Introduction and objectives Salmeterol/fluticasone propionate combination (S/F) Easyhaler provides inhaled conticosteroid (ICS) and a long acting b2-adronoreceptor agonist (LABA) therapy for patients with asthma and chronic obstructive pulmonary disease (COPD) within one easy-to-use device. Based on in vitro studies and in vivo pharmacokinetic studies, S/F Easyhaler products, 50/250 and 50/500 µg per dose, were found to be therapeutically equivalent with the corresponding Seretide Diskusproducts. We sought to test the in vitro drug delivery characteristics, delivered dose uniformity (DD) and fine particle dose (FPD) of new S/F multidose dry powder inhaler under simulated real-life conditions through container life and after expose to various stress tests (moisture, dropping, vibration and freeze-thawing cycles) which can occur in patient handling, storage or transportation of the products.

Methods Easyhaler products containing 50/250 and 50/500 µg per dose of salmeterol and fluticasone propionate were used for confirming the dosing through the inhaler, DD and FPD (<5 µm), by using sampling apparatus and procedures described in the European Pharmacopoeia at flow rate corresponding 4 kPa pressure drop across the inhaler. Amount of active drug collected on the filter was determined by high performance liquid chromatography (HPLC). A total of 68 inhalers from one or two batches of both dose strengths were used when confirming the effect of lifetime, moisture, dropping, vibration and freeze-thaw conditions. Determination of DD uniformity and FPD through inhaler life were performed during minimum dosing interval i.e. twice daily dosing, in a one-month-study.

Results The DD and FPD analyzed through the S/F Easyhaler lifetime remained stable. The effect of moisture was modest on DD and FPD. Dropping of the Easyhaler from one meter height, vibration of the device or freezing and thawing did not influence DD or FPD of neither salmeterol nor fluticasone propionate.

Conclusions Salmeterol/Fluticasone propionate Easyhaler proved to be robust in dosing accuracy under simulated real-life conditions. The in vitro performance indicates reliable and consistent treatment of patients with asthma and COPD.