Antidotes are an essential part of clinical practice. According to Drugs.com, an antidote is a drug, chelating substance, or a chemical that counteracts (neutralizes) the effects of another drug or a poison.
Antidotes help treat the patient with an overdose or toxic use of a certain substance. However, antidotes are only helpful when the patient is being treated in a timely manner. After the drug has been absorbed into the blood and it starts to show its adverse effects, antidotes may not be helpful at that time. Therefore, the timely administration of antidotes is important in saving the patient's life.
Not all substances have their antidotes. Therefore, some poisoning cases are managed only symptomatically. In this blog, we have summarized the agents that are often overdosed, their antidotes, and their dosages.
Antidotes and Reversal Agents: Dosage and Usage
Acetaminophen
Antidote: Acetylcysteine (Acetadote, Mucomyst)
Dosage:
- By mouth (PO) (Adults, Children): Loading dose: 140 milligrams (mg)/kilogram (kg), then 70 mg/kg every 4 hours for a total of 17 doses (Total dose: 1,330 mg/kg).
- Intravenous (IV) (Adults, Children): Loading dose: 150 mg/kg over 60 minutes, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours (Total dose: 300 mg/kg).
Anticholinergic Agents (e.g., atropine)
Antidote: Physostigmine
Dosage:
- Intramuscular (IM)/IV/subcutaneous (SQ) (Adults): Initially, 0.52 mg, repeat every 20 minutes as needed; Additional doses: 14 mg every 3060 minutes if life-threatening symptoms recur.
- IV (Childrenlife-threatening only): 0.02 mg/kg/dose. It may be repeated after 1520 minutes, up to 2 mg in total, or until a response occurs or adverse effects arise.
Apixaban (Eliquis)
Antidotes: Kcentra (prothrombin complex concentrate)
Dose based on INR:
- International normalised ratio (INR) 2 to < 4: 25 units/kg (max: 2,500 units)
- INR 46: 35 units/kg (max: 3,500 units)
- INR > 6: 50 units/kg (max: 5,000 units)
- Given with Vitamin K
Other antidote: Andexanet alfa (Andexxa):
- Apixaban 5 mg / Rivaroxaban 10 mg: 400 mg IV bolus, then 4 mg/min for up to 120 minutes.
- Apixaban > 5 mg / Rivaroxaban >10 mg: 800 mg IV bolus, then 8 mg/min for up to 120 minutes.
Arsenic
Antidote: Dimercaprol (BAL in oil)
Dosage:
- Mild Poisoning (IM - Adults, Children): 2.5 mg/kg every 4 hours for 6 doses, then every 6 hours for 4 doses, then every 8 hours for 3 doses, then every 12 hours for 2 doses. This is followed by once daily for 10 days.
- Moderate Poisoning (IM - Adults, Children): 2.5 to 3.5 mg/kg every 4 hours for 6 doses, then every 6 hours for 4 doses, then every 8 hours for 3 doses, then every 12 hours for 2 doses. This is followed by once daily for 10 days.
- Severe Poisoning (IM - Adults, Children): 3.5 to 5 mg/kg every 4 hours for 6 doses, then every 6 hours for 4 doses, then every 8 hours for 3 doses, then every 12 hours for 2 doses. This is followed by once daily for 10 days.
Benzodiazepines (e.g., midazolam)
Antidote: Flumazenil (Romazicon)
Dosage:
- IV (Adults): 0.2 mg over 30 seconds. May repeat 0.3 mg after 30 seconds if needed. Additional 0.5 mg doses can be given every minute (max cumulative dose: 3 mg).
- IV (Children): 0.01 mg/kg over 15 seconds (max: 0.2 mg). Repeat doses every minute (max cumulative dose: 1 mg or 0.05 mg/kg, whichever is lower).
Beta Blockers (e.g., propranolol)
Antidote: Glucagon
Dosage:
- IV (Adults): 510 mg over 1-5 minutes, followed by a continuous infusion of response dose per hour.
- IV (Pediatrics): 50 micrograms (mcg)/kg over 1-5 minutes, followed by a continuous infusion of response dose per hour.
Calcium Channel Blockers (e.g., verapamil)
Antidote: Glucagon
Dosage:
- IV (Adults): 510 mg over 1-5 minutes, followed by a continuous infusion of response dose per hour.
- IV (Pediatrics): 50 mcg/kg over 1-5 minutes, followed by a continuous infusion of response dose per hour.
Carbamate Pesticides
Antidote: Atropine
Dosage:
- IV (Adults): Initially, 13 mg. The dose should be doubled every five minutes if the previous dose provides an inadequate response.
- IV (Pediatrics): 0.05 mg/kg IV with a minimum dose of 0.1mg. The dose should be doubled every five minutes if the previous dose provides an inadequate response.
Dabigatran (Pradaxa)
Antidote: Idarucizumab (Praxbind)
Dosage:
- IV: 5 grams (G) as two separate 2.5 G doses administered no more than 15 minutes apart.
Digoxin (Lanoxin)
Antidote: Digoxin immune FAB (Digibind)
Dosage:
- Adults:
- Unknown ingestion: 800 mg IV (acute), 240 mg IV (chronic).
- Dose (# vials) = total digoxin body load in mg / 0.5 mg bound digoxin
- Dose = serum digoxin concentration (nanogram [ng]/milliliter [mL]) x weight (kg)/100
- Dose (mg) = (40 mg/vial) x serum digoxin concentration (ng/mL) x weight (kg)/100
- Dose (# vials) = serum digitoxin concentration (ng/mL) x weight (kg)/1000
- Unknown serum digoxin level and ingested amount in children: Small children can be treated empirically with 5 (200 mg) vials.
- Chronic intoxication in children: Patients weighing less than 20 kg can be given 40 mg IV.
Ethylene Glycol
Antidote: Fomepizole (Antizol)
Dosage:
- IV (Adults, Children): Loading dose 15 mg/kg over 30 minutes, then 10 mg/kg every 12 hours for 4 doses, then increase to 15 mg/kg every 12 hours. Treat until ethylene glycol levels are < 20 mg/deciliter (dL).
Extravasation (e.g., dopamine)
Antidote: Phentolamine (Regitine)
Dosage:
- Adults and Children: Infiltrate the area with 510 mg in 10 mL 0.9% NaCl within 12 hours.
Heparin
Antidote: Protamine
Dosage:
- IV (Adult): 1 mg protamine neutralizes 90115 units of heparin. Max: 50 mg.
Hyperkalemia
Antidote: Sodium polystyrene sulfonate (Kayexalate)
Dosage:
- PO (Adults): 15 g 14 times/day.
- PO (Children): 1 g/kg every 6 hours.
Hypoglycemia
Antidote: Glucagon
Dosage:
- IM/IV/SQ (Adults, Elderly, Children over 45 kg): 1 mg. Repeat after 15 minutes if needed. If there is no response, administer IV dextrose.
Iron
Antidote: Deferoxamine (Desferal)
Dosage:
- Acute IM (Adults): Initially 1,000 mg, then 500 mg every 4 hours for two doses, and if needed, an additional 500 mg every 412 hours (max: 6 G/24 hours).
- Acute IM (Children ≥3 years): 1 G initially, then 500 mg every 4 hours for 2 doses (max: 6 G/24 hours).
Isoniazid
Antidote: Pyridoxine (Vitamin B6)
Dosage:
- IV: 1 G per gram that was ingested, or 70 mg/kg if unknown (max with unclear history: 5 G).
Lead Poisoning
Antidotes:
- Calcium EDTA: IM/IV concurrent with dimercaprol for 5 days. 50 mg/kg/day over 24 hours for symptomatic patients (adults and children).
- Dimercaprol (BAL in oil): Use with calcium EDTA for lead encephalopathy. 4 mg/kg every 4 hours for 3 days and 2.5 mg/kg for 1-4 days.
Methanol
Antidote: Fomepizole (Antizol)
Dosage: Same as ethylene glycol.
Opioids (e.g., morphine)
Antidote: Naloxone (Narcan)
Dosage:
- IV/IM/SQ (Adults): 0.42 mg/dose; repeat every 23 minutes as needed. Max cumulative dose: 10 mg.
- IV (Children): 0.01 mg/kg IV, may give 0.1 mg/kg IV if response is not obtained.
Organophosphate Pesticides
Antidotes:
Warfarin (Coumadin)
Antidote: Phytonadione (Vitamin K)
Dosage:
- Adults: INR 4.5-10, no bleeding: 1-2.5 mg PO once; INR >10, no bleeding: 2.5-5 mg PO once.
Conclusion
Antidotes are a cornerstone in managing patients with overdoses and saving their lives. Ensure they are given in the optimal doses and at an appropriate time frame. Understanding the proper use of antidotes and their dosages is essential for effectively managing toxicity cases. Whether you are dealing with accidental overdoses, adverse drug reactions, or environmental poisonings, timely and accurate administration of these agents can make the difference between recovery and severe complications.
About the Author:
Mariya Rizwan is an experienced pharmacist who has been working as a medical writer for four years. Her passion lies in crafting articles on topics ranging from Pharmacology, General Medicine, Pathology to Pharmacognosy.
Mariya is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.
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