Anesthetic and analgesic action Nitrous oxide, unlike other anesthetics, has a moderate analgesic effect at subanesthetic dosages. Because it is eliminated by the opioid antagonist naloxone, the mechanism underlying this effect is most likely an interaction with the endogenous opioid system. At high doses, it can be toxic to humans. The major toxicity of nitrous oxide is its inhibition of cellular oxygen utilization by cells of various organs, especially those of the nervous system. This anesthetic inhibits cytochrome c oxidase in mitochondria, thereby blocking oxidative phosphorylation and resulting in cell death. It is this property that makes nitrous oxide an important anesthetic during surgical procedures with an increased risk of brain injury or death. The blood-brain barrier prevents most drugs from entering the brain, so any effect on the brain must occur via another route. In fact, some researchers believe that the reason why patients under nitrous oxide anesthesia appear not to suffer pain or anxiety is because they are actually using their brains more efficiently. The mind is highly plastic and will use any available resource to solve problems or achieve goals. Under normal circumstances, we would think of this as being positive but because nitrous oxide blocks cognitive function, the patient doesn't know this and thinks that something is wrong. Another interesting thing about nitrous oxide is that some people have found that it can increase their feelings of social connection.