Antidotes for some commonly used drug’s poisoning

What Is An Antidote?

The word antidote came from the Greek word “antididonai” which means “given against”. Antidotes have long been used since the ancient times.

Hundreds of years ago, potions and concoctions were formulated in apothecaries to treat poisons and stings. Nowadays, there is a wide range of antidotes made to counteract accidental or intentional over dosage in clinical settings.

Basic knowledge about antidotes is essential for healthcare providers especially those who are working in acute care settings. To help you get started, here are some of the most common drugs and their antidotes:

ANTIDOTE INDICATION MODE OF ACTION DOSAGE
Acetylcysteine

 

Paracetamol, Carbon tetra-chloride Protects against liver damage by enhancing production of glutathione thereby increasing microcirculation and increasing blood flow. Initial dosage is 150mg/kg in 200 mL of 5% dextrose through slow IV injection in a period of 15 minutes. Initial dose should be followed by 50mg/kg in 500 mL of 5% dextrose for 4 hours then 100mg/kg in 1000 mL of 5% dextrose for 16 hours.

 

Activated Charcoal

 

Most poisons Inhibits systemic absorption of toxin through its high adsorptive capacity 50 gram orally every 4 hours until it appears in the stool for adult and 10-15 gram orally every 4 hours for children until it appears in the stool.

 

Amyl Nitrite

 

Cyanide Facilitates conversion of hemoglobin to methemoglobin to inhibit cyanide’s affinity to cytochrome oxidase enzymes thereby inhibiting its toxic effects. Ampoule contents should be inhaled for 30 seconds every minute. Use new ampoule every three minutes.

 

Atropine

 

Organo-phosphates and carbamate poisoning Inhibits the action of acetylcholine at the muscarinic sites to interrupt initial effects of organophosphate and carbamate poisoning. 2 mg through IV

 

Benzylpenicillin

 

Amatoxin poisoning Protects the liver by inhibiting entry of amatoxins into the hepatic cells. 600mg/kg on the first day and 300mg/kg on the second and third day

 

Calcium Gluconate

 

Hydrofluoric acid, calcium channel blockers and oxalates Increases calcium concentration to overcome calcium channel blockade in the cells and upkeep with depletion of calcium concentration in the system. 3grams for a 10% calcium gluconate that can be repeated every 10 to 20 minutes for a total of three to four doses
Cholestyramine

 

Anti-coagulants Inhibits the absorption of anti-coagulants in the system by forming non-adsorbable complex with bile acids in the intestines. 4 grams orally for up to three times daily
Cyanokit (Hydroxo-cobalamin)

 

Cyanide poisoning Binds with cyanide ions to facilitate excretion into the urine. 5 grams through intravenous infusion for 15 minutes

 

Dicobalt edetate

 

Cyanide toxicity Forms stable ion-complexes with cyanide to facilitate its excretion in the urine. 300mg through intravenous push for 1 minute followed by 50mL of 50% dextrose. Initial dose may be repeated if inadequate and can be further followed by a 300mg dose.

 

Dimercaprol

 

Arsenic, gold and inorganic mercury poisoning Binds with heavy metals to form dimercaprol-metal complex which can be readily excreted in the urine. 2.5mg – 3mg per kilogram weight through deep IM every four hours for two days then 2-4 times daily on the third day and 1-2 times daily for 10 days until recovery.

 

Ethanol

 

Ethylene glycol and methanol poisoning Inhibits formation of toxic metabolites so the toxic alcohol ingested can be excreted in the urine. It doesn’t directly affect the presence of the toxic metabolites that have already formed so hemodialysis is also recommended. Adult dosage for 5% ethanol is 2.76/mL/kg/hr either through oral or intravenous route

 

Flumazenil

 

Benzodiazepine overdose Acts on benzodiazepine receptors to block central effects of benzodiazepine. 0.2mg through IV for 30 seconds. If there is no response, 0.3mg can be given for another 30 seconds. Additional doses at 0.5mg at 30-60 second intervals until a total dose of 3mg is achieved.

 

Glucagon

 

Beta blockers, calcium channel blockers and hypoglycemic toxicity Increases myocardial contractility and heart rate similar to beta-agonist effects. It also decreases vascular resistance to improve cardiac output. Glucagon works on improving glucose levels by activating hepatic glycogen. 2-10mg through IV push and may be repeated as required for beta blocker and calcium channel blocker toxicity. For hypoglycemic toxicity, 1-2mg through intramuscular injection.

 

Methionine

 

Paracetamol poisoning Protects against liver and renal toxicity in cases of paracetamol poisoning. It acts as a precursor of glutathione to replenish gluthione stores in the liver cells. 2-5 grams followed by three 2.5 grams doses every 4 hours.

 

Naloxone

 

Opioid overdose A specific opioid antagonist that acts directly at opioid receptors to inhibit its toxicity effects. 0.4 mg through intravenous push as initial dose which can be further repeated every 2-3 minutes to a maximum bolus of 2 mg.

 

Penicillamine

 

Lead, copper and arsenic poisoning Binds with heavy metals to form stable water-soluble complexes that can be excreted in the urine. Total of 1-2grams daily in divided doses throughout the day.

 

Phentolamine

 

Alpha-adrenergic poisoning, cocaine toxicity Blocks alpha1 adrenoreceptors to inhibit vasoconstriction and decrease peripheral resistance thereby reducing blood pressure. For cocaine toxicity, it acts as an alpha-blocker to reduce cocaine-induced coronary vasoconstriction thereby resolving cocaine-induced myocardial ischemia. 2.5mg IV bolus and maybe repeated if necessary
Phytomenadione (Vitamin K)

 

Anti-coagulant poisoning Interrupts anti-coagulant’s antagonistic effects on vitamin-dependent coagulation factors thereby reducing anti-coagulant poisoning effects. 10-20mg orally

 

Pralidoxime

 

Organo-phosphorous insecticides Restores acetylcholinesterase activity by removing phosphate compounds in the phosphorylated acetylcholinesterase to reestablish normal acetylcholinesterase activities. 30mg/kg through intravenous for five to ten minutes and may be repeated at 4-6 hour intervals.

 

Procyclidine

 

Induced dystonia caused by anti-psychotic drugs and metoclopramide Elicits anti-muscarinic actions to relieve parkinsonian symptoms caused by antipsychotic drugs and metoclopramide 5-10mg through oral, IV or IM routes. Additional oral doses may be required for 2-3 days.

 

Protamine sulfate

 

Heparin poisoning Binds with heparin to neutralize anti-coagulative effects in the bloodstream. Maximum of 50mg dosage in a ten-minute period.

 

Prussian blue

 

Thallium poisoning Mobilizes intracellular thallium by absorbing thallium into the insoluble crystal lattice of Prussian blue in the gastrointestinal tract. 250mg/kg per day orally in divided doses administered through a nasogastric tube

 

Silibinin

 

Amatoxin poisoning Protects the liver by blocking entry of amatoxins into the hepatic cells. 20mg/kg daily divided into 4 infusions with each infusion running on two-hour duration

 

Sodium Calcium Edetate

 

Lead toxicity Binds with divalent and trivalent metals like lead to form water soluble ring-compound to be readily excreted in the urine. 30-40 mg/kg through intravenous infusion either in 5% Dextrose or 0.9% saline twice daily for up to 5 days.

 

Sodium nitrite

 

Cyanide/ acrylonitrite Nitrites facilitate conversion of hemoglobin to methemoglobin. Methemoglobin has higher binding affinity to cyanide which further facilitates its excretion 10mL of 3% sodium nitrite solution through IV for 5-20 minutes followed by sodium thiosulphate

 

Sodium thiosulphate

 

Cyanide/ acrylonitrite Acts as a precursor for the enzyme rhodanase which facilitates conversion of cyanide to non-toxic thiocyanate and thereby promoting its excretion. 50mL of 25% sodium thiosulphate through IV for ten minutes

 

Starch

 

Iodine Converts iodine to iodide which is less harmful. 15gram starch in 500 mL water orally
Reference:
British National Formulary (BNF), 70th Edition.

 

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