I have a theory about
Tylenol.... It has caffeine in it and most IBSers can't handle caffeine. I took it once, a long time ago, for a headache and it messed my stomach up pretty bad (pain, nausea, D).
Vicodin isn't all that unheard of to cause stomach problems. Lots of people can't handle it because it makes them super nauseous.
I'm pretty sure both medicines side effects include constipation. If you don't drink enough water, at least 8 cups of water a day, it can cause serious constipation which results in pain. Adding fiber to your diet when taking these is recommended as well.
Personally, I've never taken either of these medications. Hopefully someone will be around who has and can give you more info.
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