When I was first diagnoses with GP and was having extreme pain, I was sent to a pain specialist. I only saw him twice but the first time, unlike the second, I was having pain so he injected botox directly where the initial pain was (same place as heartburn). It helped for a bit but after 45 minutes the pain returned. The reason it worked is because my pain is from muscle spams in the stomach area so using botox these muscles were able to relax for a while. The second time I went I wasn't having pain so there was no need for a botox injection. I never returned after that appointment because I felt if these shots were only going to last about an hour, I didn't want to have numerous amounts of botox in my abdomin like that.
A lot of people have tried the botox injections and it has helped them. For most I believe it can help with symptoms as long as a few months. It's definitely worth looking into!