This was just one of many things I found on the net about false positives, hope it helps.
Opiate False Positives Back to Top
Poppy seeds, Emprin, Tylenol with codeine, Capital with codeine, Margesic, rifampicin, Vicodin, Percodan, Percocet, Wygesic.
Benzodiazepine False Positives Back to Top
Most prescription sleeping pills and anti-anxiety medication.
Barbiturate False Positives Back to Top
Fiorinol, Donnatol, some sleeping pills, antiasthmatic preparations that contain phenobarbitol, Dilantin.
LSD False Positives Back to Top
Migraine medication: egotamine, Ergostat, Cafergot, Wigraine, Imitrex. Hydergine, bromocription, methysergiside, lisuride, lysergol, Artane, triprolidine, amitriptyline (Elavil), dicyclomine (Bentyl), antinausea medications that contain promethazine: Phenergan, Promethegan
I did just look on the web and it said it was very possible..if ibuprofin can show a false positive for methadone than it's highly likely..
I am so sorry nobody has answered..I am not sure at all why that would come up positive for barbituates..did he have them retake the test?