Lethal effects of physostigmine plus lithium in rats

The interaction between the reversible cholinesterase inhibitor, physostigmine, and lithium chloride was studied in adult male rats. A combination of lithium plus physostigmine increased lethality more than that caused by either physostigmine or lithium alone. Scopolamine completely reversed this effect. These drug interactions may have clinical significance, since lithium plus cholinesterase inhibitors may be used together in the practice of medicine.