Loperamide is an opiate that acts locally (and probably via the bloodstream too) on the intestines, but doesn’t get into the brain, so you get the anti-diarrhea effects without pain relief/getting high/slow breathing of opiates.
Some randos on the internet believe that you could consume a bottle of loperamide and overcome that inability to get into the brain. In theory that’s true (since the brain barrier is actively pumping it back out and there’s gotta be a limit to that rejection), but I don’t think it’s worked out in practice other than causing massive constipation.
The article touches on this:
> In future studies it has to be explored, for example, how loperamide can be transported into the brain and cross the blood-brain barrier. > Nanoparticles might be a feasible option.
But it remains to be seen what opiate-like effects it would have on the brain if it got through.
For a short-term treatment, this could be managed/mitigated. Mechanically (this machine will breathe for you while we knock out your drive to breathe) or chemically: an opiate-antagonist (naloxone infusion or naltrexone tablets). Whether this would counteract the effect of loperamide remains to be seen.
I also wonder what made loperamide special or if opiates in general would have the same effect. It would be interesting to see if long-term opiate users get this particular tumour less.