Will dextromethorphan show up in a drug screen?

ok, there is speculation that at higher doses (500 + mg) of DXM, certain tests will show this as a "false positive" for PCP and/or opiates as long as 3-5 days after ingestion. Though based on experience, DXM does not show up on the basic THC/METH/COC/OPI tests, which are used in most probation departments. after taking 21 maximum strength Mucinex DM pills, (which total up to 1260 mg of Dextromethorphan Hydrobromide) I tested clean 4 1/2 days after ingestion. There is ongoing debate on this matter, my experience shows evidence that it is unlikely or impossible for DXM to show up on standard drug tests.