Final answer:
Opioids are responsible for the most intentional overdose fatalities.
Step-by-step explanation:
The drug responsible for the most intentional overdose fatalities is opioids. Prescription opioids, such as oxycodone and hydrocodone, and illegal opioids, such as heroin and fentanyl, have been linked to a significant increase in overdose deaths. Opioids are central nervous system depressants that can cause respiratory depression and lead to coma or death in high doses.