Physostigmine is easily absorbed from the gastrointestinal tract and other mucous membranes. Upon entering the bloodstream, it easily permeates the blood-brain barrier. It is inactivated by cholinesterase of the plasma. Physostigmine has a minimal direct effect on cholinesterase receptors. Because of its ability to diffuse into the CNS, it is used as an antidote for toxic concentrations in the organism of drugs with anticholinergic properties such as atropine, antihistamines, phenothiazines, and tricyclic antidepressants. Its action on the organism is basically similar to that of acetylcholine, and it is used for the same indications in ophthalmology for constricting the pupil and lowering ocular pressure in glaucoma. Synonyms of this drug are eserine and mezithinonone.
Neostigmine: Neostigmine, N,N,N-trimethyl-meia-(dimethylcarbomoyloxy)-phenylam-monium methylsulfonate (13.2.9), which can be viewed as a simplified analog of physostigmine, is made by reacting 3-dimethylaminophenol with N-dimethylcarbamoyl chloride, which forms the dimethylcarbamate (13.2.8), and its subsequent alkylation using dimethylsulfate forming the desired compound (13.2.9) .
0 + 0 (CHsfeN o (CHsfeN ^-^O—C-NCCHsfe (CH&N ^^O—C-NtCHsfc
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