Pharmacological properties of 2-(2-chloro-p-toluidino)-2-imidazoline-nitrate (Tolonidine), a new antihypertensive agent. I. Action on blood pressure and heart rate.

Tolonidine, 2-(2-chloro-p-toluidino)-2-imidazoline-nitrate, a substance structurally related to clonidine, was studied for its effects on blood pressure and heart rate in anesthetized or conscious, normotensive or hypertensive animals (mainly dogs). In all cases, blood pressure was lowered by tolonidine. Initial short-lasting hypertension was observed after each i.v. administration. Heart rate was markedly lowered irrespective of the experimental process. Comparison with clonidine, guanethidine and mecamylamine in hypertensive anesthetized or unanesthetized animals made it possible to place tolonidine with respect to these reference antihypertensive drugs. A close relationship essentially appears between the effects of both derivatives of imidazoline: tolonidine and clonidine, tolonidine being, however, active at higher doses. The analysis of these results will appear at the end of a series of three articles.