Grapefruit Juice (GFJ)- I'd toyed with the thought of using grapefruit juice for a very long time but have study mixed experiences. Just lately I examine that it does not inhibit CYP2D6 but rahter 3A4 that's accountable for conversion of codeine into norcodeine. In theory by inhibiting 3A4 you leave additional codeine for 2D6 to turn into morphine.