hi David.... i was going to reply that i hadn't had this drug, but on investigation - i have, under the brand name Buscopan.
Buscopan is one of a few antispasmodics i've been on over the years - i don't take any now, except rarely i have Kolanticol gel (an antacid chalky medicine containing an antispasmodic too).... negative side effects i've noticed from antispasmodics - my eyes always go out of focus.... so don't plan to drive after taking it until you're sure this isn't one of the side effects you get... also it can, by the way it works, give you constipation, so make sure you drink extra water whilst on the treatment..
plus side - if your GI is right, and your abdominal pains are purely being caused by over-stimulation of the intestinal muscles (classic IBS symptoms) then taking an antispasmodic should really help those gripes. you've heard of the peristaltic action? the squeeze, relax, squeeze, relax motion of your small and large bowel... this in 'normal' people should be a steady & regular motion, but in IBS and other spastic bowel conditions, the bowel contracts out of sync, squeezes too hard, too fast, too slow... and pain/swelling is felt. the antispasmodic should calm this down and help things to regulate..
if you do have IBS, relaxation techniques really help... as does a caffeine free diet, & eating little & often, & not late at night. also, stomach massages can be beneficial too