GHB/Gabapentin half life/interactions?

At a 600 mg dose of gabapentin, how long should I wait after a dose until I take some GHB? I've been taking the gabapentin for awhile and was thinking about using the GHB to help with the gabapentin withdrawals (main symptom not being able to sleep). If I take it on the smaller end of the dose range, could I take it instead of gabapentin 24 hours after my last gabapentin dose, or would that be dangerous? If I dosed, say 2 g or so instead of my gabapentin tomorrow would that be dangerous because there's still a little gabapentin in my system?