Pulmonary concentrations of dirithromycin and erythromycin during acute exacerbation of mild chronic obstructive pulmonary disease

Pharmacokinetic/pharmacodynamic approaches to drug delivery design for inhalation drugs

Introduction: Inhaled drugs are important in the treatment of many lung pathologies, but to be therapeutically effective they must reach unbound concentrations at their effect site in the lung that are adequate to interact with their pharmacodynamic properties (PD) and exert the pharmacological action over an appropriate dosing interval. Therefore, the evaluation of pharmacokinetic (PK)/PD relationship is critical to predict their possible therapeutic effect.Areas covered: We review the approaches used to assess the PK/PD relationship of the major classes of inhaled drugs that are prescribed to treat pulmonary pathologies.Expert opinion: There are still great difficulties in producing data on lung concentrations of inhaled drugs and interpreting them as to their ability to induce the desired therapeutic action. The structural complexity of the lungs, the multiplicity of processes involved simultaneously and the physical interactions between the lungs and drug make any PK/PD approach to drug delivery design for inhalation medications extremely challenging. New approaches/methods are increasing our understanding about what happens to inhaled drugs, but they are still not ready for regulatory purposes. Therefore, we must still rely on plasma concentrations based on the axiom that they reflect both the extent and the pattern of deposition within the lungs.

Antibiotics for treatment of acute exacerbation of chronic obstructive pulmonary disease: a network meta-analysis

Background

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is the most common reason for the hospitalization and death of pulmonary patients. The use of antibiotics as adjuvant therapy for AECOPD, however, is still a matter of debate.

Methods

In this study, we searched the PubMed, EmBase, and Cochrane databases for randomized controlled trials published until September 2016 that evaluated the use of antibiotics for AECOPD treatment. The major outcome variables were clinical cure rate and adverse effects. The microbiological response rate, relapse of exacerbation, and mortality were also analysed. A random-effect network was used to assess the effectiveness and tolerance of each antibiotic used for AECOPD treatment.

Results

In this meta-analysis, we included 19 articles that assessed 17 types of antibiotics used in 5906 AECOPD patients. The cluster ranking showed that dirithromycin had a high clinical cure rate with a low rate of adverse effects. Ofloxacin, ciprofloxacin, and trimethoprim-sulfamethoxazole had high clinical cure rates with median rates of adverse effects. In terms of the microbiological response rate, only doxycycline was significantly better than placebo (odds ratio (OR), 3.84; 95% confidence interval (CI), 1.96–7.54; p < 0.001). There were no other significant results with respect to the frequency of recurrence or mortality.

Conclusions

Our study indicated that dirithromycin is adequate for improving the clinical cure rate of patients with AECOPD with few adverse effects. Ofloxacin, ciprofloxacin, and trimethoprim-sulfamethoxazole are also recommended for disease treatment. However, caution should still be exercised when using antibiotics to treat AECOPD.

Trial Registration Not applicable.

Electronic supplementary material

The online version of this article (doi: 10.1186/s12890-017-0541-0) contains supplementary material, which is available to authorized users.

Taste receptors in asthma

PURPOSE OF REVIEW

Although today's cornerstone therapies for asthma (inhaled bronchodilators and corticosteroids) target airway narrowing and lung inflammation, about half of treated asthmatic patients do not achieve good disease control. There is a clear need for new therapeutic approaches and novel drug targets. Recent research has unexpectedly revealed that certain taste receptors (particularly those involved in bitter taste transduction) are expressed in lung tissue.

RECENT FINDINGS

Bitter taste receptors are expressed in several cell types in the lungs (such as chemosensory cells, epithelial cells, smooth muscle cells, lymphocytes, and macrophages) and variously involved in ciliary beating, muscle relaxation, and/or inhibition of the production of inflammatory mediators. Here, we review recent research on the role of bitter taste receptors in experimental models of asthma and in asthmatics.

SUMMARY

The currently available data suggest that bitter taste receptor agonists have therapeutic potential in chronic obstructive airway diseases such as asthma.

Delivering Antibacterials to the Lungs

An important determinant of clinical outcome of a lower respiratory tract infection may be sterilization of the infected lung, which is also dependent on sustained antibacterial concentrations achieved in the lung. For this reason, recently there has been increased interest in measuring the concentration of antimicrobial agents at different potential sites of infection in the lung. Levels of antibacterials are now measured in bronchial mucosa, epithelial lining fluid (ELF) and alveolar macrophages, as well as in sputum. Penicillins and cephalosporins reach only marginal concentrations in bronchial secretions, whereas fluoroquinolones and macrolides have been shown to achieve high concentrations. The extent of penetration of different antibacterials into the bronchial mucosa is relatively high. This is also true for beta-lactams, although their tissue concentrations never reach blood concentrations. Antibacterials penetrate less into the ELF than into the bronchial mucosa, but fluoroquinolones appear to concentrate more into alveolar lavage than into bronchial mucosa. Pulmonary pharmacokinetics is a very useful tool for describing how drugs behave in the human lung, but it does not promote an understanding of the pharmacological effects of a drug. More important, instead, is the correlation between pulmonary disposition of the drug and its minimum inhibitory concentration (MIC) values for the infectious agent. The addition of bacteriological characteristics to in vivo pharmacokinetic studies has triggered a 'pharmacodynamic approach'. Pharmacodynamic parameters integrate the microbiological activity and pharmacokinetics of an anti-infective drug by focusing on its biological effects, particularly growth inhibition and killing of pathogens. Drugs that penetrate well and remain for long periods at the pulmonary site of infection often induce therapeutic responses greater than expected on the basis of in vitro data. However, although the determination of antibacterial concentrations at the site of infection in the lung has been suggested to be important in predicting the therapeutic efficacy of antimicrobial treatment during bacterial infections of the lower respiratory tract, some studies have demonstrated that pulmonary bacterial clearance is correlated more closely to concentrations in the serum than to those in the lung homogenates, probably because they better reflect antibacterial concentration in the interstitial fluid.

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.

Role of Rifampin-Based Combination Therapy for Severe Community-Acquired Legionella pneumophila Pneumonia

Objective:

To review the literature concerning the role of rifampin in the combination treatment of Legionella pneumophila pneumonia.

Data Sources:

A search of MEDLINE and Ovid databases was conducted (January 1970-May 2011) using the search terms Legionella pneumophila, pneumonia, Legionnaires' disease, rifampin or rifampicin, macrolide, fluoroquinolone, erythromycin, clarithromycin, levofloxacin, ciprofloxacin, and moxifloxacin

Study Selection and Data Extraction:

In vivo studies published in English that compared antimicrobial therapies including rifampin for the treatment of Legionella pneumonia, as well as in vitro studies including an assessment of rifampin bioactivity, were included.

Data Synthesis:

Macrolides and fluoroquinolones have been effective as monotherapy in the treatment of L. pneumophila pneumonia. This review includes evidence summaries from 4 bioactivity evaluations. 6 clinical studies, and 6 reported cases of combination rifampin use. Combined with supporting evidence, the role of combination rifampin therapy is further delineated.

Conclusions:

Interpretation of the data is limited by the potential for selection bias and lack of consistent comparators. Rifampin therapy should be considered only for patients with severe disease or significant comorbid conditions (eg. uncontrolled diabetes, smoking, or obstructive lung disease) including immunocompromised hosts and those refractory to conventional monotherapy regimens. Caution for significant adverse drug events and drug-drug interactions should be taken with the addition of rifampin.

[Blood and respiratory diffusion of antibiotics. A critical analysis of predictive parameters for clinical effectiveness]

The implementation of a treatment for lower respiratory tract infections must integrate a pharmacokinetic/pharmacodynamic (PK-PD) approach of antibiotic dosing. The activity of beta-lactam antibiotics is best predicted by the duration of time during which serum concentrations exceed the MIC (T>MIC). T>MIC of 30-40% is sufficient to achieve clinical cure in immunocompetent patients. This threshold is achieved with amoxicillin for penicillin susceptible or resistant Sreptococcus pneumoniae and with amoxicillin-clavulanate and ceftriaxone for S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. For macrolides, the activity is best predicted by T>MIC and for azithromycin and telithromycin by area-under-the-curve/MIC (AUC/MIC). Sufficient PK-PD values are only achieved for macrolides against susceptible strains of S. pneumoniae and against M. catarrhalis; for telithromycin, an AUC/MIC>25, which is necessary for bacterial eradication, is achieved in>99% of patients for S. pneumoniae and M. catarrhalis and>90% of patients for H. influenzae. For fluoroquinolones, both peak/MIC and AUC/MIC are predictors of clinical and bacteriological efficacy. AUC/MIC required ratios vary according to pathogens and severity of diseases from 48 to 125. These thresholds are reached for respiratory pathogens; for S. pneumoniae, AUC/MIC90 ratios of levofloxacin and moxifloxacin are 96 and 192, respectively; the presence of a mutation in parC increases the risk for the acquisition of additional mutations and failure.

The effect of erythromycin on mucociliary transportability and rheology of cystic fibrosis and bronchiectasis sputum

BACKGROUND

Erythromycin has been shown to diminish sputum production in hypersecretory states by a mechanism that is still unclear.

OBJECTIVES AND METHODS

We have investigated the effect of erythromycin on the ciliary transportability of cystic fibrosis and non-cystic fibrosis bronchiectasis sputum in vitro using the mucus-depleted bovine trachea.

RESULTS

Additional erythromycin in concentrations up to 20 microg/g did not significantly alter the ciliary transportability of sputum from 6 cystic fibrosis and 6 bronchiectasis patients. Sputum viscoelasticity measured with parallel-plate rheology was also little changed. These erythromycin concentrations also had little effect on the beating frequency of bovine tracheal cilia.

CONCLUSIONS

These results suggest that the presence of erythromycin in sputum neither alters the physical properties of the gel nor the activity of cilia. The clinical effects of erythromycin on pulmonary hypersecretory states therefore have another explanation.

Therapy with macrolides in patients with cystic fibrosis

Cystic fibrosis affects 1/2500 individuals and is the most common lethal autosomal recessive disease in people of northern European descent. It is characterized by chronic infections with mucoid Pseudomonas aeruginosa and progressive deterioration of respiratory function. Much research has focused on the inflammatory component of the disease. Macrolide antibiotics are postulated to suppress inflammatory mediators and interfere with biofilm formation produced by P. aeruginosa. In vitro studies show promising results, and a limited number of human studies reported improvements in respiratory function with the drugs. Macrolide antibiotics are generally safe and well tolerated and may prove to be effective in patients with cystic fibrosis.

Dirithromycin concentrations in bronchial mucosa and secretions

Since a high tissue penetration of dirithromycin (D) has been assessed in early studies, the aims of this study were to determine D concentrations in bronchial mucosa and secretions in patients suffering from an acute exacerbation of chronic bronchitis (AECB), to compare intra-individual bronchial mucosa and secretion concentrations and to relate bronchial concentrations of D and clinical efficacy. The main inclusion criteria were comprised of (1) AECB, defined by the presence of an increase in dyspnea, sputum production and change in sputum purulence, and (2) clinical indication of fiberoptic bronchoscopy allowing performance of bronchial biopsies. All patients were treated with a 500-mg once-daily D dose for 5 days. Patients were randomly divided into three groups, according to sampling times (24, 48 and 72 h after the last dose). Tissue concentration analyses were performed by one blinded microbiologist (microbiological agar diffusion assay). The results showed: (1) 37 out of the 46 patients (80.4%) had a favorable response to treatment at the time of fiberoptic bronchoscopy (14 cured, 23 improved); (2) bronchial mucosa concentrations were high in all groups, and (3) mean values at 24, 48 and 72 h after the last dose were respectively 6.51 +/- 1.44, 6. 61 +/- 2.7, 5.67 +/- 1.02 mg.kg-1; no statistical difference was observed between the groups. In bronchial secretions collected simultaneously, concentrations were lower, i.e. 1.26 +/- 0.3, 0.61 +/- 0.12, 0.84 +/- 0.12. Significant associations were observed between bronchial mucosa and secretion concentrations (r = 0.71, p = 0.0001), and between clinical response and bronchial concentrations (p = 0.03, Kruskall-Wallis test). In conclusion, these results may confirm the clinical significance of tissue concentrations measured in bronchial tissues of patients with AECB.

Effect of erythromycin on ATP-induced intracellular calcium response in A549 cells

ATP induced a biphasic increase in the intracellular Ca(2+)concentration ([Ca(2+)](i)), an initial spike, and a subsequent plateau in A549 cells. Erythromycin (EM) suppressed the ATP-induced [Ca(2+)](i) spike but only in the presence of extracellular calcium (Ca(2+)(o)). It was ineffective against ATP- and UTP-induced inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] formation and UTP-induced [Ca(2+)](i) spike, implying that EM perturbs Ca(2+) influx from the extracellular space rather than Ca(2+)release from intracellular Ca(2+) stores via the G protein-phospholipase C-Ins(1,4,5)P(3) pathway. A verapamil-sensitive, KCl-induced increase in [Ca(2+)](i) and the Ca(2+) influx activated by Ca(2+) store depletion were insensitive to EM. 3'-O-(4-benzoylbenzoyl)-ATP evoked an Ca(2+)(o)-dependent [Ca(2+)](i) response even in the presence of verapamil or the absence of extracellular Na(+), and this response was almost completely abolished by EM pretreatment. RT-PCR analyses revealed that P2X(4) as well as P2Y(2), P2Y(4), and P2Y(6) are coexpressed in this cell line. These results suggest that in A549 cells 1) the coexpressed P2X(4) and P2Y(2)/P2Y(4) subtypes contribute to the ATP-induced [Ca(2+)](i) spike and 2) EM selectively inhibits Ca(2+) influx through the P2X channel. This action of EM may underlie its clinical efficacy in the treatment of airway inflammation.

Comparative study of dirithromycin and azithromycin in the treatment of acute bacterial exacerbations of chronic bronchitis

We compared the clinical and microbiological efficacy of dirithromycin with that of azithromycin in outpatients with acute bacterial exacerbations of chronic bronchitis who could be graded into stage III according to Ball's system of stratification. A total of 80 patients was studied. Of these, 40 were treated with dirithromycin as a once-daily dose of 500 mg for 5 days, and 40 with azithromycin as a once-daily dose of 500 mg for 3 days. At post-therapy, treatment success (cure or improvement) was achieved in 36 out of 40 (90%) patients receiving dirithromycin compared with 37 out of 40 (92.5%) in the azithromycin group. At the late post-therapy visit, 34 out of 36 (94.4%) dirithromycin-treated patients were cured as were 33 of 37 (89.2%) azithromycin-treated patients. A small proportion of patients treated with dirithromycin (10%) or with azithromycin (12.5%) suffered mild side effects. Gastrointestinal disorders, including abdominal cramps, nausea, or diarrhea, were common adverse effects. The main pathogens isolated before treatment were Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Eradication rates at the end of treatment were 90% (36 out of 40) for the dirithromycin group and 92.5% (37 out of 40) for the azithromycin group. Persistence of H. influenzae isolates was found in 3 out of 11 (27.3%) patients treated with dirithromycin and in 2 out of 9 (22.2%) who had received azithromycin. At the late post-therapy visit, eradication occurred in 34 out of 36 (94.4%) strains in the dirithromycin group and in 33 out of 37 (89.2%) in the azithromycin group. We conclude that dirithromycin and azithromycin appear to be equally effective in the treatment of acute bacterial exacerbations of chronic bronchitis.

A five-day course of dirithromycin in the treatment of acute exacerbation of severe chronic obstructive pulmonary disease

Since dirithromycin persists at high concentrations in the lung for at least 3 days following the last dose of a 5-day course, we evaluated the clinical efficacy and tolerance of a 5-day course of dirithromycin in 20 patients with acute exacerbation of severe chronic obstructive pulmonary disease, treated with a total dose of 2.5 g dirithromycin (500 mg once-daily for 5 days) in an open, non-comparative study. Patients were assessed before therapy and after 5 (last administration), 10 (post-therapy) and 20 (late post-therapy) days. Pathogen elimination or presumed elimination was seen in 18/20 patients at the post-therapy visit and at the late post-therapy visit, but two Haemophilus influenzae out 5 were isolated in sputum after 10 days and only one after 20 days (Pseudomonas aeruginosa was the other pathogen). Dirithromycin was well-tolerated and only 2 patients reported mild gastrointestinal pain. This study shows that a 5-day dirithromycin therapy provides a convenient and efficient dosage regimen in acute exacerbation of chronic bronchitis. Notwithstanding its poor in vitro activity against H. influenzae, dirithromycin was fairly active against this microorganism in vivo.