Final answer:
Among the listed anesthetic agents, propofol (Diprivan) is the one administered intravenously. It is preferred due to its quick onset and reliability. Inhalational agents like enflurane, nitrous oxide, and methoxyflurane are administered via inhalation.
Step-by-step explanation:
Enflurane (Ethrane), nitrous oxide, and methoxyflurane (Penthrane) are inhaled anesthetics. Propofol, on the other hand, is known for its use in the induction and maintenance of anesthesia, often being chosen for these purposes due to its fast-acting properties and overall effectiveness. Anesthetists prefer to use intravenous injections because they are rapid, generally less painful, and more reliable than other routes.
Anesthetics can be either gases or vapors (inhalational anesthetics), or as injections (intravenous or intramuscular). Injectable anesthetics, like propofol, are often used for both inducing and maintaining unconsciousness during surgical procedures. This contrasts with older inhalation anesthetics like enflurane which, along with others like halothane and isoflurane, have seen reduced usage due to safety concerns for operating room personnel.