What is the mechanism of action of Physostigmine?

Physostigmine operates primarily by inhibiting acetylcholinesterase, which is the enzyme responsible for breaking down acetylcholine in the synaptic cleft. By inhibiting this enzyme, Physostigmine increases the concentration and duration of action of acetylcholine at cholinergic synapses. This enhanced availability of acetylcholine can lead to prolonged stimulation of both muscarinic and nicotinic receptors, which is why Physostigmine is often used in clinical settings to counteract the effects of anticholinergic toxicity or to manage certain types of glaucoma.

Blocking acetylcholine receptors, stimulating acetylcholine release, or increasing norepinephrine levels does not accurately describe the action of Physostigmine. Its primary and most important action is the inhibition of acetylcholinesterase, leading to increased levels of acetylcholine.