Bisacodyl
"I suffer from chronic constipation and after seeing my GP I was prescribed dulcolax. This medicine is as "gentle" as a hammer to the face. I took two tablets at around 2am and drunk quite a lot of water. 
I went to bed, no hot flashes, no nausea or headaches. I had very mild cramps and within an hour, I had my first BM after days. I thought that was it and went to sleep. Little did I know that at 10am I'd be woke to explosive diarrhoea. Luckily, there wasn't much pain.
Tomorrow, I will adjust the dose and take one tablet."