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Cholinesterase reactivator: Pralidoxime chloride

Pralidoxime chloride is a cholinesterase reactivator, widely used to treat patients with organophosphate poisoning.
Pralidoxime chloride is a cholinesterase reactivator, widely used to treat patients with organophosphate poisoning. It is used for
  • Reversal of paralysis or muscle weakness caused by poisoning or overdose
  • Antidote treatment of poisoning by a drug or pesticide
  • Treatment of muscle disorder

Mechanism of Action

Pralidoxime is used as an antidote in organophosphate chemicals and pesticides.
  • Organophosphates bind to the esteratic site of acetylcholinesterase
  • Leads to reversible inactivation of enzyme
  • Inhibition of acetylcholinesterase causes acetylcholine accumulation at synapses
  • Results in continuous stimulation of cholinergic fibres throughout the nervous system
If pralidoxime is administered within 24 hours of organophosphate poisoning, it activates acetylcholinesterase again by cleaving the phosphate-ester bond between acetylcholinesterase and organophosphate.

Adverse Effects

Pralidoxime chloride doesn’t have a that many severe side effects. But here’s a few that can be noted:
  • Pain at site of injection
  • Dizziness
  • Blurry vision
  • Drowsiness
  • Nausea
  • Headache

Route of Elimination

Pralidoxime chloride is rapidly excreted through urine. It is passed through urine partially unchanged and partially as a metabolite produced by the liver.


There aren’t many significant contraindications associated with the use of pralidoxime. Some of them could include hypersensitivity to the drug itself. Of course, these contraindications may also arise if the risk of administering outweighs the potential benefits of the drug.


Atropine x pralidoxime: When pralidoxime and atropine are administered together, you may observe some signs of atropinization early on, compared to when you administer atropine alone. Some of these signs include mydriasis, tachycardia, flushing, dryness of the nose and mouth. It is more prominent if there atropine dose is large and the pralidoxime administration is delayed.

Note: In the case of anticholinesterase poisoning, barbiturates should be administered carefully while treating convulsions. This owes to the fact that anticholinesterases potentiate the action of barbiturates.

Drugs such as theophylline, aminophylline, theophylline, reserpine, succinylcholine and phenothiazine-type tranquillisers shouldn’t be adminstered in patients with organophosphate poisoning.

Pralidoxime may also interact with chlorpromazine, reserpine, mesoridazine, fluphenazine, prochlorperazine, perphenazine, trifluperazine and thioridazine.


In adults, pralidoxime (30mg/kg) is adminstered intravenously (1-2g) I’ve a period of 15-30 minutes. You can repeat this after 60 minutes. Another way you can administer it is through a continuous 500mg/h IV infusion.

In children, 20-50 mg/kg pralidoxime is administered. The infusion is maintained at 5-10 mg/kg/h.

It is important to keep in mind that IV infusions can result in cardiac arrest or respiratory failure if given too rapidly.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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