LC Plus Research Articles

A Widely Available Method for the Assessment of Aerosol Delivery in Cystic Fibrosis

Whilst nebulisers are commonly used in the treatment of cystic fibrosis (CF), nebulised aerosol lung deposition in individual patients is not routinely assessed in clinical practice. The present study was designed to evaluate whether a comparative measurement of aerosol lung deposition from nebulisers using a widely available scintigraphic method could be employed to assist the selection of the best system for individual patients. Lung deposition of the radiolabelled aerosol from the Pari LC Plus (Pari Medical Ltd) nebuliser and the HaloLite Adaptive Aerosol Delivery (AAD®) system (Profile Therapeutics Ltd) was measured using planar scintigraphy in 10 healthy volunteers and 6 CF patients. The HaloLite AAD® delivered on average 2.1 times ( P=0.003) as much aerosol to the lungs compared with Pari LC Plus. Only two subjects had higher lung deposition from Pari LC Plus than HaloLite AAD® system. There was marked inter-individual variation in the deposition pattern in CF patients. The aerosol deposition from HaloLite AAD® had higher central distribution than that obtained with the Pari LC Plus. The overall intersubject variability of the delivered dose was 56% with Pari LC Plus and 24% with HaloLite AAD® ( P<0.05). The measurement of aerosol deposition from nebulisers can be performed using a simple and widely available methodology, and may improve nebuliser selection in CF patients.

Inhaled antibiotic therapy in evidence: what delivery device?

This paper evaluates the suitability of various compressors available in Europe to generate and deliver tobramycin nebulizer solution to cystic fibrosis patients from the PARI LC PLUS jet nebulizer. This evaluation has been undertaken (i) by establishing an in vitro equivalence to the DeVilbiss PulmoAide compressor (operating at 4.6 l/min) proven effective in US clinical trials, and (ii) by determining equivalent in vitro performance of the LC PLUS nebulizer driven by alternative airflows. Equivalent performance is judged as having both an aerosol output and aerosol size within ±10% of that obtained with the LC PLUS/PulmoAide combination. The two different in vitro methodologies applied to this investigation were based on the British Standard and a European Standard to assess nebulizer output. The results demonstrate that a wide range of compressed airflow rates generate aerosol output from the PARI LC PLUS equivalent to that obtained from the PulmoAide compressor. This range of airflows encompasses many compressors commonly available in Europe.

Pharmacokinetics and Bioavailability of Aerosolized Tobramycin in Cystic Fibrosis

To describe the pharmacokinetics and bioavailability of inhaled tobramycin (TOBI; Chiron Corporation; Seattle, WA), 300-mg dose, delivered by a nebulizer (PARI LC Plus; Pari Respiratory; Richmond, VA) and a compressor (Pulmo-Aide, model 5650D; DeVilbiss Health Care; Somerset, PA) in cystic fibrosis (CF) patients during the pivotal phase III trials. Data from two identical, 24-week, randomized, double-blind, placebo-controlled, parallel-group studies. US sites randomized 258 patients with CF to receive tobramycin, 300 mg twice daily, in three 28-day on/28-day off treatment cycles. Tobramycin sputum concentrations were assessed 10 min after the first and last doses were administered in the 20-week study. Serum tobramycin concentrations were assessed before and 1 h after the first and last doses had been administered. The population estimate of the apparent clearance was used to estimate the bioavailability fraction. The mean peak sputum concentration was 1,237 microg/g. About 95% of patients achieved sputum concentrations > 25 times the minimum inhibitory concentration of the Pseudomonas aeruginosa isolates. One hour after the dose, the mean serum concentration was 0.95 microg/mL. Tobramycin did not accumulate in the sputum or serum over the course of the study. Pharmacokinetic data were best represented by a two-compartment model with biexponential decay and slope estimates comparable to those following parenteral administration. The estimated systemic bioavailability after aerosol administration was 11.7% of the nominal dose. The administration of tobramycin, 300 mg bid, in a 28-day off/28-day on regimen produced low serum tobramycin concentrations, reducing the potential for systemic toxicity. High sputum concentrations ensure efficacious antibiotic levels at the site of the infection. Inhaled tobramycin significantly improved the therapeutic ratio over that of parenteral aminoglycosides.

An assessment of jet and ultrasonic nebulisers for the delivery of lactate dehydrogenase solutions

The aim of this study was to investigate the suitability of commercial jet and ultrasonic nebulisers for effective delivery of the model hydrophilic protein lactate dehydrogenase (LDH). Two jet nebulisers (Pari LC Plus and Pari LC Star) and two ultrasonic nebulisers (Sonix 2000 and Omron U1) were used to nebulise LDH solutions and the effects on protein activity and protein concentration determined. The size distribution of the aerosols produced, measured by laser diffraction analysis, temperature changes during nebulisation, the time to atomise a 5 ml dose volume and the mass output of the four nebulisers were compared. A twin impinger (TI) was used to collect the nebulised protein, which was assayed for total and active protein content. There was a large variation in the median size and size distribution of the aerosols produced by each of the nebulisers from LDH and Sørensen's modified phosphate buffer, and in the time taken to reach the sputtering phase of aerosolisation. During use, the concentration of LDH increased in the Omron U1 nebuliser, but did not change significantly in the others. The temperature of the protein solution decreased by approximately 8 °C during jet nebulisation but increased by 3 and 10 °C in the Omron U1 and Sonix 2000 nebulisers, respectively. Denaturation of LDH within the nebuliser reservoir, occurred in the order Sonix>Pari LC Plus>Pari LC Star>Omron U1, whilst the deposition of active and total protein within the stages and throat of the TI was a function of the particle size of the aerosols generated and the specific device used.

Nebulisation of rehydrated freeze-dried beclomethasone dipropionate liposomes

Beclomethasone dipropionate (BDP) liposomes were prepared from various lipids, dilauroyl phosphatidylcholine (DLPC), dimyristoyl phosphatidylcholine (DMPC), dipalmitoyl phosphatidylcholine (DPPC), and hydrogenated soybean phosphatidylcholine (Epikuron 200 SH). A lipid with a low transition temperature ( T m) (DLPC) incorporated a higher amount of BDP than lipid with a high T m. The nebulisation of rehydrated freeze-dried BDP liposomes was carried out using a Pari LC Plus nebuliser and the generated aerosol characterised by an Andersen Cascade Impactor operated at 28.3 l/min. The rehydrated BDP–DLPC liposomes showed a higher output (78.3%) and a higher fine particle fraction (FPF) (75.0%) and smaller mass median aerodynamic diameter (MMAD) (3.31 μm) than the other rehydrated liposome preparations. Liposomes containing lipid with a high T m (DPPC and Epikuron) underwent aggregation during nebulisation. This was shown by the large increase in size of the DPPC liposomes from 15.78 to 47.51 μm and the Epikuron liposomes from 5.84 to 46.70 μm.

Physical stability and in-vitro gene expression efficiency of nebulised lipid–peptide–DNA complexes

The lower respiratory tract provides a number of disease targets for gene therapy. Nebulisation is the most practical system for the aerosolisation of non-viral gene delivery systems. The aerosolisation process represents a significant challenge to the maintenance of the physical stability and biological activity of the gene vector. In this study we investigate the role of a condensing polycationic peptide on the stability and efficiency of nebulised lipid–DNA complexes. Complexes prepared from the cationic lipid 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and plasmid DNA (pDNA) at mass (w/w) ratios of 12:1, 6:1 and 3:1, and complexes prepared from DOTAP, the polycationic peptide, protamine, and pDNA (LPD) at 3:2:1 w/w ratio were nebulised using a Pari LC Plus jet nebuliser. Samples from the nebuliser reservoir (pre- and post-nebulisation) and from the aerosol mist were collected and investigated for changes, including: particle diameter, retention of in-vitro transfection activity and the relative concentration and nature of the complexed pDNA remaining after the nebulisation procedure. The process of jet nebulisation adversely affected the physical stability of lipid:pDNA complexes with only those formulated at 12:1 w/w DOTAP:pDNA able to maintain their pre-nebulisation particle size distribution (145±3 nm pre-nebulisation vs. 142±2 nm aerosol mist) and preserve significant pDNA integrity in the reservoir (35% of pre-nebulisation pDNA band intensity). The LPD complexes were smaller (102±1 nm pre-nebulisation vs. 113±2 nm aerosol mist) with considerably greater retention of pDNA integrity in the reservoir (90% of pre-nebulisation pDNA band intensity). In contrast the concentration of pDNA in the aerosol mist for both the 12:1 w/w DOTAP:pDNA and LPD complexes were significantly reduced (10 and 12% of pre-nebulised values, respectively). Despite reduced pDNA concentration the transfection (% cells transfected) mediated by aerosol mist for the nebulised complexes was comparatively efficient (LPD aerosol mist 26 vs. 40% for pre-nebulised complex; the respective values for 12: 1 w/w DOTAP:pDNA were 12 vs. 28%). The physical stability and biological activity of nebulised lipid:pDNA complexes can be improved by inclusion of a condensing polycationic peptide such as protamine. The incorporation of the peptide precludes the use of potentially toxic excesses of lipid and charge and may act as a platform for the covalent attachment of peptide signals mediating sub-cellular targetting.

An in vitro analysis of the output of budesonide from different nebulizers

Background: Inhaled corticosteroids are increasingly used in the treatment of asthma, and many different nebulizers are available to aerosolize steroid medications. There are few comparative data on their ability to do so. Objective: Our purpose was to determine the particle size and mass output of budesonide nebulizer suspension from different nebulizers. Methods: In vitro measurement of drug particle size and total drug output from 3 nebulizers (the Pari LC Plus, the Pari LC Star, and the Medicaid Ventstream) was performed under simulated breathing conditions. Nebulizers were charged with 2 mL (500 μg) of budesonide suspension. A sinus pump was used to draw aerosol from the nebulizers onto a filter during simulated inspiration at tidal volumes of 150 and 600 mL, mimicking pediatric and adult use. Aerosol particle size was determined separately by inertial impaction. Results: The LC Plus nebulizer had the highest initial output rate and delivered the most budesonide at both breathing patterns. The maximal output rates of the Ventstream and LC Star nebulizers was half that of the LC Plus, but the LC Star nebulizer continued nebulization for longer and delivered twice as much budesonide as the Ventstream did. However, the Ventstream produced the smallest particles, mass median diameter 3.1 μm compared with 3.8 μm for the LC Star and 4.1 μm for the LC Plus. Conclusions: This study has identified differences among the nebulizers that would not have been apparent with current standards for nebulizer assessment. Incorporation of breathing simulation in the study imitates patient use and allows effective nebulization times to be predicted. The results suggest that the nebulizers studied would deliver different masses of budesonide to the lungs and to the upper airway. This may have important consequences in determining the efficacy and side effect profile of budesonide. (J Allergy Clin Immunol 1999;104:1168-73.)

The output of budesonide from nebulizers

steroid therapy,1 no information is currently required by regulatory authorities on the dose of steroid actually reaching the patient from different nebulizers. As new, more efficient nebulizer designs are marketed, this information is essential to allow both therapeutic effects and side effects to be evaluated. We have studied the amount of a steroid suspension, budesonide, available for inhalation from a conventional jet nebulizer and from two newer designs. These “breath enhanced, open vent” nebulizers incorporate a system of valves to increase the gas flow through the nebulizer during inspiration, increasing drug delivery to the patient. Such nebulizers have been shown to double the delivery of a bronchodilator to the lung2 and have been suggested for use with nebulized steroids. We measured the output of budesonide from a conventional nebulizer, the Intersurgical Cirrus (Intersurgical Ltd, Wakingham, UK), which has a constant output throughout inspiration and expiration, and two breath-enhanced openvent nebulizers, the Medicaid Ventstream (Medicaid Ltd, Bognor Regis, UK) and the Pari LC Plus (Pari GmbH, Starnberg, Germany), which have enhanced output during inspiration only. In the laboratory part of our study, each nebulizer was charged with 2 mL (250 μg/mL) of budesonide suspension and operated for 5 minutes while attached to a sinus flow pump driven at different rates and volumes to represent breathing patterns of children. Budesonide was collected onto a filter and assayed with high-performance liquid chromatography. Each nebulizer type was tested 6 times. The particle size of budesonide released from each of the nebulizers was measured separately by using a glass multistage liquid impinger.3 In a parallel clinical study we measured the output of budesonide onto filters from different nebulizers when used by patients. Ten children with asthma aged 4 to 14 years used both the Ventstream and LC Plus nebulizers in random order for 5 minutes. The nebulizers contained 2 mL (500 μg) of budesonide nebulizer suspension, and drug that would have been inhaled was collected onto a The output of budesonide from nebulizers