Relationship of In Vitro Hydrolysis of 17‐Chloroacetylajmaline and 17‐Acetylajmaline in Different Animal Species

17‐Chloroacetylajmaline and 17‐acetylajmaline are reported to have in vivo antiarrhythmic activity and are metabolized by hydrolysis. Since the hydrolysis product, ajmaline, may be the actual antiarrhythmic agent, the hydrolysis of these derivatives by various tissues of the guinea pig, rat, and mouse was determined in vitro by a titrimetric method and compared to hydrolysis by α‐naphthylacetate. The heart is the most active tissue in the guinea pig for hydrolyzing 17‐chloroacetylajmaline. The hydrolyzing activity is greater in the guinea pig than in rat or mouse heart, corresponding with the more significant pharmacological activity in the guinea pig. 17‐Chloroacetylajmaline has a significantly lower Km value than 17‐acetylajmaline, which is in agreement with the in vivo activity.