The disease modifying treatments for asthma and rhinitis mirror each other. The first line therapy being the topical corticosteroids, for which there is good evidence of superiority over other therapies. They work by altering the transcription of genes involved in the inflammatory process, thereby favourably influencing the synthesis of inflammatory proteins and cytokines. They have been shown to reduce the numbers of inflammatory cells and their inflammatory action. Other disease modifying therapies such as anti-IgE antibodies improve allergic symptoms in both asthma and rhinitis. Theophylline has been used for many years as a treatment for asthma but has not been used to help patients with rhinitis.
Theophylline has been considered a weak bronchodilator for many years. However relatively recently, it was shown to have anti-inflammatory effects in patients with asthma. It reduces eosinophil counts and eosinophilic cationic protein (ECP) concentration in induced sputum of asthmatic patients. The combination of low dose theophylline has greater effects on lung function and asthma severity than high dose inhaled corticosteroids.
Aubier el al have shown, using a nasal allergen challenge model of rhinitis, that 3 weeks treatment with slow release oral theophylline reduced the increase in the concentration of eosinophilic cationic protein (ECP) and the percentage of eosinophils in nasal lavage following the challenge. Furthermore there was a significant reduction in nasal symptoms in those patients treated with theophylline. However theophylline has not previously been evaluated as a therapeutic option in patients with chronic rhinitis in the clinic setting.
Cigarette smoking is a major cause of morbidity in patients with asthma and has been shown to be independently associated with impaired quality of life in asthmatic children. Recent evidence suggests that patients with asthma who smoke are relatively resistant to inhaled or oral corticosteroid therapy, with larger doses being required for clinical benefit. The actual mechanism for this observation is unknown however one hypothesis is that smoking has an effect on histone deacetylase. It is known that theophylline can active histone deacetylase and therefore improve the efficacy of corticosteroids.
Theophylline causes significant adverse effects at high doses. Unfortunately the bronchodilator effect occurs at doses very close to those causing adverse effects. This low therapeutic index for bronchodilation means that therapeutic monitoring is required. However the anti-inflammatory effect of theophylline and the effect of theophylline on histone deacetylase activity occurs at concentrations lower therapeutic level for bronchodilation.
Why have we chosen a dose of 200mg twice daily? In the study by Evans et al which compared low dose inhaled budesonide plus theophylline to high dose inhaled budesonide, greater effects with the theophylline combination were seen in terms of pulmonary function and hyperresponsiveness at serum concentrations of theophylline that were sub therapeutic (8.7mg/ml). Anti-inflammatory effects are seen in patients with chronic obstructive pulmonary disease at theophylline concentrations that are subtherapeutic. There have been studies in patients with asthma that have shown anti-inflammatory effects at in patients with asthma at doses of 250mg twice daily and 200mg twice daily. We wish therefore to evaluate the effect of low dose theophylline in patients with asthma, given its effects as subtherapeutic concentrations and the propensity to develop adverse events at higher doses.
