Mechanisms underlying combined action of clonidine and local anesthetics.

We studied the mechanisms of combined action of clonidine and local anesthetics amethocaine and imidazo-benzimidazole derivative RU-1117. In contrast to amethocaine, RU-1117 in therapeutic concentrations binds to imidazoline receptors and, to a lesser extent, to α2A-adrenoceptors on human platelets. Clonidine and RU-1117 produce opposite effects on platelet aggregation induced by ADP in low concentrations. Our results suggest that the pharmacodynamic interaction of clonidine and RU-1117 is associated with their ability to activate the imidazolinergic system.