Device Selection and Outcomes of Aerosol Therapy: Evidence-Based Guidelines

BACKGROUND

The proliferation of inhaler devices has resulted in a confusing number of choices for clinicians who are selecting a delivery device for aerosol therapy. There are advantages and disadvantages associated with each device category. Evidence-based guidelines for the selection of the appropriate aerosol delivery device in specific clinical settings are needed.

AIM

(1) To compare the efficacy and adverse effects of treatment using nebulizers vs pressurized metered-dose inhalers (MDIs) with or without a spacer/holding chamber vs dry powder inhalers (DPIs) as delivery systems for beta-agonists, anticholinergic agents, and corticosteroids for several commonly encountered clinical settings and patient populations, and (2) to provide recommendations to clinicians to aid them in selecting a particular aerosol delivery device for their patients.

METHODS

A systematic review of pertinent randomized, controlled clinical trials (RCTs) was undertaken using MEDLINE, EmBase, and the Cochrane Library databases. A broad search strategy was chosen, combining terms related to aerosol devices or drugs with the diseases of interest in various patient groups and clinical settings. Only RCTs in which the same drug was administered with different devices were included. RCTs (394 trials) assessing inhaled corticosteroid, beta2-agonist, and anticholinergic agents delivered by an MDI, an MDI with a spacer/holding chamber, a nebulizer, or a DPI were identified for the years 1982 to 2001. A total of 254 outcomes were tabulated. Of the 131 studies that met the eligibility criteria, only 59 (primarily those that tested beta2-agonists) proved to have useable data.

RESULTS

None of the pooled metaanalyses showed a significant difference between devices in any efficacy outcome in any patient group for each of the clinical settings that was investigated. The adverse effects that were reported were minimal and were related to the increased drug dose that was delivered. Each of the delivery devices provided similar outcomes in patients using the correct technique for inhalation.

CONCLUSIONS

Devices used for the delivery of bronchodilators and steroids can be equally efficacious. When selecting an aerosol delivery device for patients with asthma and COPD, the following should be considered: device/drug availability; clinical setting; patient age and the ability to use the selected device correctly; device use with multiple medications; cost and reimbursement; drug administration time; convenience in both outpatient and inpatient settings; and physician and patient preference.

Measurement of children's asthma medication adherence by self report, mother report, canister weight, and Doser CT

BACKGROUND

Accurate assessment of medication adherence has been difficult to achieve but is essential to drug evaluation in clinical trials and improved outcomes in clinical care.

OBJECTIVE

This study was conducted to compare four adherence assessment methods: child report, mother report, canister weight, and electronic measurements of metered dose inhaler (MDI) actuation.

METHODS

Participants included 27 children with mild-to-moderate asthma who were followed prospectively for 6 months. All patients used an MDI equipped with an electronic Doser attached to their inhaled steroid. At each 2-month follow-up visit, Doser and canister weight data were recorded, while child and mother were interviewed separately regarding medication use.

RESULTS

Children and mothers reported, on average, over 80% adherence with the prescribed inhaled steroid. Canister weight revealed, on average, adherence of 69%, significantly lower than self-report. When adherence recorded by the electronic Doser was truncated to no more than 100% of prescribed daily use, average adherence was 50%. Older children and adolescents, nonwhite children, and those from poorer functioning families were least adherent.

CONCLUSIONS

Electronic adherence monitoring was significantly more accurate than self-report or canister weight measures. Such accuracy is an essential prerequisite to increasing understanding of the treatment, setting, and patient factors that influence adherence, and to the consequent design of effective intervention strategies.

Assessment of handling of inhaler devices in real life: an observational study in 3811 patients in primary care

The correct use of inhalation devices is an inclusion criterion for all studies comparing inhaled treatments. In real life, however, patients may make many errors with their usual inhalation device, which may negate the benefits observed in clinical trials. Our study was undertaken to compare inhalation device handling in real life. A total of 3811 patients treated for at least 1 month with an inhalation device (Aerolizer, Autohaler, Diskus, pressurized metered dose inhaler (pMDI), or Turbuhaler) were included in this observational study performed in primary care in France between February 1st and July 14th, 2002. General practitioners had to assess patient handling of their usual inhaler device with the help of a checklist established for each inhaler model, from the package leaflet. Seventy-six percent of patients made at least one error with pMDI compared to 49-55% with breath-actuated inhalers. Errors compromising treatment efficacy were made by 11-12% of patients treated with Aerolizer, Autohaler, or Diskus compared to 28% and 32% of patients treated with pMDI and Turbuhaler, respectively. Overestimation of good inhalation by general practitioners was maximal for Turbuhaler (24%), and lowest for Autohaler and pMDI (6%). Ninety percent of general practitioners felt that participation in the study would improve error detection. These results suggest that there are differences in the handling of inhaler devices in real life in primary care that are not taken into account in controlled studies. There is a need for continued education of prescribers and users in the proper use of these devices to improve treatment efficacy.

Effect of Design on the Performance of a Dry Powder Inhaler Using Computational Fluid Dynamics. Part 1: Grid Structure and Mouthpiece Length

This study investigates (1) the effect of modifying the design of a dry powder inhaler on the device performance, and (2) which design features significantly contribute to overall inhaler performance. Computational Fluid Dynamics (CFD) analysis was performed to determine how the flowfield generated in an Aerolizer at 60 l min(-1) varied when the inhaler grid and mouthpiece were modified. The computational models were validated by Laser Doppler Velocimetry (LDV). Dispersion performance of the modified inhalers was measured with a mannitol powder using a multistage liquid impinger at 60 l min(-1). The inhaler grid was found to significantly affect the performance of the Aerolizer. As the grid voidage was increased, the amount of powder retained in the device doubled (due to increased tangential flow of particles in the inhaler mouthpiece) and the FPF(Loaded) was reduced from 57 to 44% (due to increased mouthpiece retention). The length of the mouthpiece played a lesser role on the inhaler performance, having no significant effect on the flowfield generated in the devices. In summary, the performance of a dry powder inhaler can be affected by simple design changes. CFD, coupled with experimental results, provides a rational basis for understanding the performance difference.

Characterization of nasal spray pumps and deposition pattern in a replica of the human nasal airway

Deposition patterns are described of a nasal spray formulation for a novel rhinovirus protease inhibitor. These patterns, which were generated from different nasal spray pumps, were characterized using a multisectional nasal airway model. A human nasal replica was made from an in vivo magnetic resonance imaging (MRI) scan of an adult male human. The nasal replica consisted of 77 acrylic plastic sections, 1.5-mm thick. Our data showed that the aerosols were deposited mainly in the anterior and turbinate regions with little passing beyond the nasopharyngeal region. Detailed deposition information from the turbinate region indicated that deposition was high toward the anterior portion where most deposition was concentrated on the inferior meatus. Spray droplets were also deposited in spots of the middle and posterior portions of the turbinate region, and this nonuniform deposition pattern may be correlated with the flow pattern. The spray angle and droplet size of the nasal spray were found to be important in influencing the deposition pattern in the nasal airway. The droplet size was determined by a laser-diffraction technique and the spray angle by high-speed photography. Larger droplets and a wider spray angle increased deposition in the anterior region of the nasal airway, which prevented more material from depositing in the turbinate region.

Vapor inhalation of alcohol in rats

Alcohol dependence constitutes a neuroadaptive state critical for understanding alcoholism, and various methods have been utilized to induce alcohol dependence in animals, one of which is alcohol vapor exposure. Alcohol vapor inhalation provides certain advantages over other chronic alcohol exposure procedures that share the ultimate goal of producing alcohol dependence in rats. Chronic alcohol vapor inhalation allows the experimenter to control the dose, duration, and pattern of alcohol exposure. Also, this procedure facilitates testing of somatic and motivational aspects of alcohol dependence. Chronic exposure to alcohol vapor produces increases in alcohol-drinking behavior, increases in anxiety-like behavior, and reward deficits in rats. Alcohol vapor inhalation as a laboratory protocol is flexible, and the parameters of this procedure can be adjusted to accommodate the specific aims of different experiments. This unit describes the options available to investigators using this procedure for dependence induction, when different options are more or less appropriate, and the implications of each.

Nebulization of biodegradable nanoparticles: impact of nebulizer technology and nanoparticle characteristics on aerosol features

Nanoparticles may be effective drug delivery systems for use in various pulmonary therapeutic schemes. This study investigated the effect of nebulization technology and nanoparticle characteristics on the features of aerosol generation. Suspensions of biodegradable nanoparticles consisting of commercially available poly(lactide-co-glycolide) and novel comb polymers were nebulized with a jet, ultrasonic, and piezo-electric crystal nebulizer. The effects of the nanoparticle suspensions on the aerosol droplet size, as well as the nanoparticle size before and after nebulization, were characterized via laser diffraction. While the individual nanoparticle suspensions showed no clinically relevant influence on aerosol droplet size, as compared to control experiments, an enhanced nanoparticle aggregation within the droplets was observed. This aggregation was further characterized by fluorescence and scanning electron microscopy. Dependency of aggregation on nebulizer technology and nanoparticle characteristics was noted. Nanoparticles exhibiting the highest surface hydrophobicity were particularly susceptible to aggregation when nebulized with a jet nebulizer. Aggregation was reduced with nanoparticles exhibiting a more hydrophilic surface or when using ultrasonic nebulizers. We conclude that the biodegradable nanoparticles contained in the suspensions did not affect the aerosol droplet size in a clinically relevant manner; however, both the nanoparticle characteristics and the technique of aerosol generation influence nanoparticle aggregation occurring during aerosolization.

Poor inhalation technique, even after inhalation instructions, in children with asthma

The aim of this study was to evaluate the effect of instructions to children with asthma (given by general practitioners or by pharmacy assistants) on how to inhale from metered dose inhalers with spacers (MDI/s) or dry powder inhalers (DPI). We scored inhalation technique of asthmatic children according to criteria defined by the Netherlands Asthma Foundation, and related the performance to the inhalation instructions given. For each inhaler, a number of steps were considered essential for reliable drug delivery. Patients newly referred for asthma were asked to demonstrate their inhalation technique and to fill out a questionnaire on the inhalation instruction received prior to referral. Children participating in a clinical trial, who had received repeated comprehensive inhalation instructions, served as a control group. Sixty-six newly referred patients (1-14 years of age, median age 5 years; 37 boys) and 29 control patients (5-10 years of age, median age 7 years; 21 boys) completed the study. Sixty patients (91%) had received inhalation instruction prior to referral. Only 29% of these patients, using a dry powder inhaler, performed all essential steps correctly, compared to 67% of children using a metered dose inhaler/spacer combination (P < 0.01). Children who had received comprehensive inhalation instructions with repeated checks of proper inhalation technique at the pharmacy or in the clinical trial setting were more likely to perform all essential steps correctly (79% and 93%, respectively) than children who had received a single instruction by a general practitioner (39%, P < 0.01). Many asthmatic children use their inhalers devices too poorly to result in reliable drug delivery, even after inhalation instruction. Comprehensive inhalation instruction and repeated check-ups are needed to assure reliable inhalation technique.

Cascade Impactors for the Size Characterization of Aerosols from Medical Inhalers: Their Uses and Limitations

Cascade impactors, including the multi-stage liquid impinger, are by far the most widely encountered means for the in vitro determination of the particle size distribution of aerosols from medical inhalers, both in product development, batch release and in applications with add-on devices. This is because they directly measure aerodynamic size, which is the most relevant parameter to describe particle transport within the respiratory tract. At the same time, it is possible to quantify the mass of active pharmaceutical ingredient in different size ranges independent of other non-physiologically active components of the formulation. We begin by providing an overview of the operating principles of impactors and then highlight the various configurations and adaptations that have been adopted to characterize the various classes of inhaler. We continue by examining the limitations of the cascade impaction method, in particular looking at potential sources of measurement bias and discussing both appropriate and inappropriate uses of impactor-generated data. We also present a synopsis of current developments, including the Next Generation Pharmaceutical Impactor, and automation of cascade impactors for routine inhaler performance measurements.

Improvement in sodium cromoglycate delivery from a spacer device by use of an antistatic lining, immediate inhalation, and avoiding multiple actuations of drug

BACKGROUND

Aerosols generated from metered dose inhalers may be highly charged. The aim of this study was to determine whether lining the walls of a polycarbonate spacer device with an antistatic agent would result in an increase in drug output. The effects of multiple actuations of drug into the spacer device and increasing residence time of drug within the spacer were also determined.

METHODS

The amount of sodium cromoglycate contained in particles of various size available for inhalation (per 5 mg actuation) from a 750 ml polycarbonate spacer was determined by impinger measurement and spectrophotometric assay.

RESULTS

Lining the spacer with an antistatic agent increased the mean (SD) amount of sodium cromoglycate in particles < 5 microns available for inhalation (per 5 mg actuation) by 244% from (0.59 (0.03) to 1.44 (0.2) mg). When there was a 20 second interval between actuation into the spacer device and inhalation, sodium cromoglycate available for inhalation in particles < 5 micrograms decreased by 67% (from 0.59 (0.03) mg to 0.2 (0.01) mg). Use of the spacer device increased sodium cromoglycate available for inhalation in respirable particles (< 5 microns) by 18% compared with direct delivery by metered dose inhaler. Multiple actuations into the spacer decreased the amount of sodium cromoglycate available for inhalation in particles < 5 microns by 31% after two actuations and 56% after three acutations.

CONCLUSIONS

Multiple actuations of sodium cromoglycate into a spacer device before inhalation should be avoided, and inhalation from spacer devices should take place immediately after actuation to ensure maximum dose. Lining of a standard spacer device with an antistatic agent significantly increased output of sodium cromoglycate. This may have implications for improved therapeutic response and drug cost.

Effect of design on the performance of a dry powder inhaler using computational fluid dynamics. Part 2: Air inlet size

This study investigates the effect of air inlet size on (i) the flowfield generated in a dry powder inhaler, and (ii) the device-specific resistance, and the subsequent effect on powder deagglomeration. Computational fluid dynamics (CFD) analysis was used to simulate the flowfield generated in an Aerolizer with different air inlet sizes at 30, 45, and 60 l/min. Dispersion performance of the modified inhalers was measured using mannitol powder and a multistage liquid impinger at the same flow rates. The air inlet size had a varying effect on powder dispersion depending on the flow rate. At low flow rates (30 and 45 l/min), reducing the air inlet size increased the inhaler dispersion performance by increasing the flow turbulence and particle impaction velocities above their critical levels for maximal powder dispersion. At 60 l/min, reducing the air inlet size reduced the inhaler dispersion performance by releasing a large amount of powder from the device before the turbulence levels and particle impaction velocities could be fully developed. The results demonstrate that the maximal inhaler dispersion performance can be predicted if details of the device flowfield are known.

A collaborative European study of personal inhalable aerosol sampler performance

Following the adoption of new international sampling conventions for inhalable, thoracic and respirable aerosol fractions, a working group of Comité Européen de Normalisation (CEN) drafted a standard for the performance of workplace aerosol sampling instruments. The present study was set up to verify the experimental, statistical and mathematical procedures recommended in the draft performance standard and to check that they could be applied to inhalable aerosol samplers. This was achieved by applying the tests to eight types of personal inhalable aerosol sampler commonly used for workplace monitoring throughout Europe. The study led to recommendations for revising the CEN draft standard, in order to simplify the tests and reduce their cost. However, some further work will be needed to develop simpler test facilities and methods. Several of the samplers tested were found to perform adequately with respect to the inhalable sampling convention, at least over a limited range of typical workplace conditions. In general the samplers were found to perform best in low external wind speeds, which are the test conditions thought to be closest to those normally found in indoor workplaces. The practical implementation of the CEN aerosol sampling conventions requires decisions on which sampling instruments to use, estimation of the likely impact that changing sampling methods could have on apparent exposures, and adjustment where necessary of exposure limit values. The sampler performance data obtained in this project were affected by large experimental errors, but are nevertheless a useful input to decisions on how to incorporate the CEN inhalable sampling convention into regulation, guidance and occupational hygiene practice.

Aerosol deposition in mechanically ventilated patients. Optimizing nebulizer delivery

Previous studies have suggested that nebulizers are inefficient in delivering aerosolized medication to the lung in patients supported by mechanical ventilation. In a recent bench study, we characterized factors that may affect aerosol delivery, i.e., nebulizer type, ventilator settings (duty cycle), volume fill, and humidification as well as technical factors affecting measurement of deposition (e.g., radiolabeled compounds). Utilizing the predictions from our bench data, the present study was designed to assess nebulized aerosol delivery to ventilated patients under optimal conditions. Seven patients who were receiving mechanical ventilation (Bear II) via tracheostomy tube (TT) were studied. The humidifier was turned off. The test aerosol, a saline solution labeled with 99mTechnetium bound to human serum albumin (99mTc-HSA), was administered via a jet nebulizer (AeroTech II, 1.1 +/- 1.8 microns [mass median aerodynamic diameter, MMAD, geometric standard deviation, sigma g]), which was incorporated into the ventilator circuit and run to dryness. Inhaled and deposited radioactivity were measured by a mass balance/filter technique. TT versus lung deposition were quantified by removal of the inner cannula and direct measurement of TT deposition in a well counter. Inspiratory versus expiratory components of TT deposition were separated via bench techniques for each TT tube and breathing pattern. The regional distribution of deposited radioactivity was confirmed by gamma camera scans before and after TT removal. Measured radioactivity at each site was expressed as a percentage of nebulizer charge (i.e., the quantity of radioactivity originally placed in the nebulizer). On average, 30.6 +/- 6.3% (SD) of the charge was inhaled by the ventilated patients. Mean deposition in the TT during inspiration was 2.6 +/- 0.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Fine particle mass from the Diskus inhaler and Turbuhaler inhaler in children with asthma

The study aimed to investigate dose consistency and particle distribution from the dry powder inhalers Diskus and Turbuhaler. Full profiles of inhalation pressure versus time were recorded in 18 4 yr old and 18 8 yr old asthmatic children through Diskus and Turbuhaler inhalers. These data were used in an inhalation profile simulator to assess drug delivery from both a Diskus inhaler and a Turbuhaler inhaler, and in particular to assess the proportion of drug emitted in the coarse (>4.7 microm) and fine (<4.7 microm) particle size range from each type of inhaler. The inhalation profile more accurately represents the changes in flow rate over time through the device than the constant flow rate usually applied with an impactor alone. The aerosol cloud was released before the peak inspiratory effort had been achieved and accordingly the early part and not the peak of the inspiratory performance is a determinant of the quality of the aerosol. The mean (SD) amount of drug in large particles (>4.7 microm), fine particles (<4.7 microm) and very fine particles (<2.1 microm) in percentage of label claim from the Fluticasone Diskus was 72 (5), 15 (2) and 2 (1) from the 4 yr old children and 71 (3), 18 (2) and 2 (1) from the 8 yr old children, respectively. Similar particle fractions from the Budesonide Turbuhaler were 35 (9), 21 (10) and 7 (5) from 4 yr old children and 30 (7), 32 (9) and 12 (6) from 8 yr old children. In conclusion, the Diskus inhaler provides an improved dose consistency through the varying age groups and inspiratory flow performances when compared to the Turbuhaler in terms of the proportion of the dose emitted at each particle size. This improvement is at the expense of a low fine particle mass and a high proportion of coarse particles from the Diskus as compared with the Turbuhaler.

Delivery of a nebulized aerosol to a lung model during mechanical ventilation. Effect of ventilator settings and nebulizer type, position, and volume of fill

Several factors may affect the delivery of a nebulized aerosol to the lung through an endotracheal tube during mechanical ventilation. To study these factors in vitro, a model representing ventilation of an adult patient was constructed by linking a Servo 900C ventilator to a standard humidified circuit and an endotracheal (ET) tube positioned within a pipe representing the trachea. This was connected via a filter to a lung simulator. Nebulizers filled with 99mTc human serum albumin were positioned in the circuit, and the delivery of nebulized aerosol through the ET tube into the filter was measured using a gamma camera. With the use of an inspiratory phase-activated System 22 Acorn jet nebulizer, typical adult ventilator settings, and a 3-ml nebulizer solution volume, 5.4% of the nebulizer dose reached beyond the end of the ET tube. This was increased by increasing the inspiratory time, reducing the respiratory rate or respiratory minute volume, and by repositioning the nebulizer on the inspiratory limb of the Y-piece and was reduced by slowing the driving gas flow to the nebulizer. Under the same conditions, delivery was 3.1 and 4.4% using the Samsonic and Fisoneb ultrasonic nebulizers, respectively. Increasing the fill volume and the addition of an aerosol storage chamber increased delivery with all three nebulizers. These experiments suggest some simple ways of improving aerosol delivery during mechanical ventilation, including increasing the volume of nebulizer fill, repositioning the nebulizer in the ventilator circuit, adding an aerosol storage chamber, and adjusting ventilator settings to maximize delivery.

Is inhalation rate important for a dry powder inhaler? Using the In-Check Dial to identify these rates

The fraction of the emitted dose from an inhaler that has the potential to be deposited into the lungs is known as the fine particle dose (also the respirable dose). During inhalation all dry powder inhalers require a 'force' to be created inside the device so that a fine particle dose is generated from the formulation in the metering chamber. This 'force' is formed by the inhalation rate used together with the resistance (and hence design) inside an inhaler. Studies have shown that the fine particle dose is related to the clinical effect whilst other studies have reported that this dose can be dependent on the inhalation rate used. The inhalation technique recommended by the manufacturer of an inhaled device should, therefore, be used. For those dry powder inhalers that demonstrate significant flow dependent dosage emission it is important that patients use the most desirable rate that has been reported. The In-Check Dial is a simple and ease to use meter that can be used to measure the inhalation rate of a patient when they use each of the commonly prescribed inhalers that are currently available. This meter can be used to identify the most suitable inhaler for each individual.

Next Generation Pharmaceutical Impactor (A New Impactor for Pharmaceutical Inhaler Testing). Part II: Archival Calibration

A new seven-stage cascade impactor, the Next Generation Pharmaceutical Impactor (NGI), has been developed for the pharmaceutical industry. A calibration following "good laboratory practice (GLP)" procedures has been performed on a specific archival NGI, deemed to be representative of all NGIs. Thus, this impactor had nozzle dimensions for each stage manufactured close to the middle of the tolerance band for the design specification, and therefore the average nozzle diameter was equal to the nominal value for that stage. An essential feature of the NGI is that it is designed to operate at any flow rate between 30 and 100 L/min. Thus, the calibration was made at inlet flow rates of 30, 60 and 100 L/min representing the lower bound, mid-region and upper bound of the specified range of operation for the impactor. The calibration data were then used to develop equations that predict the particle cut size for all components of the impactor at any flow rate from 30 to 100 L/min.

Assessment of patient acceptance and inhalation technique of a pressurized aerosol inhaler and two breath-actuated devices

OBJECTIVE

To assess inhalation technique in patients after written instruction alone, written and verbal instruction, and clinical use of two new inhalation devices.

DESIGN

Randomized, crossover evaluation of the albuterol Diskhaler and the terbutaline Turbuhaler.

SETTING

Canadian tertiary-care hospital.

PATIENTS

Twenty hospitalized adults with asthma or chronic obstructive pulmonary disease currently using an albuterol metered-dose inhaler (MDI). Nineteen patients received Diskhaler, 16 received Turbuhaler, 15 received both inhalers, and 10 patients used both inhalers for three days each.

INTERVENTIONS

Patients were randomized to receive either Diskhaler or Turbuhaler for three days. Inhaler technique was assessed after written instruction, written plus verbal instruction, at the first scheduled dose after instruction, and after three days of clinical use. Patients remaining in the hospital after three days crossed over to the other study inhaler and the same protocol was followed.

MAIN OUTCOME MEASURES

Patient inhalation technique was assessed and compared for the MDI, Diskhaler, and Turbuhaler.

RESULTS

Assessment of MDI technique revealed that 35 percent of patients used their MDI correctly on the first puff, and 42 percent used it correctly on the second puff. Following written instruction alone, correct technique was demonstrated by 32 percent of patients with Diskhaler and 6 percent with Turbuhaler. Technique significantly improved following verbal instruction, although 40 percent of the patients required up to three attempts to demonstrate correct technique on at least one of the study inhalers. After three days of clinical use, correct technique was demonstrated in only 54 percent of the Diskhaler and 64 percent of the Turbuhaler assessments. Performance at this assessment was, however, significantly better on the Turbuhaler than on the MDI (p = 0.01). Performance on the Diskhaler was not significantly different from the performance on the other inhalers.

CONCLUSIONS

Written instruction alone is inadequate in teaching correct inhalation technique. Verbal instruction and technique assessment are essential for patients to achieve proper technique. Patients may perform better on the Turbuhaler than on other inhalation devices.

Influence of Humidity on the Electrostatic Charge and Aerosol Performance of Dry Powder Inhaler Carrier based Systems

To investigate the influence of storage relative humidity (RH) on the aerosolisation efficiency and tribo-electrification of carrier based dry powder inhaler (DPI) formulations using the next generation impactor (NGI) in vitro methodology and the electrostatic low pressure impactor (ELPI). Micronised salbutamol (d (0.5) 1.48 +/- 0.03 microm) was blended with 63-90 microm sieve fractioned alpha-lactose monohydrate carrier and stored at a range of humidities (0-84% RH). The aerosolisation efficiency after storage for 24 h periods was investigated using the NGI. The same experiment was conducted using the ELPI, with corona charger switched off, to measure the net charge vs. mass deposition profile. Significant variations in the aerosolisation efficiency of the formulation were observed with respect to storage RH. In general, the fine particle fraction aerosol performance measured by NGI and ELPI (fraction with mass median aerodynamic diameter <4.46 and 4.04 microm, respectively) followed a positive parabola with aerosol performance increasing over the range 0-60% RH before decreasing >60% RH. Analysis of the ELPI charge data suggested that the micronised salbutamol sulphate had an electronegative charge when aerosolised from lactose based carriers, which was most electronegative at low RH. Increased storage RH resulted in a reduction in net charge to mass ratio with the greatest reduction at RH >60%. The aerosol performance of this binary system is dependent on both electrostatic and capillary forces. The use of the ELPI allows a degree of insight into how these forces affect formulation performances after storage at different RH.

The Influence of Drug Morphology on Aerosolisation Efficiency of Dry Powder Inhaler Formulations

The physicochemical properties of two forms of spray dried bovine serum albumin (BSA) have been investigated using particle sizing, surface energy measurement, atomic force microscopy (AFM) and colloid probe microscopy. The BSA powder had similar particle size distributions and surface energy but significantly different morphologies and roughness, classified as smooth and corrugated BSA. Adhesion forces between the corrugated BSA and alpha-lactose monohydrate indicated median adhesion forces were significantly less than for smooth/carrier interaction forces. These observations correlated well with aerosolisation from BSA/carrier blends, where the corrugated BSA particles gave a higher fine particle fraction than the smooth BSA, suggesting reduced BSA/carrier adhesion and increased drug liberation. The use of corrugated drug particle morphology in drug carrier DPI systems may lead to improved aerosol performance through reduced drug carrier contact area.

Evaluation of different parameters that affect droplet-size distribution from nasal sprays using the Malvern Spraytec

The applicability of laser diffraction (Spraytec) for characterizing the droplet-size distribution (DSD) from nasal sprays was examined to understand the relationship between physical properties of nasal formulations and their spray characteristics. The impact of actuation force (3-7 kg), rheological properties from carboxymethylcellulose (CMC) and carbopol 934PNF, the influence of surfactant (Tween 80), actuation distance, and different nasal-pump designs on the aerosol DSD of nasal sprays were investigated using Spraytec((R)) with the eNSP actuation station (InnovaSystems, Moorestown, NJ). Spray-pattern analysis was performed by monitoring the emitted nasal spray containing a dye or a fluorescent marker. Parameters for DSD and spray pattern included: Dv(10), Dv(50), Dv(90), polydispersity, minimum and maximum diameters, plume area, and ovality. Increasing actuation distance from 1.5 to 6 cm from the laser beam decreased Dv(50) values by 17-27% for commercial nasal-spray products. Spray-pattern analysis revealed a power law relationship between viscosity and surface area for CMC formulations. However, this relationship could not be obtained for carbopol formulations, which was attributed to differences in their rheological behavior. The addition of surfactant (0.5-5% Tween 80) to a 2% CMC solution decreased the Dv(50) values (16-26%) and altered the rheological properties (e.g., changes in viscosity and appearance of the thixotropic system). Briefly, the characteristic of nasal aerosol generation is dependent on a combination of actuation force, viscosity, rheological properties, surface tension, and pump design. The Spraytec with the eNSP actuation station provides an efficient and reliable way of monitoring the effects of formulation variables on DSD from nasal aerosols.

The customised electronic nebuliser: a new category of liquid aerosol drug delivery systems

Inhalation of aerosols is the preferred route of administration of pharmaceutical compounds to the lungs when treating various respiratory diseases. Inhaled antibiotics, hormones, peptides and proteins are potential candidates for direct targeting to the site of action, thus minimising systemic absorption, dilution and undesired side effects, as much lower doses (as low as a fiftieth) are sufficient to achieve a similar therapeutic effect, compared with oral administration. A quick relief from the symptoms and a good tolerance are the main advantages of aerosol therapy. A new class of electronic delivery device is now starting to enter the market. The eFlow electronic nebuliser (PARI GmbH, Germany) provides improved portability and, in some instances, cuts treatment time to only a fraction of what has been experienced with current nebulised therapy. Drug formulations and the device can be mutually adapted and matched for optimal characteristics to meet the desired therapeutic target. Reformulation of known and proven compounds in a liquid format are commercially attractive as they present a relatively low development risk for potential drug candidates and, thus, have become a preferred pathway for the development of new inhalation products.

The Diskus: a review of its position among dry powder inhaler devices

The use of dry powder inhalers (DPIs) to administer treatments for respiratory diseases has increased significantly in recent years. There is now a wide range of DPIs available that vary considerably in design, required operational techniques, output characteristics and drug delivery across a range of inhalation patterns. Different patient populations may find individual types of DPI easier to use correctly than others and selecting the right DPI for particular patient requirements will improve compliance with therapy. For example, some DPIs offer a greater resistance against inspirational flow rate than others which affects the total emitted dose and also fine particle mass of the aerosol released. An individual patient may therefore receive different amounts of drug when inhaling from different DPIs. Therefore, it is important that the prescriber is fully aware of the characteristics of the different types of DPI, so that he or she can prescribe the device that is most appropriate to an individual patient's needs. This review explores the characteristics of currently available DPIs and evaluates their efficacy and patient acceptability. The differences in output characteristics, ease of use and patient preferences between available devices is shown to affect treatment efficacy and patient compliance with therapy. Changing the DPI prescribed to a patient to a cheaper or generic device may therefore adversely affect disease control and thereby increase the cost of treatment.

Effect of formulation parameters on hydrofluoroalkane-beclomethasone dipropionate drug deposition in humans

Chlorofluorocarbon metered dose inhalers (MDIs) and dry powder inhalers currently deliver drug that deposits primarily in the oropharynx and secondarily in the large central airways. Chlorofluorocarbon-beclomethasone dipropionate (CFC-BDP) MDIs deliver more than 90% of the drug in the oropharynx and less than 10% in the lungs. The elimination of chlorofluorocarbons from MDIs provided the opportunity to more optimally target corticosteroids directly to all inflammatory sites. Hydrofluoroalkane-BDP (HFA-BDP) MDIs (QVAR(trade mark)) deliver 50% to 60% of the drug to the lungs with approximately 30% delivered to the mouth. Additionally, the amount of drug delivered to the lungs is distributed throughout the large, intermediate, and small airways. Radiolabeled deposition studies have shown that the HFA-BDP MDI is a "forgiving" aerosol in that even the extreme discoordinated use of the press and breathe MDI still resulted in more than 30% lung deposition. The breath-actuated Autohaler inhaler provided the same lung deposition as an optimally used press and breathe MDI. The dose delivered from either the press and breathe HFA-BDP MDI or the Autohaler was consistent across a wide range of inspiratory flows (eg, flows of 26-137 L/min). Clinical studies have shown that the improvements in lung deposition of HFA-BDP result in equivalent efficacy at approximately one half of the total daily dose compared with current CFC-BDP products.

Inhaler technique in older people in the community

BACKGROUND

Good inhaler technique and medication concordance is important for symptom and disease control in chronic airways disease.

OBJECTIVES

Establish the prevalence of inhaler use; the main inhaler devices used by older people at home; their ability to use the inhalers they have been prescribed; and the relationship between perceived ease of use and actual performance.

DESIGN

Cross-sectional population based study.

SUBJECTS

Subjects aged 70 years and over living at home.

METHODS

500 subjects were randomly selected from 5002 subjects aged 70 years and over living at home. Inhalers used over the previous 24 hours were identified by a nurse on home visit. Those with cognitive impairment were excluded. Inhaler system was assessed and graded by a doctor as acceptable (perfect or minor errors) or unacceptable (major errors), using previously published criteria. Perceived ease of use of the device was rated as easy, moderate or difficult.

RESULTS

423 subjects participated in the study. The population prevalence of inhaler use was 15.8% (12.0, 19.7). Of the 91 inhaler devices used, 39 (42.8%) were metered dose inhalers, 34 (37.4%) were metered dose inhalers with large volume spacers, and 18 (19.8%) were breath-actuated devices. Thirty-two subjects (82.1%) using metered dose inhalers had an acceptable technique compared with 33 (97.1%) of those using metered dose inhalers with large volume spacers and 13 (72.2%) of those using breath-actuated devices (P < 0.05). Up to three quarters of inhalers were considered easy to use but 12% of subjects who rated their inhaler device as being easy to use made major errors.

CONCLUSION

Metered dose inhaler was the most frequently prescribed inhaler and was used correctly by most subjects especially in combination with large volume spacers. Major errors were more common with breath-actuated devices. Inhaler technique should be checked as patients' perception of their inhaler skills correlates poorly with actual performance.