| Drug | Duration of detectability in urine | Drugs causing false-positive preliminary urine screens |
| Amphetamines | 2 to 3 days | Ephedrine, pseudoephedrine, phenylephrine, selegiline, chlorpromazine, trazodone, bupropion, desipramine, amantadine, ranitidine |
| Cocaine | 2 to 3 days | Topical anesthetics containing cocaine |
| Marijuana | 1 to 7 days (light use); 1 month with chronic moderate to heavy use | Ibuprofen, naproxyn, dronabinol, efavirenz, hemp seed oil |
| Opiates | 1 to 3 days | Rifampin, fluoroquinolones, poppy seeds, quinine in tonic water |
| Phencyclidine | 7 to 14 days | Ketamine, dextromethorphan |
