What medications show up as methadone in your system i haven't taken it why did it show up in my drug screen?

Several possiblities: Three commonly used medications can cause false positive methadone tests on the screening test - two antihistamines commonly used - diphenhydramine (Benadryl®) and doxylamine (Unisom®). Also, Seroquel® (quetiapine), a commonly used antipsychotic and anti-anxiety medication can do this. However, confirmatory tests should show that it is a FALSE positive.