What anesthetic alternatives are there for nitrous oxide?

None: Nitrous oxide is a vapor with rapid onset and offset, poor anesthesia (amnesia) maintenance, and excellent analgesia in high concentrations. As such, it is unique in its properties. There are intravenous equivalents, but none that can be simply breathed. It's major side-effect is nausea and vomiting, so it's popularity as an anesthesia adjunct in diminishing

Nitrous: Nitrous oxide has been a wonderful help to patients that have anxiety during dental procedures and up until now sedation has been the only alternative, however there is a new relaxation method that some dentists have been using called NuCalm.

Prostanoids: There are a number of agents with similar physiologic effects and less as inhaled nitric oxide. The most researched once are inhaled prostanoids: prostacyclin and iloprost.