Gary R. Pitcairn

Radionuclide imaging technologies and their use in evaluating asthma drug deposition in the lungs.

Whole lung and regional lung deposition of inhaled asthma drugs in the lungs can be quantified using either two-dimensional or three-dimensional radionuclide imaging methods. The two-dimensional method of gamma scintigraphy has been the most widely used, and is currently considered the industry standard, but the three-dimensional methods (SPECT, single photon emission computed tomography; and PET, positron emission tomography) give superior regional lung deposition data and will undoubtedly be used more frequently in future. Recent developments in radionuclide imaging are described, including an improved algorithm for assessing regional lung deposition in gamma scintigraphy, and a patent-protected radiolabelling method (TechneCoat), applicable to both gamma scintigraphy and SPECT. Radionuclide imaging data on new inhaled asthma products provide a milestone assessment, and the data form a bridge between in vitro testing and a full clinical trials program, allowing the latter to be entered with increased confidence.

Regional lung deposition of a technetium 99m-labeled formulation of mometasone furoate administered by hydrofluoroalkane 227 metered-dose inhaler.

BACKGROUND A new inhaled suspension formulation of mometasone furoate (MF), a potent corticosteroid with minimal systemic availability, has been developed for the treatment of asthma. This formulation is delivered by metered-dose inhaler (MDI) using the nonchlorofluorocarbon propellant hydrofluoroalkane 227 (HFA-227). OBJECTIVE The primary goal of this study was to determine the respiratory tract deposition of this formulation of MF. A secondary objective was to measure plasma concentrations of MF and a putative metabolite, 6-X-OH MF, to determine the systemic exposure to corticosteroid. METHODS This was a single-dose, open-label study in which 200 microg of technetium 99m (99mTc)-radiolabeled MF was administered to patients with asthma. Gamma scintigraphy was used to quantify lung, oropharyngeal, stomach, and MDI mouthpiece deposition patterns of MF. RESULTS Eleven patients, aged 21 to 47 years, with a history of asthma were enrolled in and completed the study. The mean (+/- SD) whole lung deposition of MF was 13.9%+/-5.7% of the metered (ex-valve) dose. The central lung zone received 5.3%+/-2.8% of the dose; the intermediate zone received 4.7%+/-1.9%; and peripheral lung deposition was 4.0%+/-1.5%. The mean (+/- SD) ratio of peripheral to central lung deposition was 0.8+/-0.2. Oropharyngeal deposition was 79.1%+/-8.7% of the ex-valve dose, with 6.3%+/-7.8% deposited on the MDI mouthpiece and 0.7%+/-0.5% exhaled. The majority of plasma samples taken for analysis of MF and 6-13-OH MF concentrations were below the limit of quantification (50 pg/mL) in all patients after inhalation of 200 microg 99mTc-labeled ME CONCLUSION: The lung deposition of MF when administered via HFA-227 MDI is comparable to the 10 to 20% lung deposition seen with other corticosteroid suspension for- mulations administered by MDI that have demonstrated effectiveness in the treatment of asthma.

Aerosol delivery of ergotamine tartrate via a breath-synchronized plume-control inhaler in humans

ABSTRACT Objective: To compare systemic delivery of ergotamine tartrate (ET) via a breath-synchronized, plume-control inhaler (BSPCI) (Tempo ET*) with a sublingual ergot preparation and a commercial inhaler. Methods: Study 1 determined plasma ET concentrations in seven healthy subjects after administration of ET by a 2 mg tablet (Lingraine†) and a BSPCI delivering 258 μg of ET. Study 2 determined plasma ET concentrations in 16 healthy subjects after administration via an ET metered dose inhaler (ME) (Medihaler‡) delivering 2052 μg of ET and a BSPCI delivering 129 μg of ET. Gamma scintigraphy with 99mTc validation was used to quantify lung deposition. Results: For both studies, ET Cmax was higher with the BSPCI (study 1: sublingual ET 134 pg/mL at 37 min; BSPCI 3743 pg/mL at 3 min; study 2: metered-dose inhaler 1109 pg/mL at 4 min; BSPCI 1210 pg/mL at 2.5 min). Mean dose normalized AUC was several-fold higher with the BSPCI compared with sublingual ET and ME dosing. Lung deposition of ET with the BSPCI was 33.5, 8.9, 11.4, and 13.2% for whole, central, intermediate, and peripheral lung, respectively, with a 1.5 peripheral : central ratio. Conclusion: Based on these open-label studies, the BSPCI allows rapid delivery of potentially therapeutic plasma concentrations of ET at approximately 1/15th the dose of comparators.

Deposition of fenoterol from pressurized metered dose inhalers containing hydrofluoroalkanes

The imaging technique of gamma scintigraphy has been used to quantify the total amount of drug deposited in the lungs and the pattern of regional lung deposition, for formulations of Berodual (Boehringer Ingelheim GmbH) delivered from pressurized metered dose inhalers formulated with chlorofluorocarbons, and with hydrofluoroalkane-134a or -227. Data were expressed as the mass of fenoterol deposited in the lungs from the Berodual formulations. All the formulations tested gave a whole lung deposition less than 20% of the metered (exvalve) dose. The mass of fenoterol deposited in the lungs for a solution formulation containing hydrofluoroalkane-134a was inversely proportional to the actuator nozzle diameter. The data suggest that the total and regional lung deposition of hydrofluoroalkane-based pressurized aerosol formulations is highly product-specific and that changes in bioavailability can be brought about by varying both the constituents of the formulation and the design of the actuator.

Breath-synchronized plume-control inhaler for pulmonary delivery of fluticasone propionate.

A novel breath-synchronized, plume-control inhaler (Tempo inhaler) was developed to overcome limitations of a pressurized metered-dose inhaler. This report compared the Tempo inhaler and a commercial inhaler for fine particle distribution and lung deposition of fluticasone propionate. In vitro fine particle distribution was determined using the Andersen Cascade Impactor at inspiration rates of 28.3 and 45L/min. In vivo lung deposition was assessed in a randomized, two-arm, crossover study of (99m)Tc-radiolabeled fluticasone propionate in 12 healthy adult subjects, analyzed by gamma scintigraphy. In vitro: fine particle fractions at 28.3 and 45L/min were 88.6+/-3.6% and 89.2+/-3.0% (Tempo inhaler) versus 40.4+/-4.7% and 43.1+/-4.4% (commercial inhaler). In vivo: lung deposition was 41.5+/-9.8% (Tempo inhaler) versus 13.8+/-7.4% (commercial inhaler) and oropharyngeal deposition was 18.3+/-7.7% (Tempo inhaler) versus 76.8+/-7.1% (commercial inhaler). Variability of lung deposition was reduced from 55% (commercial inhaler) to 24% (Tempo inhaler) of the delivered dose. The Tempo inhaler produced significantly higher fine particle fraction values, reduced oropharyngeal deposition by 75%, and increased whole, central, intermediate, and peripheral lung delivery by more than 200%. Thus, the Tempo inhaler enhances efficient drug delivery to the lungs.

Pulmonary and nasal deposition of ketorolac tromethamine solution (SPRIX) following intranasal administration.

Ketorolac tromethamine is a racemic, non-steroidal, anti-inflammatory drug (NSAID). An intra-nasal (IN) formulation, SPRIX(®), is approved for the treatment of short term (up to 5 days) acute moderate to moderately severe pain. The primary objective of this study was to determine whether (99m)Tc-diethylenetriaminepenta acetic acid (DTPA) radiolabelled ketorolac tromethamine formulation (31.5 mg) was deposited in the lungs of healthy subjects (4 men and 9 women) following nasal inhalation of different intensities (gentle or vigorous sniff) and under different postural conditions (upright or semi-supine). The secondary objectives were to determine the deposition pattern of radiolabelled ketorolac solution in the nasal cavity and the clearance of the radiolabel over a 6h period post-administration. The nasal spray pump delivery device used showed a droplet size distribution with a volume mean diameter (VMD) of 50 μm and approximately 85% of the aerosol mass contained in droplets >10 μm diameter. The fraction of the dose recorded from the lung regions averaged <0.5%, and was considered to represent scattered radiation rather than true pulmonary deposition. This fraction was not affected by posture or by inhalation manoeuvre. The majority of the radiolabelled intranasal dose was deposited in the nasal cavity. The visual spread patterns within the nasal cavity were most uniform following administration in the upright position regardless of inhalation manoeuvre. Clearance from the nasal cavity was initially very rapid, with only 16-30% of the dose remaining after 10 min and 6-14% after 6 h. Retention was greatest following gentle inhalation.

In Vitro/In Vivo Correlations for Respiratory Drug Delivery

In vitro drug delivery data for pulmonary and nasal drug products have great importance, particularly for quality control and product release. However, in vitro tests which measure emitted dose and particle size distribution of both pulmonary and nasal aerosols, as well as the spray pattern and plume geometry of nasal sprays, do not take into account the interactions between the aerosol particles and the airways when inhalers are used by patients. While agreement between in vitro and in vivo data is sometimes good, in vitro data may not predict in vivo drug delivery adequately in some situations. In vivo tests of drug delivery, using either radionuclide imaging or appropriate pharmacokinetic methods, may be a useful adjunct to in vitro testing in early product development.

Defining the lung outline from a gamma camera transmission attenuation map

Segmentation of the lung outline from gamma camera transmission images of the thorax is useful in attenuation correction and quantitative image analysis. This paper describes and compares two threshold-based methods of segmentation. Simulated gamma camera transmission images of test objects were used to produce a knowledge base of the variation of threshold defining the lung outline with image resolution and chest wall thickness. Two segmentation techniques based on global (GT) and context-sensitive (CST) thresholds were developed and evaluated in simulated transmission images of realistic thoraces. The segmented lung volumes were compared to the true values used in the simulation. The mean distances between segmented and true lung surface were calculated. The techniques were also applied to three real human subject transmission images. The lung volumes were estimated and the segmentations were compared visually. The CST segmentation produced significantly superior segmentations than the GT technique in the simulated data. In human subjects, the GT technique underestimated volumes by 13% compared to the CST technique. It missed areas that clearly belonged to the lungs. In conclusion, both techniques segmented the lungs with reasonable accuracy and precision. The CST approach was superior, particularly in real human subject images.