Frequency and Dose
I have forgotten what treatments you are getting and why you need to go the hospital. As a reminder, let’s consider both of the main treatments: IVIg and plasmapheresis. The Peripheral Nerve Society calls for treatment with IVIg initially at 2 g IVIg per kg of body weight, followed by 1 g/kg every three weeks until there is clinical improvement or three months. However, many people find that they need treatment more often, sometimes even once a week. Plasmapheresis is usually given as an initial round of five treatments. What the interval to the next round should be and how many treatments are needed in each round is open to debate. However, it is not uncommon to need another round of plasmapheresis two weeks after the end of the last round. The point here is that you can receive either treatment often if needed. Also, these treatments can be given on an outpatient basis. Unless you are immobile—you cannot move even with a wheelchair—there is no obvious reason why you must be admitted to the hospital for treatment.
I can see only four reasons to wait for another treatment if you are declining. First, you are still recovering from bad side effects. Two, the side effects were terrible and you cannot bear the consequences yet. Three, you are actively trying to see how long you can go between treatments. Four, you cannot afford the treatment right now. If none of those applies and you are not improving, then you should ask your neurologist to move your treatment up again.
Unless you are absolutely tiny, like 50 pounds, 900 mg of Neurontin is nowhere near the maximum dose. I know of people who have been on 5600 mg/day, and many people don’t find adequate relief until they have much higher doses than what you are getting.
Neurontin is an odd drug in that its effectiveness drops off at higher doses. A 2400 mg dose does not put twice as much into system compared to a 1200 mg dose. So if 600 mg really did not do the job, and 900 mg barely does, the next jump might not be to 1200 mg, but perhaps to 1500 mg or 1800 mg. Neurontin is also not metabolized by the body, just used, so its safety is reasonably good, even at high doses.
Godspeed in your treatments,