I developed a tolerance for gabapentin after 6+ years taking it. I was up to 4200mgs/day and it no longer was effective. I switched to Lyrica 450mgs/day for 30 days and then went up to 600mgs/day. I've been at 600 for 3+ yrs, now and it seems to be very effective at that level. Dunno what I'll do if it stops being as effective as it is. I feel fortunate to be able to function quite well using it at that dose.