Device design inhalers

Research and development for dry powder inhalers have two main focuses the optimization of the powder formulation for use in these inhalers and investigations of novel DPI device designs and technology. An enormous literature now exists in each of these areas for more extensive reviews readers should consult refs. 33,167, or 168. 

The Solo device from Inhale Therapeutic Systems is a patient-driven unit dose inhaler. It has a built-in flow control to maximize the reproducibility of dose to patient. It is designed for short-term use and when large drug dosages are preferred. 

Peart, J. Magyar, C. Byron, P.R. Aerosol electrostatics— metered dose inhalers (MDIs) reformulation and device design issues. In Respiratory Drug Delivery VT, Dalby, R.N., Byron, P.R., Farr, S.J., Eds. Interpharm Press Buffalo Grove, IL, 1998 227-233. 

DeYoung L. The AeroDose multidose inhaler device design and delivery characteristics. Presented at Respiratory Drug Delivery VI, Hilton Head, EL, 1998. 

DeYoung L. The Aerodose multidose inhaler—device design and delivery characteristics. In Respiratory Dmg Delivery VI Dalby RN, Byron PR, Farr SJ, eds. Interpharm Press Hilton Head, SC, 1998 91-96. 

Particle size selective OEL have already been established to address the problems associated with specific health effects, especially within fields where solid aerosol particles are to be measured. A number of filter cassette designs have been tailored to sample specific size ranges of the total aerosol fraction, in order not to overestimate the exposure causing health effects by inhalation. Since only particles less than approximately 100 /rm can be inhaled and the inhaled aerosol fraction is most certainly the main contributor to specific health effects among workers exposed to isocyanates, it seems reasonable to use sampling devices designed for sampling of the inhalable... 

Masks A protective device complete with an approved filter designed to keep dangerous chemicals from being inhaled into the lungs. 

Respirator A device that is designed to protect the wearer from inhaling harmful contaminants. 

A new trend in the delivery of medicines is to employ a device component. This may be an implantable pump for insulin, a metallic stent coated with a drug, or unit capable of rapidly vaporizing a discrete dose for inhalation. Such products are regulated by the FDA as "combination" products and may be reviewed by multiple Centers within the Agency, which may require additional levels of documentation to support the product design. 

Alveolar air Collection of exhaled air using a specially-designed device to provide pure air for inhalation. Breath collected into duplicate evacuated canisters. GC/MS 0.5 pg/m (0.5 ppt, w/v) 112 (8% RSD) at 5.1 pg/m Raymer et al. 1990... 

In Section 3.5.3, dry powder inhalers have been referred to as breath-controlled devices. The efficacy of dry powder inhalation is a function of many factors, influencing the delivered dose of fine particles and the deposition of these particles in the respiratory tract. Figure 3.4 shows that DPI performance is influenced both directly and indirectly by the design of the inhalation system. The powder formulation, the dose (measuring) system and the powder disintegration principle have to be designed correctly for release of sufficient fine drug particles in... 

Laser diffraction is a fast alternative for analysis of the size distribution of particles in an aerosol cloud. The theory of laser diffraction is well understood [124,125]) but this technique requires special measures to test inhalation devices and to interpret the results correctly. One of the major problems is that flow adjustment through the inhaler is not possible. Furthermore, the presence of carrier particles from adhesive mixtures may disturb the measurement of the fine drug particles and the size distribution obtained is of an unknown dehvered mass fraction of the dose. These practical problems and limitations have been solved by the design of a new modular inhaler adapter for the Sympatec laser diffraction apparatus (Figure 3.6). 

HCG human chorionic gonadotropin HCL hairy cell leukemia Hct hematocrit HCTZ hydrochlorothiazide HD hemodialysis HDAC histone deacetylase Hep hepatitis hepatotox hepatotoxicity HER2 type of cancer gene HF heart failure HFA designation for type of inhalation device Hgb hemoglobin HIT/HITTS heparin-mduced thrombocytopenia... 

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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