# Why does cold medicine give me the runs? **URL:** \ **Category:** Factual Questions\ **Created:** [April 13, 2008, 11:16pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221 "2008-04-13T23:16:56Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [April 13, 2008, 11:16pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/1 "2008-04-13T23:16:56Z")
Every time I catch a cold bad enough to require medication (Dayquil/Nyquil, etc.), I end up with loose bowels. Why does this happen? Is the medicine tricking my body into rerouting to my colon all the fluid I’d normally be blowing out of my sinuses? ---
**Author:** ![GameHat](https://avatars.discourse-cdn.com/v4/letter/g/ed655f/32.png) [@GameHat](https://boards.straightdope.com/u/GameHat)\ **Post date:** [April 13, 2008, 11:32pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/2 "2008-04-13T23:32:09Z")
[QUOTE=Phase42] Every time I catch a cold bad enough to require medication (Dayquil/Nyquil, etc.), I end up with loose bowels. Why does this happen? Is the medicine tricking my body into rerouting to my colon all the fluid I’d normally be blowing out of my sinuses? [/QUOTE] It’s probably a side effect of the [Dextromethorphan](http://en.wikipedia.org/wiki/Dextromethorphan) that is in lots of OTC cold medicines. It acts as a cough suppressant but can also have minor gastrointestinal side effects. ---
**Author:** ![Sattua](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sattua/32/11906_2.png) [@Sattua](https://boards.straightdope.com/u/Sattua)\ **Post date:** [April 14, 2008, 1:08am UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/3 "2008-04-14T01:08:09Z")
Aren’t opiates supposed to be constipating, though? ---
**Author:** ![TV\_time](https://avatars.discourse-cdn.com/v4/letter/t/f17d59/32.png) [@TV\_time](https://boards.straightdope.com/u/TV_time)\ **Post date:** [April 14, 2008, 1:29am UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/4 "2008-04-14T01:29:00Z")
[QUOTE=Sattua] Aren’t opiates supposed to be constipating, though? [/QUOTE] Yes, they are. When I was overseas during a not too recent war in SE Asia. I used to put out some of the opiates that the government issued us for pain hoping the rats would eat it and explode from constipation or get hooked on it and do my bidding for another “fix”. Neither happened. Clearly they were too smart. ---
**Author:** ![Sophistry\_and\_Illusion](https://avatars.discourse-cdn.com/v4/letter/s/b3f665/32.png) [@Sophistry\_and\_Illusion](https://boards.straightdope.com/u/Sophistry_and_Illusion)\ **Post date:** [April 14, 2008, 1:35am UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/5 "2008-04-14T01:35:41Z")
[QUOTE=Sattua] Aren’t opiates supposed to be constipating, though? [/QUOTE] Yes, but OTC cold remedies don’t contain opiates. At least, I don’t think DM is an opiate. ---
**Author:** ![Sattua](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sattua/32/11906_2.png) [@Sattua](https://boards.straightdope.com/u/Sattua)\ **Post date:** [April 14, 2008, 1:44am UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/6 "2008-04-14T01:44:46Z")
[QUOTE=Sophistry and Illusion] Yes, but OTC cold remedies don’t contain opiates. At least, I don’t think DM is an opiate. [/QUOTE] By golly you’re right. I had somehow gotten it stuck in my head that dextromethorphan was an opiate. Never mind! > **[Dextromethorphan](https://en.wikipedia.org/wiki/Dextromethorphan)** > > Dextromethorphan is a cough suppressant used in many cough and cold medicines. In 2022, the US Food and Drug Administration (FDA) approved the combination dextromethorphan/bupropion to serve as a rapid-acting antidepressant in people with major depressive disorder. > It is in the morphinan class of medications with dissociative and stimulant properties (at lower doses). Dextromethorphan does not have a significant affinity for the mu-opioid receptor activity typical of morphinan compounds and e... ---
**Author:** ![freckafree](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/freckafree/32/3050_2.png) [@freckafree](https://boards.straightdope.com/u/freckafree)\ **Post date:** [April 14, 2008, 3:23pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/7 "2008-04-14T15:23:31Z")
I’ve had issues with the artificial sweeteners in sugar-free cough drops. I think they mostly use sugar alcohols like sorbitol and xylitol. It doesn’t take very many to set me off. You might check to see what the sweetening ingredient is in Dayquil/Nyquil. ---
**Author:** ![Shark\_Sandwich](https://avatars.discourse-cdn.com/v4/letter/s/f04885/32.png) [@Shark\_Sandwich](https://boards.straightdope.com/u/Shark_Sandwich)\ **Post date:** [April 14, 2008, 6:12pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/8 "2008-04-14T18:12:39Z")
Are you sure your…gastrointestinal distress isn’t a symptom of the illness, and not a side effect of the OTC medication? Flu and the trots tend to go hand in hand. - SS ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [April 14, 2008, 6:21pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/9 "2008-04-14T18:21:59Z")
[QUOTE=Shark Sandwich] Are you sure your…gastrointestinal distress isn’t a symptom of the illness, and not a side effect of the OTC medication? Flu and the trots tend to go hand in hand. [/QUOTE] That’s certainly possible - as is the possibility that I’m simply drinking more fluids when I’m sick. But I hate medicating myself so I’ll put off taking any medicine until I just can’t stand it any more. And that’s when the runs start. I should note that a single dose of Nyquil at bedtime doesn’t do this to me. It’s when I get on the dose-every-four-hours with the Dayquil that it happens. This isn’t explosive, desperately-hoping-to-make-it-to-the-toilet diarrhea, either. It’s just unusually soft, runny stool. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [April 14, 2008, 7:23pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/10 "2008-04-14T19:23:12Z")
Well, DXM is sort of an opiate, but it has no affinity at the opiate receptor sites that trigger decreased bowel motion, and hence constipation. Nor does it have activity at the opiate receptor sites that decrease pain or cause euphoria. It’s thought to have weak activity at the opiate receptor sites that suppress cough; but clinical studies haven’t borne this out very well. It’s probably not a real effective cough suppressant. ---
**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:** [April 14, 2008, 7:39pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/11 "2008-04-14T19:39:26Z")
Do any of the meds your taking for the cold contain guaifenesin? ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [April 14, 2008, 8:35pm UTC](https://boards.straightdope.com/t/why-does-cold-medicine-give-me-the-runs/445221/12 "2008-04-14T20:35:51Z")
[QUOTE=Joey P] Do any of the meds your taking for the cold contain guaifenesin? [/QUOTE] The Robitussin DM does …