It's an acetylcholinesterase inhibitor similar to Mestinon (pyridostigmine):

"Ambenonium is used less commonly than neostigmine or pyridostigmine but may be preferred in patients hypersensitive to the bromide ion. Ambenonium produces fewer muscarinic side effects than neostigmine, but more than pyridostigmine."
http://neurolex.org/wiki/Category:Ambenonium

Abby
just googling around