1. Introduction Methodology Results Conclusion Reference
Dose emission of Formoterol in dry powder inhalers at varied flow rates and inhalation volumes
Mohamed Ali Jwaili
Dr El Hassane Larhrib
Introduction
► Dry powder inhalers (DPIs) are a widely accepted inhaled delivery dosage to treat diseases that are 'local' to the respiratory tract like asthma and chronic obstructive pulmonary disease.
►Insufficient patient inhalation flow rates leads to reduced dose delivery leading to unsatisfactory device performance.
► Formoterol is long acting β2-agonist (LABA) bronchodilators used in the treatment of chronic obstructive pulmonary diseases.  
►The present work aimed to assess the dose emission of formoterol fumarate Easyhaler ® (12µg) and Lactose (8000µg), at different flow rates and volumes using in vitro methodology.
Methodology
Dosage unit sampling apparatus (DSU) for DPIs
Figure.1 shows the DSU which used to determine the amount of dose emission [1-3]. Total emitted dose (TED) of both formoterol and lactose was measured using DSU at three different inhalation flow rates (28.3, 60 and 90 L/min) and seven inhalation volumes (0.15, 0.25, 0.35, 0.45, 0.55, and 0.75 L). One Easyhaler® was used for each determination. Three separate determination was made for each flow rate and volume. and The residual amount left in each inhaler was emptied and captured into a DPI dose sampling unit (Copley Scientific Ltd, UK) using a flow rate of 90 L/min for 2.6 s, corresponding to an inhalation volume of 4 L as suggested by the pharmacopoeia [1]. The amount of drug deposited in the DSU was analysed using high performance liquid chromatography (HPLC) method.
Figure 1. Instrument which used to measure emission dose in the experiment [4]
Figure 2. Mean (SD) TED of formoterol and lactose using three different inhalation flow rates at seven different inhalation volume (n=3 determination using 1 dose per determination)
Results
Conclusion
A summary of the mean (SD) dose emission of both formoterol (12 µg) and lactose (8000 µg) from Easyhaler® using three different flow rates at seven different inhalation volumes are shown in Figure 2.
Consolidated results of dose emission of lactose at various flow rates of 28.3,60 and 90 L/min and at various inhalation volumes show that
►Showing that the total emitted dose increased on increasing the flow rate, but on changing the inhalation volume, it did not show a significant increase.
►Formoterol concentration in the mouthpiece shows that there is no marked increase in the dose emission on the three flow rates from 28.3 L/min to 90L /min.
► Results of the concentration of the residual amount shows that on increasing the flow rate from 28.3 L/min to 90L/min, the concentration decreased.
Reference
1) British Pharmacopoeia (BP), Preparations for Inhalation: Inhalation powder. British Pharmacopoeia, pp.III53-III55
2) European Pharmacopoeia (EP), Preparations for Inhalation: Inhalation powder, 6.0 ed. European Pharmacopoeia, pp
3) United States Pharmacopoeia (USP), Aerosol, Nasal Sprays, Metered Dose Inhalers and Dry Powder Inhalers, vol. 36. The United States Pharmacopoeia, pp
4) Copley Scientific, Quality Solutions for Inhaler Testing. [online] Available at: < [Accessed 23 July 2014]