Across BC, there have been reports of prolonged sedation where people remain sedated, or unable to wake up, for several hours after receiving naloxone and their breathing has returned to normal. Prolonged sedation after opioid poisoning may occur because of contamination of opioids with other sedating substances, such as benzodiazepines and/or xylazine. Xylazine is a potent α2 adrenergic agonist, which causes sedation, hypotension, bradycardia, or respiratory suppression. There can be transient hypertension. Xylazine can remain active for up to 4 hours after use. Like benzodiazepines, the effects of Xylazine cannot be reversed by naloxone.
Naloxone remains a mainstay for the treatment of suspected opioid drug poisoning events. If normal oxygenation/ventilation has been achieved with naloxone, but the person remains altered, higher doses of naloxone are unlikely to improve the level of consciousness and may precipitate narcotic withdrawal while sedated. For a person with prolonged sedation, consider alternate causes of altered level of consciousness [e.g., hypoglycemia, head injury, contaminants such as benzodiazepines or Xylazine]. Paramedics are reminded to involve CliniCall for clinical consultation regarding unexpected or atypical presentations involving unconscious patients. People with prolonged sedation should be conveyed to the emergency department for assessment. ACPs should obtain an ECG enroute to look for ECG abnormalities which may be a clue to other toxins.
More information on prolonged sedation can be found here: Responding to Opioid Poisoning Prolonged Sedation [bccdc.ca]