What is good medicine for ibs when it is acting up?

Fiber, water: There are prescriptions to help with spasms (levsin (hyoscyamine) is a common one) but often symptoms can be helped with fiber, water, and stress reduction.

Calming your gut: There are prescription anti-spasm medicines. Herbal remedies also include peppermint oil capsules. Figuring out and avoiding your food triggers is the bigger piece. Hope you're feeling better.