Grapefruit Juice (GFJ)- I had toyed with the concept of employing grapefruit juice for a very long time but have browse blended reviews. Just lately I examine that it doesn't inhibit CYP2D6 but rahter 3A4 that is responsible for conversion of codeine into norcodeine. In theory by inhibiting 3A4 you leave more codeine for 2D6 to grow to be morphine.