If you are trying to beat the
urine test, well, after roughly 24-48 hours you should be fine. There are always variables - how much you take, how often, your metabolism, other meds/chemicals you're on, etc.
Also of note - not all urine drug screens test for the same thing - this is usually determined by the cost factor - The more sensitive and comprehensiv ethe test, the more expensive. Darvocet tests positive if they are testing for propoxyphene - not all tests do this.