Trimethaphan 2957747 195991004 2008-03-05T07:22:18Z Hobied 6247763 /* Effects */ {{Drugbox| | IUPAC_name = decahydro-2-oxo-1,3-bis(phenylmethyl)-<br>thieno(1',2':1,2)thieno(3,4-d)imidazol-5-ium | image = Trimethaphan.svg | width = 250 px | CAS_number = 7187-66-8 | ATC_prefix = C02 | ATC_suffix = BA01 | ATC_supplemental = | PubChem = 23576 | DrugBank = APRD00044 | C = 22 | H = 25 | N = 2 | O = 1 | S = 1 | molecular_weight = 365.513 g/mol | molar_refractivity = | bioavailability = | metabolism = | elimination_half-life = | excretion = | pregnancy_AU = | pregnancy_US = | legal_status = | routes_of_administration = Oral, [[Intramuscular injection|IM]], [[Intravenous therapy|IV]] }} '''Trimethaphan''' is a drug that counteracts [[cholinergic]] transmission at the [[ganglion type receptor|ganglion type]] of [[nicotinic receptor]]s of the [[autonomic ganglia]] and therefore blocks both the [[sympathetic nervous system]] and the [[parasympathetic nervous system]]. It acts as a non-depolarizing [[competitive antagonist]] at the nicotinic [[acetylcholine]] receptor, is short-acting, and is given intravenously. ==Effects== Trimethaphan is a sufonium compound and therefore carries a positive charge. Being charged, it cannot cross [[lipid]] [[cell membrane]]s, such as those that comprise the [[blood-brain barrier]]. Due to this, trimethaphan does not have any effect on the [[central nervous system]]. The [[ciliary muscle]] of the [[eye]] functions to round the [[Lens (anatomy)|lens]] for [[accommodation]] and is controlled mainly by parasympathetic system input. With administration of a ganglion-blocking drug, the ciliary muscle cannot contract (cycloplegia) and the patient loses the ability to focus their eyes. Trimethaphan has a strong effect on the [[cardiovascular system]]. The size of blood vessels is primarily controlled by the sympathetic nervous system. Loss of sympathetic system input to the [[blood vessel]]s causes them to get larger ([[vasodilation]]) which has the effect of lowering [[blood pressure]]. [[Postural hypotension]] is a common side effect of such drugs. Effects on the [[heart]] include a decreased force of contraction and an increase in heart rate ([[tachycardia]]). Although it is important to note that this reflexive tachycardia can be diminished or undetected because Trimethaphan is also blocking the sympathetic ganglia innervating the heart. The motility of the [[gastrointestinal tract]] is regulated by the parasympathetic system, and blockage of this input results in diminished motility and [[constipation]]. ==Therapeutic uses== The therapeutic uses of trimethaphan are very limited due to the competition from newer drugs that are more selective in their actions and effects produced. It is occasionally used to treat a [[hypertensive crisis]] and [[dissecting aortic aneurysm]], to treat [[pulmonary edema]], and to reduce bleeding during [[neurosurgery]]. ==Adverse effects== The adverse effects are due to its nonselective ganglion block and are described in the "Effects" section above. The side effects are severe enough to limit this drugs use to emergency and acute situations. ==References== * "Ganglion-blocking Drugs." ''Drug Benefits and Risks: International Textbook of Clinical Pharmacology.'' (2001). ISBN 0-471-89927-5 * Katzung, Bertram G. ''Basic and Clinical Pharmacology, 9th ed.'' (2004). ISBN 0-07-141092-9 {{Antihypertensives and diuretics}} [[Category:Anticholinergics]]