When is the onset of action and peak action of the drug, amitiza (lubiprostone)? for once daily dosing, what time of day should it be taken?

A couple of hours: Amitiza (lubiprostone) can help one have a bowel movement in a couple of hours. It can be taken at anytime, but probably works better if taken with a meal that includes water or beverages. That means one should not take Amitiza (lubiprostone) without knowing where the nearest bathroom is (for 1-4 hours after taking the medicine).