ATC Group: V03AB Antidotes

Acetylcysteine is N-acetyl derivative of cysteine. Used as a mucolytic agent to reduce the viscosity of mucous secretions.

Andexanet alfa is a recombinant form of human FXa protein that has been modified to lack FXa enzymatic activity. Andexanet alfa is a specific reversal agent for FXa inhibitors. The predominant mechanism of action is the binding and sequestration of the FXa inhibitor. In addition, andexanet alfa has been observed to bind to, and inhibit tissue factor pathway inhibitor (TFPI). Inhibition of TFPI activity can increase tissue factor-initiated thrombin generation inducing a pro-coagulant effect.

Cyanide blocks intracellular respiration by binding to cytochrome oxidase. Dicobalt edetate forms a stable complex with the cyanide thereby acting as an antidote.

Dimercaprol is a chelating agent used in the treatment of acute poisoning by heavy metals.

Ethanol is an organic compound used in medical wipes and most commonly in antibacterial hand sanitizer gels as an antiseptic for its bactericidal and anti-fungal effects. Ethanol kills microorganisms by dissolving their membrane lipid bilayer and denaturing their proteins, and is effective against most bacteria, fungi and viruses. Ethanol also blocks conduction in peripheral nerve by decreasing the maximal values of both the sodium and potassium conductances and has a depressant action on the vasomotor-centre.

Flumazenil, an imidazobenzodiazepine, is a benzodiazepine antagonist which, by competitive interaction, blocks the effects of substances acting via the benzodiazepine-receptor. Neutralisation of paradoxal reactions of benzodiazepines has been reported.

Fomepizole is a competitive inhibitor of alcohol dehydrogenase. Alcohol dehydrogenase catalyzes the oxidation of ethanol to acetaldehyde and the initial steps in the metabolism of ethylene glycol and methanol to their toxic metabolites. Fomepizole is indicated as an antidote for ethylene glycol (such as antifreeze) or methanol poisoning (such as windshield washer fluid), or for use in suspected ethylene glycol or methanol ingestion, either alone or in combination with hemodialysis.

Idarucizumab is a humanized monoclonal antibody fragment (Fab) that binds to dabigatran with very high affinity, approximately 300-fold more potent than the binding affinity of dabigatran for thrombin. The idarucizumab-dabigatran complex is characterised by a rapid on-rate and extremely slow off-rate resulting in a very stable complex. Idarucizumab potently and specifically binds to dabigatran and its metabolites and neutralises their anticoagulant effect.

Ipecacuanha root extract has been widely used in syrup form as a potent and effective emetic. Ipecacuanha powder had been used to induce sweating at the onset of influenza, and small amounts of the extract have been incorporated into cough syrups as expectorants.

In vivo, in low concentration, methylthioninium chloride speeds up the conversion of methaemoglobin to haemoglobin. Methylthioninium chloride has been observed to stain tissues selectively.

Naloxone hydrochloride, a semisynthetic morphine derivative (N-allyl-nor-oxymorphone), is a specific opioid antagonist that acts competitively at opioid receptors. It reveals very high affinity for the opioid receptor sites and therefore displaces both opioid agonists and partial antagonists, such as pentazocine, for example, but also nalorphine.

Phentolamine is a competitive non-selective α₁- and α₂-adrenergic receptor blocker of relatively short duration of action. It causes vasodilatation and a fall in blood pressure resulting from the blockade of both post-junctional vascular α₁- and α₂-adrenoceptors. It also antagonises the vasoconstrictor response to noradrenaline and adrenaline infusions.

Physostigmine is a reversible inhibitor of acetylcholinesterase. As an inhibitor of acetyl-cholinesterase, physostigmine slows down the degradation of acetylcholine and acts like an indirect parasympathomimetic drug due to an increase of the acetylcholine concentration at the receptor.

Potassium iodide is indicated as a thyroid-blocking agent to prevent the uptake of radioactive iodine, for example after a nuclear accident or during a nuclear medicine investigation before administering a radioiodinated compound, which is metabolised to iodide or which contains radioiodine impurities.

Protamine is a potent antidote for heparin. Its precise mechanism of action is unknown. However, when the strongly basic protamine combines with the strongly acid heparin, a stable salt is formed lacking in anticoagulant activity.

Prussian blue insoluble binds cesium and thallium isotopes in the gastrointestinal tract after these isotopes are ingested or excreted in the bile by the liver, thereby reducing gastrointestinal reabsorption (enterohepatic circulation).

Sodium nitrite is indicated for sequential use with sodium thiosulfate for the treatment of acute cyanide poisoning that is judged to be life-threatening. Sodium nitrite is thought to exert its therapeutic effect by reacting with hemoglobin to form methemoglobin, an oxidized form of hemoglobin incapable of oxygen transport but with high affinity for cyanide.

Succimer is a lead chelator; it forms water soluble chelates and, consequently, increases the urinary excretion of lead.

Sugammadex is a modified gamma cyclodextrin which is a Selective Relaxant Binding Agent. It forms a complex with the neuromuscular blocking agents rocuronium or vecuronium in plasma and thereby reduces the amount of neuromuscular blocking agent available to bind to nicotinic receptors in the neuromuscular junction.

Sodium thiosulfate is indicated for sequential use with sodium nitrite for the treatment of acute cyanide poisoning that is judged to be life-threatening. The primary route of endogenous cyanide detoxification is by enzymatic transulfuration to thiocyanate (SCN-), which is relatively nontoxic and readily excreted in the urine.

Sodium thiosulfate is also indicated for the prevention of ototoxicity induced by cisplatin chemotherapy. The mechanism of protection against ototoxicity may include increasing levels of endogenous antioxidants, inhibition of intracellular oxidative stress, and direct interaction between cisplatin and the thiol group in sodium thiosulfate to produce inactive platinum species.

Hydroxocobalamin is a cyanide antidote. Its action in the treatment of cyanide poisoning is based on its ability to bind cyanide ions. Each hydroxocobalamin molecule can bind one cyanide ion by substituting it for the hydroxo ligand linked to the trivalent cobalt ion, to form cyanocobalamin, which is then excreted in the urine.