What is "methoxyflurane"

n. An inhalational anaesthetic of the 1960s and early 1970s, now largely abandoned because of detrimental effects on the kidneys.

Methoxyflurane ( INN), formerly marketed as Penthrane by Abbott Laboratories, is a halogenated ether that was in clinical use as a volatile inhalational anesthetic from its introduction by Joseph F. Artusio et al in 1960 until the late 1970s. It was first synthesized in the late 1940s by William T. Miller and his team of chemists following their involvement in the Manhattan Project.

Methoxyflurane is an extremely potent and highly lipid-soluble anesthetic agent, characterized by very slow induction (onset of action) and emergence (offset or dissipation) times. It is non-flammable, has relatively mild hemodynamic effects, and it does not predispose the heart to rhythm disturbances. It is, however, a significant respiratory depressant. Methoxyflurane has powerful analgesic (pain-relieving) properties at well below full anesthetic doses. It was utilized in self-administration devices for obstetric analgesia, in a manner that foreshadowed the patient-controlled analgesia infusion pumps of today.

The biodegradation of methoxyflurane produces inorganic fluoride and dichloroacetic acid (DCAA). The combined effects of these two compounds may be responsible for the toxicity of methoxyflurane to some of the major organs of the human body. Methoxyflurane was determined to be nephrotoxic (damaging to the kidneys) in a dose-dependent response and hepatotoxic (damaging to the liver) at anesthetic doses in 1973, and the drug was abandoned as a general anesthetic in the late 1970s. In 1999, the manufacturer discontinued distribution of methoxyflurane in the United States and Canada, and on September 6, 2005, the Food and Drug Administration determined that it should be withdrawn from the market for safety concerns. It is however still used in Australia as an emergency analgesic for the initial management of pain due to acute trauma, as well as for brief painful procedures such as changing of wound dressings or for transport of injured people.