Lubiprostone
constipation, drug induced
"I'd never been regular, my whole life, it was always a problem that I was lucky if it resolved itself every 3 or 4 days, but then once I aged and my rheumatoid arthritis advanced to a debilitating degree, I had to go on opiates...oh dear. 7-8 days or even more of being bound up became the norm. It was REALLY painful! The only way I could help myself was to stop taking my pain meds and overdose on laxatives and enemas every few days.
That usually worked within 24 hrs, but it really isn't good for you.
I finally confessed to my gastroenterologist that this was going on and he prescribed me Amitiza. 
It took a week to work for me, but now I have the exact opposite problem. I'm on 24 mcg 2x daily. I think maybe it needs to be just once!"