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CLINICAL STUDIES

Lung Deposition of Radiolabeled Tiotropium in Healthy Subjects and Patients With Chronic Obstructive Pulmonary Disease

Peter Brand, PhD, Thomas Meyer, MD, Thomas Weuthen, Wolfgang Timmer, MD, Erhard Berkel, Gudrun Wallenstein, PhD and Gerhard Scheuch, PhD

From Inamed Research GmbH & Co KG, Institute for Aerosol Medicine, Gauting, Germany (Dr Brand, Dr Meyer, Mr Weuthen); Boehringer Ingelheim Pharma GmbH & Co KG, Ingelheim, Germany (Dr Timmer, Mr Berkel, Dr Wallenstein); and Activaero GmbH, Gemünden, Germany (Dr Scheuch).

Address for correspondence: Peter Brand, PhD, Inamed Research GmbH & Co KG, Robert-Koch-Allee 29, D-82131 Gauting, Germany 82131; e-mail: brand{at}inamed.de.


   ABSTRACT
TOP
 ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 ACKNOWLEDGEMENTS
 REFERENCES
 
Lung deposition of 18 µg tiotropium administered via a dry-powder inhaler was investigated in 5 healthy subjects and patients with mild (n = 4), moderate (n = 6), and severe (n = 5) chronic obstructive pulmonary disease after 14 days of treatment with 18 µg tiotropium. On day 15, subjects inhaled 2 capsules of radiolabeled tiotropium, and lung deposition was assessed using {gamma} scintigraphy. Repeated plasma and urine collections were performed on days 14 and 15. Mean delivered dose from the dry-powder inhaler was 45.1%. Mean lung deposition relative to the delivered dose was 42% (19%, relative to nominal dose) with low intersubject variability (20%). Mean extrathoracic deposition was 57.5% (25.8%, relative to nominal dose). There were no significant differences in deposition among the subgroups. No significant correlation between individual tiotropium deposition and lung function was observed. These results suggest that all stages of chronic obstructive pulmonary disease may gain full therapeutic benefit from the drug.

Key Words: COPD • tiotropium • Handihaler • lung deposition

Cholinergic mechanisms play an important role in the pathophysiology of diseases characterized by chronic airway obstruction, particularly in chronic obstructive pulmonary disease (COPD). Tiotropium is a novel, once-daily inhaled anticholinergic that has been developed for the maintenance treatment of COPD.1-7 One of most important properties of tiotropium is its long duration of action that allows once-daily treatment. Tiotropium is available in a powder formulation that is inhaled using a dry-powder inhaler.8 Tiotropium powder capsules contain 18 µg tiotropium base as bromide monohydrate and have recently been registered for clinical use in many countries.

In this {gamma}-scintigraphic study, the lung deposition of tiotropium administered via the dry-powder inhalation device was investigated in a group of healthy subjects and in 3 subgroups of patients with mild, moderate, and severe COPD. Furthermore, the efficacy, tolerability, and pharmacokinetics were evaluated, and correlations between individual lung function values and tiotropium deposition were explored.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 CONCLUSION
 ACKNOWLEDGEMENTS
 REFERENCES
 
Study Design
Twenty subjects (5 healthy subjects and 15 COPD patients) participated in the study (study code 205.238). This was a single-center, open-label, 1-period, 1-treatment, repeated-dose study design. Following an initial screening visit, subjects entered a 2-week run-in period. Then, the study participants entered a 14-day treatment period during which they received a daily dose of 18 µg nonradiolabeled tiotropium. Because studies have shown that a therapeutic steady state is reached after 1 week of treatment,9 a treatment duration of 14 days seemed to be appropriate to mimic the clinical situation. On day 14, repeated pulmonary function testing was performed in the group of COPD patients. On treatment day 15, 2 capsules with the radiolabeled tiotropium powder formulation were administered, and the distribution pattern of deposited radiolabeled tiotropium was measured by {gamma} scintigraphy. Immediately prior to inhalation of the radiolabeled tiotropium, predose lung function measurements were performed both in the group of healthy subjects and COPD patients. Blood and urine samples for pharmacokinetic purposes were obtained on days 14 and 15.

Inhalation
Inhalation of tioptropium was performed using the dry-powder inhalation device (Handihaler). After loading the device with 1 capsule of tiotropium (Spiriva), the capsule is pierced, and the patient inhales the contents of the capsule through the mouthpiece according to the description in the patient's information. It was not possible to measure the actual flow rates used by each patient during the inhalation maneuver.

Subjects
A total of 20 subjects (5 healthy subjects and 15 COPD patients) completed the study. Three subjects were excluded from the study (1 healthy subject and 2 patients with COPD) due to adverse events that were not related to the study medication (1 cardiac infarction and 2 exacerbations of COPD). Fifteen patients with a clinical history of COPD were sub-classified according to their lung function at screening: 4 patients had mild COPD, 6 patients had moderate COPD, and 5 patients suffered from severe COPD. The classification was based on the criteria suggested by the American Thoracic Society.10 All COPD patients had a smoking history of more than 10 pack-years. Healthy subjects were lifelong non-smokers or ex-smokers with a nonsmoking period of at least 5 years and a maximum of 5 pack-years.

The mean age of the study participants was as follows:

Healthy subjects (n = 5): 52 years (range, 44-66 years)

Patients with mild COPD (n = 4): 55 years (range, 45-72 years)

Patients with moderate COPD (n = 6): 55 years (range, 48-62 years)

Patients with severe COPD (n = 5): 59 years (range, 57-62 years)

Patients with stable COPD had to meet the following spirometric criteria (pre-bronchodilator-forced expiratory volume in 1 second [FEV1]):

Mild COPD: 50% of pred ≤ FEV1 < 70% of pred and FEV1/FVC < 70%

Moderate COPD: 35% of pred ≤ FEV1 < 50% of pred and FEV1/FVC < 70%

Severe COPD: FEV1 < 35% of pred and FEV1/FVC < 70%

Informed written consent was obtained from each subject. The study protocol was approved by the ethics committee of the medical faculty of Ludwig-Maximilian University (Munich, Germany).

Radiolabeling
The tiotropium-lactose powder mixture, labeled 99mTechnetium (99mTc), was the following: the 99mTc (pertechnetate) from the generator was mixed with ethanol, which was reduced to 50 µL. Subsequently, n-Hexan was added to this solution. This mixture was then added to the tiotropium powder and was dried in a rotation dryer. The labeled tiotropium powder was blended with lactose. No more than 2 MBq 99mTc was added per capsule. After radiolabeling, impactor measurements were performed to demonstrate that the aerosol particle distribution of the labeled drug was the same as the distribution of commercially available tiotropium powder. In this test, the distribution of the radioactively labeled powder on the impactor stages was measured by {gamma} scintigraphy and compared to the distribution of the drug on the stages, measured by high-performance liquid chromatography (HPLC). Tiotropium was determined by HPLC with a RP-8 column and with UV detection at 240 nm. A mixture of 700 mL aqueous 1-heptane sulfonic acid solution (about 8 mM, adjusted to pH 3.2 with phosphoric acid) and 330 mL acetonitrile was used as eluent. Starting from a 1-point calibration with an external standard solution of about 1 µg/mL, the amount of tiotropium in the samples could be calculated. The variation coefficient of 6 injections should be less than 2%. The tailing factor at the beginning and at the end of the measurement has to be <2.0, and the recovery has to be 97.0% to 103.0%. The mass median aerodynamic diameter (MMAD), derived from the distribution of radioactivity, was 4.0 µm (geometric standard deviation [GSD] = 1.7). For the distribution of drug (HPLC), MMAD = 4.1 (GSD = 1.7).

Deposition Measurement
For technical reasons, 2 capsules of radiolabeled compound had to be inhaled in quick succession in front of a planar gamma camera (Siemens Diacam) to deliver a total activity that was high enough to obtain gamma pictures of good quality. Exhalation was performed into a exhalation filter. Immediately after inhalation, gamma camera images were taken (2-minute sequences up to 6 minutes after inhalation). This short acquisition time was chosen to prevent errors due to the leaching of the radiolabel and to keep the redistribution within the lungs small. To identify the lung contours and to identify regions of interest (left lung, right lung, oropharynx, stomach), a ventilation gamma scan of the lungs was obtained using 81mKrypton (81mKr) gas.

From the gamma camera image, the following parameters were calculated:

Activity within the lung region, AL

Activity within the extrathoracic region, including the oropharynx, trachea, esophagus, and stomach, AET

For the following objects, the amount of radioactivity was measured using a sensitive scintillation counter:

Activity within the filled capsule, Ao

Activity of the exhalation filter, AEx

Remaining activity within the capsule and the inhalation device, AI

From these activity data, the following parameters were calculated:

Emitted dose:

Formula

Lung deposition relative to fill weight (nominal dose):

Formula

Extrathoracic deposition relative to fill weight (nominal dose):

Formula

In addition, deposition was expressed as percentage of the emitted dose: DL,e and DE,e.

The distribution of deposition within the lungs was quantified using central to peripheral (C/P) ratios. Therefore, using the krypton ventilation scan, the lung contours were assessed. Then the lungs were approximated by 2 rectangles. Within these rectangles, 2 smaller rectangles representing central lung regions were introduced. The width of these central rectangles was chosen so that it was, horizontally as well as vertically, half the width of the whole lung rectangle. The count ratios of these rectangles were calculated (C/P) and normalized to the C/P ratio of the krypton scan. C/P increases if deposition is occurring more centrally.

Corrections for {gamma} attenuation of the body tissue were performed according to Pitcairn and Newman.11

Spirometry
All spirometric measurements were performed using a Jäger-Masterlab device (Viasys, Würzburg, Germany). Parameters of interest were the forced expiratory volume in 1 second (FEV1), the forced vital capacity (FVC), and the intrathoracic gas volume (ITGV). Measured lung function parameters were normalized to the reference values (% of predicted [%pred]) proposed by the European Community for Steel and Coal.12

Pharmacokinetic Measurements
EDTA anticoagulated blood samples for quantification of tiotropium plasma concentrations were taken predose on treatment days 1, 9, 14, and 15; on day 14 also at 5, 10, and 20 minutes and 1, 2, 4, and 8 hours after drug administration; and on day 15 also at 20 minutes and 2 hours after dosing. The blood samples for pharmacokinetic analysis were centrifuged immediately after collection for 10 minutes (3000 rpm), and 2 aliquots of EDTA plasma samples were obtained.

All urine voided during the sampling intervals from 0 to 4 hours and 4 to 8 hours after administration on days 14 and 15 was collected in containers with known empty weight. To avoid ester cleavage, 5 g of 1-M citric acid solution was given in each container beforehand. The complete urine fractions were homogenized and weighed. Aliquots of 20 mL were taken.

Tiotropium cation concentrations in plasma and urine were determined by a validated HPLC tandem mass spectrometry (MS/MS) assay. The results of these measurements were quantified by

the total tiotropium urinary excretion over 8 hours on day 15,

the maximum tiotropium plasma concentration on day 14 (Cmax), and

the area under the 4-hour time course of the plasma concentration (AUC0-4h).

Data Analysis
The aim of this study was not to test a specific hypothesis but to describe lung deposition in the study population with descriptive methods. Nevertheless, differences between group averages were tested for statistical significance using the Wilcoxon-Mann-Whitney test (SAS—procedure NPAR1WAY). Correlations between parameters were assessed using Spearman rank correlation analysis (SAS Version 8e for Windows—procedure CORR). Pharmacokinetic results and safety results were evaluated descriptively.


   RESULTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 CONCLUSION
 ACKNOWLEDGEMENTS
 REFERENCES
 
Anthropometric data and lung function parameters of the study populations are shown in Table I. The average FEV1 was 108% predicted for healthy subjects, 60% predicted for patients with mild COPD, 42% predicted for patients with moderate COPD, and 26% predicted for patients with severe COPD.


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  		Table I Anthropometric Data and Lung Function Parameters of the Study Populations

 

Deposition Data
The emitted tiotropium dose during inhalation in the 4 study populations ranged from 41% to 49% (Table II). Except for patients with moderate COPD, where the emitted dose was significantly higher (P = .02) than in the reference group, no significant differences in emitted dose among the groups were observed. Intersubject variability of drug deposition was low (about 20%) in all study groups, even in patients with severe COPD.


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  		Table II Emitted Dose and Deposition Values After Inhalation of Tiotropium in the Study Populations

 

Lung deposition ranged from 18% to 22% of the inhaler fill weight (Table II). There were no statistically significant differences between the study groups. Also, no significant differences were found for lung deposition relative to the emitted dose (41%-43%) and for extrathoracic deposition relative to the fill weight (23%-28%) and relative to the emitted dose (57%-58%).

C/P ratios, quantifying the distribution of deposition within the lungs, tended to be larger for the patients with the largest lung impairment, indicating a tendency for more central deposition in these patients (Table II). However, this difference was not statistically significant.


Figure 1
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  		Figure 1. Baseline lung function in the patient group.

 


Figure 2
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  		Figure 2. Lung deposition: forced expiratory volume in 1 second (FEV1).

 


Figure 3
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  		Figure 3. Lung deposition: forced vital capacity (FVC).

 


Figure 4
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  		Figure 4. Extrathoracic deposition: forced expiratory volume in 1 second (FEV1).

 
Lung Function
In the patient group, baseline lung function between day 1 and day 15 (before tiotropium inhalation) improved, on average, statistically significantly: after the treatment period, baseline FEV1 was 13% higher than at day 1 (P = .002), and FVC was 11% higher (P = .006) (Figure 1). There was no statistically significant correlation between the baseline FEV1 on the day of deposition measurement and lung deposition in the entire study population (coefficient of correlation, r < 0.1) (Figures 2, 3, 4 and 5). Extrathoracic deposition tended to increase with decreasing lung function (with FEV1, r = -0.15; with FVC, r = -0.4). However, this correlation was not statistically significant (P = .52 and P = .08, respectively).


Figure 5
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  		Figure 5. Extrathoracic deposition: forced vital capacity (FVC).

 
Pharmacokinetics
The pharmacokinetic results are summarized in Table III. The urinary excretion of tiotropium was similar among the subgroups. Maximum tiotropium plasma concentration and the area under the curve tended to be higher in patients with COPD as compared to healthy subjects (Table III). There were no significant correlations between FEV1 and Cmax (P = .2) and FEV1 and AUC0-4h (P = .46).


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  		Table III Pharmacokinetic Parameters Measured in the Study Population

 

Safety and Tolerability
The results of the safety measurements implemented during the study did not reveal any clinically significant findings that were considered to be drug related. Individual and median values of hematological and clinical chemistry parameters remained essentially constant during the study.


   DISCUSSION
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
CONCLUSION
 ACKNOWLEDGEMENTS
 REFERENCES
 
It has been shown in this study that lung deposition of tiotropium inhaled from the dry-powder inhaler was about 20% of the filling dose and 40% of the emitted dose, regardless of the patient's state of health. There were no differences among the 4 study groups, neither in drug deposition nor in systemic exposure. This means that COPD severity did not influence the lung deposition or subsequent systemic tiotropium exposure. However, it may be objected that, due to the small groups of subjects, the power of the study is much too low to show possible differences between the groups of subjects. Nevertheless, the results are confirmed by the correlation analysis in which it has been shown, for the entire study population of 20 subjects, that there is no significant correlation between lung deposition and FEV1. For this analysis, the total study group is large enough, and the differences in lung function are large enough to conclude that there is no lung function dependency on lung deposition.

It is generally assumed that decreased lung function in patients with COPD leads to a lower lung deposition from dry-powder inhalers compared to healthy subjects. This opinion is based on the experience that patients with severely obstructed airways usually produce lower inhalation flow rates than healthy subjects or patients with mild lung disease. In many dry-powder inhaler devices, these lower flow rates are supposed to result in a reduced device output and/or increasing particle size, which leads to decreasing lung deposition.13,14 The findings of this study suggest that there were either no significant differences in inhalation flow rates among the study groups or that the dry-powder inhaler investigated in this study does not show a considerable flow rate dependency in the range of flow rates used by the subjects. This last-mentioned interpretation is supported by a previous study8 in which it has been shown in vitro that output of the device and the fine-particle fraction remain constant over a wide range of flow rates (20-60 L/min).9 In addition, it has been shown in vivo that such flow rates can be achieved in patients even with severe COPD. These findings are supported by the in vivo deposition results of the present study in which even patients with severe COPD (FEV1 <35% predicted) had the same deposition values as the other patient groups. However, the tendency to higher C/P ratios in patients with decreased FEV1 indicates that a more central deposition in patients with severe COPD cannot be excluded.

The results of this study—that lung deposition of about 20% can be achieved with the dry-powder inhaler under consideration—are similar to the results obtained with comparable techniques in other devices. Borgstrom et al13 investigated another dry-powder inhaler and found, at high flow rates (60 L/min), lung deposition values of 20% to 30%. At low flow rates (30 L/min), lung deposition was only 15%. Also, Hirst et al15 found deposition values of about 22% in asthmatics. Other dry-powder inhalers were investigated by Fenton et al,16 Newman et al,14 and Meyer et al,17 who found lung deposition values of 20% to 30% depending on the inhalation flow rate. These data suggest that the dry-powder inhaler investigated in this study has an efficacy similar to other dry-powder inhalers.

Tiotropium is not only similarly deposited among all groups but also similarly absorbed and excreted. The systemic exposure and urinary excretion is another marker of lung deposition because of the negligible intestinal bioavailability of tiotropium. Therefore, these data support the result of lung deposition being independent of airway obstruction.


   CONCLUSION
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
ACKNOWLEDGEMENTS
 REFERENCES
 
This study has shown that tiotropium inhaled from the dry-powder inhaler shows similar delivered doses and lung deposition in healthy subjects and patients with different stages of COPD disease. Even for the severe COPD patients, tiotropium lung deposition is not reduced, which ensures full therapeutic benefit for all patients, independent of the severity of COPD.


   ACKNOWLEDGEMENTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 ACKNOWLEDGEMENTS
REFERENCES
 
Financial disclosure: This study was supported by Boehringer Ingelheim Pharma GmbH & Co KG, Ingelheim, Germany, and Pfizer Inc, New York, New York.

DOI: 10.1177/0091270006295788


   REFERENCES
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 ACKNOWLEDGEMENTS
 REFERENCES
 

1. Witek TJ, Disse B. Inhaled anticholinergic therapy: applied pharmacology and interesting developments. Curr Opin Investig Drugs. 2001;2: 53-58.[Medline] [Order article via Infotrieve]

2. Hvizdos KM, Goa KL. Tiotropium bromide. Drugs. 2002;62: 1195-1203.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

3. Disse B, Witek TJ. Anticholinergics: Tiotropium. Basel, Switzerland: Karger; 2001.

4. Littner MR, Ilowite JS, Tashkin DP, et al. Long-acting bronchodilation with once-daily dosing of tiotropium (Spiriva) in stable chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2000;161: 1136-1142.[Abstract/Free Full Text]

5. Casaburi R, Mahler DA, Jones PW, et al. A long-term evaluation of once-daily inhaled tiotropium in chronic obstructive pulmonary disease. Eur Respir J. 2002;19: 217-224.[Abstract/Free Full Text]

6. Vincken W, Bantje TA, Middle MV, et al. Long-term efficacy and safety of ipratropium bromide plus fenoterol via respimat soft mist inhaler (SMI) versus a pressurised metered-dose inhaler in asthma. Clin Drug Invest. 2004;24: 17-28.[CrossRef]

7. Donohue JF, van Noord JA, Bateman ED, et al. A 6-month, placebo-controlled study comparing lung function and health status changes in COPD patients treated with tiotropium or salmeterol. Chest. 2002;122: 47-55.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

8. Chodosh S, Flanders JS, Kesten S, et al. Effective delivery of particles with the HandiHaler dry powder inhalation system over a range of chronic obstructive pulmonary disease severity. J Aerosol Med. 2001;14: 309-315.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

9. van Noord JA, Smeets JJ, Custers FL, et al. Pharmacodynamic steady state of tiotropium in patients with chronic obstructive pulmonary disease. Eur Respir J. 2002;19: 639-644.[Abstract/Free Full Text]

10. American Thoracic Society. Standardization of spirometry: 1994 update. Am J Respir Crit Care Med. 1995;152: 1107-1136.[Web of Science][Medline] [Order article via Infotrieve]

11. Pitcairn GR, Newman SP. Tissue attenuation corrections in gamma scintigraphy. J Aerosol Med. 1997;10: 187-198.[Web of Science]

12. Quanjer PH, Tammeling GJ, Cotes JE, et al. Lung volumes and forced ventilatory flows. Eur Respir J. 1993;6: 5-40.[Medline] [Order article via Infotrieve]

13. Borgstrom L, Bondesson E, Moren F, et al. Lung deposition of budesonide inhaled via Turbuhaler: a comparison with terbutaline sulphate in normal subjects. Eur Respir J. 1994;7: 69-73.[Abstract]

14. Newman SP, Hirst PH, Pitcairn GR. Scintigraphic evaluation of lung deposition with a novel inhaler device. Curr Opin Pulm Med. 2001;7(Suppl 1): S12-S14.[Medline] [Order article via Infotrieve]

15. Hirst PH, Bacon RE, Pitcairn GR, et al. A comparison of the lung deposition of budesonide from Easyhaler, Turbuhaler and pMDI plus spacer in asthmatic patients. Respir Med. 2001;95: 720-727.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

16. Fenton C, Keating GM, Plosker GL. Novolizer: a multidose dry powder inhaler. Drugs. 2003;63: 2437-2445, discussion 2447-2438.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

17. Meyer T, Brand P, Ehlich H, et al. Deposition of Foradil P in human lungs: comparison of in-vitro and in-vivo data. J Aerosol Med. 2004;17: 43-50.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]
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