Overview Nitroprusside is a potent intravenous drug used to control hypertension.
Nitroprusside is a smooth muscle relaxant which causes vasodilation of peripheral arteries and veins. Peripheral pooling of blood reduces venous return to the heart. This acts to decrease the workload on the heart.
Systemic vascular resistance is decreased as is arterial blood pressure.
The blood pressure lowering effect of nitroprusside is seen within 1 to 2 minutes of the intravenous infusion and terminates almost as rapidly when the infusion is discontinued.
Nitroprusside is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian. It is also a controlled substance.
Nitroprusside is not approved for use in animals by the Food and Drug Administration (FDA) but may be legally prescribed by veterinarians as an extra-label drug.
Brand Names and Other Names This drug is registered for use in humans only.
Human formulations: Nitropress® (Abbott); Sodium Nitroprusside (Elkin-Sinn). Nitroprusside is supplied by drug companies with a variety of trade names and generic formulations.
Veterinary formulations: None
Uses of Nitroprusside
Nitroprusside is used in treatment of: Hypertensive crises
Acute congestive cardiac failure
Control of blood pressure when hypotension is used to facilitate surgery
Precautions and Side Effects While generally safe and effective when prescribed by a veterinarian, nitroprusside can cause side effects in some animals.
Nitroprusside should not be used in animals with compensatory hypertension, where there is inadequate cerebral circulation, or in vasodilated patients in septic shock.
Nitroprusside can cause a precipitous fall in blood pressure. For this reason, it should be administered slowly and carefully, with constant monitoring of blood pressure.
Another possibly fatal side effect is caused by the accumulation of cyanide. This toxic effect can be circumvented by ensuring the briefest periods of administration or very low infusion rates.
Serum electrolytes, especially sodium, should also be monitored.
Methemoglobinemia is also a possible sequel of nitroprusside's use.
Nitroprusside solutions are sensitive to light and should be protected from light as far as possible. Exposure to light causes reduction of contained ferric to ferrous iron with resultant loss of potency (and color change of the solution from brownish to bluish).
Drug Interactions The hypotensive effects of nitroprusside can be augmented by ganglion blocking drugs, general anesthetics, and other hypotensive agents.
How Nitroprusside is Supplied Nitroprusside is available as a 50 mg vial of powder used for injection
Dosing Information Nitroprusside is administered to hospilization patients through an intravenous infusion. After reconstitution, nitroprusside is not suitable for direct injection. The solution containing 50 mg of nitroprusside is further diluted and delivered through an infusion pump that carefully controls the rate that the medication is delivered.
Blood pressure is generally reduced slowly in It is safest to reduce blood increments, over four 4-hour periods, to allow cerebral blood vessels to accommodate.
The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects.
In dogs, the usual dose is for the initial infusion is 0.5 to 1 mcg/pound/min (1 to 2 mcg/kg/min). The infusion rate is generally increased incrementally every 3 to 5 minutes until a target arterial blood pressure is attained.
In treating heart failure, it is sometimes used with a current infusion of dobutamine at a rate of 2.5 to 5 mcg/pound/min (5 to 10 mcg/kg/min).
In cats, the usual dose fo the initial infusion is 0.25 mcg/pound/min (0.5 mcg/kg/min). The infusion rate is generally increased incrementally every 3 to 5 minutes until a target arterial blood pressure is attained.
In treating heart failure, it is sometimes used with a dobutamine infusion concurrently at a rate of 0.5 to 2.5 mcg/pound/min (1 to 5 mcg/kg/min).