Cadralazine is a new, orally effective antihypertensive vasodilator. The doses which reduce systolic blood pressure by 25% (ED25) are very similar after oral and intravenous administration (spontaneously hypertensive rats, 1.8 mg/kg, p.o.; 2.3 mg/kg, i.v.; renal hypertensive dogs, 0.26 mg/kg, p.o.; 0.24 mg/kg, i.v.; awake normotensive dogs, 0.98 mg/kg, p.o.; 1.01 mg/kg, i.v.). Cadralazine reverses hypertensive responses to epinephrine in awake normotensive dogs and anesthetized cats. The inhibition of the increase in blood pressure induced by sympathetic outflow activation in pithed rats parallels the antihypertensive activity in onset, intensity, and duration[3]. Cadralazine given i.v. (1 mg/kg) caused a sustained fall in total peripheral vascular resistances and mean blood pressure (from 103 to 90 mmHg) and an increase in heart rate (from 97 to 161 beats/min)[4]. Oral administration of 0.5 mg/kg or more of cadralazine depressed spontaneous motor activity and enhanced electroshock-induced convulsions in mice. The drug produced flush on the tail or ears at 0.5 mg/kg, p.o. or more and enhanced respiratory movement at 5.0 mg/kg, p.o. or more in rats. At 2.5 mg/kg, p.o., cadralazine prolonged the thiopental-sleeping time and inhibited methamphetamine-induced hypermotility as well as acetic acid-induced writhing in mice. Cadralazine at 5.0 mg/kg, p.o., lowered body temperature in rats[5]. Cadralazine at 2.5 mg/kg, p.o., or more reduced or tended to reduce urine volume and urinary excretion of electrolytes. Cadralazine at 5.0 mg/kg, p.o. or more antagonized carrageenin-induced hind paw edema in rats[6].
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