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 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)

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