I googled mestinon and atropine and got the following from drugs-dot-com site:

'Atropine may also be used to abolish or obtund gastrointestinal side effects or other muscarinic reactions; but such use, by masking signs of overdosage, can lead to inadvertent induction of cholinergic crisis.'

There is a lot of returns on the above search...I guess everyone has to make their own decision on pros/cons about different drugs 'playing well together in our bodies'!!