Pharmacology Notes

Pralidoxime is an oxime compound used to reactivate acetylcholinesterases inhibited by organophosphate or carbamate pesticide ingestion. It is only effective if given before irreversible binding of the pesticide occurs, a process referred to as 'ageing' of the cholinesterase. It is therefore essential that initiation of an adequate dose not be delayed. The fact that the optimal dose and duration is poorly established makes the use of pralidoxime challenging. Once pralidoxime regenerates cholinesterase function, it rapidly reverses both the nicotinic and muscarinic effects of organophosphate poisoning. Pralidoxime is generally administered concurrently with atropine; their effects at muscarinic receptors are synergistic, but atropine is ineffective at nicotinic receptors. Muscle strength generally improves within 10 to 40 minutes of pralidoxime administration. Pralidoxime is generally administered as a bolus dose followed by a continuous infusion, to rapidly achieve and maintain therapeutic levels. With some organophosphates many days to weeks of therapy may be required—such cases should be managed with the guidance of a toxicologist.

Adverse effects include nausea, headache, dizziness, drowsiness, blurred vision and hyperventilation, but these are generally of a mild nature.