Overdosage with Mestinon or other cholinesterase inhibitors may lead to cholinergic crisis that manifest themselves in, among other things, pronounced muscle weakness or exacerbated muscle weakness in patients with myasthenia.
If such a situation is overlooked, life is endangered due to paralysis of the respiratory muscles. Bradycardia and paradoxically, tachycardia are other possible effects. Counter measures include the immediate withdrawal of Mestinon or other cholinergics and the slow intravenous administration of 1-2 mg atropine sulphate. Depending on the pulse rate, this dose is to be repeated at intervals of two to four hours if required.