Physostigmine

• Physostigmine is a naturally occurring reversible cholinesterase inhibitor derived from the seeds of Physostigma venenosum (Calabar bean).
• It inhibits acetylcholinesterase, leading to increased levels of acetylcholine at synaptic and neuromuscular junctions.

Chemical Formula:

• C₁₅H₂₁N₃O₂
• 

Mechanism of Action:

• Reversible AChE inhibitor.
• Crosses blood-brain barrier (BBB) → CNS effects.

Uses of Physostigmine:

• Antidote for anticholinergic toxicity (e.g. atropine overdose)
• Glaucoma (topical, less common now)

Side Effects of Physostigmine:

• Seizures (CNS penetration)
• Bradycardia
• GI disturbances (nausea, cramping)
• Bronchoconstriction
• Sweating

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