Sodium nitroprusside (SNP), sold under the brand name Nitropress among others, is a medication used to lower blood pressure.

[3] This may be done if the blood pressure is very high and resulting in symptoms, in certain types of heart failure, and during surgery to decrease bleeding.

[4] Nitric oxide reduces both total peripheral resistance and venous return, thus decreasing both preload and afterload.

So, it can be used in severe congestive heart failure where this combination of effects can act to increase cardiac output.

[13][15] It is sometimes also used to induce hypotension (to reduce bleeding) for surgical procedures (for which it is also FDA, TGA, and MHRA labelled).

This compound has also been used as a treatment for aortic valve stenosis,[17] oesophageal varices,[18] myocardial infarction,[19] pulmonary hypertension,[20][21][22] respiratory distress syndrome in the newborn,[23][24] shock,[24] and ergot toxicity.

[25] Adverse effects by incidence and severity[13][15][26] Common Unknown frequency Serious Sodium nitroprusside should not be used for compensatory hypertension (e.g. due to an arteriovenous stent or coarctation of the aorta).

[15] Patients with conditions associated with a higher cyanide/thiocyanate ratio (e.g. congenital (Leber's) optic atrophy, tobacco amblyopia) should only be treated with sodium nitroprusside with great caution.

[13] Its use in pregnant women is advised against, although the available evidence suggests it may be safe, provided maternal pH and cyanide levels are closely monitored.

[15][27] Some evidence suggests sodium nitroprusside use in critically ill children may be safe, even without monitoring of cyanide level.

[31] As a result of its breakdown to nitric oxide (NO), sodium nitroprusside has potent vasodilating effects on arterioles and venules (arterial more than venous), whereas other nitrates exhibit more selectivity for veins (e.g.

[34] This mechanism is similar to that of phosphodiesterase 5 (PDE5) inhibitors such as sildenafil (Viagra) and tadalafil (Cialis), which elevate cGMP concentration by inhibiting its degradation by PDE5.

[47] This red-colored sodium salt dissolves in water or ethanol to give solutions containing the free complex dianion [Fe(CN)5NO]2−.

The iron center has a diamagnetic low-spin d6 electron configuration, although a paramagnetic long-lived metastable state has been observed by EPR spectroscopy.

Sodium nitroprusside is also used in microbiology, where it has been linked with the dispersal of Pseudomonas aeruginosa biofilms by acting as a nitric oxide donor.

[61] The nitroprusside reaction is a chemical test used to detect the presence of thiol groups of cysteine in proteins.

Proteins with the free thiol group give a red colour when added to a solution of sodium nitroprusside in aqueous ammonia.

[66] Sodium nitroprusside is similarly used as a presumptive test for the presence of alkaloids (amine-containing natural products) common in illicit substances.

The most common secondary amines encountered in forensic chemistry include 3,4-methylenedioxymethamphetamine (MDMA, the main component in ecstasy) and phenethylamines such as methamphetamine.

[8] Despite this, due to difficulties in its chemical preparation, it was not finally approved by the US FDA until 1974 for the treatment of severe hypertension.