Details About Overdose or Poisoning Generic Salt :: Nitroprusside
Drug Pharmacology ::
I. Pharmacology. Nitroprussideis an ultra-short-acting titratable parenteral hypotensive agent thatacts by directly relaxing vascular smooth muscle as a nitric oxidedonor. Both arterial dilation and venous dilation occur; the effect ismore marked in patients with hypertension. A small increase in heartrate may be observed in hypertensive patients. Intravenousadministration produces nearly immediate onset of action, with aduration of effect of 1–10 minutes. Resistance may occur with highrenin activity. Nitroprusside is metabolized rapidly, with a serumhalf-life of about 1–2 minutes. Cyanide is produced during metabolismand is converted to the less toxic thiocyanate. Thiocyanate has ahalf-life of 2–3 days and accumulates in patients with renalinsufficiency.
Drug Indications ::
Rapid control of severe hypertension (eg, in patients with stimulant intoxication or monoamine oxidase inhibitor toxicity).
Arterial vasodilation in patients with ergot-induced peripheral arterial spasm.
Drug Contra-Indications ::
Compensatoryhypertension, for example, in patients with increased intracranialpressure (eg, hemorrhage or mass lesion) or patients with coarctationof the aorta. If nitroprusside is required in such patients, use withextreme caution.
Use with caution in patients with hepatic insufficiency, because cyanide metabolism may be impaired.
Drug Adverse Effects ::
IV. Adverse effects
Nausea, vomiting, headache, and sweating may be caused by excessively rapid lowering of blood pressure.
Cyanide toxicity,manifested by altered mental status and metabolic (lactic) acidosis,may occur with rapid high-dose infusion (10–15 mcg/kg/min) for periodsof 1 hour or longer. Patients with depleted thiosulfate stores (eg,malnourished) may have elevated cyanide levels at lower infusion rates.Continuous intravenous infusion of hydroxocobalamin, 25 mg/h (seeHydroxocobalamin), or thiosulfate (Thiosulfate, Sodium) has been usedto limit cyanide toxicity. If severe cyanide toxicity occurs,discontinue the nitroprusside infusion and consider antidotal doses ofthiosulfate and sodium nitrite (Nitrite, Sodium and Amyl) or high-dosehydroxocobalamin (Hydroxocobalamin).
Thiocyanate intoxication,manifested by disorientation, delirium, muscle twitching, andpsychosis, may occur with prolonged high-dose nitroprusside infusions(usually 3mcg/kg/min for 48 hours or longer), particularly in patients with renalinsufficiency (may occur at rates as low as 1 mcg/kg/min). Thiocyanateproduction is also enhanced by co-administration of sodium thiosulfate.Monitor thiocyanate levels if the nitroprusside infusion lasts morethan 1–2 days; toxicity is associated with thiocyanate levels of 50mg/L or greater. Usually treat by lowering the infusion rate ordiscontinuing the use of nitroprusside. Thiocyanate is removedeffectively by hemodialysis.
Rebound hypertension may be observed after sudden discontinuance.
E. Methemoglobinemia may be observed in patients receiving more than 10 mg/kg but is typically not severe.
F. Use in pregnancy. FDAcategory C (indeterminate; see Table III–1). It may cross the placentaand may affect uterine blood flow; however, it has been usedsuccessfully in pregnant women.
Drug Lab Interactions ::
Drug or laboratory interactions. A hypotensive effect is potentiated by other antihypertensive agents and inhalational anesthetics.
Drug Dose Management ::
Dosage and method of administration
Use only in an emergency or intensive care setting with the capability of frequent or continuous blood pressure monitoring.
Dissolve50 mg of sodium nitroprusside in 3 mL of 5% dextrose; then dilute thissolution in 250, 500, or 1000 mL of 5% dextrose to achieve aconcentration of 200, 100, or 50 mcg/mL, respectively. Protect thesolution from light to avoid photodegradation (as evidenced by a colorchange) by covering the bottle and tubing with paper or aluminum foil.
Startwith an intravenous infusion rate of 0.3 mcg/kg/min with a controlledinfusion device and titrate to desired effect. The average dose is 3mcg/kg/min in children and adults (range 0.5–10 mcg/kg/min).
1. Themaximum rate should not exceed 10 mcg/kg/min to avoid the risk of acutecyanide toxicity. If there is no response after 10 minutes at themaximum rate, discontinue the infusion and use an alternativevasodilator (eg, phentolamine; see Phentolamine).
2. Sodiumthiosulfate (see Thiosulfate, Sodium) has been added in a ratio of 10mg thiosulfate to 1 mg nitroprusside to reduce or prevent cyanidetoxicity.
Drug Chemical Formulations ::
Parenteral. Nitroprusside sodium (Nitropress and others), 50 mg of lyophilized powder for reconstitution in 2- and 5-mL vials.
The suggested minimum stocking level to treat a 70-kg adult for the first 24 hours is 24 vials.