Pralidoxime Methylsulphate
Class:Antidote
Mechanism of action
Reactivates cholinesterase
that had been inactivated by phosphorylation due to exposure to organophosphate
pesticides by displacing the enzyme from its receptor sites;removes the
phosphoryl group from the active site of the inactivated enzyme.
Pharmacokinetics
Absorption:slowly
from GI tract.Metabolism:in the liver,not bound to plasma proteins.Half
life:0.8-2.7 hours.Time to peak serum concentration:IV:Within5-15 minutes.Elimination:80
to 90 percent quickly excreted in urine.
Indications
Anticholinesterase
organophosphorous derivatives or compound poisoning.
Contraindications
Hypersensitivity to
pralidoxime or any component:poisoning due to phosphorous,inorganic
phosphates,or organic phosphates without anticholinesterase activity.
Precautions
Pralidoxime must be
administered within 14 hours of poisoning to be fully effective.It has little
effect if treatment is started more than 36 hours after intoxication.The
efficacy of pralidoxime depend on the nature of organophosphorous
insecticides.It is not effective in the treatment of poisoning due to carbamate
pesticides.
Side effects
Double vision,blurred
vision,malaise,dizziness,headache,and tachycardia.
Pregnancy and lactation
Pregnancy risk factor
C.
Drug interaction
Decreased effect:Atropine,although
often used concurrently with pralidoxime to offset muscarinic stimulation,these
effect occur earlier than anticipated.Increased
effect:Barbiturates(potentiated).
Dosage
IV (in
emergencies),either directly without dilution,by slow injection(1ml/min),or
infusion after dilution of the solution with isotonic glucose or isotonic
chloride solution.SC,IM,or per os,if poisoning does not need urgent
treatment.the first injection is 200 to
400mg of pralodoxime methylsulfate(1 or 2 flasks).This dose may be increased up
to 2gm.A dose of up to 400mg should be maintained if necessary.
Brands
Inj.Contrathion
322.5mg.
