Nitroprusside

NITROPRESS

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Nitroprusside ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Nitroprusside ballicule

What it isDirect nitric oxide donor dilating arteries and veins; hypertensive emergency and acute afterload reduction.

Why this oneOnset and offset within seconds give finer control than any other agent.

What limits it⚑ Cyanide toxicity presents with unexplained acidosis; limit exposure and monitor closely. Protect the infusion from light.

Nitroprusside molecular structure (skeletal formula) — Molecular structure: Nitroprusside

FDA label

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BOXED WARNING Not for direct injection (must dilute in D5W); can cause precipitous BP decreases — continuous BP monitoring required; generates cyanide ion which can reach lethal levels; never infuse at max rate (10 mcg/kg/min) for more than 10 min — terminate if BP not controlled by then.

FDA dosing	Population	Start	Target	Max
BP reduction / hypertension (IV infusion)	Adults and pediatric patients	0.3 mcg/kg/min IV infusion (pump required)	Average effective rate ~3 mcg/kg/min IV; usual range 0.5–10 mcg/kg/min	10 mcg/kg/min IV (never >10 min at max rate)
Acute congestive heart failure	Adults and pediatric patients	0.3 mcg/kg/min IV, titrate guided by invasive hemodynamic monitoring with urine output	Titrate until cardiac output no longer increases, BP cannot be lowered further without compromising perfusion, or max rate reached	10 mcg/kg/min IV

Titration Titrate upward every few minutes; confirm drug effect at any rate for an additional 5 minutes before increasing.

Renal Prolonged infusion: do not exceed 3 mcg/kg/min (anuric patients: 1 mcg/kg/min) to keep thiocyanate <1 mmol/L; measure thiocyanate daily if faster

Hepatic Undefined

Cyanide accumulates when infusion >2 mcg/kg/min or total >500 mcg/kg given faster than 2 mcg/kg/min; infusion at 10 mcg/kg/min must never last >10 min.

Instructions

Dilute 50 mg in 250–1000 mL sterile D5W; not suitable for direct injection
Protect diluted solution from light (opaque sleeve/foil); stable 24 h if protected
Do not use discolored (blue/green/bright red) or particulate-containing solutions
No other drugs in the same solution; do not use flexible container in series connections
Infuse only via infusion pump (preferably volumetric), never gravity/mechanical clamps
Continuous BP monitoring required (continually reinflated cuff or intra-arterial sensor)
Use special caution in elderly (more sensitive to hypotensive effect)
Sodium thiosulfate co-infusion (5–10× nitroprusside rate) can reduce cyanide hazard but may potentiate hypotension and cause thiocyanate toxicity/hypovolemia

Available strengths

inj 25 mg/mL

Contraindications

Compensatory hypertension (aortic coarctation, arteriovenous shunting)
Induced hypotension during surgery in patients with inadequate cerebral circulation, or moribund (A.S.A. Class 5E) patients in emergency surgery
Congenital (Leber's) optic atrophy or tobacco amblyopia (defective/absent rhodanase — high cyanide/thiocyanate ratios)
Acute CHF with reduced peripheral vascular resistance (e.g., high-output failure of endotoxic sepsis)

Cautions

Excessive hypotension → irreversible ischemic injury or death without continuous monitoring
Cyanide toxicity (potentially lethal) except at brief/low (<2 mcg/kg/min) rates; lab tests give imperfect guidance
Methemoglobinemia in patients receiving >10 mg/kg (treat with methylene blue 1–2 mg/kg IV, cautiously)
Thiocyanate toxicity with prolonged/rapid infusion, especially in renal impairment (neurotoxic at 60 mg/L; life-threatening at 200 mg/L); interferes with thyroid iodine uptake
Elderly patients more sensitive to hypotensive effects

Adverse reactions

Too-rapid BP reduction: abdominal pain, apprehension, diaphoresis, dizziness, headache, muscle twitching, nausea, palpitations, restlessness, retching, retrosternal discomfort (resolve on slowing infusion)
Bradycardia, tachycardia, ECG changes
Increased intracranial pressure
Methemoglobinemia; thiocyanate toxicity
Rash; hypothyroidism; ileus; decreased platelet aggregation
Flushing, venous streaking, infusion-site irritation

Pregnancy Undefined

Lactation Undefined

Cost

Nitroprusside (NITROPRESS)

Strength		#/mo	generic $/unit	CostPlus
25 mg/mL	inj	per unit		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Nitroprusside is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

⚠ BOXED WARNINGS

Cyanide toxicity
Precipitous blood pressure decreases

Classes and tags

Clinical profile

Therapeutic safety burden4 / 4

Overdose danger3 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Defining liabilityRapid hypotension and cyanide poisoning

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