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