Introduction

The inhalation delivery of therapeutic agents has been known, though poorly understood, for many years. A wide variety of agents has been administered to the lung via oral inhalation, for the treatment of diverse disease states. The most frequent use of inhalation therapy is for the treatment of obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), using drugs such as short- and long-acting b sympathomimetics, corticosteroids, and anticholinergic agents. However, the respiratory route has been receiving increased attention since the early 1990s as a portal route for systemic drug delivery, most notably for the delivery of inhaled insulin [1,2].

Common to all inhalation dosage forms and delivery systems is the need to generate the optimum "respirable dose" (particles < 5.0 mm) of a therapeutic agent, and this is a central performance feature in the rational design and selection of a delivery system. Moreover, this performance, in terms of aerosol quality, should be demonstrated throughout the product's shelf life, in addition to the more usual chemical and physical stability criteria. Thus, particularly in the development of metered-dose inhalers (MDIs) and dry powder inhalers (DPIs), device design is integrated with formulation work in the overall product development strategy. Frequently, therefore, such inhalation delivery systems tend to be compound specific. Thus, the physicochemical properties and the pharmacological profile (dose) of a given compound will occasionally predispose the choice of inhalation system. Hence, a good basis of preformulation information is essential for the rational design, selection, formulation, and development of inhalation drug delivery systems.

Within the pharmaceutical industry, inhalation drug delivery system selection is a pivotal commercial decision. This should be based on factors such as:

Overall clinical objective (acute or chronic treatment)

Target patient population (e.g., ambulatory, infants, elderly)

Regulatory requirements

Competitor activity

Three basic types of commercially available inhalation drug delivery systems exist, and each is specifically addressed in this chapter.

Nebulizers: Traditionally used for the acute care of nonambulatory, hospitalized patients, particularly with coordination or dexterity difficulties. Solutions or suspensions can be nebulized by ultrasonics or an air jet and administered via a mouthpiece, ventilation mask, or tracheostomy.

Metered-dose inhalers: A versatile, multidose inhaler where the drug is formulated in a propellant mix, under pressure, with the drug being expelled (by a valve) in a metered volume from the volatile mixture as the propellant evaporates. These products have been the subject of much research interest since the early 1990s as pharmaceutical companies have sought to replace their CFC formulations with newer formulations containing the non-ozone-depleting gases (hydrofluroalkanes—HFAs).

Dry powder inhalers: These are inhalers that typically fall into two general types of commercially available systems: single-dose and multidose systems. The multidose systems have been finding increased use in recent years and are generally either "passive" devices, where the patient provides the energy to disperse the drug powder in a stream of inspired air, or "active" devices, in which the energy comes from the device.

This chapter presents an overview of formulation design, describes device function, and addresses product operation in relation to inhalation delivery system performance for nebulizers, MDIs, and DPIs. Methods of manufacture of dosage form are also briefly discussed to highlight critical features of each inhalation delivery system.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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