Which of the following medications is administered as nitrous oxide and oxygen for pain management?

Entonox is a pharmacological agent that combines nitrous oxide and oxygen, specifically formulated for pain management, particularly in emergency medical situations. It is used due to its rapid onset of pain relief, making it ideal for managing acute pain in settings such as during trauma care or certain medical procedures.

The mixture of nitrous oxide with oxygen serves to minimize the risks associated with administering pure nitrous oxide, such as hypoxia. When employed, Entonox creates a euphoric effect, providing both analgesia and anxiolysis, thus helping to alleviate anxiety that often accompanies pain.

Other medications listed do not serve the same purpose. For instance, ASA (acetylsalicylic acid) is primarily used for its anti-inflammatory properties and pain relief, not specifically formulated for emergency pain management. Gravol is an antiemetic used to prevent nausea and vomiting and has no analgesic properties. Nitroglycerin is typically employed to relieve angina and related cardiac conditions through vasodilation, rather than for direct pain management. Therefore, Entonox stands out as the correct choice for its specific application in providing pain relief.