naloxone hydrochloride /nal″əksōn/ , an opioid antagonist. ▪ INDICATIONS: It is prescribed for reversal of respiratory depression and other opioid effects in patients receiving opioid analgesics and in patients who have abused heroin, morphine, or other synthetic opioids. ▪ CONTRAINDICATIONS: Known hypersensitivity to this drug prohibits its use. ▪ ADVERSE EFFECTS: Among the most serious adverse effects when given to opioid-dependent patients are side effects associated with opioid withdrawal.