Analysis of the composition of 'original' and generic sevoflurane in routine use

Original sevoflurane (Sevofrane) contains a small amount of water, which can inhibit the production of hydrofluoric acid. Hydrofluoric acid is highly pungent, and sevoflurane that contains a high concentration of hydrofluoric acid is not suitable for volatile induction of anaesthesia. Recently, generic sevoflurane (Sevoness) has become available in some countries. The generic product is produced by a different method and kept in a different kind of bottle. We questioned whether the original and generic sevoflurane differed in their composition and thus might differ in their resistance to degradation.

Sevoflurane from groups of three bottles of Sevofrane and three bottles of Sevoness was kept in the bottle at 24-37 degrees C for 2 weeks or in two kinds of vaporizer for 3 days, and the resulting contents measured by gas chromatography.

Both products contained sevoflurane concentrations exceeding 99.998%. Fluoride ion concentration did not differ between the products (0.043 ppm). The original sevoflurane contained more (0.07% w/v) water than the generic anaesthetic (0.003% w/v). Original sevoflurane contained 5 ppm compound A, 10 ppm sevomethylether, and 5 ppm of unknown materials. Generic sevoflurane contained 32 ppm hexafluoroisopropanol and 12 ppm of unknown materials. While stored in a vaporizer for 3 days, the water content in the original sevoflurane decreased by two-thirds but the water in the generic sevoflurane increased by a factor of three-fold.

Generic sevoflurane contains high-quality sevoflurane and only a small amount of fluoride ions, making it comparable with the original sevoflurane product.