Neostigmine, sold under the brand name Bloxiverz, among others, is a medication used to treat myasthenia gravis, Ogilvie syndrome, and urinary retention without the presence of a blockage.

[3][5] Common side effects include nausea, increased saliva, crampy abdominal pain, and slow heart rate.

[3] More severe side effects include low blood pressure, weakness, and allergic reactions.

[7] The term is from Greek neos, meaning "new", and "-stigmine", in reference to its parent molecule, physostigmine, on which it is based.

[14] Some promising research results have also been reported for administering the drug nasally in order to buy time if anti-venom is not immediately available.

[18] Neostigmine can also induce generic ocular side effects including: headache, brow pain, blurred vision, phacodonesis, pericorneal injection, congestive iritis, various allergic reactions, and rarely, retinal detachment.

Neostigmine binds to the anionic and ester site of acetylcholinesterase, which blocks the enzyme from breaking down the acetylcholine molecules before they reach the postsynaptic membrane receptors.

By interfering with the breakdown of acetylcholine, neostigmine indirectly stimulates both nicotinic and muscarinic receptors.