Which medications in the drug class Antidotes, Other are used in the treatment of Smoke Inhalation Injury?

Updated: Oct 15, 2021
  • Author: Keith A Lafferty, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Answer

Antidotes, Other

Several CN antidotes exist, which work by different mechanisms of action. Hydroxocobalamin binds to CN to form cyanocobalamin. Amyl nitrite and sodium nitrite convert a portion of circulating hemoglobin to methemoglobin. Sodium thiosulfate allows the production of thiocyanate.

Sodium thiosulfate

After formation of methemoglobin and production of cyanomethemoglobin, thiosulfate acts as a sulfur donor to the endogenous enzyme rhodanese. This enzyme removes CN from the cyanomethemoglobin complex and forms thiocyanate, which is excreted renally. CN also is removed directly from cytochrome oxidase and is converted to thiocyanate in the presence of thiosulfate via the enzyme rhodanese.

Methylene blue (ProvayBlue)

Methylene blue is used to convert methemoglobin to oxyhemoglobin. It contains a tetramethyl thionine chloride moiety that is reduced (it is an electron acceptor) in the presence of nicotinamide adenine dinucleotide phosphate–oxidase (NADPH) and methemoglobin reductase to leukomethylene blue. Leukomethylene blue then becomes available to reduce methemoglobin to oxyhemoglobin.

Methylene blue may be ineffective in treating patients with glucose-6-phosphodiesterase (G-6-PD) deficiency because, in the hexose monophosphate shunt, G-6-PD is essential for the generation of NADPH. Without NADPH, methylene blue cannot act as a reducing agent in the transformation of methemoglobin to oxyhemoglobin.

Hydroxocobalamin (Cyanokit)

Hydroxocobalamin is a vitamin B-12 precursor that contains a cobalt ion, which has greater affinity for cyanide than does cytochrome oxidase. Binding of cyanide to the cobalt ion results in the formation of cyanocobalamin, which is excreted renally. Hydroxocobalamin has few adverse effects and has the following advantages over other cyanide treatments:

This agent is safe to use in victims of smoke inhalation. [59, 60] Cyanocobalamin is a pigmented compound, and interferes with spectrophotometric tests. Any necessary blood samples should be drawn prior to administration of antidote if possible, because it will not be possible to obtain accurate results for most blood tests afterward.

Amyl nitrite

In the presence of nitrites, hemoglobin is converted to methemoglobin, which has a higher binding affinity for CN than does the cytochrome oxidase complex. Administration of amyl nitrite produces a methemoglobin level of 5% and subsequent formation of cyanomethemoglobin, allowing electron transport and cellular respiration to continue. This medication is given until an IV line is established and sodium nitrite can be administered.

Sodium thiosulfate & sodium nitrite (Nithiodote)

In the presence of nitrites, hemoglobin is converted to methemoglobin that has a higher binding affinity for CN than does the cytochrome oxidase complex. Administration of sodium nitrite produces a methemoglobin level of 20-30% and subsequent formation of cyanomethemoglobin, allowing electron transport and cellular respiration to continue.


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