Bisacodyl
"I have irritable bowel syndrome C&D (constipation/diarrhea).  Lately the constipation has been the culprit. Which caused me to try Dulcolax. I took 2 pills within hours the normal cramps started.  Around early morning I still hasn't had a bm but I was vomiting with no end in sight. I lost 3 pounds within 2 hours from vomiting. Over 14 hours after taking the pills I finally had a loose bm. I can't wait for it to be over! I'll be starting a probiotic so that I can prevent this."