de Anne Boer

A comparison between spray drying and spray freeze drying to produce an influenza subunit vaccine powder for inhalation

The aim of this study was to investigate two different processes to produce a stable influenza subunit vaccine powder for pulmonary immunization i.e. spray drying (SD) and spray freeze drying (SFD). The formulations were analyzed by proteolytic assay, single radial immunodiffusion assay (SRID), cascade impactor analysis, and immunization studies in Balb/c mice. Proteolytic assay and SRID analysis showed that antigen integrity after SFD was best conserved when the formulation was buffered by Hepes buffer saline (HBS). Surprisingly, antigen integrity after SD was better conserved when the formulation was buffered by phosphate buffer saline (PBS) rather than by HBS. The dispersion from the dry powder inhaler, the Twincer, resulted in a fine particle fraction (aerodynamic particle size <5microm) of 37% and 23% for spray dried and spray freeze dried powders, respectively. Immunogenicity of both vaccine formulations (SFD/HBS and SD/PBS) was similar to conventional liquid formulation after i.m. immunization. In addition, compared to i.m. immunizations, the pulmonary immunization with the dry powders resulted in significantly higher IgG titers. Furthermore, both the formulations remained biochemically and physically stable for at least 3years of storage at 20 degrees C. Our results demonstrate that both optimized formulations are stable and have good inhalation characteristics.

Characterization of inhalation aerosols: a critical evaluation of cascade impactor analysis and laser diffraction technique

Cascade impactor analysis is the standard technique for in vitro characterization of aerosol clouds generated by medical aerosol generators. One important reason for using this inertial separation principle is that drug fractions are classified into aerodynamic size ranges that are relevant to the deposition in the respiratory tract. Measurement of these fractions with chemical detection methods enables establishment of the particle size distribution of the drug in the presence of excipients. However, the technique is laborious and time consuming and most of the devices used for inhaler evaluation lack sufficient possibilities for automation. In addition to that, impactors often have to be operated under conditions for which they were not designed and calibrated. Particularly, flow rates through impactors are increased to values at which the flow through the nozzles is highly turbulent. This has an uncontrolled influence on the collection efficiencies and cut-off curves of these nozzles. Moreover, the cut-off value varies with the flow rate through an impactor nozzle. On the other hand, the high air flow resistances of most impactors are rather restricting to the attainable (fixed) inspiratory flow curves through these devices. Especially for breath actuated dry powder inhalers, higher flow rates and flow increase rates may be desirable than can be achieved in combination with a particular type of impactor. In this paper, the applicability of laser diffraction technology is evaluated as a very fast and highly reliable alternative for cascade impactor analysis. With this technique, aerodynamic diameters cannot be measured, but for comparative evaluation and development, comprising most in vitro applications, this is not necessary. Laser diffraction has excellent possibilities for automated recording of data and testing conditions, and the size classes are independent of the flow rate. Practical limitations can be overcome by using a special inhaler adapter which enables control of the inspiratory flow curve through the inhaler, analysis of the emitted fine particle mass fraction and pre-separation of large particles during testing of dry powder inhalers containing adhesive mixtures.

Inhalation characteristics and their effects on in vitro drug delivery from dry powder inhalers Part 2: Effect of peak flow rate (PIFR) and inspiration time on the in vitro drug release from three different types of commercial dry powder inhalers

Abstract Three commercial dry powder inhalers with completely different dosing and powder disintegration principles were evaluated in an in vitro deposition study. A four-stage cascade impactor was used for the range of flow rates between 20 and 60 1/min. Turbuhaler, Diskhaler and Spinhaler showed increasing amounts of drug discharged from the dose system with increasing peak inspiratory flow rate (PIFR). Only for the Spinhaler, was discharge influenced by total inspiration time as well. All three inhalers also showed improved powder disintegration with increasing PIFR. Highest fine particle yield was obtained from the Turbuhaler, reaching a maximum of 35–40% of the nominal dose at flow rates of 50–60 l/min. In comparison, less than 10% of the nominal dose from the Spinhaler and on average 23% from the Diskhaler were released as fine drug particles at 60 l/min. From the work of inspiration involved, it has been concluded that a short and fast inspiration through the Turbuhaler gives an optimal result from fine particle output and from efficiency point of view.

Inhalation characteristics and their effects on in vitro drug delivery from dry powder inhalers. Part 1. Inhalation characteristics, work of breathing and volunteers' preference in dependence of the inhaler resistance

A test inhaler with exchangeable air flow resistances encompassing the range of commercial DPIs has been used to study the inspiratory flow curves of 39 healthy adult volunteers. A strong increase in mean Peak Inspiratory Flow Rate (PIFR) has been obtained with decreasing inhaler resistance, varying between 160 1/min for a resistance equivalent to the Rotahaler and 50 1/min for the simulated Inhalator Ingelheim at maximum inspiratory effort. The volunteers experienced on average 55% of maximum effort as comfortable (expressed in PIFR) and gave preference (82%) to relative high air flow resistances in the range of 0.4-0.9 × 105 (N0.5·s·m−4). It has been calculated that the real amount of work of breathing does not increase with increasing air flow resistance at comfortable inspiration mode. At maximum inspiration, the amount of work performed through a high resistance inhaler (1.5 × 105) is approx. 70% of that through a low resistance device (0.4 × 105). The calculated mean PIFR of 62 1/min at maximum effort through an air flow resistance of 0.9 × 105, equivalent to the Turbuhaler, is in good agreement with PIFR-values of 68.5 vs. 59 1/min from two other studies with asthmatic patients through this device. It has, therefore, been concluded that the flow curves of healthy volunteers may be used to predict the range of PIFRs for asthmatics through the same air flow resistances.

Air classifier technology (ACT) in dry powder inhalation. Part 2 : The effect of lactose carrier surface properties on the drug-to-carrier interaction in adhesive mixtures for inhalation

The effect of carrier surface properties on drug particle detachment from carrier crystals during inhalation with a special test inhaler with basic air classifier has been studied for mixtures containing 0.4% budesonide. Carrier crystals were retained in the classifier during inhalation and subsequently examined for the amount of residual drug (carrier residue: CR). Carrier surface roughness and impurity were varied within the range of their appearance in standard grades of lactose (Pharmatose 80, 100, 110, 150 and 200M) by making special sieve fractions. It was found that roughness and impurity, both per unit calculated surface area (CSA), tend to increase with increasing mean fraction diameter for the carrier. Drug re-distribution experiments with two different carrier sieve fractions with distinct mean diameters showed that the amount of drug per CSA (drug load) in the state of equilibrium is highest for the coarsest fraction. This seems to confirm that surface carrier irregularities are places where drug particles preferentially accumulate. However, a substantial increase in surface roughness and impurity appears to be necessary to cause only a minor increase in CR at an inspiratory flow rate of 30 l/min through a classifier. At 60 l/min, CR is practically independent of the carrier surface properties. From the difference in CR between 30 and 60 l/min, it has been concluded that particularly the highest adhesive forces (for the largest drug particles) in the mixture are increased when coarser carrier fractions (with higher rugosity) are used. Not only increased surface roughness and impurities may be responsible for an increase in the adhesive forces between drug and carrier particles when coarser carrier fractions are used, but also bulk properties may play a role. With increasing mean carrier diameter, inertial and frictional forces during mixing are increased too, resulting in higher press-on forces with which the drug particles are attached to carrier crystals and to each other.

Design and application of a new modular adapter for laser diffraction characterization of inhalation aerosols

An inhaler adapter has been designed for the characterization of the aerosol clouds from medical aerosol generators such as nebulizers, dry powder inhalers (dpis) and metered dose inhalers (mdis) with laser diffraction technology. The adapter has a pre-separator, for separation of large particles (i.e. carrier crystals) from the aerosol cloud before it is exposed to the laser beam. It also has a fine particle collector for measuring the emitted mass fraction of fines by chemical detection methods after laser diffraction sizing. The closed system enables flow control through the aerosol generators and all test conditions, including ambient temperature and relative humidity, are automatically recorded. Counter flows minimize particle deposition onto the two windows for the laser beam, which make successive measurements without cleaning of these windows possible. The adapter has successfully been tested for nebulizers, mdis and dpis. In a comparative study with ten nebulizers it was found that these devices differ considerably in droplet size (distribution) of the aerosol cloud for the same 10% aqueous tobramycin solution (volume median diameters ranging from 1.25 to 3.25 microm) when they are used under the conditions recommended by the manufacturers. The droplet size distribution generated by the Sidestream (with PortaNeb compressor) is very constant during nebulization until dry running of the device. Comparative testing of dpis containing spherical pellet type of formulations for the drug (e.g. the AstraZeneca Turbuhaler) with the adapter is fast and simple. But also formulations containing larger carrier material could successfully be measured. Disintegration efficiency of a test inhaler with carrier retainment (acting as a pre-separator) could be measured quite accurately both for a colistin sulfate formulation with 16.7% of a lactose fraction 106-150 microm and for a budesonide formulation with a carrier mixture of Pharmatose 325 and 150 M. Therefore, it is concluded that, with this special adapter, laser diffraction may be a valuable tool for comparative inhaler evaluation, device development, powder formulation and quality control. Compared to cascade impactor analysis, laser diffraction is much faster. In addition to that, more detailed and also different information about the aerosol cloud is obtained.

Inhalation of tobramycin in cystic fibrosis. Part 2: Optimization of the tobramycin solution for a jet and an ultrasonic nebulizer

The inhalation of tobramycin is part of current cystic fibrosis (CF) therapy. Local therapy with inhaled antibiotics has demonstrated improvements in pulmonary function. Current inhalation therapy is limited by the available drug formulations in combination with the nebulization time. The aim of this study is to develop a highly concentrated tobramycin solution for inhalation. Several tobramycin solutions, ranging from 5 to 30% (m/v), were compared after aerosolation with a jet and with an ultrasonic nebulizer. Laser diffraction and cascade impactor analysis were used for characterization of the aerosolized solutions. The output rate was determined in volume and mass output per minute. From the output rate measurements, it was concluded that a 20% tobramycin solution is the optimal and maximal concentration to be aerosolized. The jet nebulizer was most suitable. Using the jet nebulizer and the 20% solution, it is possible to administer a dosage of 1000 mg tobramycin by inhalation within 30 min.

Dry powder inhalation of colistin sulphomethate in healthy volunteers: A pilot study

BACKGROUND Pulmonary administration of the antimicrobial drugs colistin sulphomethate and tobramycin has been shown to be effective in slowing down pulmonary deterioration in cystic fibrosis (CF) patients. Both drugs are administered by liquid nebulisation, a technique known to have disadvantages. Dry powder inhalation may be an attractive alternative. We investigated inhalation of colistin sulphomethate dry powder using a newly developed Twincer device in healthy volunteers. METHODS Eight healthy volunteers inhaled a single dose of 25mg colistin sulphomethate dry powder each, using the Twincer inhaler. The median diameter (X(50)) of the dry powder was 1.6 microm (X(10)=0.7 microm, X(90)=3.1 microm), measured by laser diffraction technique. Pulmonary function tests were performed before, 5 and 30 min after inhalation. Serum samples were drawn at t=15 min, 45 min, 1.5h, 2.5h, 3.5h, 5.5h, 7.5h and 24h after inhalation. RESULTS The colistin sulphomethate dry powder inhaler was well tolerated: no clinically relevant effect on FEV(1) was observed nor did the volunteers experience adverse effects. CONCLUSION Dry powder inhalation of colistin sulphomethate using the Twincer inhaler is well tolerated by healthy volunteers. A pilot study in cystic fibrosis patients is therefore considered safe in developing a dry powder inhalation of colistin for everyday CF treatment.

Developments and strategies for inhaled antibiotic drugs in tuberculosis therapy: A critical evaluation

Inhaled antibiotics have been a valuable tool in treating pulmonary infections in cystic fibrosis patients for decades, and the pulmonary route is now becoming increasingly interesting for other infectious diseases like tuberculosis too. Especially with multidrug and extensively drug-resistant tuberculosis emerging, great effort is put into the improvement of pulmonary antibiotic administration to fight this global threat. Several reviews have been written on inhalable antibiotics, giving clear overviews of the compounds of interest. Furthermore, various formulation studies and administration strategies are on-going with these compounds. What is often missing is a critical evaluation of these developments. Several risks may be involved varying from obtaining insufficient local drug concentrations to adverse side effects and unwanted changes in physiological processes from the excipients used. In this manuscript, the pros and cons and feasibility of recent advances in pulmonary antibiotic tuberculosis therapy are presented and critically evaluated. Furthermore, the advantages of dry powder inhalation over wet nebulisation for inhaled antibiotics in developing countries where prevalence of tuberculosis is highest are discussed. It has to be concluded that a greater effort in good inhaler development and more research in the physico-chemical properties of the compounds of interest are needed.

The effect of budesonide particle mass on drug particle detachment from carrier crystals in adhesive mixtures during inhalation

The different fine particle fractions (FPFs) that are obtained, when different dry powder inhalers (DPIs) are used for the same powder formulation at the same flow rate, is the result of different powder de-agglomeration efficiencies for these DPIs. For adhesive mixtures, this is the efficiency with which the kinetic energy of the air flow through the DPI is converted into separation forces that detach drug particles from carrier crystals. We investigated the effect of drug particle diameter (mass) on drug-carrier separation during inhalation with three different inhalers (Sofotec Novolizer, Inhalator Ingelheim and a special test inhaler), at two different flow rates (30 and 60l/min). Two different size fractions were used as carrier material (45-63 and 100-150 microm). We measured decreasing amounts of residual drug on the carrier crystals after inhalation with increasing drug particle mass for all inhalers at both flow rates. The observed trends were the same for both carrier fractions. The decrease in residual drug on carrier is in agreement with increasing FPFs in an Erweka impactor. However, it has been calculated that the magnitude of the effect decreases with increasing de-agglomeration efficiency.