Pharmaceutical and biotechnological aerosols for cystic fibrosis therapy

Designing Aerosol Therapies Based on the Integrated Evaluation of In Vitro, In Vivo, and In Silico Data

Despite the advantages of the pulmonary route of administration and inhalable dosage forms, other routes of administration and dosage forms are often considered first to treat lung diseases. This occurs, in part, due to the perceived limitations of inhaled therapies resulting from the improper design and interpretation of their in vitro and in vivo evaluation. The present study outlines the elements that should be considered in the design, performance, and interpretation of the results of the preclinical evaluation of novel inhaled therapies. These elements are illustrated using an optimized model poly(lactic-co-glycolic) acid (PLGA) microparticle (MP) formulation to optimize the site of MPs deposition. The different expressions of MP size were determined, and their aerosol performance in devices used for animal (Microsprayer^® and Insufflator^®) and human studies (nebulizer and DPIs) was assessed using inertial impaction. Radiolabeled MPs were delivered to the lungs of rats by spray instillation to determine their site of deposition using single-photon emission computed tomography (SPECT) imaging. Recommendations to optimize the in vitro determinations are given, as well as suggestions to evaluate and interpret in vivo data in the context of the anatomy and physiology of the animal model and the corresponding in vitro data. Recommendations for the proper selection of in vitro parameters to inform in silico modeling are also given, as well as their integration with in vivo data.

Efficacy and safety of combined isoniazid-rifampicin-pyrazinamide-levofloxacin dry powder inhaler in treatment of pulmonary tuberculosis: A randomized controlled trial

OBJECTIVE

To determine the efficacy and safety of add-on dry powder for inhalation (DPI) of combined anti-TB agents prepared as a particulate system (study group) compared with placebo DPI (control group) in patients diagnosed with pulmonary TB.

METHODS

This study was a randomized, placebo-controlled, double-blinded parallel design. Subjects were pulmonary TB patients, new or re-treatment, aged 18 years or older. The eligible patients were randomly allocated (1:1) to either the study group or the control group using stratified blocked randomization. The add-on DPI of combined anti-TB therapy (each capsule contained isoniazid 5 mg, rifampicin 2 mg, pyrazinamide 16 mg, and levofloxacin 2 mg) was used throughout the course of the standard oral anti-TB treatment. The primary outcome was Mycobacterium tuberculosis (MTB) sputum culture conversion measured after receiving treatment for eight weeks. Secondary outcomes were clinical signs and symptoms of pulmonary TB and adverse drug reactions (ADRs) related to anti-TB agents. The percentages of patients who achieved the primary outcome were compared (95% confidence interval). All analyses were performed using the modified intention-to-treat principle.

RESULTS

91 patients were randomly allocated: 44 to the study group and 47 to the control group. Important baseline data (%peak expiratory flow rate, chest X-ray findings, resistance to anti-TB agents, renal and liver function tests) were similar between the two groups. Although the percentages of patients who achieved the primary outcome were similar in both groups (34/44 [77.3%] in the study group and (34/47 [72.3%] in the control group; relative risk [RR] 1.07, 95% CI 0.84-1.36; p = 0.589), the study group patients seemed to achieve the primary outcome earlier than the control group (22/44 [50.0%] vs 15/47 [31.9%]; RR 1.57, 95% CI 0.94-2.61; p = 0.079) at the end of week 4. Cough was significantly lower in the study group than in the control group (23/44 [52.3%] vs 43/47 [91.5%]; RR 0.57, 95% CI 0.43-0.77; p < 0.001) at week 4 of treatment. Hemoptysis was found in approximately half of each group at baseline. The percentage of patients having hemoptysis was substantially reduced at week 2 of treatment (5 [11.4%] in the study group and 11 [23.0%] in the control group, p = 0.132). Regarding safety outcomes, no dyspnea or severe ADRs were reported. Adverse events (AEs) related to oral anti-TB agents, (e.g. liver function tests) were in normal ranges in most patients in both groups during the treatment. The incidences of common AEs reported (e.g. anorexia, dizziness, numbness, arthralgia, rash, and itching) were similar between the two groups, while the incidences of nausea and vomiting were significantly lower in the study group than the control group (38.6% vs 74.5%, p = 0.001, and 43.2% vs 66.0%, p = 0.029, respectively).

CONCLUSIONS

Add-on combined anti-TB DPI therapy to the standard oral anti-TB treatment did not increase MTB sputum culture conversion at two months of treatment. However, the percentage of patients having cough in the study group was significantly lower than in the control group at two months after treatment. A reduction in cough might represent adequate response to treatment, and result in a decreased risk of spread of infection. Combined anti-TB DPI therapy was safe. Further study investigated in a larger sample using higher strengths of DPI therapy is required.

Pharmacokinetics and pharmacodynamics of high doses of inhaled dry powder drugs

For many years, administration of drugs by inhalation has been the mainstay treatment for obstructive respiratory disorders such as asthma and chronic obstructive pulmonary disease. Antibiotics and other drugs have been administered for decades as aerosols to treat other pulmonary disease in a clinical setting, but it was until the early 1980's that colistin was formally marketed as a solution for nebulization in Europe (Colomycin, Pharmax, Bexley). The solubility of other drugs and the size of the dose required to achieve therapeutic concentrations at the site of action, made treatment times long and difficult to be performed at home. High dose dry powder delivery is a potentially effective way to deliver low potency drugs such as antibiotics. There are three major barriers to achieving the desired pharmacodynamic effect with these compounds: aerosol delivery, lung deposition and clearance. The powder formulation and device technology influence aerosol generation and may influence the size of the dose that can be achieved by inhalation in one puff. The site of deposition in the lungs is dictated by mechanisms of deposition which are influenced by the aerosol properties, particularly aerodynamic particle size distribution and the anatomy and physiology of the lungs. Finally, mechanisms of clearance dictate the local and systemic disposition of the drug, which in turn affects its pharmacokinetics and ultimately the pharmacodynamic effect and efficacy of treatment. Each of these factors will be considered and the implications for antimicrobial agent delivery as a high dose delivery example will be given.

Current approaches to the discovery of novel inhaled medicines

Inhaled administration is underutilised because the drug discovery process is viewed as challenging, risky, and expensive. However, unmet medical need continues to grow, and significant opportunities exist to discover novel inhaled medicines delivering the required lung concentrations while minimising systemic exposure. This profile could be achieved by a combination of properties, including lung retention and low oral bioavailability. Property-based rules exist for orally administered compounds, but there has been limited progress defining in silico predictors to guide the discovery of novel inhaled drugs. Recently, the use of informative cell- and tissue-based screens has greatly facilitated the identification of compounds with optimal characteristics for inhaled delivery. Here, we address opportunities for novel inhaled drugs, and the key challenges and uncertainties hampering progress.

Optimization of ciprofloxacin complex loaded PLGA nanoparticles for pulmonary treatment of cystic fibrosis infections: Design of experiments approach

Design of Experiments (DoE) is a powerful tool for systematic evaluation of process parameters' effect on nanoparticle (NP) quality with minimum number of experiments. DoE was employed for optimization of ciprofloxacin loaded PLGA NPs for pulmonary delivery against Pseudomonas aeruginosa infections in cystic fibrosis (CF) lungs. Since the biofilm produced by bacteria was shown to be a complicated 3D barrier with heterogeneous meshes ranging from 100nm to 500nm, nanoformulations small enough to travel through those channels were assigned as target quality. Nanoprecipitation was realized utilizing MicroJet Reactor (MJR) technology based on impinging jets principle. Effect of MJR parameters flow rate, temperature and gas pressure on particle size and PDI was investigated using Box-Behnken design. The relationship between process parameters and particle quality was demonstrated by constructed fit functions (R²=0.9934 p<0.0001 and R²=0.9983 p<0.0001, for particle size and PDI, respectively). Prepared nanoformulations varied between 145.2 and 979.8nm with PDI ranging from 0.050 to 1.00 and showed encapsulation efficiencies >65%. Response surface plots provided experimental data-based understanding of MJR parameters' effect, thus NP quality. Presented work enables ciprofloxacin loaded PLGA nanoparticle preparations with pre-defined quality to fulfill the requirements of local drug delivery under CF disease conditions.

Improving the efficacy of inhaled drugs in cystic fibrosis: challenges and emerging drug delivery strategies

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians associated with early death. Although the faulty gene is expressed in epithelia throughout the body, lung disease is still responsible for most of the morbidity and mortality of CF patients. As a local delivery route, pulmonary administration represents an ideal way to treat respiratory infections, excessive inflammation and other manifestations typical of CF lung disease. Nonetheless, important determinants of the clinical outcomes of inhaled drugs are the concentration/permanence at the lungs as well as the ability of the drug to overcome local extracellular and cellular barriers. This review focuses on emerging delivery strategies used for local treatment of CF pulmonary disease. After a brief description of the disease and formulation rules dictated by CF lung barriers, it describes current and future trends in inhaled drugs for CF. The most promising advanced formulations are discussed, highlighting the advantages along with the major challenges for researchers working in this field.

Nebulizer Choice Affects the Airway Targeting of Amphotericin B Lipid Complex Aerosols

Background: Although amphotericin B is highly effective against fungal infections, it has serious adverse effects. Encapsulation of amphotericin B in liposomes reduces its potential for systemic side effects. Administration of liposomal amphotericin via aerosols to the lungs (a main portal of fungal infections) further reduces its toxicity while increasing its therapeutic index and prophylactic efficacy. However, the effectiveness of aerosol therapy depends on the dose deposited and the distribution of the drug within the lungs. The size of the aerosol particle is an important factor that affects the distribution of the drug within the lungs and the effectiveness of therapy. Objective: This study aims to determine the physicochemical suitability of amphotericin B lipid complex (ABLC) for aerosolization and to compare the performance of 3 commercially available air jet nebulizers in generating ABLC aerosols in terms of aerosol output (mg/min) and drug amount aerosolized within various particle-size ranges, the latter of which affects airway deposition. Methods: We aerosolized 2 concentrations (5 mg/mL and 10 mg/mL) of ABLC and evaluated their physicochemical properties, including osmolality, pH, and viscosity. The aerosolization performances of Pulmo-Aide/Micromist, Envoy/Sidestream, and Proneb/Pari LC Star systems were then evaluated in terms of output rate (mg/min), percent aerosolized, and milligram per minute of drug aerosolized within particle-size ranges of 1 to 3.5 µm, 3.5 to 6 µm, and 1 to 6 µm. Results: The output rate increased with higher drug concentration regardless of device. Pulmo-Aide/Micromist and Envoy/Sidestream showed high output rates. Proneb/Pari LC Star and Envoy/Sidestream delivered the highest percentages of aerosolized particles within the 1 to 3.5 µm particle-size range, favoring deposition within the alveolar/distal end area of the airways. Pulmo-Aide/Micromist delivered a higher percentage of aerosol within the 3.5 to 6 µm than the 1 to 3.5 µm particle-size range, favoring deposition in the central airways. Conclusion: The present study shows that different nebulizers produced different size ranges of aerosolized particles of ABLC preferentially targeting different parts of the airways. Thus, effective aerosol therapies may require the evaluation of different nebulizers for optimal targeting.

Mechanisms of absorption and elimination of drugs administered by inhalation

Pulmonary drug delivery is an effective route for local or systemic drug administration. However, compared with other routes of administration, there is a scarcity of information on how drugs are absorbed from the lung. The different cell composition lining the airways and alveoli makes this task extremely complicated. Lung cell lines and primary culture cells are useful in studying the absorption mechanisms. However, it is imperative that these cell cultures express essential features required to study these mechanisms such as intact tight junctions and transporters. In vivo, the drug has to face defensive physical and immunological barriers such as mucociliary clearance and alveolar macrophages. Knowledge of the physicochemical properties of the drug and aerosol formulation is required. All of these factors interact together leading to either successful drug deposition followed by absorption or drug elimination. These aspects concerning drug transport in the lung are addressed in this review.

Design, characterization, and aerosolization of organic solution advanced spray-dried moxifloxacin and ofloxacin dipalmitoylphosphatidylcholine (DPPC) microparticulate/nanoparticulate powders for pulmonary inhalation aerosol delivery

The aim of this study was to design and develop respirable antibiotics moxifloxacin (MOXI) hydrochloride and ofloxacin (OFLX) microparticles and nanoparticles, and multifunctional antibiotics particles with or without lung surfactant 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced by advanced spray-drying particle engineering from an organic solution in closed mode (no water) from dilute solution. Scanning electron microscopy indicated that these particles had both optimal particle morphology and surface morphology, and the particle size distributions were suitable for pulmonary delivery. Comprehensive and systematic physicochemical characterization and in vitro aerosol dispersion performance revealed significant differences between these two fluoroquinolone antibiotics following spray drying as drug aerosols and as cospray-dried antibiotic drug: DPPC aerosols. Fourier transform infrared spectroscopy and confocal Raman microspectroscopy were employed to probe composition and interactions in the solid state. Spray-dried MOXI was rendered noncrystalline (amorphous) following organic solution advanced spray drying. This was in contrast to spray-dried OFLX, which retained partial crystallinity, as did OFLX:DPPC powders at certain compositions. Aerosol dispersion performance was conducted using inertial impaction with a dry powder inhaler device approved for human use. The present study demonstrates that the use of DPPC offers improved aerosol delivery of MOXI as cospray-dried microparticulate/nanoparticulate powders, whereas residual partial crystallinity influenced aerosol dispersion of OFLX and most of the compositions of OFLX:DPPC inhalation powders.

Nanotechnology approaches for inhalation treatment of fibrosis

Cystic fibrosis (CF) is an autosomal recessive monogenetic disease that afflicts nearly 70 000 patients worldwide. The mutation results in the accumulation of viscous mucus in multiple organs especially in the lungs, liver and pancreas. High associated morbidity and mortality is caused by CF due to the lack of effective therapies. It is widely accepted that morbidity and mortality caused by CF is primarily due to the respiratory manifestations of the disease. Consequently, several approaches were recently developed for treatment of lung complications of CF. However, the lack of effective methods for delivery and especially targeted delivery of therapeutics specifically to lung tissues and cells limits the efficiency of the therapy. Local pulmonary delivery of therapeutics has two major advantages over systemic application. First, it enhances the accumulation of therapeutics specifically in the lungs and therefore increases the efficiency of the treatment. Second, local lung delivery substantially prevents the penetration of the delivered drug into the systemic circulation limiting adverse side effects of the treatment on other organs and tissues. This review is focused on different approaches to the treatment of respiratory manifestations of CF as well as on methods of pulmonary delivery of therapeutics.

Challenges and advances in the development of inhalable drug formulations for cystic fibrosis lung disease

INTRODUCTION

Cystic fibrosis (CF) is a multisystem genetic disorder, which usually results in significant respiratory dysfunction. At present there is no cure for CF, but advances in pharmacotherapy have gradually increased the life expectancy of CF patients. As many drugs used in the therapy of CF are delivered by inhalation, the demand for effective and convenient inhalational CF drug formulations will grow as CF patients live longer. Knowledge of the current limitations in inhalational CF drug delivery is critical in identifying new opportunities and designing rational delivery strategies.

AREAS COVERED

This review discusses current and emerging therapeutic agents for CF therapy, selected physiological challenges to effective inhalational medication delivery, and various approaches to overcoming these challenges. The reader will find an integrated view of the known inhalational drug delivery challenges and the rationales for recent investigational inhalational drug formulations.

EXPERT OPINION

An ideal drug/gene delivery system to CF airways should overcome the tenacious sputum, which presents physical, chemical and biological barriers to effective transport of therapeutic agents to the targets and various cellular challenges.

Evaluation of the Target Inhalation Mode (TIM) breathing maneuver in simulated nebulizer therapy in patients with cystic fibrosis

BACKGROUND

Adaptive Aerosol Delivery (AAD) systems provide efficient drug delivery and improved lung deposition over conventional nebulizers by combining real-time analyses of patient breathing patterns and precisely timed aerosol delivery. Delivery and deposition are further enhanced by breathing techniques involving slow, deep inhalations.

METHODS

This exploratory study assessed the acceptability of slow, deep inhalations in 20 patients with cystic fibrosis (CF) during up to eight simulated nebulizer treatments with the I-neb AAD System. The breathing maneuver, Target Inhalation Mode (TIM) breathing, involved the lengthening of the patient's inhalation time over successive breaths with guidance from auditory and tactile (vibratory) feedback from the device.

RESULTS

At the end of the first treatment, most patients felt that the instructions were easy to understand (90%) and that the vibratory feedback was pleasant (65%). Half of the patients found the procedure to be comfortable. At the end of the final treatment, most patients felt that the breathing maneuver was easy to understand (90%) and use (80%), but that the duration of the breath was too long (100%). Logged data revealed that 90% of patients were able to comply with the breathing maneuver. The two patients unable to comply had a forced vital capacity of <1.75 L. The average treatment time decreased from 288.4 to 141.6 sec during the first and final treatments, respectively.

CONCLUSIONS

This study provides preliminary evidence of the acceptability of the TIM breathing maneuver in patients with CF and their ability to perform repeated TIM breathing during simulated nebulizer therapy with the I-neb AAD System.

Biodegradable polymer nanoparticles that rapidly penetrate the human mucus barrier

Protective mucus coatings typically trap and rapidly remove foreign particles from the eyes, gastrointestinal tract, airways, nasopharynx, and female reproductive tract, thereby strongly limiting opportunities for controlled drug delivery at mucosal surfaces. No synthetic drug delivery system composed of biodegradable polymers has been shown to penetrate highly viscoelastic human mucus, such as non-ovulatory cervicovaginal mucus, at a significant rate. We prepared nanoparticles composed of a biodegradable diblock copolymer of poly(sebacic acid) and poly(ethylene glycol) (PSA-PEG), both of which are routinely used in humans. In fresh undiluted human cervicovaginal mucus (CVM), which has a bulk viscosity approximately 1,800-fold higher than water at low shear, PSA-PEG nanoparticles diffused at an average speed only 12-fold lower than the same particles in pure water. In contrast, similarly sized biodegradable nanoparticles composed of PSA or poly(lactic-co-glycolic acid) (PLGA) diffused at least 3,300-fold slower in CVM than in water. PSA-PEG particles also rapidly penetrated sputum expectorated from the lungs of patients with cystic fibrosis, a disease characterized by hyperviscoelastic mucus secretions. Rapid nanoparticle transport in mucus is made possible by the efficient partitioning of PEG to the particle surface during formulation. Biodegradable polymeric nanoparticles capable of overcoming human mucus barriers and providing sustained drug release open significant opportunities for improved drug and gene delivery at mucosal surfaces.

The penetration of fresh undiluted sputum expectorated by cystic fibrosis patients by non-adhesive polymer nanoparticles

Highly viscoelastic and adhesive sputum has precluded efficient nanoparticle-based drug and gene delivery to the lungs of patients with cystic fibrosis (CF). We sought to determine whether nanoparticles coated with non-mucoadhesive polymers could penetrate CF sputum, and to use these "muco-inert particles" (MIPs) as non-destructive nanoprobes to characterize the sputum microstructure. Particles as large as 200 nm in diameter that were densely coated with low MW polyethylene glycol (PEG) moved through undiluted CF sputum with average speeds up to 90-fold faster than similarly-sized uncoated particles. On the other hand, the transport of both coated and uncoated 500 nm particles was strongly hindered. The local viscosity of sputum, encountered by the fastest 10% of 200 nm MIPs, was only 5-fold higher than that of water, whereas the bulk viscosity was 10,000-fold higher at low shear rates. Using measured transport rates of various sized MIPs combined with an obstruction-scaling model, we determined that the average 3D mesh spacing of CF sputum is approximately 140+/-50 nm (range: 60-300 nm). Taken together, these results demonstrate that nanoparticles up to 200 nm in diameter that do not adhere to CF sputum can move rapidly through this critical barrier by accessing pores that are filled with a low viscosity fluid. The results also offer hope that desperately needed sputum-penetrating drug- and gene-carrier nanoparticles can be developed for CF.

Educational Practice for Inhaled Treatments in French Cystic Fibrosis Care Centers

Inhaled treatments are very common in cystic fibrosis (CF) patients. We sent a questionnaire to the 49 French Cystic Fibrosis Care Centers (CFCCs) to see how the inhalation technique of CF patients was initiated and monitored (composition and formation of a potential educational team, use of a manual for use, amount of devices available for demonstration, education to disinfection procedure, realization and frequency of the inhalation technique monitoring, use of the patient's own device, and frequency of checking when a pediatric patient transfers to an adult CFCC). Results were expressed in percent and compared with the test of the difference between two correlated proportions. Education for aerosol therapy was not performed in about 20% of the CFCCs. A specific educational member was present in 33 CFCCs (68%). CFCCs owned statistically less nebulizers for demonstration than other devices. Disinfection advices were always given for nebulizers, but less frequently for spacers (80%) and dry powder inhalers (50%). The inhalation technique was monitored less than once a year or never in 22% of the cases, and rarely with the patient's own material. This monitoring was device dependent (56% with nebulizers vs. 76% with the other devices, p < 0.05). For nebulizers, monitoring depended on the presence of an educational member (p < 0.01) and of a manual for use (p = 0.03). When transferring to an adult CFCC, the inhalation technique was checked in less than a third of the patients. The inhalation technique is poorly and insufficiently initiated and monitored in CF patients. Educational teams and programs are urgently required.

Effervescent dry powder for respiratory drug delivery

The objective of this work was to develop a new type of respiratory drug delivery carrier particle that incorporates an active release mechanism. Spray drying was used to manufacture inhalable powders containing polybutylcyanoacrylate nanoparticles and ciprofloxacin as model substances for pulmonary delivery. The carrier particles incorporated effervescent technology, thereby adding an active release mechanism to their pulmonary route of administration. Effervescent activity of the carrier particles was observed when the carrier particles were exposed to humidity. Gas bubbles caused by the effervescent reaction were visualized by confocal laser scanning microscopy. The images showed that nanoparticles were distributed throughout the gas bubble. For the effervescent formulation the average mass median aerodynamic diameter (MMAD) was 2.17 microm+/-0.42, fine particle fraction (FPF(<=5.6 microm)) was 46.47%+/-15 and the GSD was 2.00+/-0.06. The results also showed that the effervescent carrier particles released 56+/-8% ciprofloxacin into solution compared with 32+/-3% when lactose carrier particles were used. The mean nanoparticle size did not significantly change upon release when the nanoparticles were incorporated into an effervescent formulation. However, the mean size significantly increased upon release when only lactose was used as carrier particle matrix. In conclusion, effervescent carrier particles can be synthesized with an adequate particle size for deep lung deposition. This opens the door for future research to explore this technology for delivery of a large range of substances to the lungs with possible improved release compared to conventional carrier particles.

Rapid transport of large polymeric nanoparticles in fresh undiluted human mucus

Nanoparticles larger than the reported mesh-pore size range (10-200 nm) in mucus have been thought to be much too large to undergo rapid diffusional transport through mucus barriers. However, large nanoparticles are preferred for higher drug encapsulation efficiency and the ability to provide sustained delivery of a wider array of drugs. We used high-speed multiple-particle tracking to quantify transport rates of individual polymeric particles of various sizes and surface chemistries in samples of fresh human cervicovaginal mucus. Both the mucin concentration and viscoelastic properties of these cervicovaginal samples are similar to those in many other human mucus secretions. Unexpectedly, we found that large nanoparticles, 500 and 200 nm in diameter, if coated with polyethylene glycol, diffused through mucus with an effective diffusion coefficient (D(eff)) only 4- and 6-fold lower than that for the same particles in water (at time scale tau = 1 s). In contrast, for smaller but otherwise identical 100-nm coated particles, D(eff) was 200-fold lower in mucus than in water. For uncoated particles 100-500 nm in diameter, D(eff) was 2,400- to 40,000-fold lower in mucus than in water. Much larger fractions of the 100-nm particles were immobilized or otherwise hindered by mucus than the large 200- to 500-nm particles. Thus, in contrast to the prevailing belief, these results demonstrate that large nanoparticles, if properly coated, can rapidly penetrate physiological human mucus, and they offer the prospect that large nanoparticles can be used for mucosal drug delivery.

Inhaled azithromycin therapy

The treatment of pulmonary infectious diseases with pharmaceutical aerosols is an attractive option considering the accessibility of the lungs for topical drug delivery. Aerosols have been targeted to the lungs for the treatment of asthma with great success. Current therapies for other diseases, including Pseudomonas aeruginosa, Pneumocystis jirovecii (formerly Pneumocystis carinii), and mycobacterial infections, remain suboptimal due to the efficacy/safety profile. This may be improved by aerosol targeted pulmonary drug delivery. Azithromycin is a broad spectrum antibiotic that acts by inhibiting protein synthesis. It is associated with side effects that might be avoided by aerosol delivery to the lungs. In the present study three concentrations of azithromycin (10, 50, and 100 mg/mL) were delivered from three nebulizers (Acorn II, Updraft, and LC Plus) operated at 8 L/min. Particles size analyses were conducted by inertial impaction and laser diffraction. In addition, emitted doses were determined. A linear proportionality existed across the concentration range between nominal dose and both fine particle dose/fraction and emitted dose, with R2 > 0.999 in all cases. The mass median aerodynamic diameter increased from 1.4 to 1.9 microm between 10 and 100 mg/mL of azithromycin solution concentration for the Acorn II. The particle size distributions were not all log-normally distributed. The median particle size delivered from the devices was largest for the Updraft (2.8 microm) and smallest for the Acorn II (1.9 microm) for 100 mg/mL azithromycin solution concentrations. The efficiencies of small particle delivery (%<4.7 microm) were as follows, LC Plus = Acorn II (85%) > UpDraft (75%). However, the emitted dose from the LC Plus (55 mg/min) was higher than the Acorn II (31 mg/min) to maximize lung exposure to the aerosol, small median diameters and broad particle size distributions would be most effective. This study demonstrates that the dose delivered to the lungs will be maximized, under the current operating conditions by adopting the LC Plus, and high (100 mg/mL) azithromycin concentrations.

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.

Ionic interaction of amiloride and uridine 5'-triphosphate in nebulizer solutions

Combination therapy using nebulized amiloride hydrochloride and uridine-5'-triphosphate (UTP) trisodium salt aerosols has been investigated for the treatment of cystic fibrosis (CF). Amiloride in aqueous solution precipitates in the presence of UTP, reducing drug concentrations. Interactions between these drugs and NaCl in solution were studied using phase-solubility techniques monitored by UV spectrophotometry. Elemental analyses were employed for precipitate characterization. Amiloride solubility was reduced by more than 85% in saline. Amiloride solubility decreased with increasing UTP concentration, resulting in formation of a precipitated complex. The theoretical molar ratio of complexes range from 1-3 amiloride:1 UTP. At most concentrations only 3 amiloride:1 UTP complex was observed in precipitate. This is a reflection of low Ksp for the 3:1 complex of 2.92 x 10(-11) M4 compared with 2.09 x 10(-4) M2 for amiloride alone. Equilibration over excess bulk solid resulted in higher solubility estimates and different phase solubility diagrams than solubility studies utilizing precipitation technique. This may be explained by the absence of amiloride in the solid state and its impact on complex equilibria with UTP. The solubility suppressing effects of UTP and saline were largely additive. A number of ionic interactions increase complex solubility profile of amiloride hydrochloride in the presence of UTP and NaCl.

The role of branched polyesters and their modifications in the development of modern drug delivery vehicles

Branched polyesters consisting of poly (vinyl alcohol) (PVA) grafted with chains of poly (lactic-co-glycolic acid) (PLGA) represent a new class of biodegradable polymers showing significant potential for the development of a variety of drug delivery vehicles. The amphiphilic character and the resulting increase in hydrophilicity of this class of polymers provide advantages when packaging sensitive drug molecules, such as proteins, peptides or DNA. Furthermore, the PVA backbone can be modified, for example, with sulfobutyl moieties or amine structures, to create polymers with negative or positive charges. The ability to modify not only the backbone but also the length of the PLGA side chains results in an extremely flexible polymer system, which can be adapted to meet the needs of almost any drug substance. Further, the rate of biodegradation may also be manipulated through polymer modification to achieve half-lives ranging from several hours to several weeks. This review provides an overview of the three major groups of branched polyesters based upon poly (vinyl alcohol)-grafted poly (lactic-co-glycolic acid) (PVA-g-PLGA), namely, the neutrally charged PVA-g-PLGA, the negatively charged sulfobutyl-modified PVA-g-PLGA and the positively charged amine-modified PVA-g-PLGA, as well as their use in various drug delivery systems.