Marijuana. The straightforward answer is stop using.
No "flush"agent. This drug attaches to fat cells in your body and gradually leaves on its own.If your use has been heavy it may take a month or more.A few tokes one time may leave in a few days to a week. There are no "flushing" agents although some are promoted & sold on line.
Test clean.... Google it...If you are in a med pot friendly state, you have no worries as long as you have registered with the 18 or so states nationally, that have legalized cannabis as a medicine. If you are not a resident of one of these states, try the website above. Please ignore the previous dr's advice, as cannabis has been medically approved for specific medical conditions varying state by state.