Sodium nitroprusside
Encyclopedia
Sodium nitroprusside is the inorganic compound
with the formula
Na2[Fe(CN)5NO]·2H2O. This red-coloured salt, which is often abbreviated SNP, is a potent vasodilator. The sodium salt dissolves in water and to a lesser extent in ethanol to give solutions containing the dianion [Fe(CN)5NO]2−.
ferrous centre 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.
Ball-and-stick model
of part of the crystal structure
of sodium nitroprusside dihydrate
s (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, which allow vessels to 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
.
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. The cyanide can be detoxified by reaction with a sulfur
-donor such as thiosulfate
, catalysed by the enzyme rhodanese. In the absence of sufficient thiosulfate, cyanide ions can quickly reach toxic levels. The half-life of nitroprusside is 1–2 minutes, but the metabolite thiocyanate
has an excretion half-life of several days.
, 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. Colour change on the strip indicates the relative concentration of ketones.
Sodium nitroprusside is often used as a reference compound for the calibration of Mössbauer spectrometer. It is also used as an analytical reagent in qualitative organic analysis.
In combination with acetaldehyde
it is also used as a colour 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 bond
s 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 colour 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.
in deionized water to a suspected drug, followed by the addition of 2 volumes of an aqueous sodium carbonate
solution. The test turns blue for some secondary amines. The most common secondary amines encountered in forensic chemistry include 3,4-methylenedixoymethamphetamine (MDMA, the main component in Ecstasy), and phenethylamines such as methamphetamine
and amphetamine
.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Na2[Fe(CN)5NO]·2H2O. This red-coloured salt, which is often abbreviated SNP, is a potent vasodilator. The sodium salt dissolves in water and to a lesser extent in ethanol to give solutions containing the dianion [Fe(CN)5NO]2−.
Structure and properties
Nitroprusside is a complex anion that features an octahedralOctahedral molecular geometry
In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron...
ferrous centre surrounded by five tightly bound cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
ligands and one linear nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
ligand. The molecular symmetry
Symmetry group
The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...
is C4v. Linear nitrosyl ligands
Metal nitrosyl
Metal nitrosyl complexes are complexes that contain nitric oxide, NO, bonded to a transition metal. Many kinds of nitrosyl complexes are known, which vary both in structure and coligand.-Bonding and structure:...
are assigned a single positive charge, thus the iron is assigned an oxidation state of 2+. As such it has a low-spin
Crystal field theory
Crystal field theory is a model that describes the electronic structure of transition metal compounds, all of which can be considered coordination complexes. CFT successfully accounts for some magnetic properties, colours, hydration enthalpies, and spinel structures of transition metal complexes,...
d6 electron configuration and is diamagnetic
Diamagnetism
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. Specifically, an external magnetic field alters the orbital velocity of electrons around their nuclei, thus changing the...
. Its chemical reactions are mainly associated with the NO ligand.
Ball-and-stick model
Ball-and-stick model
In chemistry, the ball-and-stick model is a molecular model of a chemical substance which is to display both the three-dimensional position of the atoms and the bonds between them...
of part of the crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
of sodium nitroprusside dihydrate
Medical pharmacology
Sodium nitroprusside (Abbreviated SNP, brand name: Nitropress) has potent vasodilating effects in arterioles and venuleVenule
A venule is a very small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins. Venules range from 8 to 100μm in diameter and are formed when capillaries unite .Venules are blood vessels that drain blood...
s (arterioles more than venules). It is administered intravenously
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
in cases of acute hypertensive emergency
Hypertensive emergency
Malignant hypertension or hypertensive emergency is severe hypertension with acute impairment of an organ system and the possibility of irreversible organ-damage...
. SNP breaks down in circulation to release nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
(NO). NO activates guanylate cyclase
Guanylate cyclase
-Reaction:Guanylate cyclase catalyzes the reaction of guanosine triphosphate to 3',5'-cyclic guanosine monophosphate and pyrophosphate:-Types:...
in vascular smooth muscle and increases intracellular production of cGMP
Cyclic guanosine monophosphate
Cyclic guanosine monophosphate is a cyclic nucleotide derived from guanosine triphosphate . cGMP acts as a second messenger much like cyclic AMP...
. cGMP stimulates calcium movement from the cytoplasm to the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
and reduces calcium available to bind with calmodulin. Vascular smooth muscle relaxes, which allow vessels to dilate.
In the human heart, nitric oxide reduces both total peripheral resistance as well as venous return, thus decreasing both preload and afterload
Afterload
Afterload is the tension or stress developed in the wall of the left ventricle during ejection. Following Laplace's law, the tension upon the muscle fibers in the heart wall is the product of the pressure within the ventricle, multiplied by the volume within the ventricle, divided by the wall...
. 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
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
.
Metabolism and toxicity
Sodium nitroprusside slowly breaks down to release 5 cyanideCyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
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
Malignant hypertension
Malignant hypertension or hypertensive emergency is severe hypertension with acute impairment of an organ system and the possibility of irreversible organ-damage...
or for rapid control of blood pressure during vascular surgery and neurosurgery. The cyanide can be detoxified by reaction with a sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
-donor such as thiosulfate
Sodium thiosulfate
Sodium thiosulfate , also spelled sodium thiosulphate, is a colorless crystalline compound that is more familiar as the pentahydrate, Na2S2O3•5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.”...
, catalysed by the enzyme rhodanese. In the absence of sufficient thiosulfate, cyanide ions can quickly reach toxic levels. The half-life of nitroprusside is 1–2 minutes, but the metabolite thiocyanate
Thiocyanate
Thiocyanate is the anion [SCN]−. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates...
has an excretion half-life of several days.
Use in research
In physiology research, sodium nitroprusside is frequently used to test endothelium-independent vasodilation. IontophoresisIontophoresis
Iontophoresis is a technique using a small electric charge to deliver a medicine or other chemical through the skin. It is basically an injection without the needle...
, 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. Colour change on the strip indicates the relative concentration of ketones.
Sodium nitroprusside is often used as a reference compound for the calibration of Mössbauer spectrometer. It is also used as an analytical reagent in qualitative organic analysis.
In combination with acetaldehyde
Acetaldehyde
Acetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
it is also used as a colour 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 bond
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...
s will be broken by the released cyanide. The destruction of disulfide bonds liberates cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
from cystine
Cystine
Cystine is a dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. This organosulfur compound has the formula 2. It is a white solid, and melts at 247-249 °C...
and homocysteine
Homocysteine
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...
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 colour if the test is positive indicating that there was significant amounts of amino acid in the urine (aminoaciduria
Aminoaciduria
Aminoaciduria is the presence of amino acids in the urine. Small amounts of amino acids are also present in normal urine. Increased total urine amino acids may result from metabolic disorders, chronic liver disease or renal disorders. Aminoacidurias can be divided into primary and secondary...
). Cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
, cystine
Cystine
Cystine is a dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. This organosulfur compound has the formula 2. It is a white solid, and melts at 247-249 °C...
, homocysteine
Homocysteine
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...
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
Cystinuria
Cystinuria is an inherited autosomal recessive disease that is characterized by the formation of cystine stones in the kidneys, ureter, and bladder.-Signs and symptoms:Cystinuria is a cause of persistent kidney stones...
, 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
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
biofilms by acting as a nitric oxide donor.
Use in Forensic Science
Sodium nitroprusside is used by forensic chemists in a preliminary test in the identification of illicit substances. The test, called Simon's test, is performed by adding 1 volume of a solution of SNP and acetaldehydeAcetaldehyde
Acetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
in deionized water to a suspected drug, followed by the addition of 2 volumes of an aqueous sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
solution. The test turns blue for some secondary amines. The most common secondary amines encountered in forensic chemistry include 3,4-methylenedixoymethamphetamine (MDMA, the main component in Ecstasy), and phenethylamines such as methamphetamine
Methamphetamine
Methamphetamine is a psychostimulant of the phenethylamine and amphetamine class of psychoactive drugs...
and amphetamine
Amphetamine
Amphetamine or amfetamine is a psychostimulant drug of the phenethylamine class which produces increased wakefulness and focus in association with decreased fatigue and appetite.Brand names of medications that contain, or metabolize into, amphetamine include Adderall, Dexedrine, Dextrostat,...
.