10/29/03 Antihistamine treatment of asthmaSummaryAntihistamines (AH) have been tried in the treatment of asthma for many years. This subject was reviewed by Nelson of the National Jewish Medical and Research Center in Denver, CO. He pointed out that use of the older (first generation) AH in asthma treatment was limited by sedative and other side effects of these agents. The usual doses of currently used (non-sedating) AH such as fexofenadine or loratadine have little or no beneficial effects in asthma. However, a combination of loratadine 5 mg and pseudoephedrine 60 mg bid improved both asthma symptoms and peak expiratory flow rates. Studies of the effects of higher than usual doses of fexofenadine in asthma are underway. Cetirizine, in doses of 10-20 mg/day once or twice daily, consistently reduced asthma symptoms. A combination of loratadine 20 mg and montelukast (a leukotriene receptor antagonist) improved asthma symptoms and PEFR more than montelukast alone. The author concluded that AH in current use and under development may have direct beneficial effects in asthma when used in larger than customary doses. If such larger doses are sedative, it may be necessary to reduce the dose while adding oral decongestants or leukotriene receptor antagonists. Reference J Allergy Clin Immunol 2003; 112(4 Suppl):S96-S100 Editor's Comments The direct beneficial effects of AH in asthma have not been impressive in earlier studies. Indeed, for years it was stated that AH treatment may be deleterious in asthma, presumably because of concerns about the anti-cholinergic actions of older AH agents that might "dry up" bronchial secretions. Such a dring effect might lead to thickened mucus that obstructed lower airways. With the more selective action of current AH without anti-cholinergic effects, such concerns are unfounded. Current AH in usual doses appear to exert little direct bronchodilating effect. The ongoing trials of larger than usual doses of fexofenadine referred to above may be very worthwhile since much larger than usually administered doses of fexofenadine can be given without side effects. The same statement cannot bed said for loratadine, where 20 mg (twice the usual adult dose) can induce adverse cognitive effects in some people. The incidence of sedation with the usual 10 mg adult dose of cetirizine is 8-14% (vs 2-3% with placebo) in most studies. Increasing the dose to 20 mg is associated with an even higher incidence of sedation. It should be mentioned that control of associated allergic rhinitis by AH therapy may have significant indirect beneficial effect on asthma. Indeed, this may be the major way in which AH treatment will benefit asthma.
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