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Alternative and experimental agents for the treatment of asthma
Author Richard J Martin, MD Section Editors Bruce S Bochner, MD Robert A Wood, MD Deputy Editor Helen Hollingsworth, MD

Last literature review version 17.2: May 2009 | This topic last updated: June 8, 2009 (More) INTRODUCTION — The standard treatment of patientswith asthma is based upon trigger avoidance, combined with bronchodilator and antiinflammatory therapy. Beta agonists, glucocorticoids, leukotriene modifiers, and, to a lesser extent, methylxanthines, cromoglycates, and anticholinergics all have a role in the conventional treatment of asthma. However, some patients are difficult to treat solely with conventional therapy. For these patients,consideration may be given to the administration of nonstandard therapeutic regimens in order to ameliorate the acute or chronic manifestations of the disease. Alternative and experimental therapies for the treatment of acute and chronic asthma will be reviewed here. The standard treatment regimens for asthma are discussed separately. ( See "An overview of asthma management" and see "Treatment of acuteexacerbations of asthma in adults" ). ACUTE ASTHMA — Nonstandard therapies for the patient with an acute asthma exacerbation include the administration of helium-oxygen gas mixtures, intravenous leukotriene modifiers, empiric antibiotics, anesthesia, and nebulized furosemide . The specific recommendation of these therapies is difficult, however, since adequate controlled studies evaluating theeffectiveness of these modalities in specific asthmatic populations have not yet been performed. Two of these therapies are being used with greater See "Treatment of frequency than the others, and are discussed elsewhere. ( acute exacerbations of asthma in adults" ). Empiric antibiotics —Clinical practice guidelines recommend against empiric antibiotic therapy for the treatment of an asthmaexacerbation because most respiratory infections that trigger an exacerbation of asthma are viral rather than bacterial [ 1] . In a meta-analysis of two randomized, controlled trials (97

patients, 115 exacerbations), empiric antibiotics did not confer any benefit compared to placebo when administered to patients with asthma exacerbation [ 2] . Anesthesia — The use of anesthetic agents for patients withstatus asthmaticus has been described since the 1930s. Experience is greatest with halothane for this indication, but isoflurane , enflurane , and sevoflurane have shown effectiveness in case reports or animal models [ 3-6] . Idiosyncratic reactions to these anesthetics have been described, and a given patient may respond better to one than to another. The mechanism by which bronchodilation isproduced remains unclear; a direct relaxant effect on airway smooth muscle, and attenuation of cholinergic tone, have both been proposed [7,8] . The dose of inhalational anesthetic is titrated to the clinical response (eg, improvement in airway resistance) and avoidance of intolerable side effects. Hypotension is often the limiting factor in the administration of these agents, and myocardialdepression and increased ventricular irritability have been observed with halothane , particularly when used in the presence of acidosis, beta-agonists, and theophylline . The use of inhalational anesthetics for treatment of status asthmaticus is limited by its expense, the need for a full-time anesthesiologist at the bedside, adaptation of equipment for long-term provision of anesthetics, and the abruptreturn of bronchoconstriction upon discontinuation. There is also the issue of scavenging anesthetic gases released into the immediate environment in order to avoid second-hand inhalation of aerosolized anesthetic gases by health care personnel or other patients. There have been several case reports in which children and adults with status asthmatics have been successfully treated with...