Urine drug testing

Indications

• May be used as a baseline for patients being considered for trial of opioids for chronic pain
• Regular testing is done for patient on opioid agonist therapy to monitor for adherence, validate patient-reported use, and detect coingested substances like benzodiazepines that may affect safety

Immunoassays

• Immunoassays are cheap and fast, but are subject to cross-reactivity
• Window of detection for most metabolites is 1 to 3 days
• An initial 5-panel IA tests for amphetamines, cocaine, benzodiazepines (though not clonazepam), opiates, and methadone
• Validity is best when the urine temperature is 90 to 100ºF (within 4 minutes of voiding), urine pH 4.5 to 8, and urinary creatinine ≥20 mg/dL (if <5 mg/dL, it's not urine)

Interpretation

Substance	False positives
Alcohol	Short-chain alcohols (e.g. isopropyl alcohol)
Amphetamines	Amantadine Benzphetamine Bupropion Chlorpomazine Clobenzorex l-Deprenyl Desipramine Dextroamphetamine Ephedrine Fenproporex Isometheptene Isoxsuprine Labetalol MDMA Methamphetamine Methylphenidate Phentermine Phenylephrine Phenylpropanolamine Protethazine Pseudoephedrine Ranitidine Ritodrine Selegiline Thioridazine Trazodone Trimethobenzamide Trimipramine
Benzodiazepines	Oxaprozin Setraline
Cannabinoids	Dronabinol Efavirenz Hemp-containing foods NSAIDs Proton pump inhibitors Tolmetin
Cocaine	Coca leaf tea Topical anesthetics containing cocaine
Opioids, opiates, and heroin	Dextromethorphan Diphenhydramine Heroin Opiates (codeine, hydromorphone, hydrocodone, morphine) Poppy seeds Quinine Quinolones Rifampin Verapamil and metabolites
Phencyclidine	Dextromethorphan Diphenhydramine Doxylamine Ibuprofen Imipramine Ketamine Meperidine Mesoridazine Thioridazine Tramadol Venlafaxine and desvenlafaxine
TCAs	Carbamazepine Cyclobenzaprine Cyproheptadine Diphenhydramine Hydroxyzine Quetiapine