My urologist gave me some samples of Uribel (an anti-spasmodic). I took one at the beginning of a flare and it did seem to stop the spasming. If I'm feeling "twinges" I take one right away and it relieves the symptom. If I take it during an already established flare, it still seems to help at least lessen the symptoms a bit and take the edge off. The recommended dosage is 4x/day, but for me, at least right now, I just take one capsule when I have a flare and that seems to work. Something you may want to try.
