Sodium nitroprusside: Toxicity

Sodium nitroprusside is a medication that is used to lower blood pressure via continuous infusion. Nitroprusside is metabolized into nitric oxide, which acts as both a potent arteriolar and venous dilator. One must exercise caution when using this medication due to its toxic side effects, especially if continuously infused for a prolonged period of time. Sodium nitroprusside causes toxicity by three primary mechanisms.

1. The most common adverse effect is direct vasodilation resulting in hypotension and dysrhythmias
2. Thiocyanate toxicity occurs infrequently and results in tinnitus, altered mental status changes, nausea, and abdominal pain
3. In rare cases, cyanide toxicity can occur, resulting in coma, metabolic acidosis, or respiratory arrest. In very rare cases, methemoglobinemia can occur, which, if levels reach greater than 15 percent, can result in symptomatic cellular hypoxia.