Final answer:
Opioids weren't commonly used to treat pain until more recently due to various reasons such as lack of evidence for pain reduction, euphoric effects, and addiction concerns.
Step-by-step explanation:
Opioids weren't commonly used to treat pain until more recently due to several reasons. One of the reasons is that it was never proven that opioids could successfully reduce pain (Answer A). Additionally, opioids can create euphoric effects for the user, rather than solely alleviating pain (Answer B). Moreover, there was concern about the high chance of patients getting addicted to opioids (Answer C).
Learn more about reasons for the delayed use of opioids to treat pain