Drug solubilization in lung surfactant

Pulmonary drug delivery devices and nanosystems as potential treatment strategies for acute respiratory distress syndrome (ARDS)

Despite advances in drug delivery technologies, treating acute respiratory distress syndrome (ARDS) is challenging due to pathophysiological barriers such as lung injury, oedema fluid build-up, and lung inflammation. Active pharmaceutical ingredients (API) can be delivered directly to the lung site of action with the use of aerosol-based drug delivery devices, and this circumvents the hepatic first-pass effect and improves the bioavailability of drugs. This review discusses the various challenges and barriers for pulmonary drug delivery, current interventions for delivery, considerations for effective drug delivery, and the use of nanoparticle drug delivery carriers as potential strategies for delivering therapeutics in ARDS. Nanosystems have the added benefit of entrapping drugs, increase pulmonary drug bioavailability, and using biocompatible and biodegradable excipients that can facilitate targeted and/or controlled delivery. These systems provide an alternative to existing conventional systems. An effective way to deliver drugs for the treatment of ARDS can be by using colloidal systems that are aerosolized or inhaled. Drug distribution to the deeper pulmonary tissues is necessary due to the significant endothelial cell destruction that is prevalent in ARDS. The particle size of nanoparticles (<0.5 μm) makes them ideal candidates for treating ARDS as they can reach the alveoli. A look into the various potential benefits and limitations of nanosystems used for other lung disorders is also considered to indicate how they may be useful for the potential treatment of ARDS.

Long-term Effects of Intratracheal Budesonide and Surfactant for the Prevention of Bronchopulmonary Dysplasia: A Narrative Review

OBJECTIVE

 This study aimed to compare the safety and efficacy of intratracheal administration of budesonide and surfactant with surfactant alone for bronchopulmonary dysplasia (BPD) prevention in premature infants with respiratory distress syndrome.

STUDY DESIGN

 A literature search was performed in MEDLINE, Embase, Cochrane, ClinicalTrials.gov, and gray literature. Assessment of quality was conducted using CASP tool, ROBIS tool, and GRADE framework.

RESULTS

 A systematic review and meta-analysis and three observational studies were identified. Budesonide was associated with reduced incidence and severity of BPD, reduced mortality, patent ductus arteriosus, need for additional surfactant doses, hypotension, duration of invasive ventilation, hospital stays, salbutamol prescriptions, and hospitalizations in the first 2 years of life. The safety of budesonide on neurodevelopmental outcomes at 2 to 3 years of corrected age was reported.

CONCLUSION

 Budesonide might be associated with a reduction in BPD incidence and severity, without evidence of impaired neurodevelopment at 2 to 3 years of age. According to the GRADE framework, the level of evidence is low due to significant heterogeneity of studies and other bias.

KEY POINTS

· BPD prevention is urgently needed.. · Intratracheal budesonide and surfactant for neonatal RDS could reduce BPD.. · The grade of evidence for this intervention is low due to study heterogeneity and other bias..

Efficacy and safety of different inhaled corticosteroids for bronchopulmonary dysplasia prevention in preterm infants: A systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to evaluate the efficacy and safety of inhaled corticosteroids (budesonide, beclomethasone, or fluticasone propionate) in preventing bronchopulmonary dysplasia (BPD) for premature infants.

METHOD

Electronic databases, including PubMed, EMBASE, Web of science, Scopus, and Cochrane library, were searched from databases inception to January 2022 for eligible randomized controlled trials. Clinical outcomes such as BPD, mortality, BPD or death, adverse events, and neurodevelopmental outcomes were assessed.

RESULTS

Overall, budesonide was significantly associated with a reduction in BPD at 36 weeks' postmenstrual age (RR 0.48; 95 % CI [0.38, 0.62]) and patent ductus arteriosus (PDA) (RR 0.75; 95 % CI [0.63, 0.89]) compared with control treatments. Early longer duration inhalation of budesonide alone was associated with a lower risk of BPD at 36 weeks' postmenstrual age and PDA compared with controls. Early shorter duration intratracheal instillation of budesonide with surfactant as vehicle was associated with a lower risk of BPD at 36 weeks' postmenstrual age and all-cause mortality compared with surfactant. There was no statistically significant difference between budesonide and control groups regarding neurodevelopmental impairment. Beclomethasone and fluticasone propionate did not show any superior or inferior effect on clinical outcomes compared to control treatments.

CONCLUSION

These findings suggest that budesonide, especially intratracheal instillation of budesonide using surfactant as a vehicle, is a safe and effective option in preventing BPD for preterm infants. More well-design large-scale trials with long-term follow-ups are necessary to verify the present findings.

Nano vs Resistant Tuberculosis: Taking the Lung Route

Tuberculosis (TB) is among the top 10 infectious diseases worldwide. It is categorized among the leading killer diseases that are the reason for the death of millions of people globally. Although a standardized treatment regimen is available, non-adherence to treatment has increased multi-drug resistance (MDR) and extensive drug-resistant (XDR) TB development. Another challenge is targeting the death of TB reservoirs in the alveoli via conventional treatment. TB Drug resistance may emerge as a futuristic restraint of TB with the scarcity of effective Anti-tubercular drugs. The paradigm change towards nano-targeted drug delivery systems is mostly due to the absence of effective therapy and increased TB infection recurrent episodes with MDR. The emerging field of nanotechnology gave an admirable opportunity to combat MDR and XDR via accurate diagnosis with effective treatment. The new strategies targeting the lung via the pulmonary route may overcome the new incidence of MDR and enhance patient compliance. Therefore, this review highlights the importance and recent research on pulmonary drug delivery with nanotechnology along with prevalence, the need for the development of nanotechnology, beneficial aspects of nanomedicine, safety concerns of nanocarriers, and clinical studies.

Surfactant as a drug carrier

Drug delivery using a surfactant vehicle has the potential to prevent systemic side effects by delivering therapeutic agents directly to the respiratory system. The inherent chemical properties of surfactant allows it to readily distribute throughout the respiratory system. Therapeutic agents delivered by surfactant can primarily confer additional benefits but have potential to improve surfactant function. It is critically important that additional agents do not interefere with the innate surface tension lowering function of surfactant. Systemic evaluation through benchtop, translational and human trials are required to translate this potential technique into clinical practice.

In Vitro Dissolution and Permeability Testing of Inhalation Products: Challenges and Advances

In vitro dissolution and permeability testing aid the simulation of the in vivo behavior of inhalation drug products. Although the regulatory bodies have specific guidelines for the dissolution of orally administered dosage forms (e.g., tablets and capsules), this is not the case for orally inhaled formulations, as there is no commonly accepted test for assessing their dissolution pattern. Up until a few years ago, there was no consensus that assessing the dissolution of orally inhaled drugs is a key factor in the assessment of orally inhaled products. With the advancement of research in the field of dissolution methods for orally inhaled products and a focus on systemic delivery of new, poorly water-soluble drugs at higher therapeutic doses, an evaluation of dissolution kinetics is proving crucial. Dissolution and permeability testing can determine the differences between the developed formulations and the innovator’s formulations and serve as a useful tool in correlating in vitro and in vivo studies. The current review highlights recent advances in the dissolution and permeability testing of inhalation products and their limitations, including recent cell-based technology. Although a few new dissolution and permeability testing methods have been established that have varying degrees of complexity, none have emerged as the standard method of choice. The review discusses the challenges of establishing methods that can closely simulate the in vivo absorption of drugs. It provides practical insights into method development for various dissolution testing scenarios and challenges with dose collection and particle deposition from inhalation devices for dissolution tests. Furthermore, dissolution kinetic models and statistical tests to compare the dissolution profiles of test and reference products are discussed.

The prevention and management strategies for neonatal chronic lung disease

INTRODUCTION

Survival from even very premature birth is improving, but long-term respiratory morbidity following neonatal chronic lung disease (bronchopulmonary dysplasia (BPD)) has not reduced. Affected infants may require supplementary oxygen at home, because they have more hospital admissions particularly due to viral infections and frequent, troublesome respiratory symptoms requiring treatment. Furthermore, adolescents and adults who had BPD have poorer lung function and exercise capacity.

AREAS COVERED

Antenatal and postnatal preventative strategies and management of infants with BPD. A literature review was undertaken using PubMed and Web of Science.

EXPERT OPINION

There are effective preventative strategies which include caffeine, postnatal corticosteroids, vitamin A, and volume guarantee ventilation. Side-effects, however, have appropriately caused clinicians to reduce use of systemically administered corticosteroids to infants only at risk of severe BPD. Promising preventative strategies which need further research are surfactant with budesonide, less invasive surfactant administration (LISA), neurally adjusted ventilatory assist (NAVA) and stem cells. The management of infants with established BPD is under-researched and should include identifying the optimum form of respiratory support on the neonatal unit and at home and which infants will most benefit in the long term from pulmonary vasodilators, diuretics, and bronchodilators.

A systematic review and meta-analysis of pulmonary surfactant combined with budesonide in the treatment of neonatal respiratory distress syndrome

BACKGROUND

Neonatal respiratory distress syndrome (NRDS), if caused by a lack of pulmonary surfactant (PS), leads to progressive alveolar collapse. Glucocorticoids have anti-inflammatory and anti-allergic effects and can reduce bronchial and pulmonary edema. This research hopes to systematically evaluate the efficacy and safety of animal-derived PS combined with the glucocorticoid drug budesonide in the treatment of NRDS.

METHODS

Electronic databases (i.e., Wanfang, Weipu, CNKI, PubMed, Embase, Cochrane Library) were searched from inception until May 30th, 2021. Studies relevant to the treatment of pulmonary surfactant combined with budesonide in the treatment of neonatal respiratory distress syndrome were identified. Consequently, all the studies that met the inclusion criteria were considered qualified for screening. For the meta-analysis, all data were analyzed using RevMan 5.3 software. Furthermore, subgroup analysis was performed to evaluate the administration method of budesonide (nebulized inhalation, intratracheal instillation) combined with intratracheal instillation of pulmonary surfactant.

RESULTS

A total of 10 articles were included in this study, involving 527 children. This meta-analysis suggests that the treatment of intratracheal infusion of pulmonary surfactant combined with budesonide therapy can effectively (I) reduce the time of mechanical ventilation (OR =-1.72,95% CI: -2.44 to -1.01, P<0.00001); (II) reduce the length of stay (OR =-5.17, 95% CI: -9.35 to -0.99, P=0.02); (III) reduce the incidence of bronchopulmonary dysplasia (BPD) (OR =0.52, 95% CI: 0.39-0.68, P<0.00001); and (IV) reduce the incidence of BPD (RR =0.73, 95% CI: 0.40-1.35, P=0.32). There was no significant difference in the incidence of retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), patent ductus arteriosus (PDA), or sepsis between the experimental group and the control group.

DISCUSSION

The treatment of animal-derived pulmonary surfactant combined with budesonide can effectively shorten the hospital stay and reduce the time of invasive mechanical ventilation and the incidence of BPD. Meanwhile, it does not increase the risk of related complications or death. This approach can be applied clinically.

Effectiveness and safety of early combined utilization of budesonide and surfactant by airway for bronchopulmonary dysplasia prevention in premature infants with RDS: A meta-analysis

OBJECTIVE

To address the effectiveness and safety of early airway combined utilization of budesonide and surfactant for bronchopulmonary dysplasia (BPD) prevention in premature infants with respiratory distress syndrome (RDS).

METHODS

Literature retrieval was carried out in the PubMed, Web of Science, EMBASE, Cochrane Library, Wanfang, CQ VIP, and China National Knowledge Infrastructure databases, searching from the inception to September 2021. Stata 16.0 software was used for statistical analysis.

RESULTS

This meta-analysis suggested that early combined utilization of budesonide and surfactant by airway have a superiority on BPD incidence (risk ratio [RR] = 0.62; 95% confidence interval [CI]: 0.54-0.71, p < 0.001], mortality (RR = 0.64; 95%CI: 0.45-0.92, p = 0.016), the composite outcome of BPD or mortality (RR = 0.58; 95%CI: 0.50-0.68, p < 0.001), the additional doses of surfactant (RR = 0.53; 95%CI: 0.44-0.63, p < 0.001), the duration of assisted ventilation (standard mean difference [SMD] = -1.14; 95%CI: -1.58 to -0.70, p < 0.001), duration of invasive ventilation(SMD = -1.77; 95% CI: -2.61 to -0.93, p < 0.001), and hospital stays (SMD = -1.11; 95% CI: -1.73 to -0.49, p = 0.001) in preterm infants with RDS. And these benefits were not associated with increased adverse outcomes. Furthermore, a decreased incidence of patent ducts arterious (PDA) (RR = 0.79; 95% CI: 0.65 to 0.97, p = 0.028) was found in premature infants treated with budesonide and surfactant. Subgroup analysis based on budesonide delivery methods (inhalation or intratracheal instillation) indicated that the decrease of mortality (RR = 0.63; 95% CI: 0.43-0.93, p = 0.019), duration of assisted ventilation (SMD = -0.95; 95% CI: -1.30 to -0.61, p < 0.001), hospital stays (SMD = -1.23; 95% CI: -2.05 to -0.41, p = 0.003) and PDA incidence (RR = 0.80; 95% CI: 0.65 to 0.99, p = 0.044) were mainly in budesonide intratracheal instillation subgroup, rather than in budesonide inhalation subgroup.

CONCLUSIONS

This meta-analysis suggested that early combined utilization of budesonide and surfactant by airway might be an effective and safe clinical practice for BPD prevention in premature infants with RDS, especially when budesonide was delivered by intratracheal instillation. However, many of the included studies were small and were from Asian origin. More well-designed randomized controlled trials with larger sample sizes and longer follow-up from all over the world ought to be conducted in the future.

Protein and peptide delivery to lungs by using advanced targeted drug delivery

The challenges and difficulties associated with conventional drug delivery systems have led to the emergence of novel, advanced targeted drug delivery systems. Therapeutic drug delivery of proteins and peptides to the lungs is complicated owing to the large size and polar characteristics of the latter. Nevertheless, the pulmonary route has attracted great interest today among formulation scientists, as it has evolved into one of the important targeted drug delivery platforms for the delivery of peptides, and related compounds effectively to the lungs, primarily for the management and treatment of chronic lung diseases. In this review, we have discussed and summarized the current scenario and recent developments in targeted delivery of proteins and peptide-based drugs to the lungs. Moreover, we have also highlighted the advantages of pulmonary drug delivery over conventional drug delivery approaches for peptide-based drugs, in terms of efficacy, retention time and other important pharmacokinetic parameters. The review also highlights the future perspectives and the impact of targeted drug delivery on peptide-based drugs in the coming decade.

In-Vitro In-Vivo Correlation (IVIVC) of Inhaled Products Using Twin Stage Impinger

In vitro dissolution testing as a form of quality control has become a necessity in the pharmaceutical industry. As such, the need to establish a method that investigates the in vitro dissolution profile of inhaled products should be taken into account. The prime focus in this study was to examine the in-vitro in-vivo correlation utilising a modified version of the Twin Stage Impinger and to promote an in vitro dissolution model by enhancing the Fine Particle Dose (FPD) collection method for dry powder inhalers. The Twin Impinger was modified by inserting a stainless steel membrane holder disk in the base of the lower chamber. The design, with optimum drug deposition, was adopted for the dissolution study of budesonide and salbutamol. Afterwards, the membrane holder system was placed in the bottom of the dissolution vessel. Phosphate buffer saline (PBS), simulated lung fluid (SLF, Gamble solution) and Phosphate buffer (PB) were used in the study. The paddle dissolution apparatus, containing 300 mL of the medium, was operated at 75 rpm paddle speed. Samples were collected at defined time intervals and analysed using a validated HPLC method. The largest proportion of the budesonide dose was dissolved in PBS compared to PB and SLF. This was due to the presence of surfactant (0.2% w/v polysorbate), which enhances the wettability and the solubility of the poorly soluble drug (budesonide). The similarity factors for PBS and PB were 47.6 and 69.7, respectively, using SLF as a reference, whereas the similarity factor for salbutamol dissolution between PB and SLF was 81.3, suggesting PB is a suitable substitute. Comparison using both the predicted and actual in vivo pharmacokinetics (PK) values of the two drugs, as well as the pattern of their Concentration-Time (c-t) profiles, showed good similarity, which gave an indication of the validity of this in vitro dissolution method.

Pulmonary surfactant: a unique biomaterial with life-saving therapeutic applications

Pulmonary surfactant is a complex lipoprotein mixture secreted into the alveolar lumen by type 2 pneumocytes, which is composed by tens of different lipids (approximately 90% of its entire mass) and surfactant proteins (approximately 10% of the mass). It is crucially involved in maintaining lung homeostasis by reducing the values of alveolar liquid surface tension close to zero at end-expiration, thereby avoiding the alveolar collapse, and assembling a chemical and physical barrier against inhaled pathogens. A deficient amount of surfactant or its functional inactivation is directly linked to a wide range of lung pathologies, including the neonatal respiratory distress syndrome. This paper reviews the main biophysical concepts of surfactant activity and its inactivation mechanisms, and describes the past, present and future roles of surfactant replacement therapy, focusing on the exogenous surfactant preparations marketed worldwide and new formulations under development. The closing section describes the pulmonary surfactant in the context of drug delivery. Thanks to its peculiar composition, biocompatibility, and alveolar spreading capability, the surfactant may work not only as a shuttle to the branched anatomy of the lung for other drugs but also as a modulator for their release, opening to innovative therapeutic avenues for the treatment of several respiratory diseases.

Pharmaceutical strategies to extend pulmonary exposure of inhaled medicines

Pulmonary administration route has been extensively exploited for the treatment of local lung diseases such as asthma, chronic obstructive pulmonary diseases and respiratory infections, and systemic diseases such as diabetes. Most inhaled medicines could be cleared rapidly from the lungs and their therapeutic effects are transit. The inhaled medicines with extended pulmonary exposure may not only improve the patient compliance by reducing the frequency of drug administration, but also enhance the clinical benefits to the patients with improved therapeutic outcomes. This article systematically reviews the physical and chemical strategies to extend the pulmonary exposure of the inhaled medicines. It starts with an introduction of various physiological and pathophysiological barriers for designing inhaled medicines with extended lung exposure, which is followed by recent advances in various strategies to overcome these barriers. Finally, the applications of the inhaled medicines with extended lung exposure for the treatment of various diseases and the safety concerns associated to various strategies to extend the pulmonary exposure of the inhaled medicines are summarized.

Pharmacokinetics-On-a-Chip: In Vitro Microphysiological Models for Emulating of Drugs ADME

Despite many ongoing efforts across the full spectrum of pharmaceutical and biotech industries, drug development is still a costly undertaking that involves a high risk of failure during clinical trials. Animal models played vital roles in understanding the mechanism of human diseases. However, the use of these models has been a subject of heated debate, particularly due to ethical matters and the inevitable pathophysiological differences between animals and humans. Current in vitro models lack the sufficient functionality and predictivity of human pharmacokinetics and toxicity, therefore, are not capable to fully replace animal models. The recent development of micro-physiological systems has shown great potential as indispensable tools for recapitulating key physiological parameters of humans and providing in vitro methods for predicting the pharmacokinetics and pharmacodynamics in humans. Integration of Absorption, Distribution, Metabolism, and Excretion (ADME) processes within one close in vitro system is a paramount development that would meet important unmet pharmaceutical industry needs. In this review paper, synthesis of the ADME-centered organ-on-a-chip technology is systemically presented from what is achieved to what needs to be done, emphasizing the requirements of in vitro models that meet industrial needs in terms of the structure and functions.

Simulation of respiratory tract lining fluid for in vitro dissolution study

Introduction: Drug particles inhaled via the respiratory system must first dissolve in the respiratory tract lining fluid (RTLF) that lies on the surfaces of airways and alveoli, so that they are absorbed and have therapeutic action. Artificial simulated RTLFs are often used for in vitro dissolution studies to determine the solubility and dissolution of inhaled drug particles. Such studies can be used to predict bioavailability minimizing the requirement for in vivo studies. Numerous studies have been conducted to develop bio-relevant simulated RTLFs; however, to date, there is no singular simulated RTLF that closely resembles human RTLF.Areas covered: This review focuses on the composition of natural and simulated RTLFs and their use in in vitro dissolution studies.Expert opinion: There is variation in the composition and thickness of RTLF along the respiratory tract. Identification of the actual concentration of components of endogenous RTLF present in different areas of the respiratory tract helps in the development of region-specific simulated RTLFs. It is recommended that region-specific simulated RTLFs can be prepared by varying concentration of major RTLF components like mucus/gel simulants, lipids/surfactants, peptides/proteins, and inorganic/organic salts.

What makes flunisolide different among inhaled corticosteroids used for nebulization: a close look at the role of aqueous solubility

Evidence-based management of bronchial asthma and wheezing in children and adults recommends the employment of inhaled corticosteroids (ICSs). Difficulty in using some inhalation devices for ICS delivery, such as pressurized metered-dose and dry-powder inhalers, is common among young children and in the elderly, and for that reason, they are replaced with nebulizers. We reviewed comparative studies that evaluated funisolide with other ICSs currently available on the market, including beclomethasone dipropionate, fluticasone propionate, and budesonide. Moreover, we assessed the physicochemical properties of these ICSs in determining drug fate in the lung. Data indicate that the flunisolide output in respirable particles by any type of pneumatic nebulizer (traditional, open breath or breathenhanced) is superior to the output of other ICSs. This is principally attributed to the higher water solubility of flunisolide. Furthermore, in vivo simulation studies demonstrate that the intersubject variability of the inhaled dose among asthmatic children was much greater for suspensions of fluticasone propionate and beclomethasone dipropionate than for those of flunisolide. The physicochemical properties and pharmacokinetic profile of flunisolide favor its employment in nebulization.

A mechanistic framework for a priori pharmacokinetic predictions of orally inhaled drugs

The fate of orally inhaled drugs is determined by pulmonary pharmacokinetic processes such as particle deposition, pulmonary drug dissolution, and mucociliary clearance. Even though each single process has been systematically investigated, a quantitative understanding on the interaction of processes remains limited and therefore identifying optimal drug and formulation characteristics for orally inhaled drugs is still challenging. To investigate this complex interplay, the pulmonary processes can be integrated into mathematical models. However, existing modeling attempts considerably simplify these processes or are not systematically evaluated against (clinical) data. In this work, we developed a mathematical framework based on physiologically-structured population equations to integrate all relevant pulmonary processes mechanistically. A tailored numerical resolution strategy was chosen and the mechanistic model was evaluated systematically against data from different clinical studies. Without adapting the mechanistic model or estimating kinetic parameters based on individual study data, the developed model was able to predict simultaneously (i) lung retention profiles of inhaled insoluble particles, (ii) particle size-dependent pharmacokinetics of inhaled monodisperse particles, (iii) pharmacokinetic differences between inhaled fluticasone propionate and budesonide, as well as (iv) pharmacokinetic differences between healthy volunteers and asthmatic patients. Finally, to identify the most impactful optimization criteria for orally inhaled drugs, the developed mechanistic model was applied to investigate the impact of input parameters on both the pulmonary and systemic exposure. Interestingly, the solubility of the inhaled drug did not have any relevant impact on the local and systemic pharmacokinetics. Instead, the pulmonary dissolution rate, the particle size, the tissue affinity, and the systemic clearance were the most impactful potential optimization parameters. In the future, the developed prediction framework should be considered a powerful tool for identifying optimal drug and formulation characteristics.

The use of orally inhaled drugs for treating lung diseases is appealing since they have the potential for lung selectivity, i.e. high exposure at the site of action –the lung– without excessive side effects. However, the degree of lung selectivity depends on a large number of factors, including physiochemical properties of drug molecules, patient disease state, and inhalation devices. To predict the impact of these factors on drug exposure and thereby to understand the characteristics of an optimal drug for inhalation, we develop a predictive mathematical framework (a “pharmacokinetic model”). In contrast to previous approaches, our model allows combining knowledge from different sources appropriately and its predictions were able to adequately predict different sets of clinical data. Finally, we compare the impact of different factors and find that the most important factors are the size of the inhaled particles, the affinity of the drug to the lung tissue, as well as the rate of drug dissolution in the lung. In contrast to the common belief, the solubility of a drug in the lining fluids is not found to be relevant. These findings are important to understand how inhaled drugs should be designed to achieve best treatment results in patients.

Correlation and clinical relevance of animal models for inhaled pharmaceuticals and biopharmaceuticals

Nonclinical studies are fundamental for the development of inhaled drugs, as for any drug product, and for successful translation to clinical practice. They include in silico, in vitro, ex vivo and in vivo studies and are intended to provide a comprehensive understanding of the inhaled drug beneficial and detrimental effects. To date, animal models cannot be circumvented during drug development programs, acting as surrogates of humans to predict inhaled drug response, fate and toxicity. Herein, we review the animal models used during the different development stages of inhaled pharmaceuticals and biopharmaceuticals, highlighting their strengths and limitations.

Long-term effects of the intratracheal administration of corticosteroids for the prevention of bronchopulmonary dysplasia: A meta-analysis

BACKGROUND

Bronchopulmonary dysplasia (BPD) is one of the most common complications in premature infants. Since inflammation plays a crucial role in the pathogenesis of BPD, anti-inflammatory drugs, such as corticosteroids, have long been the focus of prevention research. In this meta-analysis, we aim to explore the long-term effects of the intratracheal administration of corticosteroids (IAC) in preventing BPD.

METHODS

EMBASE, MEDLINE, the Cochrane Library, Web of Science, CINAHL, Clinicaltrials.gov, the ISRCTN registry, and gray literature were searched to identify randomized controlled trials (RCTs) that evaluated the long-term effects of IAC for the prevention of BPD in premature infants.

RESULTS

Five RCTs (n = 1515) were eligible for further analysis. The meta-analysis revealed that the incidence of neurodevelopmental impairment (NDI) did not significantly differ between the IAC group and the control group (relative risk [RR] 0.9, 95% confidence interval [CI] 0.79 to 1.03, P = .14). There was no significant reduction in long-term mortality (RR, 1.13; 95% CI, 0.9 to 1.41; P = .3) or the incidence of rehospitalization (RR, 0.99; 95% CI, 0.89 to 1.09, P = .82). No significant differences were observed between the IAC group and the control group with regard to height, weight and head circumference at the age of 18 to 36 months of postmenstrual age (PMA) (mean difference [MD], 0.14; 95% CI, -0.26 to 0.54, P = .48).

CONCLUSIONS

Our study suggests that IAC in preterm infants does not have significant long-term benefits or adverse outcomes. However, before routine use, well-designed studies and studies involving large sample sizes are needed to confirm the pharmacokinetics and long-term effects of IAC.

Delivery of Dry Powders to the Lungs: Influence of Particle Attributes from a Biological and Technological Point of View

Dry powder inhalers are medical devices used to deliver powder formulations of active pharmaceutical ingredients via oral inhalation to the lungs. Drug particles, from a biological perspective, should reach the targeted site, dissolve and permeate through the epithelial cell layer in order to deliver a therapeutic effect. However, drug particle attributes that lead to a biological activity are not always consistent with the technical requirements necessary for formulation design. For example, small cohesive drug particles may interact with neighbouring particles, resulting in large aggregates or even agglomerates that show poor flowability, solubility and permeability. To circumvent these hurdles, most dry powder inhalers currently on the market are carrier-based formulations. These formulations comprise drug particles, which are blended with larger carrier particles that need to detach again from the carrier during inhalation. Apart from blending process parameters, inhaler type used and patient's inspiratory force, drug detachment strongly depends on the drug and carrier particle characteristics such as size, shape, solid-state and morphology as well as their interdependency. This review discusses critical particle characteristics. We consider size of the drug (1-5 µm in order to reach the lung), solid-state (crystalline to guarantee stability versus amorphous to improve dissolution), shape (spherical drug particles to avoid macrophage clearance) and surface morphology of the carrier (regular shaped smooth or nano-rough carrier surfaces for improved drug detachment.) that need to be considered in dry powder inhaler development taking into account the lung as biological barrier.

Interaction of inhalable volatile organic compounds and pulmonary surfactant: Potential hazards of VOCs exposure to lung

Exposure of volatile organic compounds (VOCs) towards lung leads to pulmonary dysfunctions and various lung diseases. However, the interaction of VOCs with pulmonary surfactant (PS) that directly comes into contact with inhaled VOCs is unknown. Here, simulated PS extracted from porcine lungs (EPS) was used to study the interaction with BTEX (i.e., benzene, toluene, ethylbenzene, and p-xylene) as representatives of VOCs. Surface pressure-area (π-A) isotherms showed that in the presence of individual BTEX, EPS monolayer's phase conversion from gas to liquid expanded phase was dramatically influenced and its collapse pressure decreased greatly compared to those of EPS alone, which was attributed to the alteration of EPS monolayer's microstructure characterized by atomic force microscopy and Brewster angle microscopy. Solubilization experiments manifested that EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited obvious solubilization effects on individual BTEX. The solubilization capacity followed an order: EPS > DPPC > BSA, which was positively correlated with hydrophobicity of individual BTEX. Synergistic solubilization test unveiled that the mixed phospholipid components were largely responsible for the solubilization capacity of EPS. These findings indicate that VOCs exposure may induce potential pulmonary health risk due to the alteration of gas-liquid interfacial properties of PS.

Interaction of pulmonary surfactant with silica and polycyclic aromatic hydrocarbons: Implications for respiratory health

Understanding the interaction between pulmonary surfactant (PS) and inhalable pollutants is vital for risk assessment of respiratory health. Here, PS extracted from porcine lung (EPS) was used to investigate the interaction of PS with nano-silica particles and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that silica significantly affected the phase behavior and foaming ability of EPS; EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited great enhancing effect on PAHs solubility, which follows the order: EPS > DPPC > BSA, and it was positively correlated with the hydrophobicity of PAHs. Further experiments demonstrated that mixed phospholipids of EPS were largely responsible for the solubilization of EPS on PAHs. In the presence of EPS, DPPC or BSA, adsorption of PAHs by silica was notably inhibited, indicating competitive adsorption between PAHs and PS components on silica. These findings provide evidence for the surface chemistry by which PS facilitates the solubilization of PAHs and reducing the adsorption of PAHs on silica, which may be helpful for deeply understanding the effects of particulate matter and PAHs on lung health.

In vitro dissolution testing of respirable size anti-tubercular drug particles using a small volume dissolution apparatus

A dissolution apparatus that uses a small volume of stationary medium (25 μL) has been developed for in vitro dissolution testing of respirable drug particles and used to evaluate the dissolution of two anti-tubercular drugs, moxifloxacin and ethionamide. Solubilities of moxifloxacin and ethionamide in phosphate buffered saline (PBS, pH 7.4) were 17.68 ± 0.85 mg mL^-1 and 0.46 ± 0.02 mg mL^-1 whereas in the presence of lung surfactant (0.4% w/v Curosurf^® in PBS) solubilities were 20.76 ± 0.35 mg mL^-1 and 0.56 ± 0.03 mg mL^-1, respectively. A fine particle dose (∼50 µg) of aerodynamically separated moxifloxacin or ethionamide particles (<6.4 µm) was collected onto a glass coverslip using a modified Twin Stage Impinger. The dissolution behaviour of the fine particle dose was evaluated at various perfusate flow rates (0.2, 0.4 and 0.8 mL min^-1 of PBS), mucus simulant concentrations (1.0, 1.5 and 2.0% w/v polyethylene oxide in PBS), and in the presence of lung surfactant. The dissolution behaviour of the respirable size particles was observed under an optical microscope and the dissolved drug that diffused into the perfusate was quantified by HPLC. The moxifloxacin particles disappeared quickly and showed faster permeation (<30 min) compared to the ethionamide particles at all the dissolution conditions evaluated. This study demonstrated the differences in the dissolution rates of moxifloxacin and ethionamide particles and may be useful to estimate the residence time of the inhaled dry powder particles in the lungs.

Chemoprevention of Lung Carcinogenesis by Dietary Nicotinamide and Inhaled Budesonide

Nicotinamide, the amide form of vitamin B3, and budesonide, a synthetic glucocorticoid used in the treatment of asthma, were evaluated to determine their individual and combinational chemopreventive efficacy on benzo(a)pyrene-induced lung tumors in female A/J mice. Nicotinamide fed at a dietary concentration of 0.75% significantly inhibited tumor multiplicity. Nicotinamide by aerosol inhalation at doses up to 15 mg/kg/day did not result in a statistically significant reduction in tumor multiplicity. Finally, dietary nicotinamide was administered with aerosol budesonide and tumor multiplicity reduced by 90% at 1 week and 49% at 8 weeks post last carcinogen dose. We conclude nicotinamide is an effective and safe agent for lung cancer dietary prevention at both early- and late-stage carcinogenesis and that efficacy is increased with aerosol budesonide. Combination chemoprevention with these agents is a well-tolerated and effective strategy which could be clinically advanced to human studies.

Inhalation and Dermal Uptake of Particle and Gas-Phase Phthalates-A Human Exposure Study

Phthalates are ubiquitous in indoor environments, which raises concern about their endocrine-disrupting properties. However, studies of human uptake from airborne exposure are limited. We studied the inhalation uptake and dermal uptake by air-to-skin transfer with clean clothing as a barrier of two deuterium-labeled airborne phthalates: particle-phase D₄-DEHP (di(2-ethylhexyl)phthalate) and gas-phase D₄-DEP (diethyl phthalate). Sixteen participants, wearing trousers and long-sleeved shirts, were under controlled conditions exposed to airborne phthalates in four exposure scenarios: dermal uptake alone and combined inhalation + dermal uptake of both phthalates. The results showed an average uptake of D₄-DEHP by inhalation of 0.0014 ± 0.00088 (μg kg^-1 bw)/(μg m^-3)/h. No dermal uptake of D₄-DEHP was observed during the 3 h exposure with clean clothing. The deposited dose of D₄-DEHP accounted for 26% of the total inhaled D₄-DEHP mass. For D₄-DEP, the average uptake by inhalation + dermal was 0.0067 ± 0.0045 and 0.00073 ± 0.00051 (μg kg^-1 bw)/(μg m^-3)/h for dermal uptake. Urinary excretion factors of metabolites after inhalation were estimated to 0.69 for D₄-DEHP and 0.50 for D₄-DEP. Under the described settings, the main uptake of both phthalates was through inhalation. The results demonstrate the differences in uptake of gas and particles and highlight the importance of considering the deposited dose in particle uptake studies.

Effects of intratracheal budesonide during early postnatal life on lung maturity of premature fetal rabbits

AIM

This study aimed to study the effects of intratracheal instillation of budesonide on lung maturity of premature fetal rabbits. The developmental pattern of pulmonary alveoli in rabbits is similar to that in humans.

METHOD

Fetal rabbits were taken out from female rabbits on the 28th day of pregnancy (full term = 31 days) by cesarean section (c-section). The fetal rabbits were divided into four groups: control (normal saline, NS), budesonide (budesonide, BUD), calf pulmonary surfactant for injection (pulmonary surfactant, PS), and calf pulmonary surfactant + budesonide for injection (pulmonary surfactant + budesonide, PS + BUD). All premature rabbits were kept warm after c-section. After 15-min autonomous respiration, a tracheal cannula was implemented for instilling NS, BUD, PS, and PS + BUD. The morphology of lung tissues of premature fetal rabbits was analyzed using optical and electron microscopes. Surfactant protein B (SP-B) mRNA and protein levels in lung tissues were determined using polymerase chain reaction and Western blotting, respectively.

RESULT

Intratracheal instillation of BUD could increase the alveolar area of the fetal rabbits (P < 0.01), decrease the alveolar wall thickness (P < 0.01), and increase the mean density of lamellar bodies (P < 0.05) and SP-B protein levels in type II epithelial cells of pulmonary alveoli (P < 0.05).

CONCLUSION

Intratracheal instillation of BUD during early postnatal life is effective in promoting alveolarization and increasing SP-B expression, the pro-pulmonary maturity of BUD combined with PS is superior to that of BUD or PS alone. However, the long-term effect of BUD on lung development needs further exploration.

Airway administration of corticosteroids for prevention of bronchopulmonary dysplasia in premature infants: a meta-analysis with trial sequential analysis

BACKGROUND

Uncertainly prevails with regard to the use of inhalation or instillation steroids to prevent bronchopulmonary dysplasia in preterm infants. The meta-analysis with sequential analysis was designed to evaluate the efficacy and safety of airway administration (inhalation or instillation) of corticosteroids for preventing bronchopulmonary dysplasia (BPD) in premature infants.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and Cochrane CENTRAL from their inceptions to February 2017. All published randomized controlled trials (RCTs) evaluating the effect of airway administration of corticosteroids (AACs) vs placebo or systemic corticosteroid in prematurity were included. All meta-analyses were performed using Review Manager 5.3.

RESULTS

Twenty five RCTs retrieved (n = 3249) were eligible for further analysis. Meta-analysis and trial sequential analysis corrected the 95% confidence intervals estimated a lower risk of the primary outcome of BPD (relative risk 0.71, adjusted 95% confidence interval 0.57-0.87) and death or BPD (relative risk 0.81, adjusted 95% confidence interval 0.71-0.97) in AACs group than placebo and it is equivalent for preventing BPD than systemic corticosteroids. Moreover, AACs fail to increasing risk of death compared with placebo (relative risk 0.90, adjusted 95% confidence interval 0.40-2.03) or systemic corticosteroids (relative risk 0.81, 95% confidence interval 0.62-1.06).

CONCLUSIONS

Our findings suggests that AACs (especially instillation of budesonide using surfactant as a vehicle) are an effective and safe option for preventing BPD in preterm infants. Furthermore, the appropriate dose and duration, inhalation or instillation with surfactant as a vehicle and the long-term safety of airway administration of corticosteroids needs to be assessed in large trials.

Small Airway Absorption and Microdosimetry of Inhaled Corticosteroid Particles after Deposition

PURPOSE

To predict the cellular-level epithelial absorbed dose from deposited inhaled corticosteroid (ICS) particles in a model of an expanding and contracting small airway segment for different particle forms.

METHODS

A computational fluid dynamics (CFD)-based model of drug dissolution, absorption and clearance occurring in the surface liquid of a representative small airway generation (G13) was developed and used to evaluate epithelial dose for the same deposited drug mass of conventional microparticles, nanoaggregates and a true nanoaerosol. The ICS medications considered were budesonide (BD) and fluticasone propionate (FP). Within G13, total epithelial absorption efficiency (AE) and dose uniformity (microdosimetry) were evaluated.

RESULTS

Conventional microparticles resulted in very poor AE of FP (0.37%) and highly nonuniform epithelial absorption, such that <5% of cells received drug. Nanoaggregates improved AE of FP by a factor of 57-fold and improved dose delivery to reach approximately 40% of epithelial cells. True nanoaerosol resulted in near 100% AE for both drugs and more uniform drug delivery to all cells.

CONCLUSIONS

Current ICS therapies are absorbed by respiratory epithelial cells in a highly nonuniform manner that may partially explain poor clinical performance in the small airways. Both nanoaggregates and nanoaerosols can significantly improve ICS absorption efficiency and uniformity.

A Biocompatible Synthetic Lung Fluid Based on Human Respiratory Tract Lining Fluid Composition

PURPOSE

To characterise a biorelevant simulated lung fluid (SLF) based on the composition of human respiratory tract lining fluid. SLF was compared to other media which have been utilized as lung fluid simulants in terms of fluid structure, biocompatibility and performance in inhalation biopharmaceutical assays.

METHODS

The structure of SLF was investigated using cryo-transmission electron microscopy, photon correlation spectroscopy and Langmuir isotherms. Biocompatibility with A549 alveolar epithelial cells was determined by MTT assay, morphometric observations and transcriptomic analysis. Biopharmaceutical applicability was evaluated by measuring the solubility and dissolution of beclomethasone dipropionate (BDP) and fluticasone propionate (FP), in SLF.

RESULTS

SLF exhibited a colloidal structure, possessing vesicles similar in nature to those found in lung fluid extracts. No adverse effect on A549 cells was apparent after exposure to the SLF for 24 h, although some metabolic changes were identified consistent with the change of culture medium to a more lung-like composition. The solubility and dissolution of BDP and FP in SLF were enhanced compared to Gamble's solution.

CONCLUSION

The SLF reported herein constitutes a biorelevant synthetic simulant which is suitable to study biopharmaceutical properties of inhalation medicines such as those being proposed for an inhaled biopharmaceutics classification system.

The influence of lung surfactant liquid crystalline nanostructures on respiratory drug delivery

The respiratory route increasingly has been used for both local and systemic drug delivery. Although drug is absorbed rapidly after respiratory delivery, the role of lung surfactant in drug delivery is not well understood. The human lung contains only around 15mL of surface lining fluid spread over ∼100m² surface. The fluid contains lung surfactant at a concentration of 8-24mg/kg/body weight; the lung surfactant which is lipo-protein in nature can form different liquid crystalline nanostructures. After a brief overview of the anatomy of respiratory system, the review has focused on the current understanding of lung surface lining fluid, lung surfactants and their composition and possible self-assembled nanostructures. The role of lung surfactant in drug delivery and drug dissolution has been briefly considered. Lung surfactant may form different liquid crystalline phases which can have an active role in drug delivery. The hypotheses developed in this review focuses on the potential roles of surface epithelial fluid containing liquid crystalline nanostructures in defining the dissolution mechanism and rate. The hypotheses also focus an understanding how liquid crystalline nanostructures can be used to control dissolution rate and how the nanostructures might be changed to influence delivery and induce toxicity.

Intratracheal Administration of Budesonide/Surfactant to Prevent Bronchopulmonary Dysplasia

RATIONALE

Bronchopulmonary dysplasia (BPD) is an important complication of mechanical ventilation in preterm infants, and no definite therapy can eliminate this complication. Pulmonary inflammation plays a crucial role in its pathogenesis, and glucocorticoid is one potential therapy to prevent BPD.

OBJECTIVES

To compare the effect of intratracheal administration of surfactant/budesonide with that of surfactant alone on the incidence of death or BPD.

METHODS

A clinical trial was conducted in three tertiary neonatal centers in the United States and Taiwan, in which 265 very-low-birth-weight infants with severe respiratory distress syndrome who required mechanical ventilation and inspired oxygen (fraction of inspired oxygen, ≥50%) within 4 hours of birth were randomly assigned to one of two groups (131 intervention and 134 control). The intervention infants received surfactant (100 mg/kg) and budesonide (0.25 mg/kg), and the control infants received surfactant only (100 mg/kg), until each infant required inspired O2 at less than 30% or was extubated.

MEASUREMENTS AND MAIN RESULTS

The intervention group had a significantly lower incidence of BPD or death (55 of 131 [42.0%] vs. 89 of 134 [66%]; risk ratio, 0.58; 95% confidence interval, 0.44-0.77; P < 0.001; number needed to treat, 4.1; 95% confidence interval, 2.8-7.8). The intervention group required significantly fewer doses of surfactant than did the control group. The intervention group had significantly lower interleukin levels (IL-1, IL-6, IL-8) in tracheal aspirates at 12 hours and lower IL-8 at 3-5 and 7-8 days.

CONCLUSIONS

In very-low-birth-weight infants with severe respiratory distress syndrome, intratracheal administration of surfactant/budesonide compared with surfactant alone significantly decreased the incidence of BPD or death without immediate adverse effect. Clinical trial registered with www.clinicaltrials.gov (NCT-00883532).

Generation of tailored aerosols for inhalative drug delivery employing recent vibrating-mesh nebulizer systems

Direct drug delivery to the lungs is considered the gold standard for the treatment of a variety of respiratory diseases, owing to the increased therapeutic selectivity of the inhalative approach. Airborne formulations with defined size characteristics are required to improve the deposition pattern within the airways. In this respect, different nebulizer systems have been conceived, which has enabled the generation of respirable medicament mists. Here, vibrating-mesh technology revealed significant potential to overcome the main shortcomings associated with ‘traditional’ devices. Tailored orifice dimensions and defined formulation characteristics are of special interest for the generation of suitable aerosol droplets for inhalative purposes. Ongoing developments in device and formulation design will optimize the clinical outcome of inhalative drug delivery under application of vibrating-mesh technology.

Inhaled nano- and microparticles for drug delivery

The 21st century has seen a paradigm shift to inhaled therapy, for both systemic and local drug delivery, due to the lung's favourable properties of a large surface area and high permeability. Pulmonary drug delivery possesses many advantages, including non-invasive route of administration, low metabolic activity, control environment for systemic absorption and avoids first bypass metabolism. However, because the lung is one of the major ports of entry, it has multiple clearance mechanisms, which prevent foreign particles from entering the body. Although these clearance mechanisms maintain the sterility of the lung, clearance mechanisms can also act as barriers to the therapeutic effectiveness of inhaled drugs. This effectiveness is also influenced by the deposition site and delivered dose. Particulate-based drug delivery systems have emerged as an innovative and promising alternative to conventional inhaled drugs to circumvent pulmonary clearance mechanisms and provide enhanced therapeutic efficiency and controlled drug release. The principle of multiple pulmonary clearance mechanisms is reviewed, including mucociliary, alveolar macrophages, absorptive, and metabolic degradation. This review also discusses the current approaches and formulations developed to achieve optimal pulmonary drug delivery systems.

The Influence of Synthetic Cannabinoid UR-144 on Human Psychomotor Performance--A Case Report Demonstrating Road Traffic Risks

OBJECTIVE

UR-144 [(1-pentyl-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)-methanone] is a synthetic cannabinoid, which has been detected in many "legal highs" seized from the global drug market since the beginning of 2012. It gained popularity as a "legal" alternative to classic cannabis in countries where it was not controlled. The popularity of UR-144 means that this substance is also abused by individuals driving motor vehicles. This article describes a case of driving under the influence (DUI) of UR-144. The aim of the undertaken case analysis and presenting description of pharmacological similarity of THC and UR-144 is to answer the question whether UR-144 can produce effects incompatible with safe driving.

METHODS

Blood from the driver was obtained by a physician approximately 2 h after the collision and 4.5 h after self-reported dosing. Police from the crash site provided behavioral observations, and the physician performed medical examination. Blood was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed method was described in detail. The method was linear in the range of 0.5-50 ng/mL; the precision and accuracy values obtained were less than 15%. The symptoms observed by police and physician who collected the blood sample were described.

RESULTS

In the blood sample collected from the driver, UR-144 and its major pyrolysis product [1-(1-pentyl-1H-indol-3-yl)-3-methyl-2-(propan-2-yl)but-3-en-1-one] were detected. Whole-blood concentration of UR-144 was 14.6 ng/mL. The result of blood analysis and observed symptoms clearly indicated that the driver was under the influence of UR-144.

CONCLUSIONS

UR-144 produces effects and impairment similar to or even more dangerous than delta-9-tetrahydrocannabinol (Δ(9)-THC), making it unsafe for driving. Therefore, UR-144 should be treated as a potentially dangerous substance in traffic safety.

Budesonide added to modified porcine surfactant Curosurf may additionally improve the lung functions in meconium aspiration syndrome

Severe meconium aspiration syndrome (MAS) in newborns is often treated by exogenous surfactant. Because its efficacy is reduced by meconium-induced inflammation, glucocorticoid budesonide was added into surfactant preparation Curosurf to enhance efficacy of the surfactant therapy in experimental model of MAS. Oxygen-ventilated rabbits were intratracheally given meconium (25 mg/ml, 4 ml/kg) to induce respiratory failure. Thirty minutes later, animals were treated by intratracheal budesonide (0.25 mg/kg) or surfactant lung lavage (10 ml/kg, 5 mg phospholipids/ml) repeated twice, followed by undiluted Curosurf (100 mg phospholipids/kg) or by the above mentioned surfactant treatment with the last surfactant dose fortified with budesonide (0.25 mg/kg) or were untreated. Animals were ventilated for additional 5 hours and respiratory parameters were measured regularly. After sacrificing animals, wet-dry lung weight ratio was evaluated and plasma levels of interleukins (IL)-1beta, -6, -8, and TNF-alpha were measured by ELISA method. Efficacy of the given therapies to enhance lung functions and to diminish lung edema formation and inflammation increased from budesonide-only and surfactant-only therapy to surfactant+budesonide therapy. Combined therapy improved gas exchange from 30 min of administration, and showed a longer-lasting effect than surfactant-only therapy. In conclusions, budesonide additionally improved the effects of exogenous surfactant in experimental MAS.

Thermoresponsive layer-by-layer assemblies for nanoparticle-based drug delivery

Layer-by-layer (LbL) capsules, known for their versatility and smart response to environmental stimuli, have attracted great interest in drug delivery applications. However, achieving a desired drug delivery system with sustained and tunable drug release is still challenging. Here, a thermoresponsive drug delivery system of solid dexamethasone nanoparticles (DXM NPs, 200 ± 100 nm) encapsulated in a model LbL assembly of tunable thickness consisting of strong polyelectrolytes poly(diallyldimethylammonium chloride)/poly(styrenesulfonate) (PDAC/PSS) is constructed. The influence of various parameters on drug release, such as number of layers, ionic strength of the adsorption solution, temperature, and outermost layer, is investigated. Increasing the number of layers results in a thicker encapsulating nanoshell and decreases the rate of dexamethasone release. LbL assemblies created in the absence of salt are most responsive to temperature, yielding the greatest contrast in drug release. Relationships between drug release and LbL architecture are attributed to the size and concentration of free volume cavities within the assemblies. By tailoring the properties of those cavities, a thermoresponsive drug delivery system may be obtained. This work provides a promising example of how LbL assemblies may be implemented as temperature-gated materials for the controlled release of drug, thus providing an alternative approach to the delivery of therapeutics with reduced toxic effects.

Pulmonary drug delivery: from generating aerosols to overcoming biological barriers-therapeutic possibilities and technological challenges

Research in pulmonary drug delivery has focused mainly on new particle or device technologies to improve the aerosol generation and pulmonary deposition of inhaled drugs. Although substantial progress has been made in this respect, no significant advances have been made that would lead pulmonary drug delivery beyond the treatment of some respiratory diseases. One main reason for this stagnation is the still very scarce knowledge about the fate of inhaled drug or carrier particles after deposition in the lungs. Improvement of the aerosol component alone is no longer sufficient for therapeutic success of inhalation drugs; a paradigm shift is needed, with an increased focus on the pulmonary barriers to drug delivery. In this Review, we discuss some pathophysiological disorders that could benefit from better control of the processes after aerosol deposition, and pharmaceutical approaches to achieve improved absorption across the alveolar epithelium, prolonged pulmonary clearance, and targeted delivery to specific cells or tissues.

Pulmonary surfactant suppressed phenanthrene adsorption on carbon nanotubes through solubilization and competition as examined by passive dosing technique

Adsorption of phenanthrene on carbon nanotubes (CNTs) was examined in the presence of pulmonary surfactant (Curosurf) and its main components, dipalmitoyl phosphatidylcholine (DPPC) and bovine serum albumin (BSA). A passive-dosing method based on equilibrium partitioning from a preloaded polymer was successfully employed to measure phenanthrene binding and speciation at controlled freely dissolved concentrations while avoiding phase separation steps. Curosurf, DPPC, and BSA could all linearly solubilize phenanthrene, and phenanthrene solubilization by Curosurf was 4 times higher than individual components (DPPC or BSA). In the presence of Curosurf, DPPC or BSA, adsorption of phenanthrene by multiwalled CNTs (MWCNTs) was suppressed, showing competitive adsorption between pulmonary surfactant (or DPPC, BSA) and phenanthrene. Competitive adsorption between Curosurf and phenanthrene was the strongest. Therefore, when phenanthrene-adsorbed CNTs enter the respiratory tract, phenanthrene can be desorbed due to both solubilization and competition. The bioaccessibility of phenanthrene adsorbed on three MWCNTs in the respiratory tract would be positively related to the size of their outer diameters. Moreover, the contribution of solubilization and competition to desorption of phenanthrene from MWCNTs was successfully separated for the first time. These findings demonstrate the two mechanisms on how pulmonary surfactants can enhance desorption and thus possibly biological absorption of phenanthrene adsorbed on CNTs.

Preservative-free triamcinolone acetonide injectable suspension versus "traditional" triamcinolone preparations: impact of aggregate size on retinal biocompatibility

PURPOSE

To evaluate the biocompatibility of the three currently most commonly used triamcinolone acetonide (TA) preparations on retinal cells.

METHODS

Preservative containing KL (Kenalog-40; Bristol-Myers Squibb, Princeton, NJ), compounded preservative-free triamcinolone acetonide (PFTA; compounded from Volon A; Dermapharm, Vienna, Austria), and preservative-free triamcinolone acetonide injectable suspension (TRIESENCE; Alcon, Inc, Fort Worth, TX) (0.01-1 mg/mL) were either added directly on top or separated by a Boyden chamber filter or by a layer of vitreous to confluent cell cultures of retinal pigment epithelial cells (ARPE19) or retinal ganglion cells (RGC5). The distribution pattern of the TA crystals was assessed microscopically. Cell viability was assessed using MTT-ELISA and Live/Dead-Assay.

RESULTS

Sedimentation of triamcinolone acetonide injectable suspension, KL, or PFTA caused a pronounced decrease in cell viability. Cytotoxicity was most pronounced when triamcinolone acetonide injectable suspension and PFTA were used. Without direct sedimentation of TA crystals on top of the cells, none of the three formulations were cytotoxic. Triamcinolone acetonide injectable suspension showed the largest and most dense TA crystal aggregates on top of the cells.

CONCLUSION

Retinal cytotoxicity of TA seems only to occur when there is intimate contact of TA crystals with the cellular membrane. Cytotoxicity depends on the number and size of TA crystal aggregates-with larger conglomerates being more harmful. Of the TA formulations tested, triamcinolone acetonide injectable suspension had the strongest tendency to form large TA crystal conglomerates and to gravitate downward.

Biophysical interaction between corticosteroids and natural surfactant preparation: implications for pulmonary drug delivery using surfactant a a carrier

Intratracheal administration of corticosteroids using a natural pulmonary surfactant as a delivery vehicle has recently received significant attention in hopes of treating premature newborns with or at high risk for chronic lung disease. As a new practice, both the surfactant preparation used as the carrier and the corticosteroid delivered as the anti-inflammatory agent, and their mixing ratios, have not been standardized and optimized. Given the concern that corticosteroids delivered via a pulmonary surfactant may compromise its surface activity and thus worsen lung mechanics, the present study was carried out to characterize the biophysical interaction between a natural surfactant preparation, Infasurf, and two commonly used inhaled corticosteroids, budesonide and beclomethasone dipropionate (BDP). Based on surface activity measurements by the Langmuir balance and lateral film structure studied by atomic force microscopy, our findings suggest that when Infasurf is used as a carrier, a budesonide concentration less than 1 wt% of surfactant or a BDP concentration up to 10 wt % should not significantly affect the biophysical properties of Infasurf, thus being feasible for pulmonary delivery. Increasing corticosteroid concentration beyond this range leads to early collapse of the surfactant film due to increased film fluidization. Our study further suggests that different affinities to the surfactant films are responsible for the different behavior of budesonide and BDP. In addition to the translational value in treating chronic lung disease, this study may also have implications in inhaled steroid therapy to treat asthma.

Ocular pharmacokinetic study of a corticosteroid by 19F MR

Traditional ocular pharmacokinetic studies are invasive and cannot be easily applied to humans in vivo. To acquire in vivo ocular pharmacokinetic data noninvasively, (19)F MR on a 3T clinical scanner was used to follow the real time dynamics of a corticosteroid in the eye. (1)H MR was also performed to locate the site of administration. Triamcinolone acetonide phosphate (TAP) was the model drug, administered by intravitreal and subconjunctival injections. TAP pharmacokinetics were monitored by changes in the (19)F spectrum of the intraocular drug in real time. The elimination half-lives of TAP in the eye after intravitreal and subconjunctival injections were 8 and 0.5 h in vivo and 17 and 6.0 h postmortem, respectively. The half-lives associated with clearance were 14 h for intravitreal injection and 0.5 h for subconjunctival injection.

Simulating dissolution of intravitreal triamcinolone acetonide suspensions in an anatomically accurate rabbit eye model

Purpose

A computational fluid dynamics (CFD) study examined the impact of particle size on dissolution rate and residence of intravitreal suspension depots of Triamcinolone Acetonide (TAC).

Methods

A model for the rabbit eye was constructed using insights from high-resolution NMR imaging studies (Sawada 2002). The current model was compared to other published simulations in its ability to predict clearance of various intravitreally injected materials. Suspension depots were constructed explicitly rendering individual particles in various configurations: 4 or 16 mg drug confined to a 100 μL spherical depot, or 4 mg exploded to fill the entire vitreous. Particle size was reduced systematically in each configuration. The convective diffusion/dissolution process was simulated using a multiphase model.

Results

Release rate became independent of particle diameter below a certain value. The size-independent limits occurred for particle diameters ranging from 77 to 428 μM depending upon the depot configuration. Residence time predicted for the spherical depots in the size-independent limit was comparable to that observed in vivo.

Conclusions

Since the size-independent limit was several-fold greater than the particle size of commercially available pharmaceutical TAC suspensions, differences in particle size amongst such products are predicted to be immaterial to their duration or performance.