That prompted me to post a link to a paper I read recently:

 

Overall, the present research shows that acetaminophen reduces empathy for the pleasurable experiences of other people. These findings not only constitute an important step forward in our understanding of the affective mechanisms underlying the experience of positive empathy but also raise concern about the societal impact of excessive acetaminophen consumption.

TDLR: 

They still don't really know how paracetamol works, but it appears to make you disassociate from / "lose empathy for" your own pain.  But that also makes you lose empathy for others.

So, even the most widely used "painkiller" is psychoactive, the impact measurable and significant enough to raise concern about the impact on society of excessive use.