Novel strategies of aerosolic pharmacotherapy

Inhaled bosentan microparticles for the treatment of monocrotaline-induced pulmonary arterial hypertension in rats

The conventional treatment of pulmonary arterial hypertension (PAH) with oral bosentan hydrate has limitations related to the lack of pulmonary selectivity. In this study, we verified the hypothesis of the feasibility of dry powder inhalation of bosentan as an alternative to oral bosentan hydrate for the treatment of PAH. Inhalable bosentan microparticles with the capability of delivery to the peripheral region of the lungs and enhanced bioavailability have been formulated for PAH. The bosentan microparticles were prepared by the co-spray-drying method with bosentan hydrate and mannitol at different weight ratios. The bosentan microparticles were then characterized for their physicochemical properties, in vitro dissolution behavior, and in vitro aerodynamic performance. The in vivo pharmacokinetics and pathological characteristics were evaluated in a monocrotaline-induced rat model of PAH after intratracheal powder administration of bosentan microparticles, in comparison to orally administered bosentan hydrate. The highest performance bosentan microparticles, named SDBM 1:1, had irregular and porous shape. These microparticles had not only the significantly highest aerosol performance (MMAD of 1.91 μm and FPF of 51.68%) in the formulations, but also significantly increased dissolution rate, compared with the raw bosentan hydrate. This treatment to the lungs was also safe, as evidenced by the cytotoxicity assay. Intratracheally administered SDBM 1:1 elicited a significantly higher C_max and AUC_0-t that were over 10 times higher, compared with those of the raw bosentan hydrate administered orally in the same dose. It also exhibited ameliorative effects on monocrotaline-induced pulmonary arterial remodeling, and right ventricular hypertrophy. The survival rate of the group administrated SDBM1:1 intratracheally was 0.92 at the end of study (Positive control and orally administrated groups were 0.58 and 0.38, respectively). In conclusion, SDBM 1:1 showed promising in vitro and in vivo results with the dry powder inhalation. The inhaled bosentan microparticles can be considered as a potential alternative to oral bosentan hydrate for the treatment of PAH.

Comparison of deposition in the USP and physical mouth-throat models with solid and liquid particles

BACKGROUND

Experimental deposition was studied using three different mouth-throat models: (1) the standard United States Pharmacopeia induction port (IP), (2) the idealized human mouth and throat replica developed by the University of Alberta (UofA replica), and (3) the conductive rubber mouth-throat cast from a human subject developed by Lovelace Respiratory Research Institute (LRRI cast).

METHODS

Both solid and liquid monodispersed fluorescent particles in the size range of 2-30 μm in diameter were delivered into the devices at flow rates of 15, 30, and 60 L min(-1). For solid particles, the study was conducted with and without grease coating inside the devices to investigate the effects of particle bounce.

CONCLUSIONS

Large amounts of rebounded particles were found for the IP and UofA replica without the coating treatment, while particle bounce was only observed at the large particle size for the LRRI cast. The UofA replica and LRRI cast agreed well for solid particles with coating treatments and liquid particles. The deposition results from this study were also compared to data of in vivo deposition studies from the literature. The deposition efficiencies in the UofA replica and LRRI cast were within the range of in vivo data, which showed a large scatter.

Needle-free influenza vaccination

Vaccination is the cornerstone of influenza control in epidemic and pandemic situations. Influenza vaccines are typically given by intramuscular injection. However, needle-free vaccinations could offer several distinct advantages over intramuscular injections: they are pain-free, easier to distribute, and easier to give to patients, and their use could reduce vaccination costs. Moreover, vaccine delivery via the respiratory tract, alimentary tract, or skin might elicit mucosal immune responses at the site of virus entry and better cellular immunity, thus improving effectiveness. Although various needle-free vaccination methods for influenza have shown preclinical promise, few have progressed to clinical trials-only live attenuated intranasal vaccines have received approval, and only in some countries. Further clinical investigation is needed to help realise the potential of needle-free vaccination for influenza.

Pharmaceutical and pharmacological importance of peptide transporters

Peptide transport is currently a prominent topic in membrane research. The transport proteins involved are under intense investigation because of their physiological importance in protein absorption and also because peptide transporters are possible vehicles for drug delivery. Moreover, in many tissues peptide carriers transduce peptidic signals across membranes that are relevant in information processing. The focus of this review is on the pharmaceutical relevance of the human peptide transporters PEPT1 and PEPT2. In addition to their physiological substrates, both carriers transport many β-lactam antibiotics, valaciclovir and other drugs and prodrugs because of their sterical resemblance to di- and tripeptides. The primary structure, tissue distribution and substrate specificity of PEPT1 and PEPT2 have been well characterized. However, there is a dearth of knowledge on the substrate binding sites and the three-dimensional structure of these proteins. Until this pivotal information becomes available by X-ray crystallography, the development of new drug substrates relies on classical transport studies combined with molecular modelling. In more than thirty years of research, data on the interaction of well over 700 di- and tripeptides, amino acid and peptide derivatives, drugs and prodrugs with peptide transporters have been gathered. The aim of this review is to put the reports on peptide transporter-mediated drug uptake into perspective. We also review the current knowledge on pharmacogenomics and clinical relevance of human peptide transporters. Finally, the reader's attention is drawn to other known or proposed human peptide-transporting proteins.

Assessment methods of inhaled aerosols: technical aspects and applications

The pulmonary route has been used with success for the treatment of both lung (asthma) and systemic diseases (diabetes). The fate of an inhaled drug (absorption and deposition) within human lungs has great importance, particularly in drug development and quality control. This article focuses on the various methods that are now applied for aerosol fate investigation. Several assessment methods, ranging from in vitro assays (impaction and optical systems) to in vivo experiments (imaging and pharmacological methods), are described. In vitro assays measure particle size distribution and emitted drug dose, which could be predictive of lung deposition pattern in vivo. However, in vivo methods provide direct information about the concentration and the location of inhaled drug within lung. Advantages and limitations of the different techniques are identified. In addition to these experimental techniques, mathematical deposition models, elaborated in more realistic conditions and designed to predict the fate of inhaled particles, are also illustrated.

Analysis of airway secretions in a model of sulfur dioxide induced chronic obstructive pulmonary disease (COPD)

Hypersecretion and chronic phlegm are major symptoms of chronic obstructive pulmonary disease (COPD) but animal models of COPD with a defined functional hypersecretion have not been established so far. To identify an animal model of combined morphological signs of airway inflammation and functional hypersecretion, rats were continuously exposed to different levels of sulfur dioxide (SO2, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm) for 3 (short-term) or 20–25 (long-term) days. Histology revealed a dose-dependent increase in edema formation and inflammatory cell infiltration in short-term-exposed animals. The submucosal edema was replaced by fibrosis after long-term-exposure. The basal secretory activity was only significantly increased in the 20 ppm group. Also, stimulated secretion was significantly increased only after exposure to 20 ppm. BrdU-assays and AgNOR-analysis demonstrated cellular metaplasia and glandular hypertrophy rather than hyperplasia as the underlying morphological correlate of the hypersecretion.

In summary, SO2-exposure can lead to characteristic airway remodeling and changes in mucus secretion in rats. As only long-term exposure to 20 ppm leads to a combination of hypersecretion and airway inflammation, only this mode of exposure should be used to mimic human COPD. Concentrations less or higher than 20 ppm or short term exposure do not induce the respiratory symptom of hypersecretion. The present model may be used to characterize the effects of new compounds on mucus secretion in the background of experimental COPD.