Pralidoxime

How it works

It reactivates acetylcholinesterase by displacing the organophosphate from the enzyme, restoring acetylcholine breakdown, but only before irreversible 'ageing' of the enzyme-organophosphate bond occurs.

Prescribing in practice

• It must be given as early as possible and always in addition to, not instead of, atropine, which remains the primary antidote for muscarinic effects.
• Efficacy falls once the inhibited enzyme has aged, so it is most useful when started promptly after exposure.
• Administer by slow intravenous infusion and follow UK poisons information advice on its use and continuation.

Monitoring

Monitor neuromuscular and respiratory function, atropinisation and, where available, cholinesterase activity to guide ongoing treatment.

Counselling the patient

• Explain to the team that this drug reactivates the poisoned enzyme but works together with atropine.
• Stress that it should be started as early as possible after organophosphate exposure.
• Note that decontamination and airway support are essential parts of management.

Evidence & guidelines

Pralidoxime with atropine is the standard antidotal regimen for organophosphate and nerve-agent poisoning, with use guided by UK poisons information (TOXBASE).