Semotiadil fumarate, a novel benzothiazine calcium antagonist, is given alone or in combination with either Enalapril or trichlormethiazide to conscious, spontaneously hypertensive, rats daily for 2 weeks. When given alone, the antihypertensive effects of Semotiadil (10 mg/kg, p.o.) and Enalapril (5 mg/kg, p.o.) first became apparent after the 3rd dose and thereafter the effects appeared to develop daily although this effect had waned by the time of the next dose. These results indicate that combined daily dosing of Semotiadil, especially with Enalapril, each at relatively low doses may be able to control hypertension in a continuous manner^[3].