# What would happen if... **URL:** \ **Category:** Factual Questions\ **Created:** [November 17, 2012, 1:54pm UTC](https://boards.straightdope.com/t/what-would-happen-if/641306 "2012-11-17T13:54:05Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![CheeseDonkey](https://avatars.discourse-cdn.com/v4/letter/c/ecae2f/32.png) [@CheeseDonkey](https://boards.straightdope.com/u/CheeseDonkey)\ **Post date:** [November 17, 2012, 1:54pm UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/1 "2012-11-17T13:54:05Z")
I took a laxative and an anti-diarrheal medicine at the same time? Would they cancel each other out? Would it cause a rift in the space-time continuum? ---
**Author:** ![spifflog](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@spifflog](https://boards.straightdope.com/u/spifflog)\ **Post date:** [November 17, 2012, 2:04pm UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/2 "2012-11-17T14:04:28Z")
Clearly you should take a double dose of both and report back here hourly. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 17, 2012, 2:19pm UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/3 "2012-11-17T14:19:20Z")
I get this question a lot. The best answer is lots and lots of cramping, bloating and discomfort. And remember, when a nurse uses the word “discomfort”, she means it hurts like a sonofabitch. Laxatives work in several different ways, but most common over-the-counter ones work by making the stool bigger with fiber or by moving water and/or broken up bits of fat into your stool so the extra bulk and slipperiness makes it easier for the muscles of your intestine to push the stool down and out. Some of them actually work by making the smooth muscle of your intestine move faster and harder, and these cause cramping all by themselves. Immodium and several other prescription antidiarrheals\* work by messing with opiod receptors on those same muscles, causing some of them not to move so often. So it’s not going to directly counter the effect of having excess bulk, water and fat in your stool - you’re going to end up with very heavy, slippery, bulky stool, and muscles that don’t want to push it out. We do give laxatives to people who overdose on antidiarrheals, and vice versa, but we don’t promise it will be a pleasant experience. Just, hopefully, a lifesaving one. \*We’re not sure how Pepto-Bismol works. It may coat the inside of the intestinal wall like the pretty picture on the ad. This could theoretically prevent water from moving into the intestine to mix with the stool. In this way, it might just rather directly “cancel out” the water additive effect of water-adding laxatives. But it’s unclear how long that coating property lasts, if it actually does that, or if it reduces diarrhea by reducing inflammation or killing bacteria causing the diarrhea. If those are the primary mechanisms of action, we wouldn’t expect it to be effective in stopping loose stools due to laxative use at all. You’ll just have wintergreen fresh smelling loose stools. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 18, 2012, 3:11am UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/4 "2012-11-18T03:11:24Z")
> [@WhyNot](#): > > Laxatives work in several different ways, but most common over-the-counter ones work by making the stool bigger with fiber or by moving water and/or broken up bits of fat into your stool so the extra bulk and slipperiness makes it easier for the muscles of your intestine to push the stool down and out. Some of them actually work by making the smooth muscle of your intestine move faster and harder, and these cause cramping all by themselves. Can you elaborate on this? Specifically, how does polyethylene glycol work? To me, that sounds just too similar to the stuff of anti-freeze, or imported Chinese toothpaste. My doc wants me to get a colonoscopy, and I’m terrified of how brutal the prep might be. From reading some few message boards on the subject, the consensus seems to be that it’s gruesome and maybe beyond gruesome. What you would call “discomfort” I gather. I did a prep several years ago with Phospho-Soda, which was totally painless. Not a hint of “discomfort”, not even slightly. Ah, but that’s no longer available. I should have bought a lifetime supply when I had the chance. ETA: Also how does Dulcolax (bisacodyl) work? They want me to ingest a recommended-lifetime-allowance of polyethylene glycol in one day, and then wash that down with a handful of Dulcolaxes. If I survive that until the following day, then they to the colonoscopy. ---
**Author:** ![Ruby](https://avatars.discourse-cdn.com/v4/letter/r/13edae/32.png) [@Ruby](https://boards.straightdope.com/u/Ruby)\ **Post date:** [November 18, 2012, 3:32am UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/5 "2012-11-18T03:32:07Z")
\ My recent colonoscopy prep was 4 dulcolax and 64 oz of Gatorade mixed with an entire bottle of Miralax. No cramping but I was afraid that I was not going to be “cleaned out” enough for the test. Ultimately all was well and the biopsies were negative. Yay! ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [November 18, 2012, 3:41am UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/6 "2012-11-18T03:41:39Z")
> [@WhyNot](#): > > \*We’re not sure how Pepto-Bismol works. It may coat the inside of the intestinal wall like the pretty picture on the ad. This could theoretically prevent water from moving into the intestine to mix with the stool. In this way, it might just rather directly “cancel out” the water additive effect of water-adding laxatives. But it’s unclear how long that coating property lasts, if it actually does that, or if it reduces diarrhea by reducing inflammation or killing bacteria causing the diarrhea. If those are the primary mechanisms of action, we wouldn’t expect it to be effective in stopping loose stools due to laxative use at all. You’ll just have wintergreen fresh smelling loose stools. But the really important question is…Why does it turn your tongue black? And after you’ve been playing stupid practical jokes on someone for 20 minutes after a night of drinking, try convincing them that their tongue is actually black. Yeah, like they’re actually going to get up and look in the mirror. “Sure Joey, do you want me to look up gullible in the dictionary next?”. I’d never seen or heard of it before then, had no idea what was going on, but she’d been working on these Pepto-Bismol tablets all day and I grabbed the package and it’s actually listed as a side effect. Weird. Actually, here’s the answer, right from PB’s website > [@](#): > > I noticed that Pepto-Bismol sometimes darkens the tongue/stool. Why does this happen and how long does it last? > The active ingredient in Pepto-Bismol contains bismuth. When a small amount of bismuth combines with trace amounts of sulfur in your saliva and gastrointestinal tract, a black-colored substance (bismuth sulfide) is formed. This discoloration is temporary and harmless. It can last several days after you stop taking Pepto-Bismol. Individual bowel habits, your age (the intestinal tract slows down with age), and the amount of the product taken all help to determine how long Pepto-Bismol is in your system. So, in short, it turns your tongue black for the same reason it makes your poop turn black. Pleasant. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [November 18, 2012, 3:50am UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/7 "2012-11-18T03:50:20Z")
Never startle your body. It has very few ways to react, and they’re generally unpleasant. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 18, 2012, 4:37am UTC](https://boards.straightdope.com/t/what-would-happen-if/641306/8 "2012-11-18T04:37:37Z")
I hope one of our friendly neighborhood pharmacists can stop by and check my work. While part of my job is teaching stuff, I only have to cover the basics, and they know worlds more. > [@Senegoid](#): > > Can you elaborate on this? Specifically, how does polyethylene glycol work? To me, that sounds just too similar to the stuff of anti-freeze, or imported Chinese toothpaste. Well, it is, really. It’s got lots of industrial uses, apparently. It’s one of those water related ones; an Osmotic laxative" in science speak. It essentially makes you retain water, but in your colon instead of your ankles. This extra water makes your stool looser and slipperier, so your colon can move it out more easily. > [@](#): > > My doc wants me to get a colonoscopy, and I’m terrified of how brutal the prep might be. From reading some few message boards on the subject, the consensus seems to be that it’s gruesome and maybe beyond gruesome. What you would call “discomfort” I gather. Colonoscopy prep is not pleasant, no. But it’s not (um, always) the nightmare you read about online. Remember that the sample of people posting their colonoscopy experiences on the internet is going to be skewed to the extreme negative. People with boring preps don’t find much motivation to post about it. Just don’t plan on going anywhere after you start, chill it well before you start, use lots of ice and consider a big straw, the wide ones they give out in some fast food places. Cold and quick, that’s the secret. And get some baby wipes; toilet paper gets irritating. (And don’t flush the baby wipes, this is not a good time to get clogged pipes.) > [@](#): > > I did a prep several years ago with Phospho-Soda, which was totally painless. Not a hint of “discomfort”, not even slightly. Ah, but that’s no longer available. Yeah, it had this pesky kidney failure side effect… > [@](#): > > ETA: Also how does Dulcolax (bisacodyl) work? That’s one of the kind that make the muscles of your colon contract more rapidly and with greater strength. So it pushes stool out better. > [@](#): > > They want me to ingest a recommended-lifetime-allowance of polyethylene glycol in one day, and then wash that down with a handful of Dulcolaxes. Yes, very common to do both. It’s the “soften up and puuuuuush 'em out!” one-two punch. > [@](#): > > If I survive that until the following day, then they to the colonoscopy. 🙂 That’s the easy part. Seriously. They give you the good stuff and most people don’t remember a thing. Good luck!