Pralidoxime belongs to a family of compounds called oximes that bind to organophosphate-inactivated acetylcholinesterase. It is used to combat poisoning by organophosphates, in conjunction with atropine.

In a normal nicotinic synaptic junction, including motor end plates and preganglionic nerve fibres, acetylcholine (ACh) is released from the presynaptic axon terminal into the synaptic cleft. The ACh then diffuses through the synaptic cleft and binds to nicotinic receptors on the postsynaptic membrane. This induces a subsequent action potential (AP) that continues through the postganglionic cell, or induces contraction in the motor end plate.

In order to prevent overstimulation or saturation of the synapse, or both, an enzyme known as acetylcholine esterase breaks down the neurotransmitter ACh. By removing the ACh, the synapse is brought to a state where it is ready for subsequent activation. Saturation of the synapse occurs when there is an excess of acetylcholine in the synaptic cleft, which inhibits further nerve transmission as the nicotinic receptors are full. Agents which inhibit acetylcholine esterase will lead to a build-up of ACh in the cleft.