Cyanokit (hydroxocobalamin, a form of vitamin B12) is an injectable therapy most often used to treat cyanide toxicity. This medication readily combines with cyanide to form cyanocobalamin thereby freeing cytochrome c oxidase to proceed with aerobic respiration in the electron transport chain.

As a cardiothoracic anesthesiologist, I’ve used Cyanokit to treat profound vasoplegia refractory to conventional vasopressors on cardiopulmonary bypass (CPB). The dysregulation of nitric oxide (NO), a potent vasodilator, has been implicated in this form of vasoplegia. In the absence of cyanide, Cyanokit binds nitric oxide to mitigate its vasodilatory effects.

Although methylene blue acts via a similar mechanism, it can precipitate serotonin syndrome with associated autonomic and neuromuscular instability. If a patient is not on an antidepressant that involves the serotonergic pathway, I’ll often start with methylene blue and escalate to Cyanokit (> $10,000 per dose at the time of this writing).

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