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ANESTHETIC PHARMACOLOGY

Sevoflurane Formulation Water Content Influences Degradation by Lewis Acids in Vaporizers

Evan D. Kharasch, MD, PhD^*, Gowdahalli N. Subbarao, PhD, Keith R. Cromack, PhD, Dennis A. Stephens, PhD, and Mario D. Saltarelli, MD, PhD^||

From the *Department of Anesthesiology, Division of Clinical and Translational Research, WA University, St. Louis, Missouri; Global Aerosol Development; Department of Cardiovascular Research; Global Analytical Research and Development; and ||GPRD, Neuroscience and Anesthesia Development, Abbott, Abbott Park, Illinois.

Address correspondence and reprint requests to Evan D. Kharasch, MD, PhD, Department of Anesthesiology, Campus Box 8054, 660 S. Euclid Avenue, St. Louis, MO 63110-1093. Address e-mail to kharasch{at}wustl.edu.

BACKGROUND: Sevoflurane is produced by several manufacturers. Currently marketed sevoflurane formulations differ in their method of synthesis, impurities, containers in which they are sold, and water content. Of the various types of chemical degradation to which sevoflurane is susceptible, the most pertinent is degradation by Lewis acids (such as metal oxides and metal halides) to hydrofluoric acid and other toxic compounds. Water inhibits such degradation. This observational study determined the degradation profile of three formulations of sevoflurane (two lower-water and one higher-water formulation) when stored in three types of vaporizers.

METHODS: Lower-water sevoflurane (Eraldin®, Laboratorios Richmond/Minrad, Argentina [19 ppm water] and generic sevoflurane, Baxter, US [57 ppm water]) and higher-water sevoflurane formulations (Ultane®, Abbott, US [352 ppm water]) were stored in three different vaporizers (Draeger Vapor 2000, GE/Datex-Ohmeda Tec 7, Penlon Sigma Delta) under accelerated storage conditions (40°C). Sevoflurane was sampled from each vaporizer immediately following filling and after 1, 2, and 3 wk, and analyzed for water content, pH, fluoride, and total degradants.

RESULTS: Lower-water sevoflurane formulations stored in the Penlon Sigma Delta vaporizers contained time dependent increases in hydrofluoric acid (pH decreased as low as 3, fluoride concentration as high as 600 ppm), and total degradants (>68,000 ppm). Penlon Sigma Delta vaporizers filled with lower-water sevoflurane formulations showed substantial etching of the sight glass and metal filler shoe after 3 wk of storage. The higher-water sevoflurane formulation (Ultane, Abbott, US [352 ppm water]) contained negligible amounts of fluoride or degradants, and small decreases in pH. Sevoflurane stored in Draeger Vapor 2000 and GE/Datex-Ohmeda Tec 7 showed negligible changes in pH, fluoride concentration, and degradants.

CONCLUSIONS: Lower-water sevoflurane underwent substantial degradation to hydrofluoric acid and other degradants during storage in the Penlon Sigma Delta vaporizer. Differences in water content of sevoflurane formulations and potential for degradation present a potential patient safety issue.

This article has been cited by other articles:

				M. T. Baker Sevoflurane-Lewis Acid Stability Anesth. Analg., June 1, 2009; 108(6): 1725 - 1726. [Full Text] [PDF]