Just to throw a little pharmaceutical info in here for those who don't know:
Yeah, this is a known effect. Not well known, but not unheard of. Your brain uses many hundreds of neurotransmitters, but the most fundamental to function are glutamate - which stimulates its target in general, and Gamma Aminobutyric Acid (GABA) - which depresses it. The "gaba" in Gabapentin reveals that it is a general CNS depressant as it enhances the function of natural GABA (yeah yeah, I can hear you yelling at me saying you already know this, but I'm equally sure some people don't, and are curious
). Benzos are the most commonly prescribed depressants that primarily affect GABA, but they actually don't quite work that way. Rather than increasing GABA directly, they make it work more efficiently. Most CNS depressants will of course help with opiate withdrawal, benzo withdrawal or any other depressant-related withdrawal, just as Clonidine does; they're all depressants in their own right, and they will usually tend to help counteract the unpleasant overstimulation of the CNS induced by withdrawal of opiates (depressants as well). Even though they have very different mechanisms of action, the net result with a proper dose is a decrease in sympathetic nervous system activity. Whether this happens by increasing GABA, mimicking it, potentiating it, inhibiting glutamate, inhibiting sympathetic neurotransmitters, etc., they're all the same in that their net effects are anxiolysis, hypnotic, myorelaxant, amnesic, and anti-seizing. At least those are the "big 5" effects of nearly all benzos, derivatives and similar drugs, including gabapentin.
Now what's happening here is that the gabapentin is actually slowing down your nervous system, as other GABAnergic/GABA enhancing drugs do. However, this effect is not quite as strong when it comes to sex drive as others. Maybe it preserves testosterone levels and function more so than benzos; in any case, it still does slow down most areas of the brain/CNS, but may allow one to reach orgasm where they likely wouldn't have been able to with similar drugs. It still does depress this function overall, however. Yet if a person on a high dose of gabapentin is aware that they can in fact achieve climax and aren't just wasting their time, they're likely to put that effort in.
Where it gets interesting - orgasm is a parasympathetic, involuntary process as we all know. Once the reflex is triggered, there's no stopping it. So what you've really ended up doing, is finding a way to allow the brain to accumulate enough stimulation to achieve this physioogical response, while at the same time DRAMATICALLY INHIBITING many of the built in mechanisms that control it; duration is greatly increased because chemicals regulating it such as prolactin are inhibited by the drug. The nervous system is essentially too sluggish to activate all regulatory mechanisms which limit both the intensity and the duration of an orgasm, as well as the mechanism for "priming" your physiology for the next one (before which, a refractory period is usually experienced). Yet since testosterone remains at relatively high levels as I described above, you can still trigger the orgasm itself. The same amount of pleasure and associated information travels up the currently depressed spine and brain, is much slower than usual to be sorted and "dealt with" possibly also including the temporal lobes as well - responsible for your perception of time and memory among many other functions, and is ultimately routed to and experienced by the frontal lobes as an extremely pleasurable experience that had lasted much longer than usual. In future, these memories will likely strengthen, and this same expectancy may further intensify the whole experience next time it's practiced. The typical "orgasm afterglow" will also feel much more powerful since it took longer to get there to begin with and therefore required more stimulation, more blood flow, etc. leading to a greater subjective satisfaction and repriming to a resting state. More so than this, however, your brain is also struggling to replenish dopamine, serotonin, acetylcholine, GABA, glutamate, adrenalin, histamine and other transmitters and chemicals - but none so much as prolactin, which like I said above, controls the refractory period as well as much of the subjective sense of pleasure during and after sexual stimulation! Oxytocin also plays a very important role in the control of the subjective pleasure of an orgasm. Yet chemicals alone cannot account for all of this; a human's largest sexual organ is his or her brain. Thought patterns, beliefs and expectations, inhibitions, etc. will all go a long way when it comes to evaluating the overall experience after the fact.
Note - all of this is still greatly simplified, of course. The fact is, much of the physiological response to drugs -including gabapentin - remains partially or wholly unknown.
