Methoxyflurane* — A New Anesthetic Agent

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METHOXYFLURANE, the most satisfactory anesthetic agent of a series of fluorinated hydrocarbons and fluorether studied clinically by Artusio and Van Poznak,1 was used by us to induce or to maintain anesthesia in 206 patients. This anesthetic agent is a nonexplosive liquid that produces profound analgesia accompanied by remarkable muscular relaxation with apparently low toxicity. In low vapor concentrations, methoxyflurane produces the same degree of analgesia produced by halothane, the same degree of muscular relaxation produced by deep levels of cyclopropane anesthesia, and possesses the same wide margin of safety as that of diethyl ether.

Introduced experimentally as DA-759, methoxyflurane is 1, 1-dichloro-2, 2-difluoro-2-methoxyethane. The chemical structure is shown in Figure 1. It is a clear, colorless liquid that boils at 104.8 C. (220 F.) ± 0.2 degrees at 760 mm. of Hg, and has a specific gravity of 1.4224. The odor is pleasant with a fruity characteristic. The explosive range is shown in Table 1. At 20 C. (68 F.) the explosive limits in air and oxygen are zero. The flash point is 56.11 C. (133 F.). The vapor density at 37 C. (98.6 F.) is 7.36 gm. per liter. It is miscible in all proportions with olive oil (liquid to liquid). Its solubility in water, according to polarographic titration is 0.22 gm. per liter of water.

The olive oil/water distribution coefficient was determined for 1 per cent methoxyflurane as 400. Using a 10 per cent concentration of methoxyflurane, the distribution constant was 39. Diethyl ether is 3.8 and halothane . . .



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