Theophylline attenuation of airway responses to allergen: comparison with cromolyn metered-dose inhaler

Xanthines and Phosphodiesterase Inhibitors

Theophylline is an orally acting xanthine that has been used since 1937 for the treatment of respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD). However, in most treatment guidelines, xanthines have now been consigned to third-line therapy because of their narrow therapeutic window and propensity for drug-drug interactions. However, lower than conventional doses of theophylline considered to be bronchodilator are now known to have anti-inflammatory actions of relevance to the treatment of respiratory disease. The molecular mechanism(s) of action of theophylline are not well understood, but several potential targets have been suggested including non-selective inhibition of phosphodiesterases (PDE), inhibition of phosphoinositide 3-kinase, adenosine receptor antagonism and increased activity of certain histone deacetylases. Although theophylline has a narrow therapeutic window, other xanthines are in clinical use that are claimed to have a better tolerability such as doxofylline and bamifylline. Nonetheless, xanthines still play an important role in the treatment of asthma and COPD as they can show clinical benefit in patients who are refractory to glucocorticosteroid therapy, and withdrawal of xanthines from patients causes worsening of disease, even in patients taking concomitant glucocorticosteroids.More recently the orally active selective PDE4 inhibitor, roflumilast, has been introduced into clinical practice for the treatment of severe COPD on top of gold standard treatment. This drug has been shown to improve lung function in patients with severe COPD and to reduce exacerbations, but is dose limited by a range side effect, particularly gastrointestinal side effects.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Allergen-induced airway inflammation and its therapeutic intervention

Allergen inhalation challenge has been useful for examining the mechanisms of allergen-induced airway inflammation and the associated physiological changes and for documenting the efficacy of drugs to treat asthma. Allergen inhalation by a sensitized subject results in acute bronchoconstriction, beginning within 15-30 min and lasting 1-3 hr, which can be followed by the development of a late asthmatic response. Individuals who develop both an early and late response after allergen have more marked increases in airway hyperresponsiveness, and greater increases in allergen-induced airway inflammation, particularly in airway eosinophils and basophils. All of the currently available and effective treatments for asthma modify some aspects of allergen-induced responses. These medications include short-acting and long-acting inhaled β₂-agonists, inhaled corticosteroids, cromones, methylxanthines, leukotriene inhibitors, and anti-IgE monoclonal antibody. In addition, allergen inhalation challenge has become a useful method which can, in a very limited number of patients, provide key information on the therapeutic potential of new drugs being developed to treat asthma.

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti-inflammatory therapies

Allergen bronchoprovocation tests have been used for more than two decades in the investigation of respiratory allergic diseases such as asthma and rhinitis. These bronchial challenges are now well standardized and can offer key information on the therapeutic potential of new agents and on their anti-inflammatory effects on the airways. Both standard and low-dose allergen provocations are safe when performed by experienced investigators and do not lead to persistent worsening of asthma or change in airway function. The evaluation of new therapeutic agents by these methods can also provide important information on the mechanisms of development and persistence of airway diseases.

Oral xanthines as maintenance treatment for asthma in children

BACKGROUND

Xanthines have been used in the treatment of asthma as a bronchodilator, though they may also have anti-inflammatory effects. The current role of xanthines in the long-term treatment of childhood asthma needs to be reassessed.

OBJECTIVES

To determine the efficacy of xanthines (e.g. theophylline) in the maintenance treatment of paediatric asthma.

SEARCH STRATEGY

A search of the Cochrane Airways Group Specialised Register was undertaken with predefined search terms. Searches are current to May 2005.

SELECTION CRITERIA

Randomised controlled trials,lasting at least four weeks comparing a xanthine with placebo, regular short-acting beta-agonist (SABA), inhaled corticosteroids (ICS), cromoglycate (SCG), ketotifen (KET) or leukotriene antagonist, in children with diagnosed with chronic asthma between 18 months and 18 years old.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected each study for inclusion in the review and extracted data. Primary outcome was percentage of symptom-free days.

MAIN RESULTS

Thirty-four studies (2734 participants) of adequate quality were included. Xanthine versus placebo (17 studies): The proportion of symptom free days was larger with xanthine compared with placebo (7.97% [95% CI 3.41, 12.53]). Rescue medication usage was lower with xanthine, with no significant difference in symptom scores or hospitalisations. FEV1 , and PEF were better with xanthine. Xanthine was associated with non - specific side-effects. Data from behavioural scores were inconclusive. Xanthine versus ICS (four studies) : Exacerbations were less frequent with ICS, but no significant difference on lung function was observed. Individual studies reported significant improvements in symptom measures in favour of steroids, and one study reported a difference in growth rate in favour of xanthine. No difference was observed for study withdrawal or tremor. Xanthine was associated with more frequent headache and nausea. Xanthine versus regular SABA (10 studies): No significant difference in symptoms, rescue medication usage and spirometry. Individual studies reported improvement in PEF with beta-agonist. Beta-agonist treatment led to fewer hospitalisations and headaches. Xanthine was associated with less tremor. Xanthine versus SCG (six studies ): No significant difference in symptoms, exacerbations and rescue medication. Sodium cromoglycate was associated with fewer gastro-intestinal side-effects than xanthine. Xanthine versus KET (one study): No statistical tests of significance between xanthine and ketotifen were reported. Xanthine + ICS versus placebo + same dose ICS (three studies) : Results were conflicting due to clinical/methodological differences, and could not be aggregated.

AUTHORS' CONCLUSIONS

Xanthines as first-line preventer alleviate symptoms and reduce requirement for rescue medication in children with mild to moderate asthma. When compared with ICS they were less effective in preventing exacerbations. Xanthines had similar efficacy as single preventative agent compared with regular SABA and SCG. Evidence on AEs (adverse effects) was equivocal: there was evidence for increased AEs overall, but no evidence that any specific AE (including effects on behaviour and attention) occurred more frequently than with placebo. There is insufficient evidence from available studies to make firm conclusions about the effectiveness of xanthines as add-on preventative treatment to ICS, and there are no published paediatric studies comparing xanthines with alternatives in this role. Our data suggest that xanthines are only suitable as first-line preventative asthma therapy in children when ICS are not available. They may have a role as add-on therapy in more severe asthma not controlled by ICS, but further studies are needed to examine this, and to define the risk-benefit ratio compared with other agents.

Double-blind, randomised, controlled trial assessing controller medications in asthma

BACKGROUND

The motive behind conducting this study was to determine if better control of asthma can be achieved by adding a second controller medication and to assess its use to reduce the dose of inhaled steroids.

OBJECTIVES

The study aimed to determine whether either oral sustained-release theophylline or montelukast added to inhaled steroids improved clinical symptoms and pulmonary function test parameters when compared to high-dose steroids alone.

METHODS

Ninety patients with incompletely controlled asthma were allocated, in a randomised, double-blind fashion, to one of three treatment groups: group A: double dose of inhaled budesonide (400 microg b.i.d.), group B: 400 mg oral sustained-release theophylline plus budesonide (200 microg b.i.d.) and group C: 10 mg montelukast plus budesonide (200 microg b.i.d.). The primary endpoints were forced expiratory volume in 1 s (FEV(1)) and mean morning peak expiratory flow rate (PEFR).

RESULTS

All three groups had improved FEV(1) and PEFR at 8 weeks (p < 0.001). Group C increased their PEFR by 18.7 l/min (95% confidence interval, CI, 12.4-25.1) more than group A and by 19.8 l/min (95% CI 13.4-26.1) more than group B (both p = 0.001). Similarly, group C had a 114 ml (95% CI 45-183 ml) greater improvement in FEV(1) than group A and a 95 ml (95% CI 26-164 ml) greater improvement than group B (both p = 0.01).

CONCLUSIONS

Addition of montelukast to budesonide is safe and results in greater improvement in pulmonary function test parameters than high-dose budesonide treatment or addition of theophylline.

Theophylline and PDE4 inhibitors in asthma

Over the past three decades, beta -adrenoceptor agonists and glucocorticosteroids have formed the mainstay of treatment for patients with asthma; during this time, only one new drug class, leukotriene receptor antagonists, have been introduced. Theophylline has also been used in the treatment of patients with asthma, although there is a perception that this drug does not offer the patient any advantages over conventional therapeutic strategies. However, a number of clinical studies have documented the efficacy of this orally active drug. The mechanism by which theophylline exerts its well recognized antiinflammatory activity remains to be established but, if explained, could lead to newer drug development with greater efficacy. The development of phosphodiesterase (PDE)4 inhibitors is one such approach, and recent studies have demonstrated the potential utility of this new drug class for the treatment of patients with asthma.(2)

Synergistic effect of theophylline and procaterol on interleukin-5-induced degranulation from human eosinophils

Inhibiting the release of toxic granule proteins from eosinophils is a possible means of treating allergic inflammation. This study was performed to examine whether procaterol and theophylline, commonly used bronchodilators in asthma, inhibit eosinophil degranulation induced by interleukin (IL)-5. Purified eosinophils from patients with asthma were incubated with IL-5 for 24 hr in the presence of theophylline, procaterol, combinations of theophylline and procaterol, or dexamethasone. Levels of eosinophil-derived neurotoxin (EDN) in the supernatants were measured with radioimmunoassay. Theophylline inhibited IL-5-induced release of EDN in a concentration-dependent manner. Procaterol inhibited degranulation only at high concentrations. However, procaterol at 10(-9) M and 10(-8) M, which are physiologic concentrations, together with theophylline at 10(-5) M, which is a concentration commonly found in the serum of patients receiving low-dose theophylline, inhibited degranulation by 43.8%. This finding indicates that theophylline and procaterol have synergistic effects. The inhibition was comparable to that with dexamethasone at 10(-9) M. Our results suggest that a combination of low-dose theophylline and procaterol exhibits antiinflammatory effects in asthma by inhibiting eosinophil-effector functions.

Drug treatment of airway inflammation in asthma

Several methods are available for assessing drug effects on airway inflammation and the antiinflammatory effects of drugs for asthma. Cromolyn and theophylline are well-established drugs for the treatment of asthma, and each has antiinflammatory properties. Drugs in development include those aimed at inhibiting inflammatory mediators and immunoglobulin E function; clinical studies, however, have been conducted largely in patients with moderate to severe asthma.

The pathobiologic implications for treatment. Old and new strategies in the treatment of chronic asthma

An increased understanding of the pathobiology of asthma has led to improved treatment for chronic asthma. This article discusses the old and new strategies of asthma therapy based on a pathobiologic approach. Therapeutic agents discussed include beta-adrenergic agonists, methylxanthines, corticosteroids, cromolyn, nedocromil, leukotriene modifiers, and new investigational agents.

Theophylline inhibits the late asthmatic response to nighttime antigen challenge in patients with mild atopic asthma

BACKGROUND

Inhaled antigen at night causes a more pronounced late asthmatic response (LAR) when compared with daytime challenges. Chronopharmacology with controlled-release theophylline given in the evening leads to a peak serum theophylline concentration (STC) in early morning which coincides with LAR that follows an evening challenge.

OBJECTIVE

To evaluate the effect of controlled-release theophylline given with the evening meal on the immediate asthmatic response (IAR) and LAR following nighttime antigen challenge in patients with mild atopic asthma.

METHODS

To qualify, subjects underwent antigen bronchoprovocation by graded nebulization until the IAR (fall in FEV1 of > or =20%) occurred; spirometry was then measured hourly for 8 hours to establish the presence of LAR (fall in FEV1 > or =15%). After 2 weeks of randomized, double-blind crossover treatment with either theophylline (target STC of 10 to 15 mg/L, (56 to 83 micromol/L)) or placebo, inhaled antigen challenge was performed at 10 PM in each subject. FEV1 values were measured immediately and then hourly for 8 hours following antigen challenge.

RESULTS

Twelve subjects completed the study. During the placebo phase, the maximal fall in FEV1 during LAR was 39 +/- 3% (mean +/- SEM) compared with 31 +/- 4% fall during theophylline treatment phase (P = .01). A reduction in LAR occurred despite higher dose (P <.05) of inhaled antigen during theophylline phase, which would have been expected to result in a more pronounced LAR. Serum theophylline concentration at 8 AM on the day following antigen challenge was 9.6 +/- 1.1 mg/L (53 +/- 6 micromol/L).

CONCLUSION

Nocturnal administration of controlled-release theophylline increases the tolerance to inhaled antigen and reduces severity of LAR. Because the LAR is linked to airway inflammation, these data support the possibility of antiinflammatory effects associated with theophylline use.

The efficacy of slow versus faster inhalation of cromolyn sodium in protecting against allergen challenge in patients with asthma

BACKGROUND

Approximately one third of patients with allergy-induced asthma who are treated with aerosolized cromolyn sodium (CS) fail to achieve a full therapeutic effect. This lack of effectiveness could involve nonhomogeneous distribution of drug in the lung as a result of high inspiratory flow rates.

OBJECTIVE

We sought to determine the efficacy of slow versus faster inhalation of CS in protecting against allergen challenge in patients with asthma.

METHODS

Eight patients with asthma underwent two allergen challenges 30 minutes after pretreatment with CS that was inhaled from a large holding chamber at approximately 30 L/min or approximately 70 L/min. Percent decreases in FEV1 at a common dose of allergen on the two challenge days were compared. Values of skew (an indicator of aerosol distribution homogeneity) obtained from gamma camera lung images after slow and faster inhalation of radiolabeled CS were also compared.

RESULTS

Mean (+/- SD) allergen-induced decrease in FEV1 was 5.4% +/- 4.2% after slow inspiration of CS, which was significantly less than the allergen-induced decrease in FEV1 after faster inhalation of CS with 12.6% +/- 11% (p < 0.05). Mean skew values were also significantly decreased after slow inspiration of CS, and differences in decreases in allergen FEV1 and skew values for the two breathing maneuvers were significantly correlated.

CONCLUSION

These data indicate that protection against allergen-induced asthma can be optimized by slowly inspiring CS from a large holding chamber compared with faster inhalation of the drug. These results appear to be related to enhanced distribution homogeneity of CS within the lungs.

Theophylline's effect on neutrophil function and the late asthmatic response

BACKGROUND

The decrement in lung function associated with the late asthmatic response after allergen challenge is believed to be mediated by an inflammatory response in the airways. Theophylline has been shown to inhibit the late asthmatic response, but the mechanisms are not clear.

OBJECTIVE

The study was designed to determine whether theophylline would inhibit the late asthmatic response by reducing neutrophil activation and subsequent superoxide production.

METHODS

Twelve subjects with asthma underwent treatment in this double-blind, randomized, crossover study. Each subject received theophylline and placebo in random order in two treatment periods of 3 weeks each. Each treatment period was followed by an allergen challenge and blood neutrophil function analysis.

RESULTS

At therapeutic levels theophylline increased FEV1 at baseline and during the allergen challenge and increased the percentage suppression of neutrophil superoxide production by adenosine.

CONCLUSION

Theophylline improved pulmonary function at baseline and during an allergen challenge, in part perhaps, by increasing the neutrophil's response to feedback inhibition by adenosine. However, theophylline did not decrease the severity and duration of the late asthmatic response.

Anti-inflammatory effects of theophylline: modulation of cytokine production

BACKGROUND

The basis for the efficacy of theophylline in the treatment of asthma remains enigmatic. Although commonly classified as a bronchodilator, its ability to dilate smooth muscle is considered fairly poor and clinical responses are often independent of bronchodilation. Recent studies have suggested that immunomodulatory activities may contribute to the therapeutic benefit mediated by theophylline.

OBJECTIVE

We performed these preliminary studies to determine whether theophylline modulates cytokine production by peripheral blood mononuclear cells.

METHODS

Peripheral blood mononuclear cells were obtained from 24 asthmatic subjects and were left in a resting state or stimulated with either mitogens (phytohemagglutinin, lipopolysaccharide) or antigen (tetanus, cat) with or without the additional presence of theophylline (15 micrograms/dL). Supernatants were collected and evaluated for cytokine concentration by ELISA.

RESULTS

Theophylline neither inhibited production of allergenic cytokines such as IL-4 nor modulated the repertoire of cytokines produced by TH cells. A statistically significant inhibition of spontaneous interferon-gamma synthesis was observed (24.5 +/- 8.6 to 13.4 +/- 4.2; P < .05). Theophylline did have anti-inflammatory effects on cytokines primarily produced by mononuclear phagocytic cells. Theophylline mediated a slight inhibition of TNF-alpha production (0.26 +/- 0.08 to 0.21 +/- 0.06; P < .05). Theophylline was also associated with a 2.8-fold increase in spontaneous production of the anti-inflammatory cytokine IL-10 (0.35 +/- 0.08 to 0.98 +/- 0.16 ng; P < .01).

CONCLUSIONS

A relative absence of IL-10 characterizes the asthmatic airways and may contribute to the development and severity of allergic inflammation. Induction of IL-10 production by theophylline may therefore mitigate inflammation and contribute to the clinical efficacy of this class of medications.

Effects of theophylline and rolipram on antigen-induced airway responses in neonatally immunized rabbits

1. The effects of the xanthine, theophylline, a non-selective phosphodiesterase (PDE) inhibitor, and the phosphodiesterase type 4 (PDE 4) inhibitor, rolipram, were evaluated in a model of antigen-induced airway responses in the allergic rabbit. 2. Adult litter-matched NZW rabbits (2.5-3.9 kg), immunized within 24 h of birth with Alternaria tenuis antigen, were pretreated twice daily for 3 days with theophylline (3 mg kg-1, i.p) or rolipram (1 mg kg-1, i.p) prior to antigen challenge (Alternaria tenuis). For each drug-treated group, a parallel group of rabbits were pretreated with the appropriate vehicle. In all groups airway responsiveness to inhaled histamine and bronchoalveolar lavage (BAL) was performed 24 h before and after antigen-challenge. 3. Basal lung function in terms of resistance (RL, cmH2O 1(-1)s-1) and dynamic compliance (Cdyn, ml cmH2O-1) were unaltered by pretreatment with theophylline or rolipram compared to their respective vehicles 24 h prior to or post antigen challenge. 4. The acute bronchoconstriction induced by inhaled Alternaria tenuis aerosol was unaffected by pretreatment with theophylline or rolipram. 5. Airway hyperresponsiveness to inhaled histamine was indicated by reduced RL PC50 (2.4-3.5 fold) and Cdyn PC35 (2.5-2.6 fold) values 24 h after antigen challenge. Treatment with rolipram, but not theophylline, prevented the increase in responsiveness to inhaled histamine 24 h after antigen challenge. 6. Total cells per ml of BAL fluid increased 24 h after antigen challenge due to the recruitment of neutrophils and eosinophils. Antigen-induced increases in pulmonary neutrophils were unaffected; however, eosinophils were reduced 57.5% in theophylline and 82% in rolipram-treated rabbits. 7. Inhalation of Alternaria tenuis aerosol elicits an acute bronchoconstriction, followed 24 h later by an increased responsiveness to inhaled histamine and pulmonary neutrophil and eosinophil recruitment in the immunized rabbit. With the dosing regimes used, both rolipram and theophylline inhibited eosinophil recruitment, whilst only rolipram prevented the development of airway hyperresponsiveness. Neither agent inhibited the acute bronchoconstriction due to inhaled antigen.