Ok, My Son Had To Have A Pee Test For

ok, my son had to have a pee test for his parole office and he just started taking this Gabapentin for 2 weeks now, and all his pee test has been clean until today. Now they say it looks like he's smoking weed. My son, I know for a fact do not do any drugs. Would there be something in this medication that would make his test come back negative?