Not sure about lime juice, but grapefruit will increase the trip quite a bit. The Grapefruit juice acts on DXM by inhibiting the activity of cytochrome P450 enzymes of the 3A and 1A groups. DXM is converted to DXO by this same enzyme, only with different groups. Therefore, with enough grapefruit juice, your overall trip should be better. Not only have I tried this and agree that it makes the DXM more potential, but others also agree. Gravol, author of the DXM Zine, has said himself that grapefruit juice in fact increases the potency of the DXM.
