Pralidoxime chloride is indicated as an antidote:

• In the treatment of poisoning caused by pesticides and chemicals (e.g., nerve agents) of the organophosphate class that possess anticholinesterase activity
• In the management of overdose of anticholinesterase drugs used in the treatment of myasthenia gravis

The main indications for Pralidoxime chloride use are muscle weakness and respiratory depression. In severe poisoning, respiratory depression may occur due to muscle paralysis.

Pralidoxime chloride is an acetylcholinesterase reactivator. Its primary action is to reactivate acetylcholinesterase (mainly outside the central nervous system) that has been inhibited by phosphorylation due to organophosphate pesticides or related compounds. This allows the breakdown of accumulated acetylcholine and restores normal neuromuscular transmission. It also slows the “aging” process of phosphorylated cholinesterase, preventing it from becoming permanently inactive, and may directly detoxify certain organophosphates through chemical interaction. The most important clinical effect is the improvement of respiratory muscle paralysis. Atropine is always required along with Pralidoxime to counteract the effects of excess acetylcholine. Pharmacokinetics: A minimum therapeutic plasma concentration of about 4 µg/ml may be achieved within approximately 16 minutes after administration of 600 mg Pralidoxime chloride. The drug is rapidly eliminated in urine, partly unchanged and partly as hepatic metabolites.

Adults and children >16 years age: Inject an initial dose of 1000 to 2000 mg of Pralidox (Pralidoxime Chloride), preferably as an infusion in 100 ml of normal saline, over a 15 to 30 minute period. If this is not practical or pulmonary edema is present the dose should be given slowly (over not less than 5 minutes) by intravenous injection, as 50 mg/ml solution (e.g. 1000 mg in 20 ml). A second dose of 1000 to 2000 mg may be indicated after about one hour if muscle weakness has not been relieved. Additional doses may be given every 10–12 hours if muscle weakness persists.

Children 16 years and under: Loading dose: 20–50 mg/kg (maximum: 2000 mg/dose) over 15–30 minutes.

Maintenance infusion: 10–20 mg/kg/hour; alternatively, a repeat bolus of 20–50 mg/kg (maximum 2000 mg/dose) may be administered after 1 hour and repeated every 10–12 hours thereafter, as needed.

Preparation of administration: For intravenous infusion: Reconstitute a single Pralidox (Pralidoxime Chloride) 1000 mg vial by adding 20 ml of Normal Saline (0.9% Sodium Chloride solution) for Injection through 10 ml syringe, which results in a 50 mg/ml concentration. The solution should be further diluted with remaining Normal Saline to achieve a concentration of 10 to 20 mg/ml (e.g. 1000 mg in 100 ml or 2000 mg in 100 ml). For fluid restricted patients or for rapid administration (over at least 5 min), a maximum concentration of 50 mg/ml may be used. Discard unused solution after dose has been withdrawn.

When atropine and Pralidoxime chloride are used together, signs of atropinization such as flushing, mydriasis, tachycardia, and dryness of the mouth and nose may appear earlier than expected compared to atropine alone. This effect is more likely when a large dose of atropine has been given and Pralidoxime chloride administration is delayed.

Pralidoxime chloride is contraindicated in patients with known hypersensitivity to any component of the formulation.

Adverse effects such as tachycardia, laryngospasm, and muscle rigidity have been reported in a few cases, usually associated with rapid intravenous injection.

Pregnancy Category C. Pralidoxime chloride should be used during pregnancy only if clearly needed. It is not known whether the drug is excreted in human breast milk. Therefore, caution should be taken when administering it to nursing mothers.

In the management of acetylcholinesterase poisoning, certain drugs should be used cautiously or avoided. Barbiturates may have increased effects and should be used carefully for convulsions. Morphine, theophylline, aminophylline, succinylcholine, reserpine, and phenothiazine-type tranquilizers should be avoided in organophosphate poisoning. Prolonged paralysis has been reported when succinylcholine is used with drugs having anticholinesterase activity; therefore, it should be used with caution.

In normal subjects, overdose may cause dizziness, blurred vision, diplopia, headache, impaired accommodation, nausea, and mild tachycardia. Treatment is mainly supportive, including artificial respiration and other necessary supportive measures.

Antidote preparations

Store in a cool, dry place away from light. Keep out of reach of children.