[Venous tonus-modifying effect, pharmacokinetics and undesired effects of dihydroergotamine]

In the present review the clinical pharmacology of dihyroergotamine (DHE) is described. The decisive pharmacodynamic effect of DHE, i.e. the tonicization of the capacitance vessels leading to the acceleration of the venous backflow is described by the methods suitable for the detection of this activity in man. In the paragraph on pharmacokinetics the kinetic parameters of DHE at present known are discussed with regard to the usual forms of application. Emphasis is placed on the poor oral bioavailability of DHE as a result of a distinct first-pass metabolism in the liver. Taking into consideration several recently published cases of ergotism after prophylactic use of DHE, the ability of DHE is discussed to raise the peripheral resistance. The symptoms and the incidence of ergotism are reported on and reference is given to particular conditions which favour its occurrence. Among the measures of a medicamentous therapy of ergotism the use of drugs such as sodium nitroprusside and nitroglycerin which exert a direct spasmolytic effect on the vascular muscles is of special importance. Since DHE is at present the only medicament that possesses a reliable constrictor effect on the capacitance vessels, its clinical application demands special caution due to the narrow therapeutic margin of safety.