Involvement of pH and Internal Surface of Cans on the Budesonide Solution Stability in HFA Metered Dose Inhaler

The purpose of stability testing is to provide evidence on how the quality of a drug substance or drug product varies with the time under the influence of a variety of environmental factors such as temperature, humidity, pH and light, and to establish a retest period for the drug substance or a shelf life for the drug product and recommended storage conditions. Due to high lipophilicity of budesonide, it is not possible to prepare simple solution having the desired concentration of this drug without using co-solvent. Aim of this study was to compare the stability of budesonide at different canisters (standard aluminium, anodized aluminium direct surface modification (DSM) and fluorocarbon polymer (FCP) and pH values. Two type of formulation without and with acid were prepared to evaluate the effect of pH on stability of budesonide solution in anodized aluminium, DSM and FCP cans. After addition of strong acid, under accelerated stability conditions, only a slight decrease in the assay is observed after six months. In this study the best results have been obtained with anodized aluminium cans and solution with a pH of 3.5.