Is it true that of you take ibuprofen you could test positive for marijuana in a drug screen?

I've heard many, but this is a new one. No. There is no chemical relationship or similarity between ibuprofen (isobutylpropanoicphenolic acid) and the primary psychoactive chemical in cannabis, THC (Tetrahydrocannabinol); so, there is no possibility that you would test positive for THC by using ibuprofen.