People make all these ridiculous assumptions about loperamide blocking you up for ridiculous lengths and so forth and it's silly. Drugs can only constipate you so much. Single doses (even large doses) likely won't constipate you for more than a couple days AT MOST and if you eat enough fiver and stay properly hydrated, it's likely you'll be able to go just fine within 24 hours.
If people already have a large tolerance to opioids, that means they are used to putting large doses of massively constipating drugs into their systems and should know how to mitigate the risks of such whether it be through diet/exercise and/or through supplementing with stool softeners or laxatives if necessary.
I have used loperamide a lot to taper off opioids and I even use loperamide sometimes alone for primarily analgesic purposes due to cost and availability so I have a lot of experience with doses up to about 75mg and even with those, I am rarely constipated. The first BM after a dose like that might be a bit hard but rarely does it even produce 1-2 days of constipation.
If someone is using large doses DAILY and not doing anything to ensure regularity, I could envision it being problematic but I just wanted to comment on the prevalence of ill-informed comments about the degree of constipation loperamide will cause in opioid-tolerant individuals.
With that said, IVing loperamide sounds risky and unnecessary... best case scenario, you get a shitty loperamide "high", worst case, it's more potent than anticipated and you kill yourself. I can't image either case ever being worth it.