Sodium Nitroprusside Injection

Sodium Nitroprusside Injection

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The principal pharmacological action of sodium nitroprusside (SNP) is the relaxation of vascular smooth muscle and consequent dilatation of peripheral arteries and veins. Sodium nitroprusside is more active on veins than on arteries, but this selectivity is much less marked than that of nitroglycerin. Dilatation of the veins promotes peripheral pooling of blood and decreases venous return to the heart, thereby reducing left ventricular end diastolic pressure and pulmonary capillary wedge pressure (preload). Arteriolar relaxation reduces systemic vascular resistance, systolic arterial pressure, and mean arterial pressure (afterload).

Baseline-controlled clinical trials have uniformly shown that the hypotensive effect of sodium nitroprusside is seen within a minute or two after the start of an adequate infusion in all populations. With increasing rates of infusion, sodium nitroprusside has been able to lower blood pressure without an observed limit of effect, with dissipation almost as rapidly after an infusion is discontinued. The hypotensive effect of sodium nitroprusside has also been shown to be associated with reduced blood loss in a variety of major surgical procedures. Finally, administration of sodium nitroprusside causes reductions in peripheral resistance, increases in cardiac output, and reductions in left ventricular filling pressure in patients with acute congestive heart failure and increased peripheral vascular resistance.

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IMPORTANT SAFETY INFORMATION for Sodium Nitroprusside Injection

See full Prescribing Information for complete WARNINGS.

WARNING - EXCESSIVE HYPOTENSION:

Sodium nitroprusside can cause precipitous decreases in blood pressure, which can lead to irreversible ischemic injuries or death in patients not properly monitored. Use only with continuous blood pressure monitoring.

WARNING - CYANIDE TOXICITY:

Except when used briefly or at low (< 2 mcg/kg/min) infusion rates, sodium nitroprusside gives rise to important quantities of cyanide ions, which can reach toxic, potentially lethal levels. The usual dose rate is 0.5-10 mcg/kg/min, but infusion at the maximum dose rate should never last more than 10 minutes. If blood pressure has not been adequately controlled after 10 minutes of infusion at the maximum rate, administration should be terminated immediately.

Sodium nitroprusside is not suitable for direct injection; further dilute in sterile 5% dextrose before infusion.

INDICATIONS & USAGE: sodium nitroprusside is indicated for

  • The immediate reduction of blood pressure of adult and pediatric patients in hypertensive crises. Concomitant longer-acting antihypertensive medication should be administered so that the duration of treatment with sodium nitroprusside can be minimized.
  • Producing controlled hypotension in order to reduce bleeding during surgery
  • The treatment of acute congestive heart failure

CONTRAINDICATIONS: sodium nitroprusside should NOT be used

  • In the treatment of compensatory hypertension, where the 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
  • In patients with congenital (Leber's) optic atrophy or with tobacco amblyopia
  • For the treatment of acute congestive heart failure associated with reduced peripheral vascular resistance

PRECAUTIONS:

  • General: Can cause increases in intracranial pressure. Use with extreme caution in patients whose intracranial pressure is already elevated.
  • Hepatic: Patients with hepatic insufficiency are more susceptible to cyanide toxicity; use caution.
  • Use in Anesthesia: If possible, correct pre-existing anemia and hypovolemia prior to administration when sodium nitroprusside is used for controlled hypotension during anesthesia. Hypotensive anesthetic techniques may also cause abnormalities of the pulmonary ventilation/perfusion ratio; patients intolerant of these abnormalities may require a higher fraction of inspired oxygen. Use extreme caution in patients who are poor surgical risks (A.S.A. Class 4 and 4E).
  • Lab Tests: The cyanide-level assay is technically difficult and cyanide levels in body fluids other than packed red blood cells are difficult to interpret. Cyanide toxicity will lead to lactic acidosis and venous hyperoxemia, but these findings may not be present until an hour or more after the cyanide capacity of the body's red-cell mass has been exhausted.
  • Drug Interactions: The hypotensive effect of sodium nitroprusside is augmented by that of most other hypotensive drugs including ganglionic blocking agents, negative inotropic agents, and inhaled anesthetics.
  • Pregnancy: Use during pregnancy only when there is no appropriate alternative for a particular patient as cyanide toxicity may be fatal to the fetus.
  • Nursing Mothers: No information about the presence of sodium nitroprusside in human milk, the effects on the breastfed infant, or the effects on milk production.

ADVERSE REACTIONS:

Excessive hypotension, cyanide toxicity, methemoglobinemia, thiocyanate toxicity, bradycardia, electrocardiographic changes, tachycardia, rash, hypothyroidism, ileus, decreased platelet aggregation, increased intracranial pressure, flushing, venous streaking and irritation at the infusion site.

OVERDOSAGE:

can be manifested as excessive hypotension, cyanide toxicity, or thiocyanate toxicity. Reasonable suspicion of cyanide toxicity is grounds for initiation of treatment; results of laboratory tests should not be awaited. Refer to Prescribing Information for information on the treatment of cyanide toxicity.

See Full Prescribing Information, including WARNINGS on excessive hypotension and cyanide toxicity.

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