In-vitro aerodynamic particle size distribution of Symbicort® Turbuhaler® at 28.3 L/min and 60 L/min inhalation flows

Background The study investigates the in-vitro aerodynamic particle size distribution of Symbicort® Turbuhaler®, a dry powder inhaler containing budesonide and formoterol, at different inhalation flows. Methods The primary objective was to assess the effect of inhalation flow on drug delivery by analyzing the fine particle dose (FPD) and mass median aerodynamic diameter (MMAD) using an Andersen Cascade Impactor at 28.3 L/min and 60 L/min inhalation flows. Results The results reveal a statistically significant impact of inhalation flow on drug deposition (p<0.05). A higher inhalation flow (60 L/min) led to an increase in FPD, a decrease in MMAD, and a higher fine particle fraction (FPF), indicating improved lung deposition. Additionally, throat deposition decreased with increasing flows, suggesting better de-aggregation and dispersion of drug particles. Despite these changes, the ratio of budesonide (R and S epimers) to formoterol remained constant, ensuring consistent pharmacological efficacy. Conclusions The findings highlight the importance of flow considerations in dry powder inhaler performance and suggest that higher inspiratory flows may enhance drug delivery efficiency. This study supports the need for variable flow testing in pharmacopoeial standards to optimize inhaler design and ensure effective drug administration for patients with asthma and chronic obstructive pulmonary disease.