Which substance is naloxone not effective against?

Naloxone is an opioid antagonist, primarily used to reverse the effects of opioid overdose. It works by binding to the same receptors in the brain that opioids target, thereby displacing them and blocking their effects. Since benzodiazepines, alcohol, and caffeine do not act on the opioid receptors, naloxone does not have any effect on them. However, it is particularly ineffective against benzodiazepines compared to the other substances listed.

Benzodiazepines are sedatives that work on the gamma-aminobutyric acid (GABA) receptors, which are distinct from the opioid receptors that naloxone targets. As such, naloxone cannot reverse the effects of a benzodiazepine overdose. This is a critical point in understanding the limits of naloxone's use in emergency situations, underlining the necessity for other treatments when dealing with overdoses of non-opioid substances.