I never gained with with Amitriptyline but i have put on a little weight slowly over last 5 years but that is due to elimination diets before i was diagnosed with STC . I have been on it since 2004. It is a tryicyclic medicine whereas prozac and newer ones are SSRI's - dont ask me the chemical differences but i dont get on with SSRI's - they give me insomnia and make me feel like i am in another world.
i only need 20mg a night as i am very sensitive to medicine (except senna ha). could be cause i dont smoke or drink maybe.
hope it helps you.