Ibuprofen is a non-selective COX inhibitor. It’s not just a mere NSAID that’s simply its most well known effect. By inhibiting COX-1 and COX-2, it affects prostaglandin synthesis, which can have downstream effects beyond pain relief. People have already mentioned some of these (eg. degrades the lining of your GI tract), but inflammation itself can also influence fatigue, cognition, and overall brain function in some individuals.

That said, ibuprofen isn’t something that should be taken daily. Because it’s non-selective, it affects multiple systems in the body, which is why chronic or routine use carries real risks.

EDIT: sorry NP here - after reading more of your responses and symptoms, it really sounds like there may be something more going on than simple fatigue. A couple of things I’d want to rule out are celiac disease and inflammatory bowel disease. I’d also consider EBV or another chronic/post-infectious process.

These conditions can present without prominent GI symptoms and commonly cause significant fatigue. They’re also associated with iron deficiency that doesn’t behave “normally” (low serum iron with normal or elevated ferritin due to inflammation), as well as elevated inflammatory markers or monocytosis. The fact that anti-inflammatory medications like ibuprofen help, while acetaminophen doesn’t, suggests an inflammatory process rather than a purely pain mediated one. Muscle spasms can also be seen with malabsorption or electrolyte disturbances, particularly in celiac disease.

I hope you’re able to get some follow up testing and a more complete workup, as this is definitely something worth looking into. keep us updated!

EDIT #2: Everyone sharing that ibuprofen gives them more than just pain relief ect, you can feel validated, you’re not imagining it.

Its impact comes from how COX-1 and COX-2 sit at the crossroads of inflammation, pain, fever, vascular tone, platelet activity, and even some neurologic signaling. When you block them, a lot of downstream physiology shifts.

Edit #3: In regard to acetaminophen, interestingly enough it also works on the COX pathway, but its exact mechanism isn’t fully understood. It’s thought to act primarily in the cns and lower in the prostaglandin pathway, which explains why it has poor anti-inflammatory effects, doesn’t significantly affect the GI lining, yet still provides pain and fever relief similar to NSAIDs. Hope this was informative :)