Originally Posted by mrsD

Gabapentin is not metabolized by our liver enzymes but is excreted whole by the kidneys. So grapefruit juice or fruit is not significant for it. Some research shows that all citrus can affect drugs that are metabolized by the liver, since small amounts of those enzymes are in the GI tract wall itself.

Where did you read this?

The only thing I know of for gabapentin is magnesium (and perhaps calcium)...used at the same time may complex the gabapentin and prevent its absorption. Gabapentin has poor % absorption to begin with in the GI tract.

Here is Wiki which mentions apple juice:
http://en.wikipedia.org/wiki/Grapefruit

Data on these interactions continues to grow and change.
Lists are always evolving concerning drug metabolism.