Prevention of fetal and maternal cyanide toxicity from nitroprusside with coinfusion of sodium thiosulfate in gravid ewes

The hepatic compensatory response to elevated systemic sulfide promotes diabetes

Impaired hepatic glucose and lipid metabolism are hallmarks of type 2 diabetes. Increased sulfide production or sulfide donor compounds may beneficially regulate hepatic metabolism. Disposal of sulfide through the sulfide oxidation pathway (SOP) is critical for maintaining sulfide within a safe physiological range. We show that mice lacking the liver- enriched mitochondrial SOP enzyme thiosulfate sulfurtransferase (Tst-/- mice) exhibit high circulating sulfide, increased gluconeogenesis, hypertriglyceridemia, and fatty liver. Unexpectedly, hepatic sulfide levels are normal in Tst-/- mice because of exaggerated induction of sulfide disposal, with associated suppression of global protein persulfidation and nuclear respiratory factor 2 target protein levels. Hepatic proteomic and persulfidomic profiles converge on gluconeogenesis and lipid metabolism, revealing a selective deficit in medium-chain fatty acid oxidation in Tst-/- mice. We reveal a critical role of TST in hepatic metabolism that has implications for sulfide donor strategies in the context of metabolic disease.

Antidotes in Poisoning

Introduction

Antidotes are agents that negate the effect of a poison or toxin. Antidotes mediate its effect either by preventing the absorption of the toxin, by binding and neutralizing the poison, antagonizing its end-organ effect, or by inhibition of conversion of the toxin to more toxic metabolites. Antidote administration may not only result in the reduction of free or active toxin level, but also in the mitigation of end-organ effects of the toxin by mechanisms that include competitive inhibition, receptor blockade or direct antagonism of the toxin.

Mechanism of action of antidotes

Reduction in free toxin level can be achieved by specific and non-specific agents that bind to the toxin. The most commonly used non-specific binding agent is activated charcoal. Specific binders include chelating agents, bioscavenger therapy and immunotherapy. In some situations, enhanced elimination can be achieved by urinary alkalization or hemadsorption. Competitive inhibition of enzymes (e.g. ethanol for methanol poisoning), enhancement of enzyme function (e.g. oximes for organophosphorus poisoning) and competitive receptor blockade (e.g. naloxone, flumazenil) are other mechanisms by which antidotes act. Drugs such as N-acetyl cysteine and sodium thiocyanate reduce the formation of toxic metabolites in paracetamol and cyanide poisoning respectively. Drugs such as atropine and magnesium are used to counteract the end-organ effects in organophosphorus poisoning. Vitamins such as vitamin K, folic acid and pyridoxine are used to antagonise the effects of warfarin, methotrexate and INH respectively in the setting of toxicity or overdose. This review provides an overview of the role of antidotes in poisoning.

How to cite this article

Chacko B, Peter JV. Antidotes in Poisoning. Indian J Crit Care Med 2019;23(Suppl 4):S241-S249.

Case Files of the University of Massachusetts Toxicology Fellowship: Does This Smoke Inhalation Victim Require Treatment with Cyanide Antidote?

Cyanide toxicity is common after significant smoke inhalation. Two cases are presented that provide framework for the discussion of epidemiology, pathogenesis, presenting signs and symptoms, and treatment options of inhalational cyanide poisoning. An evidence-based algorithm is proposed that utilizes point-of-care testing to help physicians identify patients who benefit most from antidotal therapy.