I forgot to make this clear earlier when I posted this thread: I already take Metamucil as a laxative to keep myself regular (though it seems to be less effective as time goes on). In my question I meant a laxative that acts quickly and clears out everything, like something one would take before a colonoscopy. And please...I am in pain here, and any help would be appreciated as I was turned away from the walk-in clinic today because it had filled up for the day.
I've had IBS with constipation for most of my life now. Recently, my GI told me to use Miralax every night before going to bed and Colace twice a day (although I can't use this since it's the same medication as Dulcolax, which I've developed an intolerance to) as well as the fiber, which would be the Metamucil in your case. I started using chlorella (a type of algae and is available in tablets at health food stores) as a stool softener and it seems to be doing the job. I use flaxseed meal instead of the psyllium fiber because I also have GERD, which is aggravated by psyllium fiber, and I can add it directly to food, instead of drinking it down with water, like Metamucil. The GI said it doesn't matter which fiber is used, as long as I use a fiber, which I was doing all along anyway.