Physostigmine

Physostigmine is a reversible anticholinesterase that can be found naturally in the Calabar bean or chemically synthesized in the laboratory. Since it competes with acetylcholine to bind the acetylcholinesterase, it increases the muscle contraction in force and frequency, which is one of the reasons why it is used to treat some diseases as the myasthenia gravis.

However, too elevated doses can be dangerous for the organism. An overdose can cause cholinergic syndrome and other side effects, which include nausea, vomiting, diarrhea, anorexia, dizziness, headache, stomach pain, sweating, dyspepsia, and seizures.