Pralidoxime usually as the chloride or iodide salt, belongs to a family of compounds called oximes.
Oximes bind to organophosphate-inactivated acetylcholinesterase.
Pralidoxime is used to treat organophosphate poisoning in conjunction with atropine and either diazepam or midazolam.
Pregnancy category C
Organophosphates such as sarin bind to the hydroxy component of the active site of the acetylcholinesterase enzyme, thereby blocking its activity.
Pralidoxime binds to the other half of the active site and then displaces the phosphate from the serine residue.
The conjoined poison/ antidote then unbinds from the site, and thus regenerates the fully functional enzyme.
Aged phosphate-acetylcholinesterase conjugate are resistant to antidotes such as pralidoxime.
It is often used with atropine to help reduce the parasympathetic effects of organophosphate poisoning.
Atropine antagonizes the muscarinic effects of organophosphates, and is administered before pralidoxime
Pralidoxime is only effective in organophosphate toxicity, with
no beneficial effects with neostigmine, pyridostigmine, or insecticides such as carbaryl.
It has an important role in reversing paralysis of the respiratory muscles.
It has about poor blood–brain barrier penetration, and little effect on centrally-mediated respiratory depression.
Dosing: 30 mg/kg administered by intravenous therapy over 15–30 minutes, repeated 60 minutes later.
It can also be given as a 500 mg/h continuous IV infusion.
Children: 20–50 mg/kg followed by a maintenance infusion at 5–10 mg/kg/h.
Intravenous infusions may be associated with respiratory or cardiac arrest if given too quickly.
When administered with atropine, the signs of atropine effects of flushing, mydriasis, tachycardia, dryness of the mouth and nose, may occur earlier than might be expected when atropine is used alone.