I take 2mg of klonopin per day, which lowers my T by about 30%. My doctor added 600mg gabapentin, taken once daily at night, three days ago to see if it would help. Incredibly, my T is now virtually gone. I've had T for over year since it emerged during a nasty head cold and never went away.
No major side effects at this point to report from the gabapentin other than improved sleep and slight dizziness in the morning, the latter of which goes away after a cup of coffee.
No idea where this is going and if the gabapentin will continue to work long-term. If it does, I'd love to taper off the klonopin -- even if I may need to increase the dose of gabapentin to make up for it..
The klonopin makes it clear GABA has some impact on my T. Gabapentin's mechanism of action also includes raising GABA, although, I understand the GABA it creates doesn't really bind well with GABA receptors in the brain.
But gabapentin is also a significant calcium channel blocker. It's possible the calcium channel blocking aspects of the drug could be the main mechanism of action for the minority of T suffers it helps. Calcium is an excitatory element within the brain and inner ear, and plays a significant role in auditory transmission/perception.
This is all speculatory, of course. Gabapentin is a weird drug that works for some people and not others with a variety of ailments. And no one really knows why it works when it does work.
As a side note, I've also tried Lyrica in the past -- gabapentin's improved next-generation iteration, which also includes calcium channel-blocking attributes, but it had no effect on my T.