Potentiation of tricyclic antidepressant toxicity by physostigmine in mice.

Subtoxic doses of physostigmine have been found to potentiate the convulsive toxicity and lethality of amitriptyline and imipramine in CD1 and B6A mice. Neostigmine failed to potentiate the toxicity and lethality of imipramine. Physostigmine tended to protect mice against atropine-induced lethality. These data suggest the site of toxicity of this drug-drug interaction between the tricyclic antidepressants and physostigmine may be occurring in the CNS through a mechanism distinct from the anticholinergic actions of the antidepressants.