Antidotes
Atropine
Treat muscarinic effects (especially bradycardia and increased pulmonary secretions) of organophosphate or carbamate poisoning with atropine early. Atropine requirements vary enormously between patients and different cholinergic drugs. A rapid loading protocol is required, followed by an infusion. Use:
atropine 1.2 mg (child: 0.05 mg/kg up to 1.2 mg) intravenously. Double the dose every 5 minutes until the target end points below are reached. In some cases, cumulative loading doses up to 100 mg may be required. organophosphate and carbamate poisoning - antidote atropine
Target end points for atropinisation are:
- clear chest with no wheeze on auscultation
- heart rate more than 80 beats per minute
- systolic blood pressure more than 80 mmHg.
Once target end points for atropinisation are reached, start an atropine infusion. For adults and children, use:
atropine 10 to 20% of the total loading dose per hour by intravenous infusion. A typical infusion rate is 0.5 to 5 mg/hour. atropine
While titrating the dose, observe patients closely for signs of over-atropinisation and adjust the atropine dose accordingly. The most important signs of over-atropinisation are confusion, pyrexia and absent bowel sounds.
Pralidoxime
Pralidoxime use for organophosphate poisoning is controversial and routine use is not recommended. Consider pralidoxime for patients with ongoing severe organophosphate poisoning if response to other treatments is inadequate. Pralidoxime reactivates acetylcholinesterases that are inhibited by organophosphates; however, it is only effective if ageing (irreversible inhibition) of the acetylcholinesterase-organophosphate complex has not occurred.
Response to pralidoxime varies considerably depending on the organophosphate, severity of poisoning and time to treatment. In vitro reactivation of acetylcholinesterase with pralidoxime is high for chlorpyrifos and diazinon, and limited for dimethoate, fenthion and malathion. Pralidoxime is not indicated for poisoning due to carbamates or the organophosphate profenofos.
If indicated, use:
pralidoxime iodide 1 g (child: 15 mg/kg up to 1 g) in sodium chloride 0.9% 100 mL, intravenously, over 15 minutes1 organophosphate and carbamate poisoning
FOLLOWED BY
pralidoxime iodide 250 mg/hour (child: 10 mg/kg/hour up to 250 mg/hour) by intravenous infusion1.
The optimal duration of pralidoxime therapy is unknown. In most cases, therapy should be reviewed after 12 to 24 hours. Discuss ongoing treatment with a clinical toxicologist.
Pralidoxime is largely eliminated by the kidneys, so maintenance infusion doses should be reduced proportionally in patients with kidney impairment.