Chet Leach

Particle size of inhaled corticosteroids: Does it matter?

A question with respect to asthma therapy revolves around the issue of whether better efficacy occurs with an ultrafine-particle inhaled corticosteroid because of better lung deposition into the distal airways. This article reviews particle size and delivery devices of different steroids, clinical outcomes of small- versus large-particle steroids, and the issue of pharmacoeconomics.

Characterization of respiratory deposition of fluticasone-salmeterol hydrofluoroalkane-134a and hydrofluoroalkane-134a beclomethasone in asthmatic patients

BACKGROUND Fixed combination fluticasone-salmeterol is the most used anti-inflammatory asthma treatment in North America, yet no studies report the actual respiratory tract dose or the distribution of drug within the lungs. Inflammation due to asthma affects all airways of the lungs, both large and small. Inhaled steroid delivery to airways results from a range of drug particle sizes, with emphasis on smaller drug particles capable of reaching the peripheral airways. Previous studies suggested that smaller drug particles increase pulmonary deposition and decrease oropharyngeal deposition. OBJECTIVES To characterize the dose of fluticasone-salmeterol hydrofluoroalkane-134a (HFA) (particle size, 2.7 μm) delivered to asthmatic patients and examine the drug distribution within the lungs. The results were compared with the inhalation delivery of HFA beclomethasone (particle size, 0.7 μm). METHODS A crossover study was conducted in asthmatic patients with commercial formulations of fluticasone-salmeterol and HFA beclomethasone radiolabeled with technetium Tc 99m. Deposition was measured using single-photon emission computed tomography/computed tomography gamma scintigraphy. RESULTS Two-dimensional planar image analysis indicated that 58% of the HFA beclomethasone and 16% of the fluticasone-salmeterol HFA were deposited in the patients lungs. The oropharyngeal cavity and gut analyses indicated that 77% of the fluticasone-salmeterol HFA was deposited in the oropharynx compared with 35% of the HFA beclomethasone. CONCLUSIONS The decreased peripheral airway deposition and increased oropharyngeal deposition of fluticasone-salmeterol HFA was a result of its larger particle size. The smaller particle size of HFA beclomethasone allowed a greater proportion of lung deposition with a concomitant decrease in oropharyngeal deposition.

A Pilot Study to Assess Lung Deposition of HFA-Beclomethasone and CFC-Beclomethasone from a Pressurized Metered Dose Inhaler with and without Add-On Spacers and Using Varying Breathhold Times

BACKGROUND The study objective of this pilot study was to determine the lung delivery of HFA-134a-beclomethasone dipropionate (HFA-BDP; QVAR™) and CFC-beclomethasone dipropionate (CFC-BDP; Becloforte™) with and without the add-on spacers, Aerochamber™, and Volumatic™. The smaller particles of HFA-BDP were presumed to produce greater lung deposition using spacers, with and without a delay [i.e., metered dose inhaler (MDI) actuation into the spacer and subsequent inhalation 0 and 2 sec later], compared with the larger particles of CFC-BDP. The study included a comparison of breathhold effects (i.e., 1 and 10-sec breatholds) on lung deposition. METHODS The study was an open-label design and utilized healthy subjects (n = 12 males). Each arm of the study contained three subjects; thus, outcomes were not powered to assess statistical significance. HFA-BDP and CFC-BDP were radiolabeled with technetium-99m and delivered to subjects. RESULTS Results showed that the small particle HFA-BDP lung deposition averaged 52% and was not affected by the use of Aerochamber with or without a spacer delay. The oropharyngeal deposition of HFA-BDP was reduced from approximately 28% to 4% with the Aerochamber. Lung deposition with the large particle CFC-BDP was 3-7% and generally decreased with Aerochamber or Volumatic. A 2-sec time delay between actuation and breath plus the spacer reduced lung deposition slightly but reduced oropharygeal deposition substantially (84% down to 3-20%) using the Aerochamber or Volumatic with and without a spacer delay. HFA-BDP lung deposition was dependent on the breathhold. Lung deposition with HFA-BDP was reduced by 16% with a 1-sec versus 10-sec breathhold. The difference was measured in the increased exhaled fraction, confirming that smaller particles need time to deposit and are exhaled if there is a reduced breathhold. The large particle CFC-BDP lung deposition was not affected by breathhold. CONCLUSIONS The use of Aerochamber or Volumatic spacers with HFA-BDP did not alter lung deposition but it did reduce oropharyngeal deposition. However, HFA-BDP displayed reduced oropharyngeal deposition without a spacer.

Inhalation Aspects of Therapeutic Aerosols

The pulmonary route of drug delivery can provide an excellent alternative to other routes both for local lung disease as well as systemic delivery. The year 2006 marks the 50th year since the invention of metered dose inhalers, yet inhalation is a very much underutilized route of delivery, possibly because inhalation drug development is perceived as being too difficult and expensive. However with proper knowledge these purported difficulties can be overcome. The process begins with identifying the target tissue and then utilizing technologies such as particle size adjustments through formulation techniques and delivery devices to most efficiently deliver the desired dose. There are a variety of new and existing inhaled excipients available to accomplish this goal. The active molecule can also be modified to increase solubility, decrease immunogenicity, and protect it from unwanted metabolism using PEGylation. Sustained release of an inhaled drug is also possible using biocompatible matrices such as oligolactic acid.

Biologic Comparison of Inhaled Insulin Formulations: ExuberaTM and Novel Spray-Dried Engineered Particles of Dextran-10

Inhaled peptides and proteins have promise for respiratory and systemic disease treatment. Engineered spray-dried powder formulations have been shown to stabilize peptides and proteins and optimize aerosol properties for pulmonary delivery. The current study was undertaken to investigate the in vitro and in vivo inhalation performance of a model spray-dried powder of insulin and dextran 10 in comparison to Exubera™. Dextrans are a class of glucans that are generally recognized as safe with optimum glass transition temperatures well suited for spray drying. A 70% insulin particle loading was prepared by formulating with 30% (w/v) dextran 10. Physical characterization revealed a “raisin like” particle. Both formulations were generated to produce a similar bimodal particle size distribution of less than 3.5 μm MMAD. Four female Beagle dogs were exposed to each powder in a crossover design. Similar presented and inhaled doses were achieved with each powder. Euglycemia was achieved in each dog prior and subsequent to dosing and blood samples were drawn out to 245 min post-exposure. Pharmacokinetic analyses of post-dose insulin levels were similar for both powders. Respective dextran 10-insulin and Exubera exposures were similar producing near identical area under the curve (AUC), 7,728 ± 1,516 and 6,237 ± 2,621; concentration maximums (Cmax), 126 and 121 (μU/mL), and concentration–time maximums, 20 and 14 min, respectively. These results suggest that dextran-10 and other dextrans may provide a novel path for formulating peptides and proteins for pulmonary delivery.

Respiratory Tract Deposition of HFA–Beclomethasone and HFA–Fluticasone in Asthmatic Patients

BACKGROUND The asthmatic patients respiratory tract deposition of HFA fluticasone (Flovent HFA(™)) has not been established. There is a known large particle size difference with another commercial inhaled HFA steroid (QVAR(™)). This study compared the 2D and 3D respiratory tract deposition of each inhaled steroid. METHODS This study was an open label, crossover study in eight patients diagnosed with asthma. The regional respiratory and oropharyngeal deposition of the two steroids were compared and contrasted using planar and SPECT imaging following delivery of the (99m)Tc-radiolabeled drug in each product. The SPECT images were merged with computed tomography images to quantify regional deposition within the patients. RESULTS Two-dimensional (2D) planar images indicated that 24% of the Flovent HFA dose and 55% of the QVAR dose deposited in the lungs. 2D oropharyngeal deposition indicated that 75% of the Flovent HFA dose was deposited in the oropharynx, while 42% of the QVAR dose deposited in the oropharynx. Three-dimensional (3D) SPECT data indicated that 22% of the Flovent HFA dose and 53% of the QVAR dose deposited in the lungs. 3D oropharyngeal and gut deposition indicated 78% of the Flovent HFA dose was deposited in the oropharynx, while 47% of the QVAR dose deposited in the oropharynx. The increased lung deposition and decreased oropharynx deposition for both 2D and 3D image data of QVAR were statistically different from Flovent HFA. CONCLUSIONS QVAR exhibited a significant increase in lung delivery compared to Flovent HFA. Conversely, QVAR delivered a significantly lower dose to the oropharynx than Flovent HFA. The findings were presumed to be driven by the smaller particle size of QVAR (0.7 microns MMAD) compared with Flovent HFA (2.0 microns MMAD).

Inhalation of human insulin is associated with improved insulin action compared with subcutaneous injection and endogenous secretion in dogs

This study compared the effects of endogenous (portal) insulin secretion versus peripheral insulin administration with subcutaneous or inhaled human insulin [INH; Exubera, insulin human (rDNA origin) inhalation powder] on glucose disposal in fasted dogs. In the control group, glucose was infused into the portal vein (Endo; n = 6). In two other groups, glucose was infused portally, whereas insulin was administered peripherally by inhalation (n = 13) or s.c. injection (n = 6) with somatostatin and basal glucagon. In the Endo group, over the first 3 h, the arterial insulin concentration was twice that of the peripheral groups, whereas hepatic sinusoidal insulin levels were half as much. Although net hepatic glucose uptake was greatest in the Endo group, the peripheral groups demonstrated larger increases in nonhepatic glucose uptake so that total glucose disposal was greater in the latter groups. Compared with s.c. insulin action, glucose excursions were smaller and shorter, and insulin action was at least twice as great after INH. Thus, at the glucose dose and insulin levels chosen, peripheral insulin delivery was associated with greater whole-body glucose disposal than endogenous (portal) insulin secretion. INH administration resulted in increased insulin sensitivity in nonhepatic but not in hepatic tissues compared with s.c. delivery.

Inhaled Insulin Is Associated with Prolonged Enhancement of Glucose Disposal in Muscle and Liver in the Canine

Diabetic patients treated with inhaled insulin exhibit reduced fasting plasma glucose levels. In dogs, insulin action in muscle is enhanced for as long as 3 h after insulin inhalation. This study was designed to determine whether this effect lasts for a prolonged duration such that it could explain the effect observed in diabetic patients. Human insulin was administered via inhalation (Exubera; n = 9) or infusion (Humulin R; n = 9) in dogs using an infusion algorithm that yielded matched plasma insulin kinetics between the two groups. Somatostatin was infused to prevent insulin secretion, and glucagon was infused to replace basal plasma levels of the hormone. Glucose was infused into the portal vein at 4 mg/kg/min and into a peripheral vein to maintain the arterial plasma glucose level at 160 mg/dl. Arterial and hepatic sinusoidal insulin and glucose levels were virtually identical in the two groups. Notwithstanding, glucose utilization was greater when insulin was administered by inhalation. At its peak, the peripheral glucose infusion rate was 4 mg/kg/min greater in the inhalation group, and a 50% difference between groups persisted over 8 h. Inhalation of insulin caused a greater increase in nonhepatic glucose uptake in the first 3 h after inhalation; thereafter, net hepatic glucose uptake was greater. Inhalation of insulin was associated with greater than expected (based on insulin levels) glucose disposal. This may explain the reduced fasting glucose concentrations observed in humans after administration of certain inhaled insulin formulations compared with subcutaneous insulin.

Inhalation of Human Insulin (Exubera) Augments the Efficiency of Muscle Glucose Uptake In Vivo

This study assessed the site of increased glucose uptake resulting from insulin inhalation, quantified its effect under steady-state glucose concentrations, and identified the time to onset of effect. Human insulin was administered to 13 beagles via inhalation (Exubera [insulin human (rDNA origin)] Inhalation Powder; n = 7) or infusion into the inferior vena cava (Humulin R; n = 6) using an algorithm to match plasma insulin levels and kinetics for both groups. Somatostatin and glucagon were infused. Glucose was delivered into the portal vein (4 mg · kg−1 · min−1) and a peripheral vein, as needed, to maintain arterial plasma glucose levels at 180 mg/dl. Hepatic exposure to insulin and glucose and liver glucose uptake were similar in both groups. Despite comparable arterial insulin and glucose levels, hind-limb glucose uptake increased 2.4-fold after inhalation compared with infusion due to increased muscle glucose uptake. Glucose infusion rate, nonhepatic glucose uptake, and tracer-determined glucose disposal were about twice as great compared with intravenous insulin. The effect appeared after 1 h, persisting at least as long as arterial insulin levels remained above basal. Pulmonary administration of insulin increases nonhepatic glucose uptake compared with infusion, and skeletal muscle is the likely site of that effect.