How long after a dose, is naloxone detectable in a urine screen?

Not predictable: Whether naloxone is detected on a drug screen depends on each individual's body, on how much was taken, on when it was taken, on the quality of the test, on the type of chemicals the test looks for, on the diluteness of the urine, on pure luck, etc... If the person is taking the naloxone appropriately, no worries. Otherwise, stop using the stuff, and then no worries.