Drug administration by jet nebulization

Nebulised delivery of RNA formulations to the lungs: From aerosol to cytosol

In the past decade RNA-based therapies such as small interfering RNA (siRNA) and messenger RNA (mRNA) have emerged as new and ground-breaking therapeutic agents for the treatment and prevention of many conditions from viral infection to cancer. Most clinically approved RNA therapies are parenterally administered which impacts patient compliance and adds to healthcare costs. Pulmonary administration via inhalation is a non-invasive means to deliver RNA and offers an attractive alternative to injection. Nebulisation is a particularly appealing method due to the capacity to deliver large RNA doses during tidal breathing. In this review, we discuss the unique physiological barriers presented by the lung to efficient nebulised RNA delivery and approaches adopted to circumvent this problem. Additionally, the different types of nebulisers are evaluated from the perspective of their suitability for RNA delivery. Furthermore, we discuss recent preclinical studies involving nebulisation of RNA and analysis in in vitro and in vivo settings. Several studies have also demonstrated the importance of an effective delivery vector in RNA nebulisation therefore we assess the variety of lipid, polymeric and hybrid-based delivery systems utilised to date. We also consider the outlook for nebulised RNA medicinal products and the hurdles which must be overcome for successful clinical translation. In summary, nebulised RNA delivery has demonstrated promising potential for the treatment of several lung-related conditions such as asthma, COPD and cystic fibrosis, to which the mode of delivery is of crucial importance for clinical success.

A comparative in vitro study of standard facemask jet nebulization and high-flow nebulization in bronchiolitis

Aim of Study: The use of a nebulizer paired with high-flow nasal cannulas (HFNC) has been proposed for drug delivery in bronchiolitis. Particle size nebulized is a relevant factor determining the efficacy of the nebulization. We replicated in vitro the theoretical parameters most widely used in bronchiolitis and we compared the size of the droplet nebulized with a standard nebulizer and a nebulizer integrated into HFNC. Materials and Methods: We used laser diffraction to analyze the particle size nebulized (volume median diameter Dv50). The standard system was a jet nebulizer connected to a facemask with a flow rate of 8 L/min (JN). Three designs were used as nebulizers integrated into HFNC: a vibrating mesh nebulizer set 1) before (HFNC-BH) and 2) after (HFNC-AH) the humidifier, and 3) a jet nebulizer connected before the nasal cannula (HFNC-BNC). HFNC was used with neonatal (3-8 L/min) and infant cannulas (8-15 L/min). Results: Droplet size was similar among the three drugs studied. A lower particle size was obtained when using the nebulization system integrated into HFNC compared to the standard nebulizer, regardless of the flow rate and the nasal cannula used when the position of the nebulizer was before the nasal cannula (p < 0.05): 6.89 µm (JN), 2.49 µm (HFNC-BNC 3 L/min), 2.59 µm (HFNC-BNC 5 L/min), 2.44 µm (HFNC-BNC 8 L/min), 3.22 µm (HFNC-BNC 10 L/min), 3.23 µm (HFNC-BNC 13 L/min), 3.16 µm (HFNC-BNC 15 L/min). The particle size was lower in HFNC-BF compared to the HFNC-AH using neonatal nasal cannula (3-8 L/min) (p < 0.05). Conclusion: The use of a nebulizer integrated with HFNC has shown promising results in an experimental scenario of bronchiolitis. The particle size achieved with the nebulizer placed before the humidifier is equivalent to the one obtained via conventional nebulization, and it is even smaller when the integrated nebulizer is placed before the nasal cannulas.

Comparison of aerosol delivery across combinations of drug delivery interfaces with and without concurrent high-flow nasal therapy

BACKGROUND

Current clinical practice during high-flow nasal therapy (HFNT) involves utilization of a nasal cannula to provide humidification, with a facemask placed over the cannula to deliver aerosol. Few studies have compared aerosol delivery across various delivery interfaces during HFNT. The objective of this study was to address this gap in the literature and evaluate aerosol delivery using two nebulizer types across different drug delivery interfaces, nasal cannula, facemask, and mouthpiece, during simulated adult HFNT.

METHODS

A facemask or mouthpiece and/or a nasal cannula were positioned on an anatomically correct adult head model. The head model was connected to a breathing simulator via a collection filter. Both healthy breathing pattern and distressed breathing patterns were utilized. Aerosol dose was determined by quantifying the mass of drug captured on a filter positioned distal to the trachea.

RESULTS

During simulated healthy breathing, a significantly greater aerosol dose was observed when the vibrating mesh nebulizer (VMN) was integrated with HFNT alone, supplying aerosol and humidified air simultaneously (2.88 ± 0.15%), as opposed to using with a facemask (0.33 ± 0.07%, 1.62 ± 0.46%, and 1.07 ± 0.25% at 0 L/min (LPM), 2LPM, and 6LPM, respectively) or mouthpiece (0.56 ± 0.13%, 2.16 ± 0.06%, and 1.82 ± 0.41% at 0LPM, 2LPM, and 6LPM). In addition, aerosol delivery was also significantly greater when the VMN was integrated into simulated HFNT (2.88 ± 0.15%), in comparison with using the jet nebulizer (JN) with a facemask (0.82 ± 0.16%) or a mouthpiece (0.86 ± 0.11%). During simulated distressed breathing, a significantly greater aerosol dose was observed when the VMN was integrated with HFNT, supplying aerosol and humidified air simultaneously (6.81 ± 0.45%), compared with using a facemask (0.86 ± 0.04%, 2.96 ± 0.26%, and 4.23 ± 0.93% at 0LPM, 2LPM, and 6LPM) or mouthpiece (0.73 ± 0.37%, 0.97 ± 0.20%, and 3.11 ± 0.53% at 0LPM, 2LPM, and 6LPM, respectively). Aerosol delivery was also greater when the VMN was integrated into HFNT (6.81 ± 0.45%), in comparison with using the JN with a facemask (5.72 ± 0.71%) or a mouthpiece (0.69 ± 0.53%). Furthermore, across all drug delivery interfaces, and in line with previous reports, aerosol delivery was greater during simulated distressed breathing, in comparison with simulated healthy adult breathing.

CONCLUSIONS

This article will be of considerable benefit in enhancing the understanding of aerosol delivery during HFNT, an increasingly adopted therapeutic intervention by healthcare professionals.

Inhaled epoprostenol for the treatment of pulmonary arterial hypertension in critically ill adults

Pulmonary arterial hypertension (PAH) is a progressive disease without a cure. The primary treatment goal for patients with this disease is improving pulmonary blood flow through vasodilation of the pulmonary arteries. Several drugs are available that ameliorate walk distance and hemodynamics, but their maximum tolerated doses are limited in critically ill patients with PAH because of systemic vasodilation resulting in hypotension. The ideal vasodilator would be cost-effective, safe, and selective to the pulmonary vasculature; no such agent currently exists. Inhaled nitric oxide selectively reduces pulmonary pressures without systemic hypotension. However, it is expensive, potentially toxic, and requires complex technology for monitoring and administration. Inhaled epoprostenol may be an alternative therapy to minimize systemic hypotension, which often accompanies rapid intravenous titration. To evaluate the safety and efficacy of inhaled epoprostenol in critically ill patients with PAH, we conducted a literature search by using the MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases (1966-August 2009) for relevant studies. Case reports and in vitro studies were excluded. Overall, 11 studies met the inclusion criteria. The PAH population included patients requiring cardiac surgery, lung or heart transplantation, or nonspecific intensive care. All trials showed that inhaled epoprostenol significantly decreased pulmonary pressures without lowering systemic blood pressure. The duration of therapy in most studies was 10-15 minutes, with one study evaluating its effects up to an average of 45.6 hours. Pulmonary pressures returned to baseline soon after drug discontinuation. Minimal adverse events were reported. Thus, inhaled epoprostenol in various subgroups of critically ill patients was effective in reducing pulmonary pressures. However, the significance of these effects on improving clinical outcomes remains unknown. Further studies are needed to determine the role of inhaled epoprostenol in critically ill patients with PAH.

Towards zero prevalence of chronic Pseudomonas aeruginosa infection in children with cystic fibrosis

BACKGROUND

Data from the Belgian Cystic Fibrosis Registry consistently show that in one of the seven reference centres, the prevalence of Pseudomonas aeruginosa is half that observed at the national level.

OBJECTIVES

To report the characteristics of non-transplanted patients in this clinic at the end of 2003, with special focus on paediatric patients. To describe and discuss our policy of inhaled antibiotic therapy.

FINDINGS

The prevalence of P. aeruginosa among 116 patients is 20.7%. The chronic colonization rate is 19.8% but only 2.8% in patients aged under 18 (n=72). Serologic data strongly support these results. Most paediatric patients (95%) are prescribed inhaled antibiotics, at least on an intermittent basis but the mean number of days of intravenous antibiotic treatment is four times lower than in other CF children in Belgium. 70% of children have an FEV1> or =90% predicted.

DISCUSSION

We have reported a distinctly low rate of chronic colonization by P. aeruginosa in a cohort of CF children and suspect that a strategy of early, often <<prophylactic>> use of inhaled antibiotics, progressively implemented for over 15 years has substantially contributed to these results. Given the major impact of chronic P. aeruginosa colonization on prognosis in CF, it is suggested that a large prospective study of this approach is warranted.

Aerosolised antibiotics: a critical appraisal of their use

Aerosolised antimicrobial agents have been used in clinical practice since the 1950s. The main advantage of this route of administration is the targeted drug delivery to the site of infection in the lung. Exploitation of this targeted delivery can yield high concentrations at the site of infection/colonisation while minimising systemic toxicities. It is important to note that the ability of a drug to reach the target area in the lung effectively is dependent on a number of variables, including the nebuliser, patient technique, host anatomy and disease-specific factors. The most convincing data to support the use of aerosolised antimicrobials has been generated with tobramycin solution for inhalation (TOBI, Chiron Corp.) for maintenance treatment in patients with cystic fibrosis. In addition to cystic fibrosis, the use of aerosolised antimicrobials has also been studied for the treatment or prevention of a number of additional disease states including non-cystic fibrosis bronchiectasis, ventilator-associated pneumonia and prophylaxis against pulmonary fungal infections. Key studies evaluating the benefits and shortcomings of aerosolised antimicrobial agents in these areas are reviewed. Although the theory behind aerosolised administration of antibiotics seems to be sound, there are limited data available to support the routine use of this modality. Owing to the gaps still existing in our knowledge base regarding the routine use of aerosolised antibiotics, caution should be exercised when attempting to administer antimicrobials via this route in situations falling outside clearly established indications such as the treatment of patients with cystic fibrosis or Pneumocystis pneumonia.

Suitability of Caspofungin for Aerosol Delivery

BACKGROUND

Aerosolized antifungal therapy is a promising route of drug delivery for pulmonary aspergillosis due to attainment of high localized concentrations. Caspofungin, a new antifungal agent with proven efficacy against invasive aspergillosis, has ideal potential for aerosolization.

STUDY OBJECTIVE

To examine in vitro the suitability of caspofungin for aerosol administration by characterizing factors that influence efficacy and airway tolerance of aerosol delivery: physicochemical properties, aerodynamics of drug particles, and efficiency of nebulizing systems.

DESIGN

Physicochemical characteristics of caspofungin solutions (10 mg/mL and 30 mg/mL) were analyzed: osmolality, pH, viscosity, and surface tension. A time-of-flight aerosol spectrometer API Aerosizer was used to determine aerosol particle size and distribution. Drug output was quantified by high-performance liquid chromatography assay. Nebulizer efficiency was measured by drug output and respirable fraction (percentage of aerosolized particles with a 1 to 5 mum aerodynamic diameter) and compared among three jet nebulizer/compressor systems: device 1, Micromist (Hudson RCI; Temecula, CA)/Pulmo-Aide (model 5650D; DeVilbiss; Somerset, PA); device 2, Sidestream MS 2400/Envoy model IRC 1192 (Invacare; Elyria, OH); and device 3, Pari LC Star/Proneb Ultra (Pari Respiratory Equipment; Midlothian, VA).

MEASUREMENTS AND RESULTS

Caspofungin requires 0.9% NaCl rather than sterile water as the diluent and addition of 0.3N NaOH buffer to adjust acidity of solutions (pH 6.17 to 6.26) in order to achieve optimal physicochemical properties for airway tolerability (osmolality, 150 to 550 milliosmol per kilogram; chloride ion, 31 to 300 mmol/L; and pH 7.4). The drug output rate increased with higher concentrations of drug solution: device 1, 4.0 mg/min vs 12.5 mg/min; device 2, 5.4 mg/min vs 14.7 mg/min; and device 3, 2.3 mg/min vs 12 mg/min, respectively. The percentage of particles within the respirable range varies depending on device and concentration of drug solutions (10 mg/mL vs 30 mg/mL): device 1, 85% vs 38%; device 2, 44% vs 57%; and device 3, 83% vs 93%, respectively.

CONCLUSION

Caspofungin solution with adjustments appears to have physicochemical and aerodynamic characteristics suitable for aerosolization when used with either the Pari LC Star/Proneb Ultra or Micromist/Pulmo-Aide devices. Further in vivo testing is warranted.

Electrohydrodynamic Comminution: A Novel Technique for the Aerosolisation of Plasmid DNA

PURPOSE

Naked plasmid DNA (pDNA) is a potential gene transfer agent for lung gene therapies but cannot be aerosolised without degradation using conventional nebulisation devices. This study investigated the viability of an alternative nebulisation technique, electrohydrodynamic (EHD) comminution for the aerosol delivery of naked DNA in vivo.

METHODS

Naked pDNA was aerosolised using jet and ultrasonic nebulisers, and by EHD comminution. Degradation associated with the aerosolisation process was investigated using gel electrophoresis and by transfection studies in cell culture. Optimised formulations for EHD aerosolisation of pDNA were developed and in vivo deposition and reporter gene expression were investigated in mice.

RESULTS

Unlike conventional nebulisation devices, EHD comminution of plasmids up to 15 kb in size resulted in no detectable pDNA degradation. EHD formulations containing up to 1 mg/ml pDNA were developed and shown to produce monodisperse aerosols suitable for targeted lung delivery in humans. Aerosolisation studies in vivo demonstrated detectable levels of pDNA deposition and measurable luciferase reporter gene expression in the lungs of exposed mice.

CONCLUSIONS

This study demonstrates for the first time that respirable aerosols of naked pDNA can be generated without plasmid degradation and that EHD comminution is an appropriate technique for the aerosolisation of delicate gene transfer agents.

Aerosol delivery of an enhanced helper-dependent adenovirus formulation to rabbit lung using an intratracheal catheter

BACKGROUND

Poor transduction of the ciliated airway epithelium and inefficient airway delivery of viral vectors are common difficulties encountered in lung gene therapy trials with large animals and humans.

METHODS

We delivered a helper-dependent adenovirus vector, incorporating a human epithelial cell-specific expression cassette, to rabbit lung. An intratracheal device was used to aerosolize a moderate dose of virus (5 x 10(11) particles), mixed with the enhancing agent LPC (L-alpha-lysophosphatidylcholine), directly into the airways. Lung mechanics, body weight and temperature, transgene expression and histopathology were studied at day 5.

RESULTS

Transgene expression was seen in the epithelium of large and small airways, from trachea to terminal bronchioles, with a strong tendency toward the right lung. All cell types of the surface epithelium were transduced. Extensive transduction of the epithelium (66% of cells in trachea) was obtained using virus formulated in isotonic 0.1% LPC, while virus formulated in 0.01% LPC transduced fewer cells (24% in trachea). A transient decrease in dynamic lung compliance was observed immediately following aerosol delivery. Fever and mild-to-moderate patchy pneumonia without edema were also observed.

CONCLUSION

These data demonstrate a strategy for efficient and effective transduction of airway epithelium in a large animal.

Comparison of Breath-Enhanced to Breath-Actuated Nebulizers for Rate, Consistency, and Efficiency

OBJECTIVES

To evaluate differences between three new-generation nebulizers-Pari LC Star (Pari Respiratory Equipment; Mississauga, ON, Canada), AeroEclipse (Trudell Medical International, London, ON, Canada), and Halolite (Medic-Aid Limited, West Sussex, UK)-in terms of rate and amount of expected deposition as well as the consistency of the doses delivered.

METHODS

The in vitro performance characteristics were determined and then coupled to the respiratory pattern of seven patients with cystic fibrosis (age range, 4 to 18 years) in order to calculate expected deposition. The Pari LC Star and AeroEclipse were characterized while being driven by the Pari ProNeb Ultra compressor (Pari Respiratory Equipment) for home use, and by a 50-psi medical air hospital source. The Halolite has its own self-contained compressor. Algorithms for the rate of output for the inspiratory flow were developed for each device. Patient flow patterns were divided into 5-ms epochs, and the expected deposition for each epoch was calculated from the algorithms. Summed over a breath, this allowed the calculation of the estimated deposition for each patient's particular pattern of breathing.

RESULTS

The rate of deposition was highest for the Pari LC Star and lowest for the Halolite. Rate of deposition was independent of respiratory pattern for the Pari LC Star and AeroEclipse, but proportional to respiratory rate for the Halolite. The differences between the Pari LC Star and AeroEclipse were less when driven by the 50-psi source. The AeroEclipse had the least amount of drug wastage. As designed, the Halolite delivered a predetermined amount of drug very accurately, whereas expected deposition when run to dryness of the other two devices had significant variations.

CONCLUSIONS

To minimize treatment time, the Pari LC Star would be best. To minimize drug wastage, the AeroEclipse would be best. To accurately deliver a specific drug dose, the Halolite would be best.

General principles of asthma management: pharmacotherapy

Asthma, a disease of urbanized societies, has been increasing at an alarming rate on a worldwide basis. In recognition of this problem, the NHLBI developed the NAEPP in 1991. An expert panel was appointed that developed guidelines for the diagnosis and management of asthma. The original report has been updated several times, most recently in 2002. In this article the author focuses on the general principles of asthma pharmacotherapy in accordance with the conceptual framework that characterizes drugs as relievers or controllers. The preeminent use of ICS in the management of asthma sufferers who are characterized as having more than mild intermittent disease is emphasized, as is the principle of matching therapy with severity of disease.

Inhaled epoprostenol (prostacyclin) and pulmonary hypertension before cardiac surgery

OBJECTIVE

Pulmonary hypertension is commonly found in patients undergoing valvular surgery and can be worsened by cardiopulmonary bypass. Inhaled epoprostenol (prostacyclin) has been used for the treatment of pulmonary hypertension, but its effects compared with those of placebo on hemodynamics, oxygenation, echocardiographic examination, and platelet function have not been studied during cardiac surgery.

METHODS

Twenty patients with pulmonary hypertension undergoing cardiac surgery were randomized in a double-blind study to receive inhaled epoprostenol (60 microg) or placebo. The inhalation occurred after induction of anesthesia and before surgical incision. The effects on left and right systolic and diastolic cardiac functions evaluated by means of pulmonary artery catheterization and transesophageal echocardiography, as well as oxygenation and platelet aggregation, were studied.

RESULTS

Inhalation of epoprostenol significantly reduced indexed right ventricular stroke work from 10.7 +/- 4.57 g. m. m(-2) to 7.8 +/- 3.94 g. m. m(-2) (P =.003) and systolic pulmonary artery pressure from 48.4 +/- 18 mm Hg to 38.9 +/- 11.9 mm Hg (P =.002). The effect was correlated with the severity of pulmonary hypertension (r = 0.76, P =.01) and was no longer apparent after 25 minutes. There was no significant effect on systemic arterial pressures, left ventricular function, arterial oxygenation, platelet aggregation, and surgical blood loss.

CONCLUSION

Inhaled epoprostenol reduces pulmonary pressure and improves right ventricular stroke work in patients with pulmonary hypertension undergoing cardiac surgery. A dose of 60 microg is hemodynamically safe, and its effect is completely reversed after 25 minutes. We did not observe any evidence of platelet dysfunction or an increase in surgical bleeding after administration of inhaled epoprostenol.

Management of acute pediatric asthma

Pediatric asthma prevalence, morbidity, and severity are increasing. Direct costs associated with providing emergency department and inpatient care account for more than 40% of overall dollars spent for this disease in the United States. Physicians in many health care settings may be required to treat a child in severe respiratory distress caused by acute asthma. This article reviews the pathophysiology, evaluation, and treatment of severe asthma exacerbations, or status asthmaticus.

The equivalence of compressor pressure-flow relationships with respect to jet nebulizer aerosolization characteristics

Manufacturers of aerosolized medications, approved by the Food and Drug Administration, specify the nebulizer(s) and compressor to be used with their product, in an attempt to achieve efficacy comparable to that obtained in the clinical trials. The need to limit the compressor to that used in the trials has not been investigated in detail. We suggest a technique to determine the equivalency of different compressors such that a chosen nebulizer's performance is not significantly altered. Aerosol particle size (MMD) was measured with a laser; compressor flow and pressure were measured with a mass flow meter and pressure gauge, respectively. For all models of nebulizer, increased flow or driving pressure caused a decrease in aerosol MMD. The flow resistance of nebulizer models varied, and the flow output of compressors decreased as imposed nebulizer resistance increased. However, for any specific compressor-nebulizer combination there is a unique flow and pressure, and the nebulizer generates a given MMD. We demonstrate methods to choose alternate compressors that may be used to drive a nebulizer and yet keep the nebulizer's MMD and performance within predetermined limits. Once an acceptable range of variance in a nebulizer's MMD is defined, alternate compressors may be safely chosen. We recommend that these techniques be used by manufacturers of medications and of compressors to safely determine the acceptability of several rather than a single model compressor to drive a chosen nebulizer. The techniques assure consistency of the nebulizer's clinically demonstrated performance characteristics.

Evaluation of pulsed and breath-synchronized nebulization of budesonide as a means of reducing nebulizer wastage of drug

The aim of this open, randomized, crossover study was to compare the inhaled mass of budesonide suspension delivered by nebulization, using constant output, breath-synchronized, or pulsed jet nebulization techniques. The inhaled mass was defined as the amount of drug deposited on a filter between the inspiratory port of the nebulizer and the face mask or mouthpiece used by the subjects. The breath-synchronized nebulization delivered aerosol during the whole inspiration, whereas the pulsed nebulization was adjusted to deliver aerosol for up to 1 sec from the start of inspiration. Budesonide suspensions, 2 mL of 0.5 mg mL(-1), or 2 mL of 0.25 mg mL(-1), in single-dose respules, were used (AstraZeneca R&D Lund, Lund, Sweden). Eleven children (7 boys, age range 2.5-5.8 years) with either a clinical suspicion or a confirmed diagnosis of asthma and 11 healthy adolescents and adults (6 male, age range 13-52 years) were enrolled. With constant output nebulization, the median inhaled mass of budesonide was about 17.6% (range 9.6-21.2%) of the nominal dose (i. e., dose of drug in the respule per label claim) in adolescents and adults, and 18.1% in children (15.7-21.4%). With pulsed nebulization the median inhaled mass increased to 23.4% (22.0-28.1%) in children and to 32.8% (24.8-38.0%) in adolescents and adults (P < 0.001). With breath-synchronized nebulization median inhaled mass increased to 30.1% (21.7-28.1%) in children, but was unchanged (30.8%, 27.0-38. 0%) in adolescents and adults. The mode of nebulization (i.e., constant or breath-synchronized) had a statistically significant effect on the inhaled mass in children and adolescents or adults (P < 0.001). There was a statistically significant difference in inhaled mass between the breath-synchronized and pulsed nebulization in children only (P < 0.05). The results support the use of breath-synchronized but not pulsed nebulization with conventional nebulizers. The results of pulsed nebulization in children warrants further clinical studies.