Distigmine is a parasympathomimetic. Distigmine is similar to pyridostigmine

Pyridostigmine

Pyridostigmine is a parasympathomimetic and a reversible cholinesterase inhibitor. Since it is a quaternary amine, it is poorly absorbed in the gut and does not cross the blood-brain barrier, except possibly in stressful conditions.-Mode of action:...

 and neostigmine

Neostigmine

Neostigmine is a parasympathomimetic that acts as a reversible acetylcholinesterase inhibitor.- Synthesis :Neostigmine was first synthesized by Aeschlimann and Reinert in 1931....

but has a longer duration of action. It is available as tablets on prescription only. Distigmine has a greater risk of causing cholinergic crisis because of accumulation of the drug being more likely than with neostigmine or pyridostigmine and so distigmine is rarely used as a treatment for myasthenia gravis, unlike pyridostigmine and neostigmine.