Why should we preceed neostigmine by atropine in tubocurarine toxicity?

Question

Why should we precede neostigmine by atropine in tubocurarine toxicity ?I know that neostigmine act as anticholinesterase thus increasing the number of Ach molecules rendering them able to displace the tubocurarine, but I don't get the idea of atropine I know it's muscarinic inhibitor but we are speaking about nicotinergic receptors?

Answer 1

The reason for the atropine is to block the effect of the "extra" ACh generated by the neostigmine from acting at the muscarinic receptors. So, when you administer the neostigmine, it blocks AChE, thus allowing more ACh to accumulate. This extra ACh will then overcome the blockade of the nicotinic receptors produced by the d-tubo. However, the extra ACh will also interact with muscarinic receptors. In order to prevent untoward effects of this activation, a muscarinic receptor antagonist (atropine) in given prior to the esterase inhibitor.