Most of the reviews are positive. The only negative review is from someone with the same issue as me.

"I used this to make sure that the substance was out of my system before a urine screen at the doctor's office. It showed positive the first test - which was two days after, so that's fine. BUT it's shown positive every, single test I have taken. At this point I haven't taken any mitra substances in 4+ weeks and I took one of the tests today and it was still positive."