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.

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.

Iobenguane, mainly use as a radiopharmaceutical, used in a scintigraphy method called MIBG scan. Synthetic guanethidine derivative that locates phaeochromocytomas and neuroblastomas. The radioisotope used can either be iodine-123 for imaging or iodine-131 for destruction of tissues that metabolize noradrenaline. Iodine 123 is a cyclotron-produced radionuclide that decays to Te 123 by electron capture. Images are produced by a I123 MIBG scintigraphy. It localizes to adrenergic tissue and thus can be used to identify the location of tumors such as pheochromocytomas and neuroblastomas. With I-131 it can also be used to eradicate tumor cells that take up and metabolize norepinephrine. The radioactive iodine component is responsible for its imaging properties. Iobenguane and guanethidine are substrates for the norepinephrine transporter (NET) and accumulate by the uptake mechanism into presynaptic nerve endings. Unlike norepinephrine, these drugs are protonated under physiologic conditions; therefore, they do not cross the blood–brain barrier and in vivo uptake is limited primarily to systemic neuronal tissue. The accumulation of iobenguane in myocardial tissue is also dictated by the high fraction of aortic blood flow that enters the coronary arteries. This physiology constitutes an ideal molecular targeting mechanism for diagnosis of various cardiac diseases, including heart failure, heart transplant rejection, ischemic heart disease, dysautonomia, and drug-induced cardiotoxicity, as well as cardiac neuropathy related to diabetes mellitus and Parkinson disease