Do medications interfere?
There are some prescriptions that contain the same drugs that are commonly found “on the street”. There is no easy way to distinguish between the two forms of the drug. However, the problem is not as big as it would seem. There are no prescriptions for PCP or cocaine. It is extremely rare to find cocaine used in a medical setting, although it happens occasionally, usually to control bleeding from the eye or nose. If used, it will be well documented in the person’s medical file. Such use would cause the urine to test positive for cocaine metabolite for a few days, but would not be sufficient to cause a positive hair test. Heroin is rarely prescribed in the United States, but again would be well documented. It appears that poppy seeds do not interfere in hair testing. Other prescribed opiates may occasionally cause a positive screen, but are sorted out in a confirmation test. There are some prescription diet pills that contain either amphetamine or methamphetamine, as well as a drug for
