Management of Asthma and Chronic Airflow Limitation (Part 4)
Methylxanthines in Maintenance Therapy of Asthma
Methylxanthines continue to be used by many physicians, usually in sustained-release formulations, as first-line treatment in the maintenance therapy of asthma. However, this class of drugs has numerous and commonly occurring side effects as will be discussed subsequently. Other drugs such as cromolyn and inhaled corticosteroids, which have minor side effects, and which address the underlying inflammation in the case of the latter, are effective prophylactic agents in contrast to simple bronchodilators such as methylxanthines and adrenoceptor agonists.
Methylxanthines are relatively weak bronchodilators and additional bronchodilatation can be obtained with the addition of an aerosol betag agonist to the regimen. It also has been demonstrated that aerosolized beta2 agonists alone are much more potent than aminophylline at so-called “therapeutic” concentrations. Furthermore, in patients on optimal doses of theophylline, addition of a beta agonist may contribute to improvement of peak flow rates and reduction of symptoms. However, a number of reports suggest that regimens consisting of theophylline alone or combined with betaa agonists are superior to beta2 agonists alone in the maintenance therapy of asthma. buy asthma inhalers
A major weakness of some of these studies is the use of ingested adrenoceptor agonists, since it has been convincingly demonstrated that aerosols are associated with only minor and relatively infrequent side effects at doses which achieve about twice as much bronchodilation than maximum tolerated doses of the same drug following ingestion.