Improving Inhalation Devices
With advancements in the biomedical device technology industry, more efficient delivery systems capable of delivering finer particles into the lungs have started to show on the market and in hospitals. There is a wide variety of device and formulation combinations that can be utilized to target specific cells or regions of the lung, and understanding this dynamic can be crucial for developing an efficient delivery system. Pharma IQ interviewed Hugh Smyth, PhD, Associate Professor of Pharmaceutics at the University of Texas, Austin, about making inhalation devices better:
Pharma IQ: Can you give us an overview of the current types of compact portable devices, including meter-dose inhalers and dry powder inhalers?
Dr. Smyth: There are three major types of portable devices. The metered dose inhaler, the portable nebulizer type inhalers, and the dry powder inhalers.
The metered dose inhaler, or MDI, is that type of device that contains a propellant under pressure that is used to disperse the drug formulation as a fine aerosol when the patient actuates the device. The key elements here are the propellant that provides the energy to create the aerosol, the valve that allows precise metering of the aerosol, and the patient who operates the device.
Portable liquid nebulizer devices are relatively new and include smaller nebulizers based on vibrating mesh technology, ultrasound, and mechanical aerosolization of aqueous based formulations. There are no propellants with these devices which rely on external energy to produce the aerosol.
Thirdly, is the dry powder inhaler type. This type is the fastest growing category of portable inhalers but still is significantly less prescribed than the metered dose inhalers. The dry powder inhalers are a diverse range of devices that use many different methods to disperse a powder into a respirable aerosol. Generally the patient provides the energy for dispersion when they inhale through the device.
Pharma IQ: What are the advantages and disadvantages of each device?
Dr. Smyth: Metered dose inhalers are very familiar and they are typically cheap to manufacture. They also perform quite well upon testing their aerosolization efficiency. However, because these devices require coordination (press and breath at the same time) often patients will not derive benefit from the device due to incorrect use. In addition, there can be some complicated formulation issues due to the propellants we use in these devices.
Portable nebulizers have mainly arisen from precision mesh technologies that have given rise to smaller vibrating mesh nebulizers and also liquid based aerosols from other technologies like the Respimat and AERx inhalers. These devices have many advantages such as control over emitted droplet sizes, slower moving aerosols that are easier to coordinate breathing with, and well defined formulation approaches. The disadvantages are perhaps their need for more complex device components and the costs of these components. Stability of formulations can be a problem and certain types of aerosols are not always compatible with this diverse range of devices (e.g. suspensions or viscous formulations can be incompatible).
The third class is the dry powder inhalers that have seen a dramatic rise in popularity with the phase out of CFC propellants in inhaler devices. In fact that number one selling inhaled product is a dry powder inhaler. These devices are very diverse unlike the MDIs. However, the advantages are applicable to most device designs including the absence of any propellants, no need for patient breath coordination, high dose payloads possible, chemical stability and others. However, these devices suffer from generally poorer efficiencies of lung delivery and their efficiencies are often heavily dependent on the force of inhalation. What this means is that there is often considerable variability in the dose delivered from inhalation to inhalation and often, patients with poorer lung function or children cannot derive benefit from the devices.
Pharma IQ: What sorts of advancements are being made, and where do you see the future of novel pipeline pulmonary drug delivery technology?
Dr. Smyth: In each of these three inhaler device classes considerable efforts and advancements are being made in the technology performance.
For metered dose inhalers for example, efforts to develop excipients acceptable for use in inhalation are being performed. In addition, formulation of larger molecules like proteins, peptides, and nanoparticles are being actively researched.
In liquid based aerosols the advancements are in the control of aerosol delivery and integration of flow profile feedback into the device sensors. These type of higher level device control allow optimized inhalation coordination, more efficient lung delivery, and even potential for data capture/recording. Advancements in portability and costs of devices are likely to occur also.
For dry powder inhalers the major advances being made here are the improvement in lung delivery efficiency, now reaching up to 80% fine particle fraction. In addition, the dependency on inhalation efforts is being removed from device performance, opening up these devices to young children and patients with severe lung disease without loss of performance.
Pharma IQ: What about costs – are they feasible?
Dr. Smyth: In terms of costs, there was a tendency for novel technologies to incorporate complex components or expensive electronics, but as we see increased pressures on lowering health care costs, it is likely that the simplest device solutions will be the ones that thrive. High performing, easy to use, cheap, simple to manufacture inhalers are the next generation devices that will emerge.
Dr. Smyth is a speaker at the upcoming 3rd Asthma & COPD Summit, October 17 and 18, 2011 in Philadelphia, PA.
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