Review Question - QID 100604

Nitroprusside is used for rapid blood pressure reduction in hypertensive emergency. However, it is metabolized to release cyanide and nitric oxide, and cyanide toxicity is a potential complication.

Nitroprusside is the drug of choice when it comes to the treatment of a hypertensive emergency. Nitroprusside is initially metabolized to cyanide and is therefore toxic until it is further metabolized to thiocyanate in the liver by enzyme rhodanase. Nitroprusside works by releasing nitric oxide, which works by relaxing vascular smooth muscle resulting in vasodilation.

Sanders discusses hypertensive emergencies. A hypertensive emergency can be described as an acute elevation in blood pressure that can lead to progressive end-organ damage. A critical goal in patient care is the prompt administration of antihypertensive agents. However, care must be taken not to lower blood pressure too quickly, which can exacerbate symptoms through decreased end-organ perfusion. Medications such as nitroprusside allow minute-to-minute regulation of the patient's blood pressure and clinical symptoms.

Hall et al. report on nitroprusside-induced cyanide intoxication and prevention with sodium thiosulfate prophylaxis. Concurrent infusion of thiosulfate with nitroprusside provides a sulfur donor necessary to prevent cyanide accumulation. Cyanide will then be able to combine with thiosulfate to form a less toxic compound called sodium thiocyanate. This combined therapy does not alter the efficacy of nitroprusside.

Illustration A demonstrates the physiology of nitroprusside action.
Illustration B depicts the mechanism of action of nitroprusside with concurrent administration of thiosulfate administration.

Incorrect Answers:
Answers 1-4: None of these choices would be likely considering nitroprusside's adverse effect profile.