Incredible: I hadn’t heard of this up to now, and my 4 months of amitriptyline last year didn’t do anything except zombify me plus 7 further increasing sfx.
But I’ve found evidence all over the place that it is defo. used for this, amongst other antidepressants, in low dose, even if people haven’t got FM.
- cmljournal says you need to take it >8 weeks, 50-75mg plus psych. strategies.
- dchft.nhs.uk says it’s unclear how it works, complicated, research ongoing.
- Dr. Blume on scarysymptoms says it’s GI analgesic, may decrease spasm in your GI tract.
- thehealthboard says it’s esp. good for IBSD, you work up from 10mg(-150mg).
- There are studies from 2008 and 2009 about it helping.
- med.unc.edu says "there is recovery of more normal brain-gut function, possibly by helping the brain send down signals to block incoming pain impulses. Like other TCAs it helps more with IBS-D, SSRIs with IBS-C. SNRIs may work too, e.g. duloxetine, venlafaxine, milnacipram. Also others antidepressants like trazodone.
- mayoclinic’s page on IBSD: “frequently used to treat patients with severe or refractory IBS symptoms and may have analgesic and neuromodulatory benefits in addition to their psychotropic effects. In one trial, nearly 70 percent of patients receiving 10 mg of amitriptyline experienced a complete loss of IBS symptoms compared with 28 percent of those on placebo.”
(Interesting for me personally that I read that “agents that modulate … serotonin” can help, as my supps do that - so maybe GABA is even helping my gut 
)