Direct measurement of BDP and 17-BMP in bronchial and peripheral lung tissue after inhalation of HFA- vs CFC-driven aerosols

Pharmacodynamic and pharmacokinetic considerations in choosing an inhaled corticosteroid

Inhaled corticosteroids are effective in controlling airway inflammation. Their anti-inflammatory effect is primarily topical, at the site of deposition in the airways. Consequently, traditional pharmacodynamic and pharmacokinetic concepts, which rely on measuring blood concentrations of drug, have limited applicability for evaluating the efficacy of topically acting inhaled corticosteroids. Important factors affecting efficacy of inhaled corticosteroids are: (i) intrinsic properties of the drugs, particularly their affinity for the corticosteroid receptor; and (ii) the newer pharmacodynamic concept of deposition characteristics of the drug formulation. Small particle formulations, especially those developed in the metered-dose inhaler with the new hydrofluoroalkane propellant, deposit to a much greater extent in the lung and may consequently have improved clinical efficacy. Lipid conjugation of inhaled corticosteroids within the lung may allow prolonged duration of effect, enabling once-daily administration. Pharmacodynamic and pharmacokinetic principles probably do not play a role in describing upper airway adverse effects occurring with inhaled corticosteroids. These are probably also determined by intrinsic properties of the drug and deposition characteristics. However, pharmacodynamic and pharmacokinetic principles seem to be important in addressing systemic safety concerns with inhaled corticosteroids. Those inhaled corticosteroids with a longer serum half-life, especially if they have higher affinity for the corticosteroid receptor, may be associated with greater systemic effects. A new pharmacokinetic concept suggests that increased protein binding within the systemic circulation and high systemic clearance of an inhaled corticosteroid may reduce the risk for systemic effects. These new pharmacodynamic and pharmacokinetic concepts provide a useful framework for identifying the characteristics of an inhaled corticosteroid with an improved benefit-to-risk profile. Increased lung deposition and reduced deposition in the upper airway should result in an inhaled corticosteroid with favorable clinical efficacy and a decreased risk for topical upper airway adverse effects. An inhaled corticosteroid with high plasma protein binding and rapid clearance might pose much less risk for systemic adverse effects than currently available drugs in this class.

Challenges in the management of exercise-induced asthma

Exercise and physical activity are common triggers of symptoms in patients with asthma, although some individuals - especially athletes - may have symptoms with exercise alone. Exercise-induced bronchospasm (EIB) describes airway hyper-reactivity that is observed following exercise in a patient who is not otherwise diagnosed with asthma; exercise-induced asthma (EIA) describes airway hyper-reactivity associated with exercise in a patient who has persistent asthma. Specific challenges affecting both the diagnosis and treatment of these conditions are discussed in this review. The past decade has seen substantial advances in our understanding of EIA and EIB, including new guidelines on their management. With appropriate therapy, all patients with exercise-related symptoms should be able to reach their desired level of performance.

The small airways and distal lung compartment in asthma and COPD: a time for reappraisal

The involvement of small airways in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been debated for a long time. However, a proper definition of small airway disease is still lacking, and neither a widely accepted biomarker nor a functional parameter to assess small airway abnormalities and to explore the effect of tested compounds on small airways is available. Aiming towards increased knowledge and consensus on this topic, this perspective paper intends to (i) strengthen awareness among the scientific community on the role of small airways in asthma and COPD; (ii) examine the pros and cons of some biological, functional and imaging parameters in the assessment of small airway abnormalities; and (iii) discuss the evidence for distal airway pharmacological targeting in asthma and COPD.

In vitro metabolism of beclomethasone dipropionate, budesonide, ciclesonide, and fluticasone propionate in human lung precision-cut tissue slices

Background

The therapeutic effect of inhaled corticosteroids (ICS) may be affected by the metabolism of the drug in the target organ. We investigated the in vitro metabolism of beclomethasone dipropionate (BDP), budesonide (BUD), ciclesonide (CIC), and fluticasone propionate (FP) in human lung precision-cut tissue slices. CIC, a new generation ICS, is hydrolyzed by esterases in the upper and lower airways to its pharmacologically active metabolite desisobutyryl-ciclesonide (des-CIC).

Methods

Lung tissue slices were incubated with BDP, BUD, CIC, and FP (initial target concentration of 25 μM) for 2, 6, and 24 h. Cellular viability was assessed using adenosine 5'-triphosphate content and protein synthesis in lung slices. Metabolites and remaining parent compounds in the tissue samples were analyzed by HPLC with UV detection.

Results

BDP was hydrolyzed to the pharmacologically active metabolite beclomethasone-17-monopropionate (BMP) and, predominantly, to inactive beclomethasone (BOH). CIC was hydrolyzed initially to des-CIC with a slower rate compared to BDP. A distinctly smaller amount (approximately 10-fold less) of fatty acid esters were formed by BMP (and/or BOH) than by BUD or des-CIC. The highest relative amounts of fatty acid esters were detected for BUD. For FP, no metabolites were detected at any time point. The amount of drug-related material in lung tissue (based on initial concentrations) at 24 h was highest for CIC, followed by BUD and FP; the smallest amount was detected for BDP.

Conclusion

The in vitro metabolic pathways of the tested ICS in human lung tissue were differing. While FP was metabolically stable, the majority of BDP was converted to inactive polar metabolites. The formation of fatty acid conjugates was confirmed for BMP (and/or BOH), BUD, and des-CIC.

Access to inhaled corticosteroids is key to improving quality of care for asthma in developing countries

Asthma is a worldwide public health problem affecting about 300 million people. The majority of persons living with asthma are in the developing world where there is limited access to essential drugs. The financial burden for persons living with asthma and their families, as well as for healthcare systems and governments, is very high. Inadequate treatment and the high cost of medications leads to disability, absenteeism and poverty. Despite the existence of effective asthma medications and international guidelines, and progress made in the implementation of such guidelines over the last decade, the high cost of essential asthma medications remains a major obstacle for patient access to treatment in developing countries. The International Union Against Tuberculosis and Lung Disease has evaluated this problem and created an Asthma Drug Facility (ADF) so that countries can purchase affordable, good quality essential drugs for asthma. The ADF uses pooled procurement along with other purchasing and supply strategies to obtain the lowest possible prices. Accompanied by the implementation of standardized asthma management, the increased affordability of drugs provided by the ADF should bring rapid and significant health and cost benefits for patients, their communities and governments.

Propellant-driven metered-dose inhalers for pulmonary drug delivery

The current market for pulmonary drug delivery is at a bottleneck. The therapeutic advantages of inhalation aerosols, and the potential for the lungs as a route for systemically acting drugs, vaccines and gene therapeutic agents, have resulted in a rapid growth of the industry. Alongside this, the environment of inhaler design and formulation has changed markedly in recent years. Environmental concerns over propellants, the commercial success of dry powder inhalers, and the apparent lack of advancement of propellant-driven metered-dose inhalers (pMDIs) has led to a less clear future for these devices. This review critically assesses these pressures and also potential opportunities for the pMDI. It is proposed that the future role of pMDIs will be determined by several important forces that can be classified under 'technology development' or 'market climate' categories. Technology development forces will be strengthened by the ability of the industry to have a systematic understanding of mechanisms of spray formation, perform subsequent and continued device and formulation advances, and a focus on all patient groups: particularly paediatric and geriatric populations. The ability to succeed in these areas will be largely determined by the willingness to invest in fundamental research of pMDI technologies.

Monitoring the initial pulmonary absorption of two different beclomethasone dipropionate aerosols employing a human lung reperfusion model

BACKGROUND

The pulmonary residence time of inhaled glucocorticoids as well as their rate and extend of absorption into systemic circulation are important facets of their efficacy-safety profile. We evaluated a novel approach to elucidate the pulmonary absorption of an inhaled glucocorticoid. Our objective was to monitor and compare the combined process of drug particle dissolution, pro-drug activation and time course of initial distribution from human lung tissue into plasma for two different glucocorticoid formulations.

METHODS

We chose beclomethasone dipropionate (BDP) delivered by two different commercially available HFA-propelled metered dose inhalers (Sanasthmax/Becloforte and Ventolair/Qvar). Initially we developed a simple dialysis model to assess the transfer of BDP and its active metabolite from human lung homogenate into human plasma. In a novel experimental setting we then administered the aerosols into the bronchus of an extracorporally ventilated and reperfused human lung lobe and monitored the concentrations of BDP and its metabolites in the reperfusion fluid.

RESULTS

Unexpectedly, we observed differences between the two aerosol formulations Sanasthmax/Becloforte and Ventolair/Qvar in both the dialysis as well as in the human reperfusion model. The HFA-BDP formulated as Ventolair/Qvar displayed a more rapid release from lung tissue compared to Sanasthmax/Becloforte. We succeeded to explain and illustrate the observed differences between the two aerosols with their unique particle topology and divergent dissolution behaviour in human bronchial fluid.

CONCLUSION

We conclude that though the ultrafine particles of Ventolair/Qvar are beneficial for high lung deposition, they also yield a less desired more rapid systemic drug delivery. While the differences between Sanasthmax/Becloforte and Ventolair/Qvar were obvious in both the dialysis and lung perfusion experiments, the latter allowed to record time courses of pro-drug activation and distribution that were more consistent with results of comparable clinical trials. Thus, the extracorporally reperfused and ventilated human lung is a highly valuable physiological model to explore the lung pharmacokinetics of inhaled drugs.