Antiasthmatic agents

Asthma is an extremely complex condition characterized by variable and reversible airways obstmction combiaed with nonspecific bronchial hypersensitivity (1 3). The cause of asthma, which is not always readily diagnosed (4), remains unknown. Days, if not weeks, ate needed to document the spontaneous reversal of the airways obstmction ia some patients. Asthmatics experience both an immediate hypersensitivity response and a delayed late-phase reaction, each mediated by a different pathway. Chronic asthma has come to be viewed as an inflammatory disease (5). The late-phase reaction plays a key role ia iaduciag and maintaining the inflammatory state which ia turn is thought to iaduce the bronchial hyperresponsiveness (6). The airways obstmction results from both contraction of airways smooth muscle and excessive bronchial edema. Edema, a characteristic of inflammatory states, is accompanied, ia this case, by the formation of a viscous mucus which can completely block the small airways. 

Asthma affects 3—5% of the population and is one of the most common chronic illnesses (7—9). Both the frequency and severity of asthma appear to be increasing (10—13). Acute, severe asthma has the potential to be fatal. The disease may first appear ia childhood and iadividuals so affected can suffer recurrent episodes throughout their Hves or they may outgrow the condition at puberty. On the other hand, there is also adult-onset asthma. These people show no symptoms as children or as young adults, but suddenly develop symptoms later ia life. There have been many reports of bronchial infections preceding the appearance of asthma. However it is not known whether these infections contributed to the development of the disease or whether iadividuals who are already predisposed to asthma ate more likely to experience bronchospasms as a result of a bronchial infection (14). 

Intrinsic asthma, also called idiopathic asthma, usually develops in adulthood. In intrinsic asthma allergic factors are not demonstrable. Episodes of intrinsic asthma may be triggered by a variety of stimuli, eg, emotional state, exposure to cold air, or inert dusts. Both intrinsic and extrinsic asthmatics can be prone to exercise-induced attacks. Individuals who experience a combination of extrinsic and intrinsic asthmatic reactions have mixed asthma. Status asthmaticus refers to an especially acute life-threatening asthma attack which is resistant to normal treatments and which may require hospitalization in order to stabilize the patient. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Improvements in asthma treatment include the development of more effective, safer formulations of known dmgs. The aerosol adrninistration of P2-agonists or corticosteroids results in a decrease in side effects. Also, the use of reUable sustained release formulations has revolutionized the use of oral xanthines which have a very narrow therapeutic index (see Controlled release technology). For many individuals, asthma symptoms tend to worsen at night and the inhaled bronchodilatots do not usually last through an entire night s sleep (26,27). 

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Antianxiety agents Antiaiis toxicaiia An ti air hy thnu c Antiairhythnnc agents Antiaithritics Antiasthmatic agents... 

IRACE AND RESIDUE ANALYSIS] (Vol 24) -endogenous [ANTIASTHMATIC AGENTS] (Vol 2)... 

The use of metered-dose valves in aerosol medical appHcations permits an exact dosage of an active dmg to be deHvered to the respiratory system where it can act locally or be systemicaHy absorbed. For example, inhalers prescribed for asthmatics produce a fine mist that can penetrate into the bronchial tubes (see Antiasthmatic agents). 

Dimethylaminoethyl-2,4,6-trimethoxybenzoates and similar esters are useful as spasmolytics and in relieving indigestion (180). Bis-chromonyl compounds derived from phloroglucinol are valuable in the treatment of asthma (see Antiasthmatic agents) (181). 

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