Deposition and effects of inhaled corticosteroids

Co-electrospraying technology as a novel approach for dry powder inhalation formulation of montelukast and budesonide for pulmonary co-delivery

In the current study electrospraying methodology was used for particle engineering of montelukast and budesonide to prepare a combined inhalable dry powder formulation applicable as a smart regimen in asthma treatment. For this, electrospraying was carried out using different solvents and drug concentrations. No carrier was added for the formulation of montelukast-budesonide combination as montelukast played the role of both active ingredient and carrier. Scanning electron microscopy, particle size analysis, gas chromatography, powder X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry were used to evaluate the physicochemical properties of the produced drug particles. In vitro drug deposition pattern was assessed using next generation impactor, and the dissolution profile of the selected formulations was characterized via modified diffusion franz cell method. The FPF value for the co-electrosprayed carrier free formulation of montelukast-budesonide was 38% with a significantly enhanced dissolution rate for budesonide compared to the budesonide alone formulations. The pharmacological effects of hypothesized combined formulation was assessed by measuring its power to inhibit the production of reactive oxygen species in human normal lung cells. The results showed that the combination of montelukast and budesonide can exert a synergistic effect. The findings in the current study emphasize that using montelukast as a carrier for budesonide not only has greatly improved the aerosolization behavior and dissolution rate of budesonide but also has resulted in synergistic pharmacological effects, indicating the suitability of this combination as an anti-asthmatic therapeutic.

Size distribution of salbutamol/ipratropium aerosols produced by different nebulizers in the absence and presence of heat and humidification

BACKGROUND

Few studies have evaluated the size distribution of inhaled and exhaled aerosolized drugs, or the effect of heated humidification on particle size and lung deposition. The present study evaluated these aspects of bronchodilator (salbutamol/ipratropium) delivery using a lung model in the absence and presence of heat and humidification.

METHODS

We positioned filters to collect and measure the initial drug, inhaled drug, and exhaled drug. Particle size distribution was evaluated using an 8-stage Marple personal cascade impactor with 0.2-μm polycarbonate filters.

RESULTS

A greater inhaled drug mass was delivered using a vibrating mesh nebulizer (VMN) than by using a small volume nebulizer (SVN), when heated humidifiers were not employed. When heated and humidified medical gas was used, there was no significant difference between the inhaled drug mass delivered by the VMN and that delivered by the SVN. A significantly greater mass of inhaled 1.55-μm drug particles was produced by the VMN than with the SVN, under heated and humidified conditions. However, the mass median aerodynamic diameters (MMADs) of the aerosolized drug produced by the SVN and VMN did not differ significantly under the same conditions.

CONCLUSIONS

The VMN produced more fine particles of salbutamol/ipratropium, and the drug particle size clearly increased in the presence of heat and humidification.

Metabolism of beclomethasone dipropionate by cytochrome P450 3A enzymes

Inhaled glucocorticoids, such as beclomethasone dipropionate (BDP), are the mainstay treatment of asthma. However, ≈ 30% of patients exhibit little to no benefit from treatment. It has been postulated that glucocorticoid resistance, or insensitivity, is attributable to individual differences in glucocorticoid receptor-mediated processes. It is possible that variations in cytochrome P450 3A enzyme-mediated metabolism of BDP may contribute to this phenomenon. This hypothesis was explored by evaluating the contributions of CYP3A4, 3A5, 3A7, and esterase enzymes in the metabolism of BDP in vitro and relating metabolism to changes in CYP3A enzyme mRNA expression via the glucocorticoid receptor in lung and liver cells. CYP3A4 and CYP3A5 metabolized BDP via hydroxylation ([M4] and [M6]) and dehydrogenation ([M5]) at similar rates; CYP3A7 did not metabolize BDP. A new metabolite [M6], formed by the combined action of esterases and CYP3A4 hydroxylation, was also characterized. To validate the results observed using microsomes and recombinant enzymes, studies were also conducted using A549 lung and DPX2 liver cells. Both liver and lung cells produced esterase-dependent metabolites [M1-M3], with [M1] correlating with CYP3A5 mRNA induction in A549 cells. Liver cells produced both hydroxylated and dehydrogenated metabolites [M4, M5, and M6], but lung cells produced only the dehydrogenated metabolite [M5]. These studies show that CYP3A4 and CYP3A5 metabolize BDP to inactive metabolites and suggest that differences in the expression or function of these enzymes in the lung and/or liver could influence BDP disposition in humans.

Aerosol deposition in health and disease

The success of inhalation therapy is not only dependent upon the pharmacology of the drugs being inhaled but also upon the site and extent of deposition in the respiratory tract. This article reviews the main mechanisms affecting the transport and deposition of inhaled aerosol in the human lung. Aerosol deposition in both the healthy and diseased lung is described mainly based on the results of human studies using nonimaging techniques. This is followed by a discussion of the effect of flow regime on aerosol deposition. Finally, the link between therapeutic effects of inhaled drugs and their deposition pattern is briefly addressed. Data show that total lung deposition is a poor predictor of clinical outcome, and that regional deposition needs to be assessed to predict therapeutic effectiveness. Indeed, spatial distribution of deposited particles and, as a consequence, drug efficiency is strongly affected by particle size. Large particles (>6 μm) tend to mainly deposit in the upper airway, limiting the amount of drugs that can be delivered to the lung. Small particles (<2 μm) deposit mainly in the alveolar region and are probably the most apt to act systemically, whereas the particle in the size range 2-6 μm are be best suited to treat the central and small airways.

Convective flow dominates aerosol delivery to the lung segments

Most previous computational studies on aerosol transport in models of the central airways of the human lung have focused on deposition, rather than transport of particles through these airways to the subtended lung regions. Using a model of the bronchial tree extending from the trachea to the segmental bronchi (J Appl Physiol 98: 970-980, 2005), we predicted aerosol delivery to the lung segments. Transport of 0.5- to 10-μm-diameter particles was computed at various gravity levels (0-1.6 G) during steady inspiration (100-500 ml/s). For each condition, the normalized aerosol distribution among the lung segments was compared with the normalized flow distribution by calculating the ratio (R(i)) of the number of particles exiting each segmental bronchus i to the flow. When R(i) = 1, particle transport was directly proportional to segmental flow. Flow and particle characteristics were represented by the Stokes number (Stk) in the trachea. For Stk < 0.01, R(i) values were close to 1 and were unaffected by gravity. For Stk > 0.01, R(i) varied greatly among the different outlets (R(i) = 0.30-1.93 in normal gravity for 10-μm particles at 500 ml/s) and was affected by gravity and inertia. These data suggest that, for Stk < 0.01, ventilation defines the delivery of aerosol to lung segments and that the use of aerosol tracers is a valid technique to visualize ventilation in different parts of the lung. At higher Stokes numbers, inertia, but not gravitational sedimentation, is the second major factor affecting the transport of large particles in the lung.

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.

A multinational, 12-week, randomized study comparing the efficacy and tolerability of ciclesonide and budesonide in patients with asthma

BACKGROUND

Ciclesonide is a new lung-activated inhaled corticosteroid (ICS) that has shown efficacy in previous placebo-controlled and comparative studies in patients with persistent asthma. It is important to compare new treatments with existing ICSs to obtain relative data concerning their efficacy and tolerability.

OBJECTIVE

This study compared the efficacy and tolerability of ciclesonide QD with budesonide BID in patients with asthma.

METHODS

This 12-week, randomized study was conducted at 62 study sites across Europe. Male and female patients aged 12 to 75 years with primarily mild to moderate asthma were enrolled. This study was double blind with respect to the ciclesonide dose and open label for budesonide, as placebofor budesonide was not available. Patients were randomly assigned to receive inhaled ciclesonide 80 or 320 microg QD (morning) or budesonide 200 microg BID for 12 weeks. Efficacy and tolerability assessments were performed at weeks 0 (baseline), 4, 8, and 12. The primary end point was the change from baseline in forced expiratory volume in 1 second (FEV1) at 12 weeks. Secondary end points were changes from baseline in morning peak expiratory flow (PEF), asthma symptom scores, and rescue medication use. Tolerability was assessed throughout the study by monitoring of standard laboratory variables (hematology and biochemistry); physical examination, including vital signs; reporting of adverse events (AEs); and 24-hour urinary cortisol as a measure of hypothalamic-pituitary-adrenal-axis function.

RESULTS

Five hundred fifty-four patients were randomized (301 men, 253 women; mean age, 41.3 years; ciclesonide 80 microg QD, 182 patients; ciclesonide 320 microg QD, 195; budesonide 200 microg BID, 177). Demographic and baseline clinical characteristics, including age, sex, weight, and (FEV1) were similar between the 3 groups. Compared with baseline values, week-12 FEV1 (least squares mean [LSM] [SEM] A, +0.267 [0.035], +0.256 [0.033], and +0.355 [0.034] L, respectively; all, P<0.001) and morning PEF (LSM [SEM] Delta, +12 [5], +17 [4], and +21 [4] L/min, respectively; all, P<or=0.008) were significantly improved with ciclesonide 80 and 320 microg QD and budesonide 200 microg BID. At 12 weeks, ciclesonide was found to be noninferior to budesonide with regard to mean changes from baseline in (FEV1) (intent to treat [ITT]: 97.5% CI for ciclesonide 80 microg QD vs budesonide 200 microg BID, -0.192 to 0.015; 97.5 CI for ciclesonide 320 microg QD vs budesonide 200 microg BID, -0.200 to 0.001) and morning PEF (ITT. 97.5% CI for ciclesonide 80 microg QD vs budesonide 200 microg BID, -22 to 5; 97.5% CI for ciclesonide 320 microg QD vs budesonide 200 microg BID, -17 to 10). Similar findings were seen in the per-protocol population. Week-12 daily, daytime, and nighttime asthma symptom scores and rescue medication use were significantly decreased from baseline in all 3 treatment groups (all, P<0.001). The prevalences of AEs were similar across all 3 treatment groups. Week-12 mean urinary cortisol excretion was statistically similar to baseline with both ciclesonide doses (Delta, -0.54 and +0.16 nmol/mmol creatinine with ciclesonide 80 and 320 microg QD, respectively) but was significantly reduced from baseline with budesonide (Delta, -1.42 nmol/mmol creatinine; P<0.05).

CONCLUSIONS

The results of this study in patients with primarily mild to moderate asthma suggest that ciclesonide 80 and 320 microg QD were similar to budesonide 200 microg BID in improving pulmonary function, controlling asthma symptoms, and reducing the need for rescue medication use. Unlike budesonide, ciclesonide was not associated with significant urinary cortisol suppression in these patients.

In Vitro metabolism of ciclesonide in human lung and liver precision-cut tissue slices

Ciclesonide is a new-generation inhaled corticosteroid developed to treat the inflammation associated with persistent asthma. In order to identify the properties of ciclesonide responsible for anti-inflammatory activity, ciclesonide metabolism was investigated in human lung and liver precision-cut tissue slices. Three human lung and three human liver tissue slices were incubated with 25 microM [14C]-ciclesonide for 2, 6 and 24 h. Cellular viability was assessed using adenosine 5'-triphosphate content and protein synthesis in lung slices and adenosine 5'-triphosphate content and potassium retention in liver slices. Ciclesonide and ciclesonide metabolites were analysed in tissue samples using high-performance liquid chromatography with ultraviolet and radiochemical detection. Metabolite identity was confirmed using mass spectrometry. In lung slices, the inactive parent compound, ciclesonide, was initially converted to the active metabolite, desisobutyryl-ciclesonide, and subsequently converted to fatty acid conjugates. The reversible formation of fatty acid conjugates was a major pathway of ciclesonide metabolism in human lung slices. The primary conjugate was identified as desisobutyryl-ciclesonide oleate. Ciclesonide was metabolized to at least five polar metabolites in the liver. Dihydroxylated desisobutyryl-ciclesonide was the major polar metabolite in liver slices. Activation and fatty acid esterification in the lung followed by rapid inactivation in the liver may explain the improved safety profile and prolonged anti-inflammatory activity of ciclesonide.

Side effects with inhaled corticosteroids: the physician's perception

The National Asthma Education and Prevention Program 1997 guidelines and 2002 update provide an overview of potential local and systemic side effects associated with inhaled corticosteroids (ICS) and suggest ways of minimizing the risk of these side effects occurring. Despite the guidelines and extensive clinical experience of the safe use of ICS, a significant number of physicians retain concerns regarding side effects. Local side effects may lead to patients discontinuing therapy, with or without the knowledge of their physicians. In particular, concerns regarding systemic side effects, such as growth retardation in children and osteoporosis, remain relatively widespread. Pharmacokinetic studies reveal that different ICS compounds and formulations result in different degrees of systemic bioavailability, indicating possible differences in their potential to cause systemic side effects. However, clinical studies that can be used to differentiate between ICS formulations are generally lacking. Consequently, there is a need to continue to further our understanding of side effects with ICS, with the aim of identifying formulations, devices, and doses with an optimal risk/benefit ratio. The introduction of new agents with potentially improved safety profiles may reassure physicians and patients as to the relative benefits of ICS therapy in asthma.

Pharmacokinetic/pharmacodynamic evaluation of inhalation drugs: application to targeted pulmonary delivery systems

Inhaled therapy with either glucocorticoids and/or beta(2)-adrenergic drugs remains the mainstay of asthma treatment. In the last few years, a number of new products have been introduced into the market with the goal of improving efficacy and safety. This review article summarises the pharmacokinetic and pharmacodynamic properties of inhaled drugs for topical delivery necessary to achieve this goal. Pharmacokinetic properties include a high pulmonary deposition, low oral bioavailability, optimised pulmonary residence time and a very high systemic clearance. Optimisation of pharmacodynamic properties, such as receptor selectivity, may also yield drugs with improved pulmonary selectivity. As existing drugs also provide high efficacy and safety profiles, future developments will represent only slight improvements and quantum leap improvements are unlikely to occur.

Formation of fatty acid conjugates of ciclesonide active metabolite in the rat lung after 4-week inhalation of ciclesonide

Ciclesonide, an inhaled corticosteroid (ICS) with prolonged anti-inflammatory activity, is being developed for the treatment of asthma. Fatty acid conjugation of ICS is thought to be related to prolonged ICS activity. In vitro studies demonstrated that ciclesonide is converted to an active metabolite, desisobutyryl-ciclesonide (des-CIC), which undergoes reversible fatty acid conjugation. We tested the in vivo metabolism of ciclesonide in the lung by exposing rats to inhaled ciclesonide (0.16 mg/kg/day) for 1h daily over 4 weeks. Lungs (n=6 per time point) were extracted with ethanol 2, 5, and approximately 27 h after the final treatment. Ciclesonide and des-CIC concentrations were determined using solid-phase extraction and reverse-phase high-performance liquid chromatography with tandem mass spectrometry (LC/MS/MS). Concentrations of fatty acid ester conjugates were indirectly assessed using enzymatic de-esterification before LC/MS/MS. At 2 and 5 h, fatty acid conjugates of des-CIC were the major metabolites (61 and 55%, respectively). Ciclesonide, des-CIC, and fatty acid conjugates of des-CIC were clearly present in lung samples the day after the last inhalation. This in vivo study confirmed ciclesonide activation to des-CIC and formation of fatty acid conjugates. The presence of des-CIC fatty acid conjugates at >24 h after dosing suggests that ciclesonide is appropriate for once-daily dosing.

Comparative improvement of asthma symptoms and expiratory flows after corticosteroid treatment: a method to assess the effect of corticosteroids on large vs. small airways?

The magnitude of improvement of respiratory symptoms (RS) and expiratory flows (EF) following corticosteroid treatment may vary from one asthmatic patient to another. The distribution of ratio of improvement of the above parameters was assessed in 937 patients with asthma of variable severity who took part in three clinical trials comparing the effects of chlorofluorocarbon-propelled beclomethasone dipropionate (CFC-BDP) with similar (n:316) or half-doses (n:581) of extrafine hydrofluoroalkane-propelled (HFA-BDP) on asthma control. We calculated the ratio of improvement of shortness of breath, wheezing, sleep disturbance, cough, and chest tightness over the following physiological parameters: forced expiratory volume in 1s (FEV1), FEF(25/75%), morning peak expiratory flow, and FVC, from the baseline value to the last set of measures in the study, while on the study medication. We hypothesized that the ratio of RS/EF would have a normal distribution and would be higher with extrafine HFA-BDP compared with CFC-BDP, which has a larger particle size, when FEV1 is used, as it mostly assesses large airways. Ratios of improvement were normally distributed for both drugs and no significant shift in its distribution curve was found for HFA-BDP. The ratio of changes in FEF(25/75%)/FEV1 was similar in the two groups. In conclusion, the ratio of improvement of RS/EF is normally distributed over a narrow range, showing a generally good correlation between improvements in EF and symptoms in asthma; it was, however, similar for the two BDP molecules tested. This may suggest that this ratio is not useful for evaluating the effect of corticosteroids on small airways, or that extrafine HFA-BDP acts at the level of large- to moderate-caliber airways to produce most of its beneficial effect.