available evidence indicates that sympatholytic agents such as guanethidine and reserpine , alpha 2-adrenergic agonists such as methyldopa and clonidine , the alpha 1-blocking agent prazosin , and the vasodilators captopril and hydralazine produce few , if any , clinically important changes in glucose tolerance .
C1373110
alpha 2-adrenergic
C0009014
clonidine