line
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
| Opiates | Semi-Synthetic | Synthetic |
|---|---|---|
| Opium | Heroin | Fentanyl |
| Morphine | Hydrocodone | Methadone |
| Codeine | Hydromorphone | Tramadol |
| | Oxycodone | ||
| | Oxymorphone | ||
| | Buprenorphine |
- Oxycodone, a semi-synthetic, is similar to morphine.
- Methadone, a synthetic, has a completely unrelated structure.
LEARNING POINTS
- 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.
Bottom Line
A negative result doesn't rule out opioid ingestion, and a positive result only guarantees that heroin, morphine, or codeine is present.
References
- 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
