 [ Symptoms ] can any otc cause positive test for methadone ie nyquil nighttime cold medicine [ Disease ] the short answer to your question is yes  but that is not the end of the story a 2010 study published in the american journal of health system pharmacy noted that several categories of medications were linked to various types of false positive urine drug screen tests including screens for methadone among the specific medications that caused false positives were antihistamines including diphenhydramine better known as benadryl and doxylamine    both of which are ingredients in many over the counter cough and cold remedies however these antihistamines were not specifically linked to false positives for methadone in the study it is worth noting that employers and others who perform routine drug screenings are not required to give you a do over they can choose to accept the initial test results at face value i wish you all the best with this