The Food and Drug Administration (FDA) has approved Nipride RTU (sodium nitroprusside; Exela Pharma) in 0.9% sodium chloride injection for the immediate reduction of blood pressure. Nipride RTU is also approved for producing controlled hypotension to reduce bleeding during surgery and for the treatment of acute heart failure to reduce left ventricular end-diastolic pressure, pulmonary capillary wedge pressure, peripheral vascular resistance and mean arterial blood pressure.

Nipride RTU carries a Boxed Warning describing the possibility of excessive hypotension and cyanide toxicity. Sodium nitroprusside can cause precipitous decreases in blood pressure which can lead to irreversible ischemic injuries or death. Patients receiving the drug should be continuously monitored; elderly patients may be more sensitive to the hypotensive effects of the drug.

In addition, sodium nitroprusside metabolism can produce dose-related cyanide, which can be lethal. A patient’s ability to buffer cyanide will be exceeded in less than one hour at the maximum dose rate (10mcg/kg/min); patients with hepatic dysfunction may be more susceptible to toxicity. Infusions at the maximum rate should be limited to as short a duration as possible. An early sign of cyanide toxicity is increasing dosage requirement to maintain blood pressure control; if toxicity develops, the drug should be discontinued. 

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Sodium nitroprusside interacts with oxyhemoglobin to produce methemoglobin, cyanide, and nitric oxide (NO). NO then reacts with guanylate cyclase in vascular smooth muscle to produce cGMP that reduces intracellular calcium concentrations resulting in relaxation of vascular smooth muscle and consequent dilatation of peripheral arteries and veins. 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). Dilatation of the coronary arteries also occurs.

Nipride RTU will be available in a ready-to-use 100mL vial containing 0.9% sodium chloride and is stable for 24 months from manufacturing. Each 100mL vial contains 50mg of sodium nitroprusside (0.5mg/mL).

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