Tolmesoxide, a drug that lowers blood pressure by a direct relaxant effect on vascular smooth muscle

1 The blood pressure of conscious, deoxycorticosterone acetate (DOCA) hypertensive and 1 kidney Goldblatt hypertensive rats and renal hypertensive and normotensive cats was reduced by tolmesoxide (4,5-dimethoxy-o-tolyl methyl sulphoxide). 2 Tachycardia accompanied the hypotension. In rats the increase in heart rate was abolished by concurrent administration of propranolol. Tachycardia did not occur in pithed rats. 3 Vascoconstriction induced by sympathetic stimulation, noradrenaline, tyramine, angiotensin or vasporessin was antagonized by tolmesoxide. 4 The antagonism of vasoconstrictor responses produced by tolmesoxide was unaffected by beta-adrenoceptor, muscarinic or histamine antagonists. 5 It is concluded that the lowering of pressure produced by tolmesoxide results from a defect relaxant effect on vascular smooth muscle.