Atropine is useful in organophosphate poisoning  because it:
Reactivates acetylcholinesterase
Competes with acetylcholine release
Binds with both nicotinic and muscarinic acetylcholine receptors
Is a competitive antagonist of acetylcholine
Atropine acts as an antagonist at muscarinic receptors. It has no activity on nicotinic receptors and does not interfere with the release of ACh.