Acquired myasthenia gravis (MG) is a chronic autoimmune disorder of the neuromuscular junction, characterized clinically by muscle weakness and abnormal fatigability on exertion. Current guidelines and recommendations for MG treatment are based largely on clinical experience, retrospective analyses and expert consensus. Pyridostigmine (under the trade names Mestinon (Valeant Pharmaceuticals)), has been used as a treatment for MG for over 50 years and is generally considered safe. It is suitable as a long-term treatment in patients with generalized non-progressive milder disease, and as an adjunctive therapy in patients with severe disease who are also receiving immunotherapy. Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft by competing with acetylcholine for attachment to acetylcholinesterase, thus slowing down the hydrolysis of acetylcholine, and thereby increases efficiency of cholinergic transmission in the neuromuscular junction and prolongs the effects of acetylcholine. The side effects of Mestinon are most commonly related to over dosage and generally are of two varieties, muscarinic and nicotinic. Among those in the former group are nausea, vomiting, diarrhea, abdominal cramps, increased peristalsis, increased salivation, increased bronchial secretions, miosis and diaphoresis. Nicotinic side effects are comprised chiefly of muscle cramps, fasciculation and weakness. Muscarinic side effects can usually be counteracted by atropine, but for reasons shown in the preceding section the expedient is not without danger. As with any compound containing the bromide radical, a skin rash may be seen in an occasional patient. Such reactions usually subside promptly upon discontinuance of the medication.