Final answer:
Naloxone is the opioid antagonist used to treat opioid overdose and respiratory depression.
Step-by-step explanation:
The opioid antagonist used to treat opioid overdose and respiratory depression is Naloxone.
Naloxone antagonizes the actions of morphine at all its receptors and is administered to reverse the respiratory depression that follows acute narcotic intoxication. It is also used to reverse narcotic-induced respiratory depression in newborns of mothers who have received narcotics.
The use of naloxone is limited by a short duration of action and the necessity of parenteral route of administration.