Also Known As: Pyridostigmine, Mestinon, Regonol
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.
Pyridostigmine is used to treat muscle weakness in people with myasthenia gravis and to combat the effects of curariform drug toxicity. Pyridostigmine bromide has been FDA approved for military use during combat situations as an agent to be given prior to exposure to the nerve agent Soman in order to increase survival. Used in particular during the first Gulf War, pyridostigmine bromide has been implicated as a causal factor in Gulf War syndrome.
Pyridostigmine sometimes is used to treat orthostatic hypotension. and it may also be of benefit in chronic axonal polyneuropathy. 
It is also being prescribed 'off-label' for the Postural Tachycardia Syndrome
Pyridostigmine bromide is available under the trade names Mestinon (Valeant Pharmaceuticals) and Regonol.