Devices for Pulmonary Drug Delivery

Delivery devices play a major role in the efficiency of pulmonary delivery, and major advances have been made in the development of new devices in recent years. The most commonly used devices for pulmonary drug delivery include nebulizers, metered-dose inhalers (MDIs) and dry-powder inhalers (DPIs). These de- 

MDI delivery efficiency depends on the patient s inspiratory flow rate, breathing pattern and hand-mouth coordination. Increases in tidal volume and decreases in respiratory frequency enhance the peripheral deposition in the lung. Most patients need to be trained to use the MDI correctly, as up to 70% of patients fail to do so [26, 30]. 

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The technology and the science of a device for pulmonary drug delivery have been described (35). The core of this device is a centimeter-size, clog-free silicon-based ultrasonic nozzle with multiple Fourier horns in resonance at a frequency in the MHz range. 

The third common type of device for pulmonary drug delivery is the dry powder inhaler (DPI). This device now has many forms, some of which appear remarkably simple in their design (Figure 14.4). Particular effort has gone into the formulation of the powder. In most cases the drug is of the order a few micrometre in size and is adhered - usually by natural forces - to inert carrier... 

The first commercially available DPI system appeared on the market in 1949, developed and marketed by Abbott under the name Aerohaler. Like all early pulmonary drug-delivery devices, it delivered small-molecule compoimds (bronchodilators or inhaled corticosteroids) to the airways (not necessarily the deep limg) for the treatment of asthma or chronic obstructive pulmonary disease. Table 6 lists some of the early DPI systems used for asthma and COPD the energy somces in these devices were mechanical and patient inspiration. 

Administration Iloprost is intended for inhalation administration only via the Prodose AAD system, a pulmonary drug delivery device. It has not been studied with any other nebulizers. 

Prior to clinical evaluations, comprehensive studies were conducted to characterize prototype EHD pulmonary drug delivery devices for emitted dose uniformity and reproducibility of particle size distribution. Table 16 shows the dose uniformity. 

Advances in the equipment for the administration of aerosol medication to horses have facilitated the widespread use of inhalation therapy in equine medicine. Newer aerosolization devices ease administration and make pulmonary drug delivery efficient. Aerosol therapy is likely to become the mainstay of treatment for horses with heaves and may prove beneficial in the treatment of infectious respiratory disease in horses. 

Intimately related to these factors is the design of the device, formulation, and the interface with the patient. Much of the discussion below will focus on the implications of excipients on formulation challenges for inhaled aerosol products. This chapter summarizes excipients for pulmonary formulations from several perspectives (i) excipient selection based on principles of delivery, (ii) physicochemical requirements for excipients, and (iii) specific challenges for formulations faced with aerosol drug delivery systems, including (a) biological aspects, (b) microbiological aspects, (c) analytical issues, and (d) future prospects. 

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