My husband drinks a lot of grapefruit juice and recently was required to have a urine drug test to make sure he was taking his Lortab, Xanax, Soma & Celexa. When the results came back, they said it showed that there was none of these medications present, as if he had not been taking them. He has been taking pain meds and Xanax for about 15 or more yrs. on a daily basis, after a car accident. What would cause this not to show up? Could it be the grapefruit juice he is drinking?