Pulmonary pharmacokinetics of cyclosporin A liposomes

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.

Formulation and in vitro evaluation of ciprofloxacin containing niosomes for pulmonary delivery

In order to develop a niosome-encapsulated ciprofloxacin (CPFX) HCl formulation for pulmonary delivery, the feasibility of encapsulation of CPFX in niosomes, its stability and nebulization capability was evaluated. Various combinations of nonionic surfactants with cholesterol were used to prepare the formulations. The in vitro deposition data of the niosomal formulations were examined using an Andersen cascade impactor. Formulations composed of Span 60 and Tween 60 in combination with 40 mol% of cholesterol exhibited high encapsulation efficacy and stability and also had fine particle fraction and nebulization efficiency of about 61.9% ± 1.0 and 77.9 ± 2.8, respectively. Minimal inhibitory concentration of the niosomal CPFX against some pulmonary pathogens were lower than free CPFX. Using the MTT assay in human lung carcinoma cell line (A549), niosome-entrapped CPFX showed significantly lower cytotoxicity in comparison to the free drug. These results indicate that niosome can be used as a carrier for pulmonary delivery of CPFX via nebulization.

Nanocarriers for pulmonary administration of peptides and therapeutic proteins

Peptides and therapeutic proteins have been the target of intense research and development in recent years by the pharmaceutical and biotechnology industry. Preferably, they are administered through the parenteral route, which is associated with reduced patient compliance. Formulations for noninvasive administration of peptides and therapeutic proteins are currently being developed. Among them, inhalation appears as a promising alternative for the administration of such products. Several formulations for pulmonary delivery are in various stages of development. Despite positive results, conventional formulations have some limitations such as reduced bioavailability and side effects. Nanocarriers may be an alternative way to overcome the problems of conventional formulations. Some nanocarrier-based formulations of peptides and therapeutic proteins are currently under development. The results obtained are promising, revealing the usefulness of these systems in the delivery of such drugs.

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.

Aerosol delivery of robust polyethyleneimine-DNA complexes for gene therapy and genetic immunization

Aerosol delivery of plasmid DNA to the lungs offers the possibility of direct application of gene preparations to pulmonary surfaces as a means of treating a variety of genetic pulmonary disorders. However, the process of jet nebulization rapidly degrades naked DNA, viral vectors, and many lipid-based formulations. While complexing DNA with cationic lipids has been shown to significantly stabilize plasmid DNA, losses of biological activity often occur during nebulization, severely limiting the efficiency of aerosol delivery of many such complexes. In conjunction with the design of aerosol delivery systems appropriate for DNA delivery, we have developed formulations using polyethyleneimine (PEI, a polycationic polymer) and DNA that result in a high level of pulmonary transfection (10- to 100-fold greater than many cationic lipids) and are stable during nebulization. In addition, these PEI-based formulations exhibit a high degree of specificity for the lungs. The properties of PEI-based formulations that make them resistant to nebulization and efficient as DNA delivery vectors for pulmonary sites have been investigated. Potential applications of this technology, including the use of aerosolized PEI-DNA for genetic immunization, are discussed.

Nebulizer-compatible liquid formulations for aerosol pulmonary delivery of hydrophobic drugs: glucocorticoids and cyclosporine

This review discusses pulmonary delivery of glucocorticoids and cyclosporine in pharmaceutically acceptable organic solvents and liposomes, as well as in micellar solutions and microemulsions, by means of liquid aerosols generated by nebulizers. The review points out the importance of a variety of parameters for successful treatment of immunologically mediated lung diseases by inhalation of drug containing aerosols with particular references to physico-chemical properties of formulations, aerosol parameters, pharmacokinetics, and lung deposition in experimental animals and humans. The prospects for the use of these types of formulations for clinical treatment of asthma, lung transplant rejection processes and other lung diseases are summarized.

Pharmacokinetics of liposomal aerosolized cyclosporine A for pulmonary immunosuppression

BACKGROUND

The results of pulmonary transplantation are compromised by acute and chronic rejection. We hypothesized that a liposomal form of aerosolized cyclosporine A (CsA) would be selectively deposited and concentrated in the lungs. The theoretical advantage of this therapy is selective pulmonary immunosuppression with prolonged utilization.

METHODS

Eighteen dogs were endotracheally intubated; aerosolized liposomal CsA was administered for 15 min. CsA levels were measured in whole blood, lung, trachea, heart, kidney, liver, and spleen at various times after treatment.

RESULTS

The lung rapidly absorbs aerosolized liposomal CsA; other organs have much lower concentrations. The retention of pulmonary CsA delivered by liposome aerosol is approximately 120 min in this model.

CONCLUSIONS

Aerosolized liposomal CsA is selectively deposited and concentrated in the lungs; other organs absorb less CsA.

Stabilization of aerosolized IFN-gamma by liposomes

Aerosolized IFN-gamma is very unstable. We have improved the stability of IFN-gamma in the jet nebulizer by adding small liposomes. Aerosolized IFN-gamma was recovered in PBS solution by bubbling and its concentration was determined. After nebulization for 30 min, aerosolized IFN-gamma was detected only 0.4+/-0.2% of the initial amount in the PBS solution and 3.1+/-0.7% in the reservoir. On the other hand, the addition of small liposomes (HSPC/DSPG=10/1 (molar ratio), 45+/-24 nm) in the nebulizer increased the stability of IFN-gamma, 27.2+/-4.7% of the initial amount in the PBS solution and 25.7+/-12.6% in the reservoir. The present study also examined the effects of composition and concentration of liposomes on the stabilization of aerosolized IFN-gamma. Liposome prepared from distearoyl phosphatidylcholine (DSPC) or hydrogenated soy phosphatidylcholine (HSPC) was very effective for stabilization of aerosolized IFN-gamma (DSPC/DPPG=10/1, HSPC/DSPG=10/1). HSPC/DSPG liposome was efficient at the concentration higher than 12.5 micromols/ml for the stabilization of 5x10(5) JRU/ml of IFN-gamma. In considering the mechanism of this stabilization, the results of gel filtration chromatography suggest that IFN-gamma is inactivated by polymerization or aggregation in nebulization, while the inactivation is suppressed by liposomes due to their adsorption to IFN-gamma.