The interference of tricyclic antidepressants with the central hypotensive effect of clonidine

From clinical experience it is known that the hypotensive action of clonidine may be antagonized by simultaneously administrated desipramine. In the present experiments it has been demonstrated that pretreatment of anaesthetized cats with desipramine, imipramine, amitryptyline and protryptyline reduced the central hypotensive action of clonidine. Since both clonidine and the tricyclic antidepressive drugs were administered via the vertebral artery in low doses it may be concluded that the interaction occurs in the CNS, i.e. the rhombencephalon. The experiments suggest that interaction between tricyclic antidepressants and clonidine is not restricted to desmethylimipramine. Therefore combination of clonidine with these drugs should be avoided.