Stability of some bronchodilator solutions during ultrasonic nebulization

The effect of ultrasonic nebulization on the stability of isoetharine hydrochloride and isoproterenol hydrochloride solutions was studied. Commercially available solutions of isoetharine hydrochloride 1%, isoproterenol hydrochloride 1%, and isoproterenol hydrochloride 0.5% were diluted to 0.25%, 0.125%, and 0.125%, respectively. The solutions were nebulized for 10 or 15 minutes using three ultrasonic nebulizers at 0, 3, 6, 8, and 24 hours. Before and after nebulization, the solutions were assayed for intact drug by chemical assay and by thin-layer chromatography (TLC). The nebulized mist was also collected and assayed. The extent of drug degradation from ultrasonic nebulization was calculated as the apparent percent loss of active drug. Results of the chemical and TLC analyses for samples from two nebulizers showed no substantial chemical degradation of isoetharine hydrochloride or isoproterenol hydrochloride in any solution. Chemical assay was not performed for the third nebulizer, but results of TLC analysis showed no substantial degradation of either drug in any solution. Under the simulated-use conditions of this study, solutions of isoetharine hydrochloride and isoproterenol hydrochloride were stable when nebulized ultrasonically.