The effects of 10% methohexital on the rectal mucosa in mice

The effects of 10% methohexital (pH 10 and osmolarity 820) on the mucosal lining of the mouse rectum was examined after transrectal instillation and application to a rectal mucosal pouch. In addition to 10% methohexital, control solutions of pH 4, 7, 12, and osmolarities of 823 mOsm/1, 1027 mOsm/1, and 1372 mOsm/1 were also applied to the rectal pouch. Using a lesion index scoring system for grading macroscopic and microscopic changes in the rectal pouch 10% methohexital produced a superficial mucosal lesion of significantly higher severity score than that produced by control and solutions of varying pH or osmolarities. The methohexital-induced rectal mucosal lesion had its onset within minutes of drug application to the mucosal lining, appeared to mature by 60 min and left minimal effects 24 h after mucosal contact. The lesion appeared to be due to the methohexital itself and not secondary to the alkalinity or hyperosmolarity. In summary, the authors' data in mice supports an extensive 20-yr clinical experience that 10% rectal methohexital, despite inducing a transient mucosal lesion, is free of long-term serious complication related to this lesion.