Can grapefruit juice cause pain medications to not show up on a urine drug test?

I may not offer much help but I do know this. They say that drinking grapefruit juice while on methadone (an opiate) may cause you to feel more effects of the methadone. So, it would make u feel like u have taken more than u have. But, it never mentioned that it may alter the results of a drug screen. Look it up on the internet, thats what I always do. I did drink grapefruit juice before a drug test and it didn't alter mine. But I only drank a glass and wasn't drinking it on a regular basis. Ask him to ask the drug screening place if his urine was diluted. If so, maybe he drank too many fluids and flushed his system. Good luck to him. Hope I was some what helpful.

According to Mayo Clinic, "Yes. Grapefruit and certain other citrus fruits and products can interfere with several kinds of prescription medications."

Some can cause potentially dangerous health problems. Mayo recommends checking with your doctor or pharmacist before consuming any grapefruit or other citrus products if you take prescription medications. The time of day that you drink the juice makes no difference.

The medication may stay in your body for too short or too long a time, so the medication may not work or can lead to an increase to potentially dangerous levels, causing serious side effects.