Stability of methacholine chloride in bronchial provocation test solutions

Area of Science:

• Pharmaceutical Chemistry
• Analytical Chemistry

Background:

• Methacholine chloride is a deliquescent drug requiring stable stock solutions.
• Previous suggestions indicated rapid degradation of methacholine chloride in saline.

Purpose of the Study:

• To determine the stability of methacholine chloride (5 mg/ml) in 0.9% sodium chloride solution.
• To establish optimal storage conditions for methacholine chloride stock solutions.

Main Methods:

• Colorimetric assay (530 nm) utilizing hydroxamic acid-iron complex formation.
• Stability testing at various temperatures (4, 20, 37, 60, 80°C).
• Kinetic analysis using an Arrhenius plot.

Main Results:

• Methacholine chloride degradation followed first-order kinetics across all tested temperatures.
• Observed half-lives ranged from 29.3 days (80°C) to 693 days (4°C).
• Less than 10% degradation is predicted within two months at 30°C and five months at 4°C.

Conclusions:

• Methacholine chloride in 0.9% sodium chloride solution exhibits greater stability than previously reported.
• Refrigerated storage (4°C) or controlled room temperature (30°C) supports the preparation and use of methacholine chloride stock solutions.