AZO is an OTC medicine used to relieve symptoms of a urinary infection. The active ingredient is Phenazopyridine Hydrochloride. With the pyridine, the concern here is that it might be detected and flagged as an adulterant. My donor has a UTI and has taken AZO. She got started on Bactrim (which may also test positive for certain off-topic drugs as well-- but I digress). Coincidentally, I'm also being treated for a UTI, also with Bactrim-- but I'm not using AZO. I'm sticking with the cranberry juice! But if I use her sample, could the AZO affect the results, and would going in with a box of AZO and verification from my doctor that I'm being treated for a UTI (or at least the scrip of Bactrim) be sufficient to cover the "adulterant--pyridium" result if it happens?