Lubiprostone
"I've been taking 8mcg Amitiza twice a day, for two months, to treat Irritable Bowel Syndrome. Finally! A Dr. who actually listened to me and provided a solution instead of blaming me for the GI/bowel problems. (i.e., "You need more fiber," "It's your nerves," or "It's caused by the NSAIDS you take."). Almost 40 years of daily chronic painful bloating, constipation & pain under my left ribcage is almost gone, (I'm 50.) 
It did take a few weeks to adjust to it. By that, I mean: 1.) Discovering that taking Fiber Supplements with the prescription caused painful gas/bloating, 2.) Determining exactly how much food/drink to ingest with each dose, to avoid gas/bloating or a headache & 3.) Remembering to take it with a meal. 
I'd give it a 10 if there was 0 bloating and no headaches."