I've been on Gabapentin for almost 2 years for nerve pain from lyme and co's. It was an absolute Godsend at the time as my symptoms were unmanageable and severely impaired every moment of every day. I've noticed more recently when I miss my doses by more than an hour (i take it 3x a day) I come crashing down really hard.
At first I thought man this disease has really made major strides against me what the heck have I been treated this past 2 years? Then I realized its more likely my body has reacted to the artificial supplementation of Gaba and lessened its creation of it. Here's a blurb from an article confirming this and a link to the overall article which is excellent for those trying to better understand the glutamine-glutamate-GABA relationship which is behind many of the neuro and nerve issues us lymies have.
"There are many drugs that target your GABA receptors like Ativan, Xanax, Klonopin, Valium, and Neurontin (Gabapentin) and others. These drugs look similar in chemical structure as gamma-aminobutyric acid so they can fit in your GABA receptors, which artificially stimulates them, but they do not actually increase production. Therefore they do not address the underlying problem of not producing enough because there must be some level of GABA present in order for these drugs to have an effect. Furthermore, anytime a substance is used to artificially stimulate a neurotransmitter the brain responds by reducing production or responsiveness, which results in more depletion of the neurotransmitter, which in this case is GABA. Therefore, any drugs that target GABA receptors or manipulates GABA or glutamate, will inhibit your ability to acquire and maintain balance.
This is also true of herbs that are used to increase GABA levels such as Valerian Root, Kava Kava, or any other herb used for this purpose. The brain responds to herbs that manipulate neurotransmitter levels in the same manner as a pharmaceutical – it will downregulate responsiveness or production of GABA, thus making the problem worse."
http://www.holistichelp.net/blog/how-to-increase-gaba-and-balance-glutamate/