Aerosols and anti-infectious agents

Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses

BACKGROUND

Nebulisation of the injectable dexamethasone sodium phosphate (DSP) would offer an inexpensive way of delivering a potent corticosteroid directly to the lungs of horses with asthma. However, this approach would be advantageous only if systemic absorption is minimal and if the preservatives present in the formulation do not induce airway inflammation.

OBJECTIVE

To investigate the bioavailability of nebulised DSP and determine whether it induces airway inflammation or hypothalamic-pituitary-adrenal (HPA) axis suppression in healthy adult horses.

STUDY DESIGN

Randomised crossover experiment.

METHODS

Dexamethasone sodium phosphate was administered to six healthy adult horses at a dose of 5 mg q. 24 h for 5 days via nebulised, or intravenous (i.v.) routes. Plasma dexamethasone concentrations were measured by UPLC/MS-MS to calculate bioavailability. Cytological examination of bronchoalveolar fluid was performed at baseline and after the last dose of DSP. A validated chemiluminescent immunoassay was used to measure basal serum cortisol concentrations.

RESULTS

After nebulisation to adult horses, dexamethasone had a mean (±s.d.) maximum plasma concentration of 0.774 ± 0.215 ng/mL and systemic bioavailability of 4.3 ± 1.2%. Regardless of route of administration, there was a significant decrease in the percentage of neutrophils in bronchoalveolar lavage fluid over time. During i.v. administration, basal serum cortisol concentration decreased significantly from baseline to Day 3 and remained low on Day 5. In contrast, basal serum cortisol concentration did not change significantly during administration via nebulisation.

MAIN LIMITATIONS

Small sample size and short period of drug administration.

CONCLUSIONS

Dexamethasone sodium phosphate administered via nebulisation had minimal systemic bioavailability and did not induce lower airway inflammation or HPA axis suppression in healthy horses.

Clinical experimentation with aerosol antibiotics: current and future methods of administration

Currently almost all antibiotics are administered by the intravenous route. Since several systems and situations require more efficient methods of administration, investigation and experimentation in drug design has produced local treatment modalities. Administration of antibiotics in aerosol form is one of the treatment methods of increasing interest. As the field of drug nanotechnology grows, new molecules have been produced and combined with aerosol production systems. In the current review, we discuss the efficiency of aerosol antibiotic studies along with aerosol production systems. The different parts of the aerosol antibiotic methodology are presented. Additionally, information regarding the drug molecules used is presented and future applications of this method are discussed.

Antibiotics for treatment and prevention of exacerbations of chronic obstructive pulmonary disease

Acute exacerbations (AE) can be recurrent problems for patients with moderate-to-severe chronic obstructive pulmonary disease (COPD) increasing morbidity and mortality. Evidence suggests that ≥50% of acute exacerbations involve bacteria requiring treatment with an antibiotic which should have high activity against the causative pathogens. However, sputum analysis is not a pre-requisite for antibiotic prescription in outpatients as results are delayed and patients are likely to be colonised with bacteria in the stable state. Clinicians rely on the clinical symptoms, sputum appearance and the patient's medical history to decide if an AE-COPD should be treated with antibiotics. This article reviews the available data of antibiotic trials in AE-COPD. Management of frequent exacerbators is particularly challenging for physicians. This may include antibiotic prophylaxis, especially macrolides because of anti-inflammatory properties; though successful in reducing exacerbations, concerns about resistance development remain. Inhalation of antibiotics achieves high local concentrations and minimal systemic exposure; therefore, it may represent an attractive alternative for antibiotic prophylaxis in certain COPD patients. Inhaled antibiotic prophylaxis has been successfully used in other respiratory conditions such as non-cystic fibrosis bronchiectasis which itself might be present in COPD patients who have chronic bacterial infection, particularly with Pseudomonas aeruginosa.

Development of nano alpha-ketoglutarate nebulization formulation and its pharmacokinetic and safety evaluation in healthy human volunteers for cyanide poisoning

Development of nano alpha-ketoglutarate (A-KG) nebulization formulation for neutralization of inhaled cyanide ion toxicity. Objectives of the present study were to (a) develop a novel A-KG nebulization formulation against cyanide poisoning, particularly hydrogen cyanide gas (b) validate its respiratory fraction in vitro and in vivo, and (c) create its pharmacokinetic data in human volunteers. The formulation was optimized on the basis of particle size of aerosolized droplets after nebulization in 6 volunteers. Gamma scintigraphy was used to quantify total and regional lung deposition of nebulized A-KG after radiolabeling it with Technetium-99m. The formulation was optimized using 30% ethanol-saline with particle size in the range of 300-500 nm. In vitro and in vivo studies showed that drug nebulization resulted in a significant respirable fraction of 65 ± 0.6% with whole lung deposition of 13 ± 1%. Human pharmacokinetic data was derived in 6 healthy human volunteers with peak serum concentration (C(max)) of 39 ± 3 μg/ml, while the area under curve (AUC) after inhalation was 376 ± 23 μg × h/ml indicating that the drug was rapidly and completely absorbed when targeted directly to lungs. Significant lung deposition of A-KG was achieved with the developed formulation. The formulation appears to have several advantages, including the potential of neutralizing inhaled CN(-) ions in the lungs themselves. It is a safe and efficacious procedure, suitable for hospital or ambulance use in accidental cyanide poisoning cases, or as a preventive approach for fire-rescue teams.

Ultrasonic nebulization platforms for pulmonary drug delivery

IMPORTANCE OF THE FIELD

Since the 1950s, ultrasonic nebulizers have played an important role in pulmonary drug delivery. As the process in which aerosol droplets are generated is independent and does not require breath-actuation, ultrasonic nebulizers, in principle, offer the potential for instantaneously fine-tuning the dose administered to the specific requirements of a patient, taking into account the patient's breathing pattern, physiological profile and disease state. Nevertheless, owing to the difficulties and limitations associated with conventional designs and technologies, ultrasonic nebulizers have never been widely adopted, and have in recent years been in a state of decline.

AREAS COVERED IN THIS REVIEW

An overview is provided on the advances in new miniature ultrasonic nebulization platforms in which large increases in lung dose efficiency have been reported.

WHAT THE READER WILL GAIN

In addition to a discussion of the underlying mechanisms governing ultrasonic nebulization, in which there appears to be widely differing views, the advantages and shortcomings of conventional ultrasonic nebulization technology are reviewed and advanced state-of-the-art technologies that have been developed recently are discussed.

TAKE HOME MESSAGE

Recent advances in ultrasonic nebulization technology demonstrate significant potential for the development of smart, portable inhalation therapy platforms for the future. Nevertheless, there remain considerable challenges that need to be addressed before such personalized delivery systems can be realized. These have to be addressed across the spectrum from fundamental physics through to in vivo device testing and dealing with the relevant regulatory framework.

A review on the clinical use of inhaled amphotericin B

BACKGROUND

Despite the systemic toxicity of amphotericin B (AMB), it still has a place in treatment or prophylactic regimes of fungal infections.

METHODS

A strategy for minimizing the potential of systemic side effects is to bring it in direct contact with the body site most likely to be infected, such as the administration of AMB as an aerosol. Nebulized amphotericin has been used in humans since 1959. However, due to a lack of sufficient data regarding efficacy, its use is still not established. Little is known about the optimal dose, frequency, duration of administration, and the pharmacokinetics of inhaled AMB in humans.

RESULTS AND CONCLUSIONS

In this review, published data regarding inhaled AMB are summarized, including available descriptions regarding preparation, dose, efficacy, and toxicity, and its place in therapy is discussed. The results from the studies that were reviewed in this article indicate that inhaled AMB may have a place in the prophylactic regimens of patients with prolonged neutropenia and in lung transplant recipients. Furthermore, nebulized (liposomal) AMB may have a place in the treatment of allergic bronchopulmonary aspergillosis (ABPA) in patients with corticosteroid-dependent ABPA.

Gemcitabine aerosol: in vitro antitumor activity and deposition imaging for preclinical safety assessment in baboons

AIM

To characterize gemcitabine aerosol, its in vitro activity against lung cancer cells, its deposition, and tolerance in a non-human primate model.

METHODS

In vitro cytotoxicity of nebulized gemcitabine against NCI-H460 and A549 lung cancer cells was tested using a growth inhibition assay and compared with non-nebulized gemcitabine. The (99m)Tc-DTPA-radiolabeled gemcitabine aerosol was characterized by cascade impaction and the gemcitabine mass/(99m)Tc activity relationship was established for further quantitative nuclear imaging. Nine weekly inhalations at a target dose of 1 mg/kg body weight of gemcitabine were performed in three baboons using dynamic scintigraphic acquisitions for continuous monitoring of gemcitabine delivery during inhalation. Gemcitabine plasma concentrations were measured during the first inhalation.

RESULTS

Growth inhibition assays for both NCI-H460 and A549 cells did not differ between nebulized and non-nebulized gemcitabine. Aerosol characterization showed a particle mass median aerodynamic diameter of 3.7+/-0.8 microm and a linear relationship between gemcitabine mass (y) and (99m)Tc activity (x) (y=0.82x - 10(-5), R (2)=0.88). No toxicity was observed after nine weekly inhalations of a mean dose of gemcitabine of 11.1 mg (88% of the target dose) as assessed from scintigraphic data. A dose-dependent peak plasma concentration of gemcitabine (20-74 ng/ml) was observed by the tenth minute of inhalation.

CONCLUSIONS

We have characterized a gemcitabine aerosol suitable for intrathoracic airway deposition and demonstrated that jet nebulization does not alter the cytotoxic properties of the drug. In a primate model, we have developed a scintigraphic procedure for the monitoring of aerosol deposition, and we have demonstrated the safety of nine weekly aerosol administrations of gemcitabine.

In vitro evaluation of nebulization properties, antimicrobial activity, and regional airway surface liquid concentration of liposomal polymyxin B sulfate

PURPOSE

To manipulate the activity of polymyxin B sulfate (PXB sulfate) by encapsulation in liposomes derived from appropriately selected surfactants that exhibit optimum entrapment and aerosol delivery of encapsulated PXB sulfate.

METHODS

A combination of phospholipid (DMPG) and nonionic surfactants (Span 20 + Tween 80) was selected to encapsulate PXB sulfate. The nebulization properties were evaluated by nebulizing the liposomal dispersions with Pari LC Star nebulizers. The in vitro antibacterial activities of the original and nebulized liposomal formulations were evaluated against Pseudomonas aeruginosa (ATCC 27853) strains by broth microdilution. and their minimum inhibitory concentrations (MICs) were compared with those of free PXB sulfate and colistin methanesulfonate. Measurements of the aerosol properties during nebulization were used as input for a mathematical model of airway surface liquid in the lung of an average adult, to estimate the airway surface liquid concentration of the deposited liposomal PXB sulfate.

RESULTS

The selected combination of surfactants showed maximum nebulization efficiency without compromising liposomal integrity during nebulization. PXB sulfate was added at a concentration of 10 mg/ml, and a molar ratio of PXB sulfate to dimyristoyl phosphatidylglycerol (DMPG) (sodium salt) of 1:5 was required to achieve 100% entrapment of PXB sulfate and no leakage on nebulization. Another formulation comprising half the concentrations of the optimized non-ionic surfactants and DMPG was prepared to achieve a balance between the toxicity and efficacy after nebulization of encapsulated PXB sulfate. The in vitro antibacterial activities against Pseudomonas aeruginosa indicated that the activity of PXB sulfate could be manipulated by appropriate concentrations of the selected surfactants to achieve activity equivalent to that of colistin methanesulfonate, which is known to be less toxic than unencapsulated PXB sulfate. The estimated airway surface liquid concentrations of the deposited liposomal PXB sulfate reveal that the MIC of the nebulized liposomal PXB sulfate can be achieved over most of the tracheobronchial region, using a jet nebulizer with a volume fill of 2.5 ml or more.

CONCLUSION

It was established from this study that the encapsulation of PXB sulfate in liposomes reduces its activity against P. aeruginosa strains. Concentrations of PXB sulfate deposited in the tracheobroncial region, predicted using a mathematical model, were above the measured MICs except in the case of very high mucus production rate and low mucus velocities.

Improving drug delivery from medical nebulizers: the effects of increased nebulizer flow rates and reservoirs

Drug delivery from jet nebulizers can be considered in terms of the dose inhaled and the respirability of that dose. It is proposed that dose respirability and dose per breath can be controlled through specification of the driving gas flowrate, and that the dose inhaled per breath can also be increased through the use of nebulizer reservoirs. When a Hudson Micromist nebulizer was used and assessments of respirability were made utilizing phase Doppler interferometry, it was noted that the portion of the spray mass in droplet sizes of <or=5 microm (general respirability) and in droplet sizes of <or=3 microm (deep lung respirability) increased linearly with gas flowrate for both tank air and helium-oxygen (70/30). Drug mass in the 2-6 microm range (tracheobronchial respirability) peaked at air flowrates of 8-10 LPM and decreased slightly for higher flowrates. Two portable compressors provided respirabilities similar to tank air at the same flowrates. Changing the nebulizer flowrate did not affect the ratio of the inhaled dose to the dose expelled by exhalation when a typical breathing pattern was simulated. A version of the Micromist with an attached reservoir (the Hudson AeroTee) provided a higher dose per breath to the patient and a higher total dose for the same treatment time by conserving the aerosol generated during exhalation. The inhaled dose increased approximately 28% when compared to a standard Micromist, despite significant deposition in the reservoir bag. Nebulizer reservoirs could be used to attain higher doses or to more efficiently utilize expensive medications.