[Stability of liquid ergotalkaloid preparations as a function of the solvent polarity (author's transl)].

The degradation of dihydroergotamine-, dihydroergocornine-, dihydroergocryptine- (both isomers) and dihydroergocristine-mesilate in solution was studied as a function of the temperature and the dielectric constant of the composition. The degradation reactions of the studied hydrogenated ergopeptide alkaloids gave pseudo first-order kinetics. The pseudo first-order rate constants at room temperature were calculated using the Arrhenius equation. It was found that the stability of the studied hydrogenated ergopeptide alkaloids in solution is a function of the dielectric constant of the composition, and that stable solutions can be obtained by the use of water-alcohol mixtures having dielectric constants between 30 and 45. Solutions of the hydrogenated ergot alkaloids in predominantly organic media have the advantage that the degradation to the corresponding aci-forms, hydrolysis products and oxidation products is reduced. For this reason it is not necessary to carry out the filling operation under an inert gas atmosphere in order to protect the hydrogenated ergot alkaloids from oxidation. These results present an important technological advance.