It is 3600mg. Usually it is administered 900mg 4x per day at that dose. I was at that dosage for a couple years. When needed, lower dosages are slowly raised by a doctor after side effects and benefits are evaluated at lower dosages.
There is a lot of information out there that indicates its effectiveness wears out for some people and an increase may be needed. However, once you are at 3600mg, you have no place to go.
Personally, I would recommend trying to not go past 2700mg, so you have the mental encouragement that it can be raised if things get worse. People at these pain levels need psychological strengths as well. At 3600mg, you might be able to find a doctor that will prescribe Lyrica in addition to get to a higher dose of gaba receptors. I would suggest researching the FDA guidelines first on that issue. Everyone reacts differently to meds.
I cannot say it was the high dosages or even related to gabapentin, but the less than common challenges I was suspicious about were: vision changed every few months, some florescent lighting caused a reaction, ganglion tumor caused by feet swelling, and multiple pneumonias but mostly aspirated pneumonia.
The more common challenges were weight gain, loss of concentration, lethargy, and occasional dizziness. All of these were lesser evils in my case. At one point, I was getting 100 debilitating pain attacks per day. Later, trying to get my life back, I pushed to see if I would still get horrible pain attacks if lowering the dosage via my gp. It ended up that my pain attacks were gone without gabapentin, but I still have chronic pain.
Without attacks, I felt there were other ways to work on pain management other than gabapentin so I could drive, work more, and exercise enough to improve my life span. I haven’t had pneumonia since either. The withdrawal symptoms for me were horrible. The ringing in my ears still hasn’t gone away, so am guessing ear drum ruptures. You need to have a doctor involved. Sorry for so long of post. I am trying to retrain my brain.
To the best of my knowledge, the max dose of gabapentin is 3600mg per day. I currently take 2700mg myself on a daily basis. I take it for fibro and neuropathic pain.