Nitrous Oxide (chemical symbol N2O) is a colorless, odorless gas used as an anesthetic. It is often called "laughing gas" because in lower doses it lowers inhibitions, resulting in euphoria. It was the first practical anesthetic and was developed for use in dentistry. It was later developed as a surgical anesthetic.

The anesthetic effect of the gas was noted by accident. A dentist at a "nitrous party" noted a person who had badly injured their leg had not noticed that their leg was injured to the point of bleeding. The dentist tested it on patients and successfully extracted teeth without pain.

However, the medical profession was less accepting. Dentistry was not seen to be of the same caliber as medicine at the time, and doctors doubted that the dental profession could have come up with something useful. Unfortunately, during the first public demonstration, the anesthetic didn't take, resulting in a total failure. Ether generally became the anesthetic of choice for the medical profession, although nitrous oxide is still in use.

Nitrous oxide does have some deleterious effects, but it does still have some uses although other anesthetics are now in wider use in medicine. Nitrous oxide is still very common in dentistry. First, some patients do not react to nitrous oxide and remain sensitive to pain. Second, like most other general anesthetics, nitrous oxide does cause nausea and can't be used on a patient who has recently eaten.

Nitrous oxide is still abused for its euphoric effect. However, long term use can cause health problems.

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