Nitroprusside sodium
Nitroprusside sodium (Nitropress)
Nitroprusside sodium
(nye-troh- PRUS-eyed)
Pregnancy Category: C Nitropress (Rx)

Classification: Antihypertensive, direct action on vascular smooth muscle

Action/Kinetics: Direct action on vascular smooth muscle, leading to peripheral vasodilation of arteries and veins. Acts on excitation-contraction coupling of vascular smooth muscle by interfering with both influx and intracellular activation of calcium. No effect on smooth muscle of the duodenum or uterus and is more active on veins than on arteries. May also improve CHF by decreasing systemic resistance, preload and afterload reduction, and improved CO. Onset (drug must be given by IV infusion): 0.5-1 min; peak effect: 1-2 min; t 1/2: 2 min; duration: Up to 10 min after infusion stopped. Reacts with hemoglobin to produce cyanmethemoglobin and cyanide ion. Caution must be exercised as nitroprusside injection can result in toxic levels of cyanide. However, when used briefly or at low infusion rates, the cyanide produced reacts with thiosulfate to produce thiocyanate, which is excreted in the urine.

Uses: Hypertensive crisis to reduce BP immediately. To produce controlled hypotension during anesthesia to reduce bleeding. Acute CHF. Investigational: In combination with dopamine for acute MI. Left ventricular failure with coadministration of oxygen, morphine, and a loop diuretic.

Contraindications: Compensatory hypertension where the primary hemodynamic lesion is aortic coarctation or AV shunting. Use to produce controlled hypotension during surgery in clients with known inadequate cerebral circulation or in moribund clients. Clients with congenital optic atrophy or tobacco amblyopia (both of which are rare). Acute CHF associated with decreased peripheral vascular resistance (e.g., high-output heart failure that may be seen in endotoxic sepsis). Lactation.

Special Concerns: Use with caution in hypothyroidism, liver or kidney impairment, during lactation, and in the presence of increased ICP. Geriatric clients may be more sensitive to the hypotensive effects of nitroprusside; also, a decrease in dose may be necessary in these clients due to age-related decreases in renal function.

Side Effects: Excessive hypotension. Large doses may lead to cyanide toxicity. Following rapid BP reduction: Dizziness, nausea, restlessness, headache, sweating, muscle twitching, palpitations, abdominal pain, apprehension, retching, retrosternal discomfort. Other side effects: Bradycardia, tachycardia, ECG changes, venous streaking, rash, methemoglobinemia, decreased platelet aggregation, flushing, hypothyroidism, ileus, irritation at injection site, hypothyroidism. Symptoms of thiocyanate toxicity: Blurred vision, tinnitus, confusion, hyperreflexia, seizures. CNS symptoms (transitory): Restlessness, agitation, increased ICP, and muscle twitching. Vomiting or skin rash.

Overdose Management: Symptoms: Excessive hypotension, cyanide toxicity, thiocyanate toxicity. Treatment: Measure cyanide levels and blood gases to determine venous hyperoxemia or acidosis. To treat cyanide toxicity, discontinue nitroprusside and give sodium nitrite, 4-6 mg/kg (about 0.2 mL/kg) over 2-4 min (to convert hemoglobin into methemoglobin); follow by sodium thiosulfate, 150-200 mg/kg (about 50 mL of the 25% solution). This regimen can be given again, at half the original doses, after 2 hr.

Drug Interactions: Concomitant use of other antihypertensives, volatile liquid anesthetics, or certain depressants nitroprusside response.

How Supplied: Injection: 25 mg/mL; Powder for injection: 50 mg

Dosage
?IV Infusion Only Hypertensive crisis.
Adults: average, 3 mcg/kg/min. Range: 0.3-10 mcg/kg/min. Smaller dose is required for clients receiving other antihypertensives. Pediatric: 1.4 mcg/kg/min adjusted slowly depending on the response.
Monitor BP and use as guide to regulate rate of administration to maintain desired antihypertensive effect. Do not exceed a rate of administration of 10 mcg/kg/min.