Aerosol-based efficient delivery of telithromycin, a ketolide antimicrobial agent, to lung epithelial lining fluid and alveolar macrophages for treatment of respiratory infections

A Review: Effects of Macrolides on CYP450 Enzymes

As a kind of haemoglobin, cytochrome P450 enzymes (CYP450) participate in the metabolism of many substances, including endogenous substances, exogenous substances and drugs. It is estimated that 60% of common prescription drugs require bioconversion through CYP450. The influence of macrolides on CYP450 contributes to the metabolism and drug-drug interactions (DDIs) of macrolides. At present, most studies on the effects of macrolides on CYP450 are focused on CYP3A, but a few exist on other enzymes and drug combinations, such as telithromycin, which can decrease the activity of hepatic CYP1A2 and CYP3A2. This article summarizes some published applications of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. And the article may subsequently guide the rational use of drugs in clinical trials. To a certain extent, poisoning caused by adverse drug interactions can be avoided. Unreasonable use of macrolide antibiotics may enable the presence of residue of macrolide antibiotics in animal-origin food. It is unhealthy for people to eat food with macrolide antibiotic residues. So it is of great significance to guarantee food safety and protect the health of consumers by the rational use of macrolides. This review gives a detailed description of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. Moreover, it offers a perspective for researchers to further explore in this area.

[Intrapulmonary Pharmacokinetics and Drug Distribution Characteristics for the Treatment of Respiratory Diseases]

This study was designed to clarify the intrapulmonary pharmacokinetics and distribution characteristics of drugs in order to develop better therapies for respiratory diseases, including respiratory infections and pulmonary fibrosis. The distribution characteristics of three macrolide antimicrobial agents-clarithromycin, azithromycin, and telithromycin-in plasma, lung epithelial lining fluid (ELF), and alveolar macrophages (AMs), were examined for the optimization of antimicrobial therapy. The time course of the uptake of these agents in ELF and AMs, following oral administration to rats, resulted in markedly higher concentrations than that in plasma. The high concentration of the agents in AMs was due to their sustained distribution to ELF via multidrug resistance protein 1 and to high uptake by AMs themselves via active transport mechanisms and trapping and/or binding in acidic organelles. The intrapulmonary pharmacokinetics of aerosolized model compounds administered to animals with bleomycin-induced pulmonary fibrosis via aerosol formulations of model compounds (MicroSprayer) were then evaluated. The concentrations of these compounds in the plasma of pulmonary fibrotic rats were markedly higher than in that of control rats. The expression of epithelial tight junctions decreased in pulmonary fibrotic lesions. The accumulation of extracellular matrix inhibited the intrapulmonary distribution of aerosolized model compounds, indicating that aerosolized drugs are easily absorbed after leakage through damaged alveolar epithelia, but cannot become widely distributed in the lungs because of interruption by the extracellular matrix. This review provides useful findings for the development of therapies for respiratory infections and pulmonary fibrosis.

Investigational inhaled therapies for non-CF bronchiectasis

INTRODUCTION

Bronchiectasis not related to cystic fibrosis (non-CF bronchiectasis) are associated with a high unmet therapeutic need due to the lack of specifically authorized medications, especially via the inhalation route. In non-CF bronchiectasis chronic infection with Pseudomonas aeruginosa is common and favored by the persistent local inflammation and viscid sputum production. Therefore inhaled antibiotics, mucolytics or anti-inflammatory agents could represent appropriate therapeutic interventions in this setting.

AREAS COVERED

This review herein discusses the inhaled therapies currently under investigation for non-CF bronchiectasis and their potential therapeutic positioning in exacerbation versus stable state.

EXPERT OPINION

Inhaled antipseudomonal antibiotics are of promising efficacy, but further efforts should also be made to detect bactericidal approaches against Burkholderia cepacia complex, and to interfere chronic inflammation topically.

The Rationale and Evidence for Use of Inhaled Antibiotics to Control Pseudomonas aeruginosa Infection in Non-cystic Fibrosis Bronchiectasis

Non-cystic fibrosis bronchiectasis (NCFBE) is a chronic inflammatory lung disease characterized by irreversible dilation of the bronchi, symptoms of persistent cough and expectoration, and recurrent infective exacerbations. The prevalence of NCFBE is on the increase in the United States and Europe, but no licensed therapies are currently available for its treatment. Although there are many similarities between NCFBE and cystic fibrosis (CF) in terms of respiratory symptoms, airway microbiology, and disease progression, there are key differences, for example, in response to treatment, suggesting differences in pathogenesis. This review discusses possible reasons underlying differences in response to inhaled antibiotics in people with CF and NCFBE. Pseudomonas aeruginosa infections are associated with the most severe forms of bronchiectasis. Suboptimal levels of antibiotics in the lung increase the mutation frequency of P. aeruginosa and lead to the development of mucoid strains characterized by formation of a protective polysaccharide biofilm. Mucoid strains of P. aeruginosa are associated with a chronic infection stage, requiring long-term antibiotic therapy. Inhaled antibiotics provide targeted delivery to the lung with minimal systemic toxicity and adverse events compared with oral/intravenous routes of administration, and they could be alternative treatment options to help address some of the treatment challenges in the management of severe cases of NCFBE. This review provides an overview of completed and ongoing trials that evaluated inhaled antibiotic therapy for NCFBE. Recently, several investigators conducted phase 3 randomized controlled trials with inhaled aztreonam and ciprofloxacin in patients with NCFBE. While the aztreonam trial results were not associated with significant clinical benefit in NCFBE, initial results reported from the inhaled ciprofloxacin (dry powder for inhalation and liposome-encapsulated/dual-release formulations) trials hold promise. A more targeted approach could identify specific populations of NCFBE patients who benefit from inhaled antibiotics.

Inhaled anti-infective chemotherapy for respiratory tract infections: successes, challenges and the road ahead

One of the most common causes of illnesses in humans is from respiratory tract infections caused by bacterial, viral or fungal pathogens. Inhaled anti-infective drugs are crucial for the prophylaxis and treatment of respiratory tract infections. The benefit of anti-infective drug delivery via inhalation is that it affords delivery of sufficient therapeutic dosages directly to the primary site of infection, while minimizing the risks of systemic toxicity or avoiding potential suboptimal pharmacokinetics/pharmacodynamics associated with systemic drug exposure. This review provides an up-to-date treatise of approved and novel developmental inhaled anti-infective agents, with particular attention to effective strategies for their use, pulmonary pharmacokinetic properties and safety.

Inhalation of macrolides: a novel approach to treatment of pulmonary infections

Systemic antibiotic treatment is established for many pulmonary diseases, e.g., cystic fibrosis (CF), bronchiectasis and chronic obstructive pulmonary disease (COPD) where recurrent bacterial infections cause a progressive decline in lung function. In the last decades inhalative administration of antibiotics was introduced into clinical routine, especially tobramycin, colistin, and aztreonam for treatment of CF and bronchiectasis. Even though they are important in systemic treatment of these diseases due to their antimicrobial spectrum and anti-inflammatory and immunomodulatory properties, macrolides (e.g., azithromycin, clarithromycin, erythromycin, and telithromycin) up to now are not administered by inhalation. The number of in vitro aerosol studies and in vivo inhalation studies is also sparse. We analyzed publications on preparation and administration of macrolide aerosols available in PUBMED focusing on recent publications. Studies with solutions and dry powder aerosols were published. Publications investigating physicochemical properties of aerosols demonstrated that macrolide aerosols may serve for inhalation and will achieve sufficient lung deposition and that the bitter taste can be masked. In vivo studies in rats demonstrated high concentrations and areas under the curve sufficient for antimicrobial treatment in alveolar macrophages and epithelial lining fluid without lung toxicity. The obtained data demonstrate the feasibility of macrolide inhalation which should be further investigated.

[Designs of optimized microbial therapy systems of respiratory infections]

Several respiratory infections are frequently induced by pathogenic microorganisms in lung epithelial lining fluid (ELF) and alveolar macrophages (AM). Then, two studies concerning designs of antimicrobial therapy systems of respiratory infections were carried out; one was the distribution mechanisms of three macrolide and ketolide antibiotics, clarithromycin (CAM), azithromycin (AZM) and telithromycin (TEL) in plasma, ELF and AM, and the other was the efficient drug delivery to AM by pulmonary administration of fluoroquinolone antibiotic, a ciprofloxacin (CPFX) incorporated into liposomes (CPFX-liposome). In the first study, the areas under drug concentration-time curves (AUCs) in ELF following oral administration of three macrolide and ketolide antibiotics to rats were significantly higher than AUCs in plasma, furthermore AUCs in AM significantly higher than AUCs in ELF. The high distribution of these antibiotics to the respiratory infection site is due to the transport from blood to ELF via MDR1 in lung epithelial cells as well as the uptake by AM. These antibiotics were taken up by AM via active transport system and the trapping in organelles. In the second study, drug delivery efficacy of CPFX-liposome to AM was particle size-dependent over the 100-1000 nm and then become constant at over 1000 nm by pulmonary aerosolization to rats. This result indicates that the most effective size is 1000 nm. Furthermore, the drug delivery efficacy of mannosylated CPFX-liposome (particle size: 1000 nm) was highly delivered to AM and antibacterial effects were significantly higher than those of unmodified CPFX-liposome. This review provides useful findings for microbial therapy systems of respiratory infections.

New insights in the production of aerosol antibiotics. Evaluation of the optimal aerosol production system for ampicillin-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam

BACKGROUND

Several aerosol antibiotics are on the market and several others are currently being evaluated. Aim of the study was to evaluate the aerosol droplet size of five different antibiotics for future evaluation as an aerosol administration.

MATERIALS AND METHODS

The nebulizers Sunmist(®), Maxineb(®) and Invacare(®) were used in combination with four different "small <6 ml" residual cups and two "large <10 ml" with different loadings 2-4-6-8 ml (8 ml only for large residual cups) with five different antibiotic drugs (ampicilln-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam). The Mastersizer 2000 (Malvern) was used to evaluate the produced droplet size from each combination

RESULTS

Significant effect on the droplet size produced the different antibiotic (F=96.657, p<0.001) and the residual cup design (F=68.535, p<0.001) but not the different loading amount (p=0.127) and the nebulizer (p=0.715). Interactions effects were found significant only between antibiotic and residual cup (F=16.736, p<0.001). No second order interactions were found statistically significant.

CONCLUSION

Our results firstly indicate us indirectly that the chemical formulation of the drug is the main factor affecting the produced droplet size and secondly but closely the residual cup design.

Penetration of anti-infective agents into pulmonary epithelial lining fluid: focus on antibacterial agents

The exposure-response relationship of anti-infective agents at the site of infection is currently being re-examined. Epithelial lining fluid (ELF) has been suggested as the site (compartment) of antimicrobial activity against lung infections caused by extracellular pathogens. There have been an extensive number of studies conducted during the past 20 years to determine drug penetration into ELF and to compare plasma and ELF concentrations of anti-infective agents. The majority of these studies estimated ELF drug concentrations by the method of urea dilution and involved either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Antibacterial agents such as macrolides, ketolides, newer fluoroquinolones and oxazolidinones have ELF to plasma concentration ratios of >1. In comparison, β-lactams, aminoglycosides and glycopeptides have ELF to plasma concentration ratios of ≤1. Potential explanations (e.g. drug transporters, overestimation of the ELF volume, lysis of cells) for why these differences in ELF penetration occur among antibacterial classes need further investigation. The relationship between ELF concentrations and clinical outcomes has been under-studied. In vitro pharmacodynamic models, using simulated ELF and plasma concentrations, have been used to examine the eradication rates of resistant and susceptible pathogens and to explain why selected anti-infective agents (e.g. those with ELF to plasma concentration ratios of >1) are less likely to be associated with clinical treatment failures. Population pharmacokinetic modelling and Monte Carlo simulations have recently been used and permit ELF and plasma concentrations to be evaluated with regard to achievement of target attainment rates. These mathematical modelling techniques have also allowed further examination of drug doses and differences in the time courses of ELF and plasma concentrations as potential explanations for clinical and microbiological effects seen in clinical trials. Further studies are warranted in patients with lower respiratory tract infections to confirm and explore the relationships between ELF concentrations, clinical and microbiological outcomes, and pharmacodynamic parameters.