Minimum alveolar concentrations and oil/gas partition coefficients of four anesthetic isomers.

We determined the minimum alveolar concentration (MAC) of four structural isomers having the empirical formula C3H2F5CIO in dogs. MAC for three of the four isomers (including isoflurane and enflurane) ranged from 1.41 to 2.67 (volumes per cent at one atmosphere pressure). The olive oil/gas partition coefficients at 37 degrees C for these isomers ranged from 90.8 to 96.6. In contrast, MAC for the fourth isomer, compound 485, was 12.53 per cent atm. However, the oil/gas partition coefficient for that compound was 25.8. These results suggest that isomer 485, despite its high MAC, does not deviate strikingly from the established correlation between anesthetic potency and lipid solubility.