Guanidine is a small basic compound. Guanidine stimulates the neuromuscular junction presynaptically by inhibiting voltage-gated potassium (Kv) channels, leading to the enhanced release of acetylcholine in the synaptic cleft. This stimulatory effect of guanidine underlies its use in the therapy for the neuromuscular diseases. The hydrochloride salt of guanidine was approved by FDA for the reduction of the symptoms of muscle weakness and easy fatigability associated with the myasthenic syndrome of Eaton-Lambert.