They are synthetic. The cutoff level
for opiods is 2000 ng/ml, the cutoff
for opiads like
oxycodone is 100 ng/ml. Either a more sensitive test needs to be used or a test specific to opiads must be used to avoid a false negative. An excellent Federal resource for this info is published by the U.S. gov., valid and current as of May, 2010, reference SAMHSA. Got hit by a truck doing 60 mph 29 years ago, so been here and done this.