Currently available dry powder inhalers (DPIs) for drug delivery to the lungs require turbulent energy to generate and disperse aerosol particles in the respirable range ≤5μm during inhalation. The patient's inspiratory effort together with the resistance inside the device creates this energy. Different inhalers provide varying degrees of resistance to inhalation flow and require different inhalation techniques for the generation and delivery of drug fine particles in respirable size range to the lungs. The aim of this research programme was to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of the salbutamol Accuhaler®, Easyhaler®, and Clickhaler® and the terbutaline Turbuhaler® DPIs. A high-performance liquid chromatography method for the assay of salbutamol sulphate and terbutaline sulphate in aqueous samples was modified and accordingly validated. In-vitro dose emission of the four different DPIs was measured using the pharmacopoeia method with modifications to simulate varying inhalation flows within patient and between patients. The ranges of the total emitted dose (% nominal dose) at the inhalation flow range of 10 - 60 Lmin-1, following one and two inhalations per metered dose for 2L and 4L inhaled volumes were as follows: the Accuhaler (52.64- 85.11; 61.88-85.11 and 59.23-85.11; 62.81-85.11); the Easyhaler (68.35-91.99; 79.94-91.99 and 73.83-92.51; 80.40-92.51); the Clickhaler (46.55-96.49; 51.12-96.49 and 51.18-101.39; 59.71-101.39) as well as the Turbuhaler (46.08-88.13; 51.95-88.13 and 48.05-89.22; 48.64-89.22). The results highlight that the four inhalers have flow-dependent dose emission property to a varying degree using 2L and 4 L inhaled volumes. There was no significant difference in the total emitted dose between a 2L inhaled volume and a 4L inhaled volume at each inhalation flow. Furthermore, the total emitted dose from the Easyhaler®, Clickhaler®, and Turbuhaler® was significantly (p≤0.001) greater with two inhalations than one inhalation per metered dose across the range of inhalation flow (10-60) Lmin-1. This effect was only observed at inhalation flow less than 30 Lmin-1 with the Accuhaler®. Overall there is a significant difference in the total emitted dose. The ex-vivo dose emission of the four different DPIs has been determined using the In- Check Dial device to train twelve non-smoking healthy adult volunteers to inhale at slow (30 Lmin-1) and fast (60 L min-1) inhalation flows through the device with its dial set corresponding to each inhaler. Subsequently each volunteer inhaled at the trained inhalation flows through each active inhaler. The local ethics committee approval was obtained prior to the study and all volunteers gave signed informed consent. The results obtained demonstrate that the studied inhalers have flow-dependent dose emission, thereby enhancing confidence in the use of the In-Check Dial® to identify a patient's inhalation flows through a variety of DPIs. Also the total emitted dose determined by ex-vivo methodology was significantly (p≤0.05) greater with two inhalations than one inhalation per metered dose. The results of the in-vitro aerodynamic dose emission characteristics highlight that the fine particle dose (FPD) from the four studied inhalers is flow dependent. Also the minimum inhalation flow to generate the (FPD) with the appropriate characteristics for lung deposition has been identified to be 20 L min⁻¹ for the Accuhaler®, Easyhaler® and Clickhaler®, while that for the Turbuhaler® is about 30 L min⁻¹. Also the inhalation volume above 2L and the number of inhalations for each dose have respectively no significant (p≤0.05) influence on the FPD emitted from the four studied inhalers. The results support the present instructions to patients using these inhalers to inhale once for each dose as fast as they can.

Currently available dry powder inhalers (DPIs) for drug delivery to the lungs require turbulent energy to generate and disperse aerosol particles in the respirable range ¿5¿m during inhalation. The patient's inspiratory effort together with the resistance inside the device creates this energy. Different inhalers provide varying degrees of resistance to inhalation flow and require different inhalation techniques for the generation and delivery of drug fine particles in respirable size range to the lungs. The aim of this research programme was to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of the salbutamol Accuhaler®, Easyhaler®, and Clickhaler® and the terbutaline Turbuhaler® DPIs. A high-performance liquid chromatography method for the assay of salbutamol sulphate and terbutaline sulphate in aqueous samples was modified and accordingly validated. In-vitro dose emission of the four different DPIs was measured using the pharmacopoeia method with modifications to simulate varying inhalation flows within patient and between patients. The ranges of the total emitted dose (% nominal dose) at the inhalation flow range of 10 - 60 Lmin-1, following one and two inhalations per metered dose for 2L and 4L inhaled volumes were as follows: the Accuhaler (52.64- 85.11; 61.88-85.11 and 59.23-85.11; 62.81-85.11); the Easyhaler (68.35-91.99; 79.94-91.99 and 73.83-92.51; 80.40-92.51); the Clickhaler (46.55-96.49; 51.12-96.49 and 51.18-101.39; 59.71-101.39) as well as the Turbuhaler (46.08-88.13; 51.95-88.13 and 48.05-89.22; 48.64-89.22). The results highlight that the four inhalers have flow-dependent dose emission property to a varying degree using 2L and 4 L inhaled volumes. There was no significant difference in the total emitted dose between a 2L inhaled volume and a 4L inhaled volume at each inhalation flow. Furthermore, the total emitted dose from the Easyhaler®, Clickhaler®, and Turbuhaler® was significantly (p¿0.001) greater with two inhalations than one inhalation per metered dose across the range of inhalation flow (10 ¿ 60) Lmin-1. This effect was only observed at inhalation flow less than 30 Lmin-1 with the Accuhaler®. Overall there is a significant difference in the total emitted dose. The ex-vivo dose emission of the four different DPIs has been determined using the In- Check Dial device to train twelve non-smoking healthy adult volunteers to inhale at slow (30 Lmin-1) and fast (60 L min-1) inhalation flows through the device with its dial set corresponding to each inhaler. Subsequently each volunteer inhaled at the trained inhalation flows through each active inhaler. The local ethics committee approval was obtained prior to the study and all volunteers gave signed informed consent. The results obtained demonstrate that the studied inhalers have flow-dependent dose emission, thereby enhancing confidence in the use of the In-Check Dial® to identify a patient¿s inhalation flows through a variety of DPIs. Also the total emitted dose determined by ex-vivo methodology was significantly (p¿0.05) greater with two inhalations than one inhalation per metered dose. The results of the in-vitro aerodynamic dose emission characteristics highlight that the fine particle dose (FPD) from the four studied inhalers is flow dependent. Also the minimum inhalation flow to generate the (FPD) with the appropriate characteristics for lung deposition has been identified to be 20 L min-1 for the Accuhaler®, Easyhaler® and Clickhaler®, while that for the Turbuhaler® is about 30 L min-1. Also the inhalation volume above 2L and the number of inhalations for each dose have respectively no significant (p¿0.05) influence on the FPD emitted from the four studied inhalers. The results support the present instructions to patients using these inhalers to inhale once for each dose as fast as they can.

This study provides, for the first time, an ex vivo comparative evaluation of formulations of budesonide with crystallised β-form mannitol, commercial DPI grade mannitol and lactose. The lactose-budesonide was the marketed Easyhaler® 200 g formulation. Ex vivo assessment of deposition using the Easyhaler® multi-dose high resistance inhaler with reservoir was compared with the RS01® single dose capsule low resistance inhaler at two different inhalation rates. Aerodynamic characteristics, flow and surface energies were investigated together with in vitro and ex vivo assessment of drug deposition. Dose emission was greater for all formulations with higher inhalation flow, indicating greater detachment of drug from carrier, and greater with the Easyhaler®, highlighting the importance of correct device for formulation. Emission was lowest at both inhalation rates for crystallised mannitol due to poor flowability associated with elongated particle shape which resulted in interception deposition. Surface energies were also implicated; closely matched polar surface energy of carrier and drug may be an important inhibiting factor. The promising aerodynamic characteristics of crystallised mannitol with the RS01® inhaler and lactose-budesonide from in vitro assessment were not supported by ex vivo results, highlighting the need for careful selection of device.

The present work aimed at assessing the dose emission and aerodynamic particle size characteristics of formoterol fumarate from Atimos Modullite, a metered dose inhaler (MDI) and Foradil Aeroliser, Easyhaler, and Oxis Turbuhaler dry powder inhalers (DPI) at different inhalation flow rates and volumes using in vitro methodology. Recognised methods have been adopted and validated to generate the results. The in vitro characteristics of formoterol were measured according to standard pharmacopeial methodology with adaptation to simulate routine patient use. The dose emission from the Atimos Modulite was determined using inhalation volumes of 4 and 2 L and inhalation flows of 10, 28.3, 60, and 90 L/min. The %nominal dose emitted was consistent between the various flow rates and inhalation volumes of 4 and 2L. The particle size distribution was measured using an Anderson Cascade Impactor (ACI) combined with a mixing inlet valve to measure particle size distribution at inhalation flow rates below 30 L/min. The particle size distribution of formoterol from Atimos Modulite was measured using inhalation flows of 15, 28.3, 50, and 60 L/min with and without different spacers, Aerochamber and Volumatic. The mean fine particle dose (%nominal dose) through an Atimos without spacer were 53.52% (2.51), 54.1% (0.79), 53.37% (0.81), 50.43% (1.92) compared to Aerochamber 63.62% (0.44), 63.86% (0.72), 64.72% (0.47), 59.96% (1.97) and Volumatic 62.40% (0.28),63.41% (0.52), 64.71% (0.61), 58.43% (0.73), respectively. A small decrease in the fine particle dose was observed as the inhalation flow increased, but this was not significant. The respective mean mass aerodynamic diameter (MMAD) increased as the flow rate was increased from 15 of 60 L/min. Results also suggests that the use of spacers provides better lung deposition for patients with problems using MDI. The dose emission from the Foradil Aeroliser was determined using inhalation volumes of 4 and 2 L, at inhalation flows of 10, 15, 20, 28.3, 60, and 90 L/min plus two inhalations per single dose. The %nominal dose emitted using 2 L inhalation volume was approximately half when compared to results obtained using inhalation volume of 4 L. A significantly (p<0.001) higher amount of drug was also emitted from Easyhaler® at inhalation volume of 4 L through flow rates of 10, 20, 28.3, 40, and 60 L/min compared 2 L. Similar results were observed through Oxis Turbuhaler at inhalation flow rates of 10, 20, 28.3, 40, and 60 L/min. Comparative studies were also carried out to evaluate the particle size distribution of formoterol through the DPIs. The nominal fine particle dose through Aeroliser using inhalation flows of 10, 20, 28.3, 60 and 90 L/min were 9.23%, 14.70 %, 21.37%, 28.93%, and 39.70% for the 4 L and 4.17%, 5.55%, 7.28%, 8.41%, and 11.08% for the 2 L, respectively. The respective MMAD significantly (p<0.001) decreased with increasing flow rates. Aeroliser performance showed significant (p<0.001) increase in the % nominal fine particle dose for two inhalations compared to one inhalation at both 4 and 2 L. The Easyhaler was measured using inhalation flows of 10, 20, 28.3, 40, 60 L/min. The nominal fine particle dose were 19.03%, 27.09%, 36.89%, 49.71% and 49.25% for the 4 L and 9.14%, 15.44%, 21.02%, 29.41%, 29.14% for the 2 L, respectively. The respective MMAD significantly (p<0.001) decreased with increasing flow rates. Easyhaler performance at both 4 and 2 L showed no significant differences between one and two inhalations at low flow rates (10, 20, 28.3), but this was significant (p<0.05) at higher flow rates (40 and 60 L/min). The Oxis Turbuhaler was also measured using inhalation flows of 10, 20, 28.3, 40, 60 L/min. The nominal fine particle dose were 12.87%, 24.51%, 28.25%, 34.61%, 40.53% for the 4 L and 8.55%, 15.31%, 21.36%, 19.53%, 22.31% for the 2 L, respectively. Turbuhaler performance showed significant (p<0.05) differences between one and two inhalations at varying flow rates 2 L inhalation volumes, but not at 4 L. The use of Foradil Aeroliser delivers small particles as the Oxis Turbuhaler using two inhalations hence delivering formoterol deep into the lungs. Also, this thesis shows that high flow resistance of Turbuhaler will indeed influence the ability of patients with severe asthma or children to use the system. Beside, Easyhaler produced the highest drug delivery to the lungs, thus, making it a more desirable system to use, especially for children and asthma sufferers.

The present work aimed at assessing the dose emission and aerodynamic particle size characteristics of formoterol fumarate from Atimos Modullite, a metered dose inhaler (MDI) and Foradil Aeroliser, Easyhaler, and Oxis Turbuhaler dry powder inhalers (DPI) at different inhalation flow rates and volumes using in vitro methodology. Recognised methods have been adopted and validated to generate the results. The in vitro characteristics of formoterol were measured according to standard pharmacopeial methodology with adaptation to simulate routine patient use. The dose emission from the Atimos Modulite was determined using inhalation volumes of 4 and 2 L and inhalation flows of 10, 28.3, 60, and 90 L/min. The %nominal dose emitted was consistent between the various flow rates and inhalation volumes of 4 and 2L. The particle size distribution was measured using an Anderson Cascade Impactor (ACI) combined with a mixing inlet valve to measure particle size distribution at inhalation flow rates below 30 L/min. The particle size distribution of formoterol from Atimos Modulite was measured using inhalation flows of 15, 28.3, 50, and 60 L/min with and without different spacers, Aerochamber and Volumatic. The mean fine particle dose (%nominal dose) through an Atimos without spacer were 53.52% (2.51), 54.1% (0.79), 53.37% (0.81), 50.43% (1.92) compared to Aerochamber 63.62% (0.44), 63.86% (0.72), 64.72% (0.47), 59.96% (1.97) and Volumatic 62.40% (0.28),63.41% (0.52), 64.71% (0.61), 58.43% (0.73), respectively. A small decrease in the fine particle dose was observed as the inhalation flow increased, but this was not significant. The respective mean mass aerodynamic diameter (MMAD) increased as the flow rate was increased from 15 of 60 L/min. Results also suggests that the use of spacers provides better lung deposition for patients with problems using MDI. The dose emission from the Foradil Aeroliser was determined using inhalation volumes of 4 and 2 L, at inhalation flows of 10, 15, 20, 28.3, 60, and 90 L/min plus two inhalations per single dose. The %nominal dose emitted using 2 L inhalation volume was approximately half when compared to results obtained using inhalation volume of 4 L. A significantly (p<0.001) higher amount of drug was also emitted from Easyhaler® at inhalation volume of 4 L through flow rates of 10, 20, 28.3, 40, and 60 L/min compared 2 L. Similar results were observed through Oxis Turbuhaler at inhalation flow rates of 10, 20, 28.3, 40, and 60 L/min. Comparative studies were also carried out to evaluate the particle size distribution of formoterol through the DPIs. The nominal fine particle dose through Aeroliser using inhalation flows of 10, 20, 28.3, 60 and 90 L/min were 9.23%, 14.70 %, 21.37%, 28.93%, and 39.70% for the 4 L and 4.17%, 5.55%, 7.28%, 8.41%, and 11.08% for the 2 L, respectively. The respective MMAD significantly (p<0.001) decreased with increasing flow rates. Aeroliser performance showed significant (p<0.001) increase in the % nominal fine particle dose for two inhalations compared to one inhalation at both 4 and 2 L. The Easyhaler was measured using inhalation flows of 10, 20, 28.3, 40, 60 L/min. The nominal fine particle dose were 19.03%, 27.09%, 36.89%, 49.71% and 49.25% for the 4 L and 9.14%, 15.44%, 21.02%, 29.41%, 29.14% for the 2 L, respectively. The respective MMAD significantly (p<0.001) decreased with increasing flow rates. Easyhaler performance at both 4 and 2 L showed no significant differences between one and two inhalations at low flow rates (10, 20, 28.3), but this was significant (p<0.05) at higher flow rates (40 and 60 L/min). The Oxis Turbuhaler was also measured using inhalation flows of 10, 20, 28.3, 40, 60 L/min. The nominal fine particle dose were 12.87%, 24.51%, 28.25%, 34.61%, 40.53% for the 4 L and 8.55%, 15.31%, 21.36%, 19.53%, 22.31% for the 2 L, respectively. Turbuhaler performance showed significant (p<0.05) differences between one and two inhalations at varying flow rates 2 L inhalation volumes, but not at 4 L. The use of Foradil Aeroliser delivers small particles as the Oxis Turbuhaler using two inhalations hence delivering formoterol deep into the lungs. Also, this thesis shows that high flow resistance of Turbuhaler will indeed influence the ability of patients with severe asthma or children to use the system. Beside, Easyhaler produced the highest drug delivery to the lungs, thus, making it a more desirable system to use, especially for children and asthma sufferers.

There has been very little research into the bioanalytical application of Microemulsion High Performance Liquid Chromatography (MELC), a recently established technique for separating an active pharmaceutical ingredient from its related substances and for determining the quantity of active drug in a dose. Also, the technique is not good at separating hydrophilic drugs of very similar chemical structures. Different phase diagrams of oil (octane or ethyl acetate), co-surfactant (butanol), surfactant (sodium dodecyl sulphate (SDS) or Brij-35) and buffer (Phosphate pH 3) were developed and several nanoemulsion mobile phases identified. Nanoemulsion mobile phase that is, prepared with SDS, octane, butanol and a phosphate buffer, failed to separate hydrophilic compounds with a very close chemical structure, such as terbutaline and salbutamol. A nanoemulsion mobile phase containing a non-ionic surfactant (Brij-35) with ethyl acetate, butanol and a phosphate buffer, was, however, successful in achieving a base line separation, and the method was validated for simultaneous determination of terbutaline and salbutamol in aqueous and urine samples. An oil-in-water (O/W) NELC method was developed and validated for the determination of formoterol in an Oxis® Turbuhaler® using pre-column fluorescence derivatisation. Although the same mobile phase was extended for separation of formoterol in urine, the formoterol peak's overlap with endogenous peaks meant that fluorescence detection could not determine formoterol in urine samples. Solid phase extraction, concentrating the final analyte 40 times, enabled determination of a low concentration of formoterol in urine samples by UV detection. The method was validated and an acceptable assay precision %CV <4.89 inter-day and %CV <2.33 intra-day was achieved. Then after the application of O/W nanoemulsion mobile phase for HPLC was extended for the separation of lipophilic drugs. The nanoemulsion liquid chromatography (NELC) method was optimised for the determination of salmeterol and fluticasone propionate in good validation data was achieved. This thesis shows that, in general, the performance of O/W NELC is superior to that of conventional High Performance Liquid Chromatography (HPLC) for the analysis of both hydrophilic and lipophilic drugs in inhaled dosage formulations and urine samples. It has been shown that NELC uses cheaper solvents and that analysis time is faster for aqueous and urine samples. This considerable saving in both cost and time will potentially improve efficiency within quality control.

There has been very little research into the bioanalytical application of Microemulsion High Performance Liquid Chromatography (MELC), a recently established technique for separating an active pharmaceutical ingredient from its related substances and for determining the quantity of active drug in a dose. Also, the technique is not good at separating hydrophilic drugs of very similar chemical structures. Different phase diagrams of oil (octane or ethyl acetate), co-surfactant (butanol), surfactant (sodium dodecyl sulphate (SDS) or Brij-35) and buffer (Phosphate pH 3) were developed and several nanoemulsion mobile phases identified. Nanoemulsion mobile phase that is, prepared with SDS, octane, butanol and a phosphate buffer, failed to separate hydrophilic compounds with a very close chemical structure, such as terbutaline and salbutamol. A nanoemulsion mobile phase containing a non-ionic surfactant (Brij-35) with ethyl acetate, butanol and a phosphate buffer, was, however, successful in achieving a base line separation, and the method was validated for simultaneous determination of terbutaline and salbutamol in aqueous and urine samples. An oil-in-water (O/W) NELC method was developed and validated for the determination of formoterol in an Oxis® Turbuhaler® using pre-column fluorescence derivatisation. Although the same mobile phase was extended for separation of formoterol in urine, the formoterol peak¿s overlap with endogenous peaks meant that fluorescence detection could not determine formoterol in urine samples. Solid phase extraction, concentrating the final analyte 40 times, enabled determination of a low concentration of formoterol in urine samples by UV detection. The method was validated and an acceptable assay precision %CV <4.89 inter-day and %CV <2.33 intra-day was achieved. Then after the application of O/W nanoemulsion mobile phase for HPLC was extended for the separation of lipophilic drugs. The nanoemulsion liquid chromatography (NELC) method was optimised for the determination of salmeterol and fluticasone propionate in good validation data was achieved. This thesis shows that, in general, the performance of O/W NELC is superior to that of conventional High Performance Liquid Chromatography (HPLC) for the analysis of both hydrophilic and lipophilic drugs in inhaled dosage formulations and urine samples. It has been shown that NELC uses cheaper solvents and that analysis time is faster for aqueous and urine samples. This considerable saving in both cost and time will potentially improve efficiency within quality control.

This thesis is based around examination of three mainstream inhaled drugs Formoterol, Budesonide and Beclomethasone for treatment of asthma and COPD. The areas investigated are these which have been raised in reports and studies, where there are concern, for drug use and assessment of their use. In reporting this work the literature study sets out a brief summary of the background and anatomy and physiology of the respiratory system and then discuses the mechanism of drug deposition in the lung, as well as the methods of studying deposition and pulmonary delivery devices. This section includes the basis of asthma and COPD and its treatment. In addition, a short section is presented on the role of the pharmacist in improving asthma and COPD patient's care. Therefore the thesis is divided into 3 parts based around formoterol, budesonide and beclomethasone. In the first case the research determines the in-vitro performance of formoterol and budesonide in combination therapy. In the initial stage a new rapid, robust and sensitive HPLC method was developed and validated for the simultaneous assay of formoterol and the two epimers of budesonide which are pharmacologically active. In the second section, the purpose was to evaluate the aerodynamic characteristics for a combination of formoterol and the two epimers of budesonide at inhalation flow rates of 28.3 and 60 L/min. The aerodynamic characteristics of the emitted dose were measured by an Anderson cascade impactor (ACI) and the next generation cascade impactor (NGI). In all aerodynamic characterisations, the differences between flow rates 28.3 and 60 were statistically significant in formoterol, budesonide R and budesonide S, while the differences between ACI and NGI at 60 were not statistically significant. Spacers are commonly used especially for paediatric and elderly patients. However, there is considerable discussion about their use and operation. In addition, the introduction of the HFAs propellants has led to many changes in the drug formulation characteristics. The purpose of the last section is to examine t h e performance of different types of spacers with different beclomethasone pMDIs. Also, it was to examine the hypothesis of whether the result of a specific spacer with a given drug/ brand name can be extrapolated to other pMDIs or brand names for the same drug. The results show that there are different effects on aerodynamic characterisation and there are significant differences in the amount of drug available for inhalation when different spacers are used as inhalation aids. Thus, the study shows that the result from experiments with a combination of a spacer and a device cannot be extrapolated to other combination.

This thesis is based around examination of three mainstream inhaled drugs Formoterol, Budesonide and Beclomethasone for treatment of asthma and COPD. The areas investigated are these which have been raised in reports and studies, where there are concern, for drug use and assessment of their use. In reporting this work the literature study sets out a brief summary of the background and anatomy and physiology of the respiratory system and then discuses the mechanism of drug deposition in the lung, as well as the methods of studying deposition and pulmonary delivery devices. This section includes the basis of asthma and COPD and its treatment. In addition, a short section is presented on the role of the pharmacist in improving asthma and COPD patient¿s care. Therefore the thesis is divided into 3 parts based around formoterol, budesonide and beclomethasone. In the first case the research determines the in-vitro performance of formoterol and budesonide in combination therapy. In the initial stage a new rapid, robust and sensitive HPLC method was developed and validated for the simultaneous assay of formoterol and the two epimers of budesonide which are pharmacologically active. In the second section, the purpose was to evaluate the aerodynamic characteristics for a combination of formoterol and the two epimers of budesonide at inhalation flow rates of 28.3 and 60 L/min. The aerodynamic characteristics of the emitted dose were measured by an Anderson cascade impactor (ACI) and the next generation cascade impactor (NGI). In all aerodynamic characterisations, the differences between flow rates 28.3 and 60 were statistically significant in formoterol, budesonide R and budesonide S, while the differences between ACI and NGI at 60 were not statistically significant. Spacers are commonly used especially for paediatric and elderly patients. However, there is considerable discussion about their use and operation. In addition, the introduction of the HFAs propellants has led to many changes in the drug formulation characteristics. The purpose of the last section is to examine t h e performance of different types of spacers with different beclomethasone pMDIs. Also, it was to examine the hypothesis of whether the result of a specific spacer with a given drug/ brand name can be extrapolated to other pMDIs or brand names for the same drug. The results show that there are different effects on aerodynamic characterisation and there are significant differences in the amount of drug available for inhalation when different spacers are used as inhalation aids. Thus, the study shows that the result from experiments with a combination of a spacer and a device cannot be extrapolated to other combination.