None of these medicines are reported to cause a false positive for barbiturates. The most common medicine to cause a false positive test for barbiturates are anti-inflammatory medicines, such as ibuprofen or naproxen.It also has been reported with Dilantin.Dr. D. Love, Doctor.he most common medicine to cause a false positive test for barbiturates are anti-inflammatory medicines, such as ibuprofen or naproxen. It also has been reported with Dilantin.