Pyridostigmine, a closely related structure to neostigmine that incorporates the charged nitrogen into a pyridine ring, acts by the same
mechanism as physostigmine, but it lacks CNS activity. It is orally effective and, compared to neostigmine, has a longer duration of action and a lower incidence of side effects. Thus, it is a better choice for oral therapy of myasthenia gravis. It is approved for U.S. military use as an adjunct for prophylaxis of soman nerve gas exposure. It is also administered parenterally to reverse the effects of nondepolarizing neuromuscular blocking agents. Its elimination half-life is 1 to 2 hours.
Pyridostigmine, 3-[(dimethylaminocarbonyl)oxy]-1-methyl pyridinium
bromide (13.2.11), is synthesized from 3-hydroxypiridine, which is reacted with
dimethylaminocarbamoyl chloride, which gives 3-(dimethylaminocarbamoyl)piridine
(13.2.10). The last is reacted with methylbromide, giving pyridostigmine (13.2.11)
[44].
