Antibiotics May Change Drug Testing Results

One common drug screen performed is for opiates (codeine, etc). This test can sometimes result in a false-positive, i.e. caused by a defect in the drug screening, a mistake in performing the drug screen or through the presence of some other substance that has a chemical similarity to the target drug.

Researchers have reported that the following drugs may cause false-postive results on opiate screens:
Rifampacin-A drug used to treat tuberculosis
Quinolones-Ciprofloxacin among other antibiotics
Doxylamine-An antihistamine found in Unisom" OTC for slpeep and in some cold remedies
Hordenine-A substance present in beer made from barley