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In Vitro - Ex Vivo Correlation of
Fluticasone Propionate Pharmacokinetic Profiles
Maria Börjel1,2, Ewa Selg2 and Per Gerde1,2 ([email protected])
1 Inhalation Sciences Sweden AB, Stockholm, Sweden; 2 Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
INTRODUCTION

In inhalation drug development there is a need not only for traditional particle
Analytical quantitation of FP in all samples from the DissolvIt® and IPL experiments was The key exposure and pharmacokinetic parameters for the IPL and DissolvIt® system characterization data such as size distribution and physicochemical data on the performed by LC/MS/MS, with a LLOQ of 100 pg/ml. are presented in Table 1. formulations, but also for in vitro methods producing data more indicative of subsequent in vivo pharmacokinetic behavior. Here we have compared the pharmacokinetic profiles of the low-solubility inhalation steroid fluticasone propionate (FP) in the promising in FP (Flixotide)
FP (Flutiform)
vitro dissolution/absorption method DissolvIt® (DS) [1] with the well-established Parameter
experimental model for lung pharmacokinetic studies, the ex vivo isolated perfused and The concentration of absorbed FP in the perfusate/blood simulant over time is shown in ventilated rat lung (IPL) [2, 3]. Figure 2A (Flixotide) and 2B (Flutiform). In Figure 2C (Flixotide) and 2D (Flutiform) for both models the amount of FP cleared with the perfusate during each sample interval has been Exp. duration, (min)
expressed as percent of the initially deposited dose clearing per second. This compensates both for the differing deposited doses of the two exposure models and for Tot. Deposited dose, (µg)
the difference between the varying perfusate flow rate of the IPL and the constant flow rate of the DissolvIt® system. In Figure 3A (Flixotide) and 3B (Flutiform) is shown the amount of FP Deposited dose, (µg)
FP still retained in the rat lung and the DissolvIt® lung simulant model at each sample time, expressed as fraction of the initially deposited dose. The retained FP fraction represents , perfusate, (ng/mL)
either undissolved particles or dissolved substance not yet absorbed by the perfusate buffer/blood simulant. Figure 1. The particle size distributions of the generated aerosols for the pMDI formulations containing FP:
Flixotide (1A) and Flutiform (1B).
Fraction retained
(120 min)
Table 1. Key exposure and pharmacokinetic parameters (± standard deviation) for FP (Flixotide and
Two marketed formulations of FP were tested: Flixotide (GSK), (FP, strength 50 µg) and Flutiform) in the IPL and DissolvIt® system. C
: Maximum concentration of drug in the perfusate;
Flutiform (Mundipharma), (FP, strength 250 µg and formoterol strength 10 µg) provided FP (Flixotide) IPL, mean+SD (n=3)
FP (Flutiform) IPL, mean+SD (n=3)
FP (Flutiform) DS, mean+SD (n=3)
: Time to maximum concentration in the perfusate; Fraction perf
: Peak values for the fraction of the
FP (Flixotide) DS, mean+SD (n=3)
as pressurized metered dose inhalers (pMDIs). The canisters were connected to the US deposited dose clearing with the perfusate per second; t
: Time at which Fraction perf
Pharmacopeia Induction Port No 1 of the PreciseInhale® aerosol system and actuated Fraction retained
: Fraction of deposited FP dose left in the DissolvIt® lung simulant and in the rat
(120 min)
into an air flow of 15 L/min. The aerosols were collected in the PreciseInhale® aerosol lung after the 120 min perfusion period; t
: Estimated half-time of drug clearance with the perfusate after
fitting the fraction retained values to a first order decay curve. holding chamber and immediately dispensed to the DissolvIt® and IPL modules at flow rates of 1000 mL/min and 250 mL/min, respectively. DISCUSSION AND CONCLUSIONS
Particle size distributions of the generated aerosols (Figure 1) were measured with an 8-stage Marple cascade impactor at a flow rate of 2 L/min. Previously published methods on in vitro dissolution testing in inhalation drug development, such as the flow through cell, paddle apparatus and the Franz cell, all give At the start of the DissolvIt® experiment, the aerosol particles deposited on the cover slip cumulative dissolution/absorption curves [5, 6] which are not easily comparable to in vivo (with PreciseInhale®) are brought into contact with the mucus consisting of 1.5% pharmacokinetic profiles. In contrast, the DissolvIt® in vitro dissolution/absorption method polyethylene oxide [4] and 0.4% L-alphaphosphatidyl choline (Sigma). The mucus FP (Flixotide) IPL, mean+SD (n=3)
FP (Flutiform) IPL, mean+SD (n=3)
FP (Flixotide) DS, mean+SD (n=3)
FP (Flutiform) DS, mean+SD (n=3)
[1] has a dynamic flow-past perfusion strategy which generates concentration curves simulant had been applied to a polycarbonate membrane corresponding to the basal values. These values can be more readily compared with human membrane of the airway mucosa. The mucus simulant together with the polycarbonate Figure 2. Two different scales are used on the y axes: black for IPL values and pink for DissolvIt® values. The
clinical pharmacokinetic profiles. Here, the rat IPL, previously shown to be a good membrane constitutes the diffusion barrier. On the other side of the membrane, the blood concentrations of FP from the two formulations: Flixotide (A) and Flutiform (B) in the perfusate/blood simulant pharmacokinetic model [2, 3], was used for comparison. over time in the IPL (black curves) and the DissolvIt® (pink curves). Panels C (Flixotide) and D (Flutiform) show simulant (perfusate consisting of phosphate buffer with 4% albumin) is streaming. the percent of deposited doses (IPL black curves and DissolvIt® pink curves) clearing with the perfusate per Dissolved particles were absorbed at a perfusate flow rate of 0.4 ml/min. Dissolution was In Figure 2 it is shown that the profiles in the DissolvIt® are very similar to the IPL profiles, studied by observing particle disappearance using optical microscopy, and by chemical especially for Flixotide. For the normalized perfusate clearance values, the curves are also analysis of substance removed by absorption in the flow-past perfusate. The amount of quite similar in shape. The curves on fraction retained (Figure 3) in the IPL and DissolvIt® FP retained in the system (comparable with the amount of drug retained in lung tissue in models rank both FP formulations similarly. A large fraction of drug is retained in the IPL) was analysed at the end of the 2 h experiments. air/perfusate barriers of both systems, as expected from the low solubility of the FP formulations. One factor contributing to the faster clearance of Flixotide compared to Flutiform in both exposure models, is likely to be the finer particle size distribution of The IPL was prepared as previously described [2]. Briefly, whole lungs were isolated from Flixotide. Clearance with the perfusate from the IPL is faster than from the DS system for female CD IGS (Sprague Dawley) rats (Charles River, Sulzfeld, Germany). The lungs both formulations, which is evident both from the steeper declining retention curves were ventilated with a negative alternating pressure and perfused in single-pass mode (Figure 3) and the nearly doubled normalized perfusate clearance rate of the IPL, as with a Krebs-Henseleit buffer containing 4% albumin. For the exposures of the IPL, the shown in Figures 2C and D. The main reason for this difference is likely to be the thicker FP aerosols actuated via the induction port, were delivered to the lungs (n=3 per 60 µm diffusion barrier of the DS compared to the air/blood barrier of the IPL being formulation) by the PreciseInhale® active dosing system, which calculates in real time the dominated by the µm-thick barrier in the alveolar region. cumulative inhaled aerosol dose. The system automatically terminates the exposure when the inhaled target dose is reached. The liquid propellant evaporated within FP single (Flixotide) IPL, mean+SD (n=3)
FP (FP+FFD/ Flutiform) IPL, mean+SD (n=3)
FP single (Flixotide) DS, mean+SD (n=3)
FP (FP+FFD/ Flutiform) DS, mean+SD (n=3)
It is evident, however, that DissolvIt® can generate pharmacokinetic profiles of FP that PreciseInhale® system, and thus did not reach the lung. The perfusate was repeatedly resemble those in the rat lung. This indicates that DissolvIt® may be a valuable in vitro sampled in an automatic fraction collector during a 2 h period post exposure. Thereafter, Figure 3. The amount of FP from the two formulations: Flixotide (A) and Flutiform (B), as normalized to the
dissolution/absorption method to use for IV-IVC in the development of new and generic the lungs and trachea were harvested for analysis of the amount of FP retained in the initially deposited dose, retained in the rat lung (black curves) and in the DissolvIt® model (pink curves) over tissues after the perfusion period.
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