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Nitroprusside Sodium

Pronunciation: nye-troe-PRUSS-ide SO-dee-uhm
Class: Agent for hypertensive emergencies

Trade Names

Nitropress
- Powder for injection 50 mg/vial

Nipride (Canada)

Pharmacology

Relaxes vascular smooth muscle and dilates peripheral veins and arteries.

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Indications and Usage

Immediate reduction of BP in hypertensive crisis; production of controlled hypotension to reduce bleeding during surgery; for acute congestive heart failure.

Unlabeled Uses

Has been used alone or with dopamine in acute MI.

Contraindications

Treatment of compensatory hypertension, in which primary hemodynamic lesion is aortic coarctation or arteriovenous shunting; to produce hypotension during surgery in patients with known inadequate cerebral circulation or in moribund patients (A.S.A. Class 5E) coming to emergency surgery; patients with congenital (Leber's) optic atrophy or with tobacco amblyopia; acute CHF associated with reduced peripheral vascular resistance.

Dosage and Administration

Give by IV infusion using infusion pump, preferably volmetric pump.

Adults and Children

IV 0.3 mcg/kg/min initially; titrate upward gradually every few minutes to desired effect. Do not exceed 10 mcg/kg/min. Do not use maximum rate for more than 10 min. Average rate of infusion is 3 mcg/kg/min; some patients require much lower doses, especially if other hypotensive agents are used.

General Advice

  • Dilute 50 mg in 2 mL D5W. Add to 250 to 500 mL D5W. Resulting solution is 200 mcg/mL or 100 mcg/mL. Use only D5W. No other medication should be infused with nitroprusside. Protect solution from light. However, it is not necessary to protect drip chamber or tubing.
  • Do not use if solution is discolored or if particulate matter is seen.

Storage/Stability

Store diluted solution at room temperature (59° to 86°F) for no longer than 24 h and protect from light.

Drug Interactions

Antihypertensives, ganglionic blocking agents, volatile anesthetics (eg, enflurane, halothane)

Additive hypotensive effects.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Evidence of rapid BP reduction (eg, abdominal pain; apprehension; diaphoresis; dizziness; headache; muscle twitching; nausea; palpitations; restlessness; retching; retrosternal discomfort); bradycardia; ECG changes; tachycardia.

Dermatologic

Flushing; venous streaking; irritation at infusion site; rash.

GI

Ileus.

Hematologic

Methemoglobinemia; decreased platelet aggregation.

Metabolic

Hypothyroidism.

Miscellaneous

Thiocyanate toxicity; cyanide toxicity; increased intracranial pressure.

Precautions

Warnings

Administration

Administration is not suitable for direct injection and requires dilution prior to infusion.

Cyanide toxicity

Accumulation of cyanide ion may occur.

Hypotension

Hypotension can cause significant drops in BP leading to irreversible ischemic injury or death. Requires appropriate monitoring equipment and experienced personnel.


Pregnancy

Category C .

Lactation

Undetermined.

Elderly

May be more sensitive to hypotensive effects.

Hepatic Function

Cyanide may accumulate in patients with hepatic function impairment.

Anesthesia

Patient's ability to compensate for anemia and hypovolemia may be diminished during anesthesia.

Cyanide toxicity

Infusions faster than 2 mcg/kg/min generate cyanide faster than body can dispose of it. Symptoms of cyanide toxicity include venous hyperoxemia with bright red venous blood, metabolic (lactic) acidosis, air hunger, confusion and death.

Intracranial pressure

Use with extreme caution in patients with elevated intracranial pressure; nitroprusside can increase intracranial pressure.

Methemoglobinemia

Clinically significant methemoglobinemia is seen rarely, but suspect condition in patients who have received more than 10 mg/kg of nitroprusside and who have signs of impaired oxygen delivery despite adequate cardiac output and arterial Po 2 . Blood may be chocolate brown.

Severe renal disease, anuria

Thiocyanate may accumulate.

Thiocyanate toxicity

Cyanide is eliminated in form of thiocyanate. When cyanide elimination is accelerated by infusion of thiosulfate or when prolonged infusions are used, thiocyanate levels may increase. Thiocyanate is neurotoxic (tinnitus, miosis, hyperreflexia) and toxicity may be life threatening.

Overdosage

Symptoms

Severe hypotension, dyspnea, loss of consciousness, metabolic acidosis, headache, death.

Patient Information

  • Instruct patient to report the following symptoms to health care provider: dizziness; retching, nausea, abdominal pain, chest pain, palpitations, tinnitus, or flushing.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.

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