An evaluation of the ability of priscoline, regitine, and roniacol to overcome vasospasm in normal man; estimation of the probable clinical efficacy of these drugs in vasospastic peripheral vascular disease.

This paper is a study of the comparative efficacy of Priscoline, Regitine, and Roniacol in relaxing vasospasm in the extremities of normal human subjects. A total of 60 studies were performed on 14 subjects. Severe cutaneous vasospasm was induced by exposure of the lightly clad subject to an environmental temperature of 20 C. for one hour or more. In half the tests the severe vasospasm was reduced to moderate vasospasm by application of heat to the torso of the chilled subjects. The effectiveness of the drugs was tested by giving them by intravenous infusion after the appropriate state of vasospasm had been obtained. The degree of relaxation of vasospasm was estimated from the resulting changes in cutaneous temperature recorded with thermocouples. IN EACH of the peripheral vascular disease entities, the vasomotor component varies. Thromboangiitis obliterans exhibits a decreasing vasospastic element as the organic oc-clusive element increases.' In Raynaud's phenomenon and allied conditions, however, the vasospastic element predominates.2 Some vaso-constriction is often present in arteriosclerosis. The usage of drugs which abolish vasospasm is, therefore, a helpful adjunct in determination of the degree of vasospasm, in differentiation of the disease entities, and in the treatment of disease where vasoconstriction plays a part in the presenting symptoms. In previous papers usage of such agents in the evaluation of the degree of vasospasm has been discussed.3' 4 This paper presents a method for estimating the probable clinical effectiveness of drugs designed to relax vaso-spasm. In principle, a reproducible degree of vasospasm is induced in normal subjects and the ability of the drug to overcome this vaso-spasm is tested. The ideal therapeutic agent for this disease group would be one which induced maximal vasodilation in the extremities with minimal untoward side effects. In this paper we will consider three agents and compare the results of their trial upon normal subjects. These agents are: (1) Priscoline,* (2) Regitine,* (3) Roniacol. t The chemical formulas for these drugs are: