For me Amitriptyline is great reducing my migraines from more than 10 days a month to usually under 3 days a month!
After visiting the NMC I was prescribed Amitriptyline starting on a low dose and then increasing to 35mg for 2-3 weeks, then 40mg for 2-3 weeks and was told that if I had no increased side effects with that dose to increase again to 50mg, which is the dose I am on and have been for 2 years. The NMC also said that in some cases it may be necessary to increase up to 75mg if only partial benefit is achieved with lower doses.
I am therefore puzzled as to why your GP has told you that you cannot have a higher dose than 35mg and wanted to let you know my experience and treatment at the NMC.