Difference between revisions of "Sodium nitroprusside"
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Latest revision as of 15:48, 27 September 2010
| Sodium nitroprusside | |
|---|---|
| Sample of sodium nitroprusside | |
| Sodium nitroprusside | |
| Sodium pentacyanonitrosylferrate(II) | |
| Other names Sodium nitroprusside Sodium nitroferricyanide Sodium pentacyanonitrosylferrate SNP | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 14402-89-2  , (anhydrous)13755-38-9 (dihydrate) |
| PubChem | 26256 |
| EC number | 238-373-9 |
| DrugBank | APRD01143 |
| RTECS number | LJ8750000 |
| ATC code | C02 |
| style="background: #F8EABA; text-align: center;" colspan="2" | Properties | |
| Molecular formula | Na2[Fe(CN)5NO] |
| Molar mass | 261.92 g/mol (anhydrous) 297.95 g/mol (dihydrate) |
| Appearance | red powder |
| Solubility in water | good |
| Solubility in ethanol | soluble |
| style="background: #F8EABA; text-align: center;" colspan="2" | Structure | |
| octahedral at Fe | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Pharmacology | |
| Routes of administration |
Intravenous |
| Metabolism | Circulatory |
| Elimination half-life |
2 minutes (metabolites: several days) |
| Excretion | Renal |
| Legal status |
|
| Pregnancy category |
C |
| style="background: #F8EABA; text-align: center;" colspan="2" | Hazards | |
| EU Index | Not listed |
| Flash point | Non-flammable |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Sodium nitroprusside is the inorganic compound with the formula Na2[Fe(CN)5NO]·2H2O.[1] This red-coloured salt, which is often abbreviated SNP, is a potent vasodilator.
Contents
Structure and properties
Nitroprusside is a complex anion that features an octahedral ferrous center surrounded by five tightly bound cyanide ligands and one linear nitric oxide ligand. The molecular symmetry is C4v. Linear nitrosyl ligands are assigned a single positive charge, thus the iron is assigned an oxidation state of 2+. As such it has a low-spin d6 electron configuration and is diamagnetic. Its chemical reactions are mainly associated with the NO ligand.[2]
The sodium salt dissolves in water and to a lesser extent in ethanol to give solutions containing the dianion [Fe(CN)5NO]2−. This metal nitrosyl complex is the active agent in medical applications.
Ball-and-stick model of part of the crystal structure of sodium nitroprusside dihydrate[3]
Medical pharmacology
Sodium nitroprusside (SNP) has potent vasodilating effects in arterioles and venules (arterioles more than venules). It is administered intravenously in cases of acute hypertensive emergency. SNP breaks down in circulation to release nitric oxide (NO). NO activates guanylate cyclase in vascular smooth muscle and increases intracellular production of cGMP. cGMP stimulates calcium movement from the cytoplasm to the endoplasmic reticulum and reduces calcium available to bind with calmodulin. Vascular smooth muscle relaxes and vessels dilate.
In the human heart, nitric oxide reduces both total peripheral resistance as well as venous return, thus decreasing both preload and afterload. For this reason, it can be used in severe cardiogenic heart failure where this combination of effects can act to increase cardiac output. In situations where cardiac output is normal, the effect is to reduce blood pressure.
Metabolism and toxicity
Sodium nitroprusside slowly breaks down to release 5 cyanide ions, especially upon exposure to UV light. Despite the toxic potential of cyanide, nitroprusside remains an effective drug in certain clinical circumstances such as malignant hypertension or for rapid control of blood pressure during vascular surgery and neurosurgery. By the action of the enzyme rhodanase, the cyanide can be detoxified by reaction with a sulfur donor such as thiosulfate. In the absence of sufficient thiosulfate, cyanide ions can quickly reach toxic levels.[4] The half-life of nitroprusside is 1–2 minutes although thiocyanate has an excretion half life of several days.
Use in research
In physiology research, sodium nitroprusside is frequently used to test endothelium-independent vasodilation. Iontophoresis, for example, allows local administration of the drug, preventing the systemic effects listed above but still inducing local microvascular vasodilation.
Sodium nitroprusside is also used in the presence of buffers as a reagent for ketone strips, which test the ketone levels in the urine of a diabetic. Color change on the strip indicates the relative concentration of ketones.
In combination with acetaldehyde it is also used as a color reagent in the development of thin layer chromtography plates, particularly for N-heterocyclic compounds.
Sodium nitroprusside is also used in a urinalysis test, called the cyanide nitroprusside test, also known as Brand's test. In this test sodium cyanide is added first to urine and let stand for approximately 10 minutes. In this time disulfide bonds will be broken by the released cyanide. The destruction of disulfide bonds liberates cysteine from cystine and homocysteine from homocystine. Next sodium nitroprusside is added to the solution and it reacts with the newly freed sulfhydryl groups. The test will turn a red/purple color if the test is positive indicating that there was significant amounts of amino acid in the urine (aminoaciduria). Cysteine, cystine, homocysteine and homocystine all react when present in the urine when this test is performed. This test can indicate inborn errors of amino acid transporters such as cystinuria, which results from pathology in the transport of dibasic amino acids.
SNP is also used in microbiology, where it has been linked with the dispersal of Pseudomonas aeruginosa biofilms by acting as a Nitric Oxide donor.
References
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zh:硝普钠- ↑ A. R. Butler, I. L. Megson (2002). "Non-Heme Iron Nitrosyls in Biology". Chemical Reviews. 102: 1155–1165. doi:10.1021/cr000076d.
- ↑ Coppens, P.; Novozhilova, I.; Kovalevsky, A. (2002). "Photoinduced Linkage Isomers of Transition-Metal Nitrosyl Compounds and Related Complexes". Chem. Rev. 102: 861–883. doi:10.1021/cr000031c.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ http://www.rxlist.com/nitropress-drug.htm
