Systematic Evaluation of the Effect of Formulation Variables on In Vitro Performance of Mometasone Furoate Suspension-Metered Dose Inhalers.

The therapeutic benefits of metered dose inhalers (MDIs) in pulmonary disorders are mainly driven by aerosol performance, which depends on formulation variables (drug and excipients), device design, and patient interactions. The present study provides a comprehensive investigation to better understand the effect of formulation variables on mometasone furoate (MF) suspension-based MDI product performance. The effects of MF particle size (volume median diameter; X50) and excipient concentration (ethanol and oleic acid, cosolvent, and surfactant, respectively) on selected critical quality attributes (delivered dose (DD), fine particle dose of particles lesser than 5 µm (FPD < 5), ex-throat dose and median dissolution time (MDT)) were studied. Eight MF-MDI formulations (one per batch) were manufactured based on a reduced factorial design of experiment (DOE) approach, which included relevant formulation levels with varying X50 (1.1 and 2 µm), concentration of ethanol (0.45, 0.9, 1.8, and 3.6%w/w), and oleic acid (0.001 and 0.025%w/w). The in vitro evaluation of these MF-MDI formulations indicated the importance of drug particle's X50, oleic acid, and ethanol canister concentration as critical formulation variables governing the performance of MF suspension-based MDI products. The effect of these formulation variables on DD, FPD < 5, ex-throat dose, and MDT was subsequently utilized to develop empirical relationships linking formulation factors with effects on in vitro performance measures. The developed strategy could be useful for predicting MF-MDI product performance during MDI product development and manufacturing. The systematic DOE approach utilized in this study may provide insights into the understanding of the formulation variables governing the MF-MDI product performance.

Pressurized Metered Dose Inhaler Technology: Manufacturing.

While first introduced in the 1950s, pressurized metered dose inhalers (pMDIs) remain as a first line treatment of pulmonary conditions. With expanding applications of pMDIs beyond asthma and chronic obstructive pulmonary disease (COPD), the development of therapies utilizing the pMDI platform will undoubtedly continue. Recent guidances and the introduction of quality by design initiatives further emphasize the requirement of formulators to understand the relationships between product attributes and production strategies and their impact on product performance. This review summarizes common manufacturing processes of pMDIs across multiple stages of the development cycle, from academia to commercial production, and provides insight as to the benefits and limitations of each process in regard to formulation type.

Effects of Formulation Variables on Lung Dosimetry of Albuterol Sulfate Suspension and Beclomethasone Dipropionate Solution Metered Dose Inhalers.

The performance of pressurized metered dose inhalers (MDIs) is affected by formulation and device variables that impact delivered dose, aerodynamic particle size distribution, and consequently lung deposition and therapeutic effect. Specific formulation variables of relevance to two commercially available products-Proventil® HFA [albuterol sulfate (AS) suspension] and Qvar® [beclomethasone dipropionate (BDP) solution]-were evaluated to determine their influence on key performance attributes measured experimentally with in vitro cascade impaction studies. These commercial MDIs, utilized as model systems, provided mid-points for a design of experiments (DoE) plan to manufacture multiple suspension and solution MDI formulations. The experimental results were utilized as input variables in a computational dosimetry model to predict the effects of MDI formulation variables on lung deposition. For the BDP solution DoE MDIs, increased concentrations of surfactant oleic acid (0-2% w/w) increased lung deposition from 24 to 46%, whereas changes in concentration of the cosolvent ethanol (7-9% w/w) had no effect on lung deposition. For the AS suspension DoE MDIs, changes in oleic acid concentration (0.005-0.25% w/w) did not have significant effects on lung deposition, whereas lung deposition decreased from 48 to 26% as ethanol concentration increased from 2 to 20% w/w, and changes in micronized drug volumetric median particle size distribution (X50, 1.4-2.5 µm) increased deposition in the tracheobronchial airways from 5 to 11%. A direct correlation was observed between fine particle fraction and predicted lung deposition. These results demonstrate the value of using dosimetry models to further explore relationships between performance variables and lung deposition.

Impact of droplet evaporation rate on resulting in vitro performance parameters of pressurized metered dose inhalers.

Pressurized metered dose inhalers (pMDIs) are widely used for the treatment of pulmonary diseases. The overall efficiency of pMDI drug delivery may be defined by in vitro parameters such as the amount of drug that deposits on the model throat and the proportion of the emitted dose that has particles that are sufficiently small to deposit in the lung (i.e., fine particle fraction, FPF). The study presented examines product performance of ten solution pMDI formulations containing a variety of cosolvents with diverse chemical characteristics by cascade impaction with three inlets (USP induction port, Alberta Idealized Throat, and a large volume chamber). Through the data generated in support of this study, it was demonstrated that throat deposition, cascade impactor deposition, FPF, and mass median aerodynamic diameter of solution pMDIs depend on the concentration and vapor pressure of the cosolvent, and the selection of model throat. Theoretical droplet lifetimes were calculated for each formulation using a discrete two-stage evaporation process model and it was determined that the droplet lifetime is highly correlated to throat deposition and FPF indicating that evaporation kinetics significantly influences pMDI drug delivery.

Influence of Formulation Factors on the Aerosol Performance of Suspension and Solution Metered Dose Inhalers: A Systematic Approach.

Metered dose inhalers (MDIs) are complex drug-device combination products widely used to treat pulmonary disorders. The efficacy, driven by aerosol performance of the products, depends on a multitude of factors including, but not limited to, the physicochemical properties of drug and nature and amount of excipient(s). Under the quality by design (QbD) paradigm, systematic investigations are necessary to understand how changes in critical quality attributes (CQAs) of formulation, device, and manufacturing process influence key product performance parameters, such as delivered dose (DD) and fine particle dose (FPD). The purpose of this work is to provide a better understanding of the effects of different levels of excipients and drug particle size distribution on the aerosol performance of MDI products, while using two fundamentally different MDI products as relevant model systems, Proventil® HFA (albuterol sulfate suspension) and Qvar® (beclomethasone dipropionate solution). These MDI products, as model systems, provided mid-points around which a design of experiments (DOE), consisting of 22 suspension and 9 solution MDI formulations, were defined and manufactured. The DOE included formulations factors with varying ethanol (2 to 20% w/w and 7 to 9% w/w for the suspension and solution, respectively) and oleic acid concentrations (0.005 to 0.25% w/w and 0 to 2% w/w for the suspension and solution, respectively) and drug volumetric median particle size distribution (PSD D50, 1.4 to 2.5 µm for the suspension). The MDI formulations were analyzed using compendial methods to elucidate the effect of these formulation variables (ethanol, oleic acid, and PSD D50) on DD and FPD. The outcomes of this study allowed defining design spaces for the formulation factors, such that DD and FPD would remain within specific pre-defined requirements. The systematic approach utilized in this work can contribute as a QbD tool to evaluate the extent to which the formulation factors govern the aerosol performance of MDI drug products, helping to design MDI formulations with desired product performance parameters.

Modeling and Understanding Combination pMDI Formulations with Both Dissolved and Suspended Drugs.

A simulation model has been established to predict the residual aerodynamic particle size distribution (APSD) of dual-component pressurized metered dose inhalers (pMDIs). More specifically, this model estimates the APSD of pMDI formulations containing dissolved and suspended compounds for various formulations, and has been verified experimentally. Simulated and experimental data illustrate that APSDs of the dissolved and suspended components of the pMDI are influenced by concentrations of the dissolved and micronized suspended drugs, along with suspended drug size. Atomized droplets from such combination formulations may contain varying number of suspended drug particles and a representative concentration of dissolved drug. These sub-populations of atomized droplets may explain the residual APSDs. The suspended drug follows a monomodal, lognormal distribution and is more greatly impacted by the size and concentration of the suspended drug in comparison to the concentration of dissolved drug. On the other hand, dissolved drug illustrates a bimodal, lognormal residual particle size distribution both theoretically and experimentally. The smaller mode consists of residual particles made of dissolved drug only, while the larger mode consists of residual particles that contain both dissolved and suspended drugs. The model effectively predicted the size distributions of both the dissolved and suspended components of combination formulations (r(2) value of 0.914 for the comparison of simulated versus experimental MMAD values for the formulations examined). The results demonstrate that this model is a useful tool that may be able to expedite the development of combination pMDI formulation.

Factors influencing aerodynamic particle size distribution of suspension pressurized metered dose inhalers.

Pressurized metered dose inhalers (pMDIs) are frequently used for the treatment of asthma and chronic obstructive pulmonary disease. The aerodynamic particle size distribution (APSD) of the residual particles delivered from a pMDI plays a key role in determining the amount and region of drug deposition in the lung and thereby the efficacy of the inhaler. In this study, a simulation model that predicts the APSD of residual particles from suspension pMDIs was utilized to identify the primary determinants for APSD. These findings were then applied to better understand the effect of changing drug concentration and micronized drug size on experimentally observed APSDs determined through Andersen Cascade Impactor testing. The experimental formulations evaluated had micronized drug mass median aerodynamic diameters (MMAD) between 1.2 and 2.6 µm and drug concentrations ranging from 0.01 to 1% (w/w) with 8.5% (w/w) ethanol in 1,1,1,2-tetrafluoroethane (HFA-134a). It was determined that the drug concentration, micronized drug size, and initially atomized droplet distribution have a significant impact in modulating the proportion of atomized droplets that contain multiple suspended drug particles, which in turn increases the residual APSD. These factors were found to be predictive of the residual particle MMAD for experimental suspension HFA-134a formulations containing ethanol. The empirical algebraic model allows predicting the residual particle size for a variety of suspension formulations with an average error of 0.096 µm (standard deviation of 0.1 µm).

In vitro evaluation of nonconventional accessory devices for pressurized metered-dose inhalers.

BACKGROUND: The selection of accessory devices for pressurized metered-dose inhalers (pMDIs) by health care professionals is typically cost driven without consideration of how the device modifies clinical outcomes. OBJECTIVE: To evaluate nonconventional accessory devices and the open-mouth technique with and without ideal coordination of actuation and inhalation to identify and understand the considerations for recommending potential inexpensive devices. METHODS: In vitro performance parameters of the beclomethasone dipropionate pMDI were evaluated with several devices (AeroChamber, toilet paper roll, paper towel roll, rolled paper, plastic bottle spacer, bottle-holding chamber, and nebulizer reservoir tubing). RESULTS: Compared with the pMDI alone, all the accessory devices evaluated have significantly lower drug exposure and throat deposition and higher respirable fractions, with the paper towel roll having the greatest effect of the devices evaluated (exposure decreased from a mean [SD] of 76.1 [4.8] µg to 49.2 [2.0] µg, throat deposition decreased from 32.0 [3.2] µg to 0.8 [0.3] µg, and respirable fraction increased from 49.8% [3.2%] to 96.4% [0.4%]). Introduction of a delay between actuation and inhalation resulted in greater variability in performance metrics for the devices evaluated, and the bottle-holding chamber and paper towel roll were most effective in mitigating the effect of the delay. The open-mouth technique was found to decrease throat deposition and respirable mass compared with the pMDI alone. CONCLUSION: In addition to cost, the amount of drug that deposits in the throat and the lungs and the effect of asynchronous actuation and inhalation can vary with the selection of an accessory device, which may affect the therapeutic benefits of the pMDI selected.

Advances in metered dose inhaler technology: formulation development.

Pressurized metered dose inhalers (MDIs) are a long-standing method to treat diseases of the lung, such as asthma and chronic obstructive pulmonary disease. MDIs rely on the driving force of the propellant, which comprises the bulk of the MDI formulation, to atomize droplets containing drug and excipients, which ideally should deposit in the lungs. During the phase out of chlorofluorocarbon propellants and the introduction of more environmentally friendly hydrofluoroalkane propellants, many improvements were made to the methods of formulating for MDI drug delivery along with a greater understanding of formulation variables on product performance. This review presents a survey of challenges associated with formulating MDIs as solution or suspension products with one or more drugs, while considering the physicochemical properties of various excipients and how the addition of these excipients may impact overall product performance of the MDI. Propellants, volatile and nonvolatile cosolvents, surfactants, polymers, suspension stabilizers, and bulking agents are among the variety of excipients discussed in this review article. Furthermore, other formulation approaches, such as engineered excipient and drug-excipient particles, to deliver multiple drugs from a single MDI are also evaluated.

Advances in metered dose inhaler technology: hardware development.

Pressurized metered dose inhalers (MDIs) were first introduced in the 1950s and they are currently widely prescribed as portable systems to treat pulmonary conditions. MDIs consist of a formulation containing dissolved or suspended drug and hardware needed to contain the formulation and enable efficient and consistent dose delivery to the patient. The device hardware includes a canister that is appropriately sized to contain sufficient formulation for the required number of doses, a metering valve capable of delivering a consistent amount of drug with each dose delivered, an actuator mouthpiece that atomizes the formulation and serves as a conduit to deliver the aerosol to the patient, and often an indicating mechanism that provides information to the patient on the number of doses remaining. This review focuses on the current state-of-the-art of MDI hardware and includes discussion of enhancements made to the device's core subsystems. In addition, technologies that aid the correct use of MDIs will be discussed. These include spacers, valved holding chambers, and breath-actuated devices. Many of the improvements discussed in this article increase the ability of MDI systems to meet regulatory specifications. Innovations that enhance the functionality of MDIs continue to be balanced by the fact that a key advantage of MDI systems is their low cost per dose. The expansion of the health care market in developing countries and the increased focus on health care costs in many developed countries will ensure that MDIs remain a cost-effective crucial delivery system for treating pulmonary conditions for many years to come.

The influence of initial atomized droplet size on residual particle size from pressurized metered dose inhalers.

Pressurized metered dose inhalers (pMDIs) are widely used for the treatment of diseases of the lung, including asthma and chronic obstructive pulmonary disease. The mass median aerodynamic diameter of the residual particles (MMADR) delivered from a pMDI plays a key role in determining the amount and location of drug deposition in the lung and thereby the efficacy of the inhaler. The mass median diameter of the initial droplets (MMDI), upon atomization of a formulation, is a significant factor influencing the final particle size. The purpose of this study was to evaluate the extent that MMDI and initial droplet geometric standard deviation (GSD) influence the residual aerodynamic particle size distribution (APSDR) of solution and suspension formulations. From 48 solution pMDI configurations with varying ethanol concentrations, valve sizes and actuator orifice diameters, it was experimentally found that the effective MMDI ranged from 7.8 to 13.3 µm. Subsequently, computational methods were utilized to determine the influence of MMDI on MMADR, by modulating the MMDI for solution and suspension pMDIs. For solution HFA-134a formulations of 0.5% drug in 10% ethanol, varying the MMDI from 7.5 to 13.5 µm increased the MMADR from 1.4 to 2.5 µm. For a suspension formulation with a representative particle size distribution of micronized drug (MMAD=2.5 µm, GSD=1.8), the same increase in MMDI resulted in an increase in the MMADR from 2.7 to only 3.3 µm. Hence, the same increase in MMDI resulted in a 79% increase in MMADR for the solution formulation compared to only a 22% increase for the suspension formulation. Similar trends were obtained for a range of drug concentrations and input micronized drug sizes. Thus, APSDR is more sensitive to changes in MMDI for solution formulations than suspension formulations; however, there are situations in which hypothetically small micronized drug in suspension (e.g. 500 nm MMAD) could resemble trends observed for solution formulations. Furthermore, the relationship between APSDR and drug concentration and MMDI is predictable for solution pMDIs, but this is not as straightforward for suspension formulations. In addition, the MMADR was relatively insensitive to changes in initial droplet GSD (from 1.6 to 2.0) and the solution and suspension pMDI residual particle GSDs were essentially identical to the initial droplet GSDs.

A model for predicting size distributions delivered from pMDIs with suspended drug.

A new model has been developed for predicting size distributions delivered from pressurized metered dose inhalers (pMDIs) that contain suspended drug particles. This model enables the residual particle size distribution to be predicted for a broad range of formulations. It expands on previous models by allowing for polydisperse micronized input drug, multiple suspended drugs, dissolved drug, and dissolved or suspended excipient to be included in the formulation. The model indicates that for most pMDI configurations, the majority of droplets contain no drug or a single drug particle and the residual particle size distribution delivered from the pMDI is essentially equivalent to the size distribution of the micronized drug used in the formulation. However, for pMDIs with a high drug concentration or that use small micronized drug particles, there can be a substantial fraction of the droplets that contain multiple drug particles. The residual particle size distribution obtained from these pMDIs can be substantially larger than the size distribution of the micronized drug. Excellent agreement was observed between size distributions predicted using this model and those obtained from experimental cascade impactor measurements (r(2)=0.97), thus demonstrating the ability of the model to accurately predict the size distributions obtained from suspension pMDIs.