Functional shelf life of methacholine and atropine methylnitrate solutions

A functional assay was performed to determine the shelf life of methacholine at 25 mg/mL and atropine methylnitrate at 10 mg/mL stored up to 12 months after being placed in solution. When compared with freshly made solutions, there was essentially no loss in potency in the concentrations studied at the end of 6 months, but some loss was observed in those which had been in solution 12 months.