A strong organic base existing primarily as guanidium ions at physiological pH. It is found in the urine as a normal product of protein metabolism. It is also used in laboratory research as a protein denaturant. (From Martindale, the Extra Pharmacopoeia, 30th ed and Merck Index, 12th ed) It is also used in the treatment of myasthenia and as a fluorescent probe in HPLC. [PubChem]
Indication
For the reduction of the symptoms of muscle weakness and easy fatigability associated with the myasthenic syndrome of Eaton-Lambert. It is not indicated for treating myasthenia gravis.
Pharmacology
Guanidine apparently acts by enhancing the release of acetylcholine following a nerve impulse. It also appears to slow the rates of depolarization and repolarization of muscle cell membranes.
Toxicity
LD50 = 475 mg/kg (oral, rat). Can cause severe gastrointestinal symptoms (nausea, vomiting and diarrhea), bone marrow suppression, renal insufficiency and other hematologic abnormalities (anemia, leucopenia). Severe guanidine intoxication is characterized by nervous hyperirritability, fibrillary tremors and convulsive contractions of muscle, salivation, vomiting, diarrhea, hypoglycemia, and circulatory disturbances.
