Which antidote is commonly carried on BLS units for reversing narcotic overdose?

Naloxone is the correct answer because it is an opioid antagonist specifically designed to reverse the effects of narcotic overdose. When administered, naloxone works by competitively binding to the same receptors in the brain that opioids affect, thus reversing the physiological effects such as respiratory depression, sedation, and hypotension associated with an overdose.

Bicarbonate, diazepam, and sodium nitrate do not target the same receptor mechanisms as naloxone and are used for other medical issues. Bicarbonate is typically utilized to treat certain types of metabolic acidosis or overdose of specific medications, diazepam is a benzodiazepine used for anxiety or seizure control, and sodium nitrate is used primarily in cases of cyanide poisoning. Naloxone's rapid action and specificity for opioid receptors make it the standard first-line treatment for reversing opioid overdoses in pre-hospital care settings.