Adrenal suppression from high-dose inhaled fluticasone propionate in children with asthma.

This cross-sectional study was designed to examine the prevalence of adrenocortical suppression in children with asthma treated with high-dose inhaled fluticasone propionate (FP). Children and adolescents (n=50) with asthma, treated with inhaled FP at a dose of > or = 1,000 mg a day for > or = 6 months, were enrolled. Early morning serum cortisol was performed. Subjects with a serum cortisol of < 400 nmol x L(-1) had a tetracosactrin stimulation test. Fifty subjects of mean age 13.1 yrs were treated with a mean dose of 924.7 microg x m(-2) x day(-1) FP for a mean duration of 2 yrs. Of the 50 subjects, 36 (72%) had serum cortisol levels of < 400 nmol x L(-1) and underwent tetracosactrin stimulation test. Of these, 6 (17%) demonstrated a less than two-fold increase in serum cortisol from baseline and peak cortisol level of < or = 550 nmol x L(-1) at 30 or 60 min poststimulation. There was a significant negative correlation between the dose of FP x m(-2) and stimulated peak cortisol level. Biochemical evidence of adrenocortical insufficiency was demonstrated in 12% of the subjects, indicating that high-dose fluticasone propionate use may be associated with dose-dependent adrenocortical suppression.     

Systemic effects of inhaled fluticasone propionate and budesonide in adult patients with asthma.

We assessed the systemic effects of budesonide (BUD) and fluticasone propionate (FP) in 23 patients with asthma, using a double-blind, placebo-controlled, double-dummy, and cross-over design. The following five treatments were given in a randomized order for 1 wk with a washout period in between of 2 wk: (1) placebo; (2) FP, 200 micrograms twice a day, inhaled from a Diskhaler; (3) FP, 1,000 micrograms twice a day, inhaled from a Diskhaler; (4) BUD, 200 micrograms twice a day, inhaled from a Turbuhaler; and (5) BUD, 800 micrograms twice a day, inhaled from a Turbuhaler. The primary variable was the area under the curve of serum cortisol versus time (AUC0-20), derived from serum samples taken every 2 h over a 20-h period following the last evening dose at 10:00 P.M. The lower doses of BUD and FLU did not cause any adrenal suppression. Compared with placebo, however, FP (1, 000 micrograms, twice daily and BUD (800 micrograms, twice daily) decreased the AUC0-20 by 34 and 16%, respectively. Fluticasone (1,000 micrograms, twice daily) was more suppressive than BUD (800 micrograms, twice daily) (p = 0.0006). The FEV1, measured the morning after the last inhalation, was significantly higher after the active treatments, compared with placebo (p < 0.02), but did not differ between all active treatments. We conclude that high doses of BUD and FP (in particular the latter), inhaled via their respective dry powder inhalers for 1 wk, result in a measurable systemic activity in patients with asthma.     

Step-down compared to fixed-dose treatment with inhaled fluticasone propionate in asthma

BACKGROUND: Inhaled corticosteroids (ICSs) are an effective treatment of asthma even when administered at a low dose. Once asthma is controlled, current guidelines recommend that the dose of ICS be reduced to the lowest possible and effective dose. Although the most appropriate strategy for the stepping down has not yet been defined, quantification of sputum eosinophils and bronchial hyperresponsiveness (BHR) are indeed measures of asthma control. OBJECTIVE: To compare the efficacy of step-down and fixed-dose strategies in the control of BHR to methacholine and eosinophilic inflammation patients with mild-to-moderate asthma. METHODS: We performed a double-blind, randomized study to compare inhaled fluticasone propionate (FP), 1,000 microg/d, then reduced to 200 microg/d (group 1; n = 18) to a fixed dose of FP, 200 microg/d (group 2; n = 17) administered for 6 weeks and then 8 weeks in reducing the provocative dose of methacholine causing a 20% fall in FEV1 (PD20) and sputum eosinophils in 35 patients. The duration of the efficacy was also followed subsequently after 8 weeks of placebo treatment. RESULTS: PD20 remarkably increased with both treatment strategies, but differences between groups were not significant. Sputum eosinophils (median values, percentage) at baseline and after each treatment period were not different (group 1, 16.4 to 1.0 to 2.7%; group 2, 16.7 to 2.8 to 2.8%, respectively). The percentages of patients in whom sputum eosinophilia was normalized (< or = 3%) were as follows: group 1, 69% and 60%; group 2, 50% and 57%. After placebo treatment, sputum eosinophils were still "normalized" in approximately one third of patients. CONCLUSION: Step-down and fixed-dose strategies with FP improved PD20 and sputum eosinophilia to a similar degree. The effect on sputum eosinophils persisted longer than that on methacholine.     

The cost-effectiveness of inhaled fluticasone propionate and budesonide in the treatment of asthma in adults and children.

Inhaled corticosteroids form the mainstay of the treatment and management of asthma and the results of a meta-analysis comparing two of the most frequently prescribed inhaled corticosteroids, fluticasone propionate and budesonide, administered in a clinically equivalent 1:2 dose ratio to 1980 patients with asthma, demonstrated that fluticasone propionate had an improved efficacy:safety ratio. However, limited data are available on the relative economic benefits of fluticasone propionate and budesonide. The database for clinically relevant parameters, for which the efficacy:safety meta-analysis had demonstrated statistical significance between the two corticosteroids, was used for this pharmacoeconomic analysis. Treatment with fluticasone propionate was more cost-effective than budesonide with respect to improvement in morning peak expiratory flow rate, successfully treated weeks, symptom-free days, symptom-free 24 h and episode-free days. The costs of treatment for fluticasone propionate and budesonide were 7.78 Pounds per week and 12.33 Pounds per week, respectively. The main contributing factor to the higher costs of budesonide was the higher cost of health care contacts, which were 4.53 Pounds per week for budesonide and 0.57 Pounds per week for fluticasone propionate. The pharmacoeconomic difference increased in favour of fluticasone propionate as the criteria for success were made more stringent. These results demonstrate that, for asthma patients requiring modification of therapy treatment with fluticasone propionate is more effective and also cheaper, in terms of overall health-care costs, than treatment with budesonide.     

Dose-responses over time to inhaled fluticasone propionate treatment of exercise- and methacholine-induced bronchoconstriction in children with asthma

When treating bronchial hyperresponsiveness to so-called direct and indirect stimuli, distinct pathophysiological mechanisms might require differences in dose and duration of inhaled corticosteroid therapy. To test this hypothesis in children with asthma, we investigated the time- and dose-dependent effects of 2 doses of fluticasone propionate (FP, 100 or 250 microg bid.) in improving exercise- (EIB) and methacholine-induced bronchoconstriction during 6 months of treatment, using a placebo-controlled parallel group study design. Thirty-seven children with asthma (aged 6 to 14 years; forced expired volume in 1 sec (FEV(1)) >/=70% predicted; EIB >/=20% fall in FEV(1) from baseline; no inhaled steroids during the past 4 months) participated in a double-blind, placebo-controlled, 3-arm parallel study. Children receiving placebo were re-randomized to active treatment after 6 weeks. Standardized dry air treadmill exercise testing (EIB expressed as %fall in FEV(1) from baseline) and methacholine challenge using a dosimetric technique (expressed as PD(20)) were performed repeatedly during the study. During FP-treatment, the severity of EIB decreased significantly as compared to placebo within 3 weeks, the geometric mean % fall in FEV(1) being reduced from 34.1% to 9.9% for 100 microg FP bid, and from 35.9% to 7.6% for 250 microg FP bid (P < 0.05). These reductions in EIB did not differ between the 2 doses and were sustained throughout the treatment period. PD(20) methacholine improved significantly during the first 6 weeks as compared to placebo (P < 0.04) and steadily increased with time in both treatment limbs (P = 0.04), the difference in improvement between doses (100 microg FP bid, 1.6 dose steps; 250 microg FP bid, 3.3 dose steps) approaching significance after 24 weeks (P = 0.06). We conclude that in childhood asthma, the protection afforded by inhaled fluticasone propionate against methacholine-induced bronchoconstriction is time- and dose-dependent, whereas protection against EIB is not. This suggests different modes of action of inhaled steroids in protecting against these pharmacological and physiological stimuli. This has to be taken into account when monitoring asthma treatment.     

Comparison of twice-daily inhaled ciclesonide and fluticasone propionate in patients with moderate-to-severe persistent asthma

OBJECTIVE: To investigate the relative efficacy of ciclesonide and fluticasone propionate (FP) administered at comparable microgram doses in maintaining asthma control in patients with moderate-to-severe persistent asthma. METHODS: This randomized, open-label, parallel-group study enrolled patients aged 12-75 years with a 6-month history of bronchial asthma. To enter a 2-week run-in period, patients had to have received FP 500-1000 microg/day or equivalent at a stable dose for 4 weeks and have a forced expiratory volume in 1s (FEV 1) 80% of predicted. To enter the treatment period, patients had to have the following during run-in: FEV 1 80% of predicted; reversibility of Delta FEV 1 12% after 200-400 microg salbutamol; and 1 day without asthma symptoms during the last 7 days. Patients were randomized to twice-daily ciclesonide 320 microg (ex-actuator) or twice-daily FP 330 microg (ex-actuator) for 6 months. Efficacy was assessed by lung function, asthma exacerbations, asthma symptoms and rescue medication use. Patients completed the standardized version of the Asthma Quality of Life Questionnaire (AQLQ[S]). Adverse events (AEs), including local oropharyngeal AEs, were recorded. RESULTS: 528 patients were randomized (ciclesonide, n=255; FP, n=273). In both groups, FEV 1 was maintained from baseline to study end (mean increase: ciclesonide 11 mL, FP 24 mL; intention-to-treat [ITT] analysis). The least squares mean+/-standard error of the mean for the treatment difference was -13+/-29 (95% confidence interval [CI]: -70, 44) in the ITT analysis and -27+/-34 (95% CI: -93, 40) in the per-protocol (PP) analysis, demonstrating non-inferiority of ciclesonide to FP. Morning, evening and site-measured PEF improved significantly with both treatments (ITT and PP analyses: p<0.05). Six patients receiving ciclesonide and seven receiving FP (ITT analysis) experienced an asthma exacerbation requiring treatment with oral corticosteroids. Both treatments significantly decreased asthma symptom score sum (ITT and PP analyses: p0.0001) and rescue medication use (ITT and PP analyses: p<0.05), with no significant difference between treatments. Both treatments significantly improved overall AQLQ(S) score (ITT and PP analyses: p<0.05). Significantly more patients experienced candidiasis and dysphonia with FP compared with ciclesonide (p=0.0023). CONCLUSION: Ciclesonide 320 microg and FP 330 microg administered twice daily over 6 months provided similar efficacy in patients with moderate or severe persistent asthma previously well-controlled by high doses of ICS at baseline. Ciclesonide was associated with fewer local AEs than FP.     

Controlled trial of inhaled fluticasone propionate in moderate to severe COPD

Inhaled corticosteroids are often used in the treatment of stable chronic obstructive pulmonary disease (COPD), however, studies of these agents have had mixed results. Previous trials have often excluded subjects with bronchodilator response, have failed to evaluate effect on gas exchange, and have usually looked at only post- rather than prebronchodilator forced expiratory volume (FEV). Our objective was to better assess the efficacy of topical corticosteroids in the treatment of COPD. We used a prospective, randomized, double-blinded, placebo-controlled, crossover study at the Outpatient Department, Department of Veterans Affairs Medical Center. Thirty-six COPD patients with a mean (± SD) FEV1 of 1.10 ± 0.43 L, with or without significant bronchodilator response participated in the study. Subjects received a 3-month course of inhaled fluticasone propionate (220 mg/puff) or identical-appearing placebo by metered-dose inhaler at 2 puffs twice daily, followed by crossover to the alternative inhaler for an additional 3 months. Fluticasone treatment resulted in a higher prebronchodilator FEV1 (1.17 ± 0.08 L [mean ± SEM] versus 1.07 ± 0.08 L, p = 0.001), a higher PaO2 (66.6 ± 1.4 mmHg versus 63.6 ± 1 .6 mmHg, p = 0.002), and a better dyspnea score on the chronic respiratory questionnaire (3.70 ± 0.18 versus 3.47 ± 0.19, p = 0.03). A trend towards fewer exacerbations with fluticasone did not quite meet statistical significance (p = 0.11). Inhaled fluticasone over 3 months improved prebronchodilator airflow obstruction and oxygenation while decreasing dyspnea in moderate to severe COPD. Postbronchodilator FEV1 was not significantly changed.     

Efficacy of nebulized fluticasone propionate compared with oral prednisolone in children with an acute exacerbation of asthma

The aim of the present study was to investigate the efficacy and safety of nebulized fluticasone propionate (FP Nebules) compared with oral soluble prednisolone in children with an acute exacerbation of asthma. The study used an international, multi-centre, randomized, double-blind, parallel group design. Three hundred and twenty-one patients, aged 4-16 years old, who presented with an acute exacerbation of asthma, were randomly allocated to either nebulized FP (1 mg b.d.) or oral prednisolone (2 mg kg(-1) day(-1) for 4 days then 1 mg kg(-1) day(-1) for 3 days) for 7 days. Patients in the FP group showed a significantly greater increase in diary card morning peak expiratory flow (PEF) over 7 days compared with patients in the prednisolone group (difference = 9.51 min(-1), CI = 2.1, 16.8, P = 0.034). Similar increases for both treatments were shown for evening PEF. Clinic PEF improved with both treatments, but was significantly greater in patients taking FP after 7 days (difference = 11.41 min(-1), CI = 2.8, 20.0, P = 0.029). Both treatments reduced symptom scores to a similar extent. The two treatments were well tolerated, and there was no difference in the incidence of adverse events. The present study demonstrated that nebulized FP is at least as effective as oral prednisolone in the treatment of children presenting with an acute exacerbation of asthma.     

The effect of inhaled fluticasone propionate in the treatment of young asthmatic children: a dose comparison study.

The response in asthmatic young children to inhaled steroids within the usual pediatric dose range is unknown. We therefore evaluated the dose-related response in young children with moderate asthma to inhaled fluticasone propionate (FP) (delivered via the Babyhaler spacer device) within the pediatric dose range. A total of 237 children (mean age 28 mo, range 12 to 47) with moderate asthmatic symptoms were studied in this multicenter, randomized, double-blind, parallel group, placebo-controlled study of 12 wk treatment following a 4-wk run-in period. The median use of rescue medication was 1 dose in 2 d during the run-in period. FP 50 micrograms twice daily (FP100) and 100 micrograms twice daily (FP200) was compared with placebo inhaled from a pressurized metered-dose inhaler (pMDI) and the Babyhaler spacer device. With FP200 there was a statistically significant improvement from baseline, as compared with the placebo group, in 8 of 10 diary card parameters, including the three symptom domains of wheeze, cough, and breathlessness, and use of rescue medication. FP100 produced a significant reduction in 5 of these 10 parameters, whereas no significant differences were found between the FP200 and FP100. The numbers of patients with at least one exacerbation during treatment with placebo, FP100, and FP200 were 37%, 26%, and 20%, respectively. This difference between placebo and FP200, as well as the dose-related order was significant (p < 0.05). Both FP doses were as well tolerated as placebo over the 12 wk treatment with a similar incidence of adverse effects. Asthmatic symptoms in 1- to 3-yr-old children responded in a significant and dose-related manner to treatment with FP within a pediatric dose range.     

Beclometasone dipropionate extrafine aerosol versus fluticasone propionate in children with asthma

Beclometasone dipropionate (BDP) extrafine is a hydrofluoroalkane-based, chlorofluorocarbon (CFC)-free inhalation aerosol. This study was conducted to determine whether BDP extrafine and CFC-fluticasone proprionate (FP) aerosols were equivalent in terms of efficacy and tolerability in children with symptomatic mild-to-moderate asthma. Male and female patients (aged 5-12 yr) with an asthma diagnosis for > or =3 months, peak expiratory flow (PEF) > or =60% of predicted normal and suboptimal asthma control were randomised to double-blind treatment with BDP extrafine 200 microg day(-1) (n=139) or CFC-FP 200 microg day(-1) (n=141) for up to 18 weeks. After 6 and 12 weeks, study medication was 'stepped down' to 100 and 50 microg day(-1), respectively, if patients had achieved good asthma control. Patients with poor asthma control discontinued from the study and those with intermediate control continued in the study but did not undergo a dose reduction. The estimated treatment difference in morning PEF% predicted at 6 weeks was -1.9% (90% CI -4.9, 1.0). There was a trend towards a greater increase in forced vital capacity (% predicted) in the BDP extrafine group (5.3 versus 0.4%; p=0.084). A 'step-down' in therapy to 100 microg day(-1) was possible in 36% and 42% of patients in the BDP extrafine and CFC-FP groups, respectively, at 6 weeks. Both drugs were well tolerated. BDP extrafine and CFC-FP aerosols were equally effective at improving asthma control in children with mild-to-moderate asthma at the same daily dose.     

Improved safety with equivalent asthma control in adults with chronic severe asthma on high-dose fluticasone propionate

OBJECTIVE: High-dose inhaled corticosteroids (ICS) have been associated with the same side-effects as oral corticosteroids. Beclomethasone dipropionate (BDP) and budesonide (BUD) in doses greater than 2000 microg/day are used regularly in severe asthma, despite the fact that safety and efficacy data at such high doses are limited. Fluticasone propionate (FP) has been promoted as being twice as potent clinically as BDP or BUD at doses of 2000 microg/day or less with a similar safety profile. The aim of this study was to compare the efficacy and safety of FP with BDP and BUD in 133 symptomatic adult asthmatics requiring at least 1750 microg/day of BDP or BUD. METHODOLOGY: Patients fulfilling the entry criteria were randomized to receive either their regular ICS medication or FP at approximately half the microgram dose for 6 months in an open, parallel group study. The primary efficacy measure was based on morning peak expiratory flow measurements recorded by patients on daily record cards, while determination of safety was based on a number of endpoints including changes in bone turnover indices, the incidence of topical side-effects and assessments of quality of life. RESULTS: It was shown that patients who were switched to FP, but not those continuing with BDP or BUD, had significant increases in levels of morning serum cortisol and the urine cortisol:creatinine ratio while maintaining asthma control. Serum osteocalcin and the pyridinoline:creatinine ratio, as well as the deoxypyridinoline:creatinine ratio, were also shown to increase only in the FP group. Subjective assessments such as quality of life score, the incidence and ease of bruising, and reports of hoarseness also favoured the FP group. CONCLUSIONS: It is concluded that, at the doses studied and with the delivery devices used clinically, FP is at least as effective as BDP/BUD in the management of severe asthma and may offer clinical advantages with respect to steroid-related adverse effects.     

A comparison of short-term treatment with inhaled fluticasone propionate and zafirlukast for patients with persistent asthma

PURPOSE: To compare the short-term efficacy and safety of low-dose fluticasone propionate with that of oral zafirlukast therapy for patients previously treated with beta-2-agonists alone, and to evaluate the potential therapeutic benefit of switching from zafirlukast to a low-dose inhaled corticosteroid. SUBJECTS AND METHODS: This study consisted of a 4-week randomized, double-blind treatment period followed by a 4-week open-label period. Two hundred ninety-four patients > or =12 years old with asthma previously uncontrolled with beta-2-agonists alone were randomly assigned to treatment with low-dose inhaled fluticasone (88 microg twice daily) or oral zafirlukast (20 mg twice daily). After 4 weeks, all patients discontinued their double-blind therapy and received open-label fluticasone (88 microg twice daily). Outcomes included pulmonary function, asthma symptoms, albuterol use, asthma exacerbations, and adverse events. RESULTS: During the double-blind treatment period, fluticasone patients had significantly greater improvements in morning peak flow (29.3 L/min vs. 18.3 L/min), percentage of symptom-free days (19.8% vs. 11.6%), and daily albuterol use (-1.8 puffs per day vs. -1.1 puffs per day) compared with zafirlukast patients (P < or =0.025, each comparison). During the open-label treatment period, patients switched from zafirlukast to fluticasone experienced additional improvements in morning peak flow (17.2 L/min), evening peak flow (13.6 L/min), and FEV(1) (0.11 liter) and daily albuterol use (-0.9 puffs daily) compared with values obtained at the end of the double-blind treatment period (P < or =0.001, each comparison). CONCLUSION: Low-dose fluticasone was more effective than zafirlukast in improving pulmonary function and symptoms in patients with persistent asthma. In addition, switching patients from zafirlukast to fluticasone further improved clinical outcomes.     

HPA-axis effects of nebulised fluticasone propionate compared with oral prednisolone in childhood asthma

The aim of this study was to compare the effect of 7 days nebulised fluticasone propionate (FP) with oral prednisolone on 24-h urinary-free cortisol excretion, systemic exposure and safety. This was a randomised, double-blind, double-dummy, two-way crossover study. Thirty-one children (19 male, 12 female, mean age 8 years) with stable asthma were randomly assigned to 7 days treatment with either FP Nebules (2 x 0.5 mg/2 ml bd) or prednisolone tablets once daily (2 mg/kg/day for 4 days [maximum 40 mg] followed by 1 mg/kg/day or half the original dose for 3 days [maximum 20 mg]). After a 2-4 week washout period, patients received the second treatment for 7 days, followed by a 2-week follow-up visit. The primary outcome measure was 24-h urinary-free cortisol concentrations corrected for creatinine. Nebulised FP (1 mg bd) had significantly less effect on 24-h urinary-free cortisol excretion than oral prednisolone (8.9 ng/ml for FP and 5.0 ng/ml for prednisolone, P = 0.001). Systemic exposure to FP was also low. In conclusion, FP Nebules had significantly less effect on hypothalamic-pituitary-adrenal axis function than oral prednisolone in asthmatic children when used at doses recommended for the treatment of an acute exacerbation of asthma.     

Interferon-alphacon-1 treatment of three patients with severe glucocorticoid-dependent asthma. Effect on disease control and systemic glucocorticosteroid dose

We report herein the therapeutic effect of interferon (IFN)-alphacon in three patients with severe persistent asthma and long-term oral glucocorticoid treatment. IFN-alphacon (9 microg) administered subcutaneously thrice a week over a period of more than 24 months led to a substantial clinical improvement with regard to the number of daily asthma attacks, nighttime disturbance, emergency visits and hospitalizations. In addition, lung function and exercise capacity improved. At the same time, treatment with IFN allowed discontinuation of the daily glucocorticoid dose in all patients for the first time in more than 8 years. Our findings suggest that IFN-alphacon leads to a significant clinical improvement while at the same time allowing reduction and discontinuation of the glucocorticoid treatment in severe persistent glucocorticoid-dependent asthma.     

Comparison of add-on therapy to inhaled fluticasone propionate in children with asthma: residual volume and exhaled nitric oxide as outcome measures.

The purpose of this study was to evaluate changes in lung function and fractional exhaled nitric oxide (FeNO) in children with mild to moderate persistent asthma treated with low-dose inhaled steroids but still manifesting significantly increased residual volume (RV). This was a crossover study evaluating lung function and FeNO before and after a 2-week crossover therapy period by adding either montelukast or salmeterol to inhaled fluticasone propionate in 12 children with asthma. Salmeterol increased forced expiratory volume at 1 second (FEV(1)) and decreased RV without effects on eNO. Addition of montelukast produced a statistically significant decrease both for RV (from 191.7 +/- 60.8% to 132.4 +/- 36.1%; p = 0.03) and for eNO (from 14.0 +/- 6.3 ppb to 8. 5+/- 5.0 ppb; p < 0.01). No effect was observed for the montelukast treatment period in FEV(1) and forced expiratory flow at 25-75%. Add-on therapy may reduce RV and decrease levels of FeNO, leading to consideration of a possible anti-inflammatory additive effect that could improve the control of the disease.     

Bioavailability of inhaled fluticasone propionate via chambers/masks in young children

We determined lung bioavailability of a fluticasone propionate (FP) pressurised metred-dose inhaler (Flovent HFA; GlaxoSmithKline, Research Triangle Park, NC, USA) administered via AeroChamber Plus (Monaghan Medical, Plattsburgh, NY, USA) with Facemask and Babyhaler (GlaxoSmithKline) valved holding chambers (VHCs) using a population pharmacokinetic approach. Children from 1 to <4 yrs of age with stable asthma but a clinical need for inhaled corticosteroid therapy were administered 88 μg FP hydrofluoroalkane (2 × 44 μg) twice daily delivered through the two devices in an open-label, randomised crossover manner for 8 days each. Patients were randomised to one of three sparse sampling schedules for blood collection throughout the 12-h dosing interval on the 8th day of each treatment for pharmacokinetic analysis. The area under the FP plasma concentration-time curve (AUC) was determined for each regimen. 17 children completed the study. The population mean AUC following FP with AeroChamber Plus with Facemask was 97.45 pg·h·mL(-1) (95% CI 85.49-113.32 pg·h·mL(-1)) and with Babyhaler was 51.55 pg·h·mL(-1) (95% CI 34.45-64.46 pg·h·mL(-1)). The relative bioavailability (Babyhaler/AeroChamber Plus) was 0.53 (95% CI 0.30-0.75). Clinically significant differences in lung bioavailability were observed between the devices. VHCs are not interchangeable, as differences in drug delivery to the lung may occur. A population pharmacokinetic approach can be used to determine lung bioavailability of FP.