Sustained release theophylline in nocturnal asthma

Design and optimization of colon-targeted system of theophylline for chronotherapy of nocturnal asthma

The objective of the present work was to develop a delayed-onset controlled-release colon-targeted system of theophylline, and to achieve the chronotherapy of nocturnal asthma. The formulation consisted of a core tablet containing hydroxypropyl methylcellulose used for achieving controlled release of drug, and a Eudragit S100:ethyl cellulose (EC) coating capable of delaying the drug release. The system was optimized using a 3(2) full factorial design, wherein two factors [ratio of Eudragit S100:EC and the coating level (% w/w)] were evaluated for lag time, t(50) and t(80) . The optimum formulation consisted of Eudragit S100:EC in a 60:40 ratio and a coating level of 7.5% (w/w). Results showed that the tablets prepared according to the optimized values released no drug in the upper part of gastrointestinal tract; drug release was initiated at pH 6.4 (colon) after a lag time of 5 h. In vivo evaluation (pharmacokinetic studies and roentgenography) in rabbits revealed that the tablet remained intact until it reaches the colon and the drug release was initiated after a lag time of 5 h. Thus, it can be concluded that the developed system exhibited a promising colonic targeting and hence may be used for chronotherapy of nocturnal asthma.

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.

Nocturnal asthma: underlying mechanisms and treatment

Nocturnal asthma is defined by a drop in forced expiratory volume in 1 second (FEV(1)) of at least 15% between bedtime and awakening in patients with clinical and physiologic evidence of asthma. Nocturnal symptoms are a common part of the asthma clinical syndrome; up to 75% of asthmatics are awakened by asthma symptoms at least once per week, and approximately 40% experience nocturnal symptoms on a nightly basis. An extensive body of research has demonstrated that nocturnal symptoms such as cough and dyspnea are accompanied by increases in airflow limitation, airway hyperresponsiveness, and airway inflammation. Treatment strategies in nocturnal asthma are similar to those used in persistent asthma, although dosing of medications to target optimum delivery during periods of nocturnal worsening is beneficial.

Nocturnal asthma uncontrolled by inhaled corticosteroids: theophylline or long-acting beta2 agonists?

Asthma is an inflammatory disease of the airways that is frequently characterised by marked circadian rhythm. Nocturnal and early morning symptoms are quite common among patients with asthma. Increased mortality and decreased quality of life are associated with nocturnal asthma. Although numerous mechanisms contribute to the pathophysiology of nocturnal asthma, increasing evidence suggests the most important mechanisms relate to airway inflammation. According to international guidelines, patients with persistent asthma should receive long term daily anti-inflammatory therapy. A therapeutic trial with anti-inflammatory therapy alone (without a long-acting bronchodilator) should be assessed to determine if this therapy will eliminate nocturnal and early morning symptoms. If environmental control and low to moderate doses of inhaled corticosteroids do not eliminate nocturnal symptoms, the addition of a long-acting bronchodilator is warranted. Long-acting inhaled beta2 agonists (e.g. salmeterol, formoterol) are effective in managing nocturnal asthma that is inadequately controlled by anti-inflammatory agents. In addition, sustained release theophylline and controlled release oral beta2 agonists are effective. In patients with nocturnal symptoms despite low to high doses of inhaled corticosteroids, the addition of salmeterol has been demonstrated to be superior to doubling the inhaled corticosteroid dose. In trials comparing salmeterol with theophylline, 3 studies revealed salmeterol was superior to theophylline (as measured by e.g. morning peak expiratory flow, percent decrease in awakenings, and need for rescue salbutamol), whereas 2 studies found the therapies of equal efficacy. Studies comparing salmeterol to oral long-acting beta2 agonists reveal salmeterol to be superior to terbutaline and equivalent in efficacy to other oral agents. Microarousals unrelated to asthma are consistently increased when theophylline is compared to salmeterol in laboratory sleep studies. In addition to efficacy data, clinicians must weigh benefits and risks in choosing therapy for nocturnal asthma. Long-acting inhaled beta2 agonists are generally well tolerated. If theophylline therapy is to be used safely, clinicians must be quite familiar with numerous factors that alter clearance of this drug, and they must be prepared to use appropriate doses and monitor serum concentrations. Comparative studies using validated, disease specific quality of life instruments (e.g. Asthma Quality of Life Questionnaire) have shown long-acting inhaled beta2 agonists are preferred to other long-acting bronchodilators. Examination of costs for these therapeutic options reveals that evening only doses of long-acting oral bronchodilators are less expensive than multiple inhaled doses. However, costs of monitoring serum concentrations, risks, quality of life and otheroutcome measures must also be considered. Long-acting inhaled beta2 agonists are the agents of choice for managing nocturnal asthma in patients who are symptomatic despite anti-inflammatory agents and other standard management (e.g. environmental control). These agents offer a high degree of efficacy along with a good margin of safety and improved quality of life.

A double-blind, placebo-controlled comparison of the efficacy of standard and individually titrated doses of theophylline in patients with chronic asthma

Forty adult patients with chronic asthma completed a 3-month double-blind crossover study to compare the effect of sustained-release theophylline given both as a fixed 300 mg twice daily dose (standard) and an individually titrated dose (titrated) with placebo. Theophylline was given in addition to other usual therapy, inhaled bronchodilators, inhaled steroids and, in 12 patients, oral steroids. The 3-month period was preceded by a run-in phase to determine the dose of theophylline which each subject required to achieve peak serum levels of 12-20 mg/litre and trough levels of 8-12 mg/litre. Doses ranged from 300 mg to 700 mg twice daily. Twenty-one patients needed more than the standard dose to achieve satisfactory serum levels. Patients recorded daily peak flow rates and symptom scores and were seen at monthly intervals to measure lung function, check serum theophylline levels and change treatments, which were given in random order. FEV1 was significantly higher for the whole group after standard (2.11 litres) and titrated (2.15 litres) theophylline therapy than after placebo (1.89 litres), as was FVC, but in the large subgroup whose titrated dose was greater than the standard dose, the FEV1 only improved with the titrated dose. Peak flow measurements at home showed the same pattern. Patients taking oral steroids appeared to derive less benefit from theophylline than others. It is concluded that theophylline can usefully be added as a third-line drug in chronic asthma, but that since half the patients are likely only to benefit from a dose greater than 300 mg twice daily, while the other half may have high serum levels above this dose, it is essential to measure serum levels in order to use the drug effectively and safely.

A once daily theophylline preparation in prevention of nocturnal symptoms in childhood asthma

Twenty school children with chronic asthma who despite regular prophylactic therapy continued to have troublesome nocturnal wheeze or cough entered a double-blind cross-over study in which a once daily theophylline preparation was compared with placebo to assess control of these symptoms. Seventeen children completed both phases of the study. Significant improvement was noted in the day and night symptom scores, the morning dip index and daily peak flow readings with a significant reduction in rescue bronchodilator inhaler usage during the active treatment period. Satisfactory serum theophylline concentrations were obtained 11-12 h post dose in all children using a standard dose of 18 mg/kg per day at 2000 hours. Three children were withdrawn because of minor side-effects. The theophylline preparation studied in conjunction with other conventional anti-asthma therapy was thus effective in controlling nocturnal symptoms.

Breathing during sleep in stable asthmatic subjects. Influence of inhaled bronchodilators

The bronchoconstriction of asthma displays a circadian rhythm with exacerbations often occurring in the early morning hours. Gas exchange abnormalities during sleep in patients with severe asthma have been documented; however, the influence of sleep on gas exchange in the asthmatic with few or no daytime or nocturnal symptoms is poorly understood. To determine if abnormalities in oxygenation might occur during sleep, we studied 12 stable adult asthmatic patients with reversible airflow obstruction during sleep on three consecutive nights, with night 1 being for acclimatization. On test nights 2 and 3, the subjects received, in random double-blind fashion, either inhaled fenoterol or its placebo. Spirometry was performed before and after bronchodilator treatment and on the next morning. The mean FEV1 was 63 percent predicted before treatment. There was significant (p less than 0.05) improvement in FEV1 on fenoterol night after treatment which was also present the next morning. Mean prefenoterol FEV1 was 2.04 +/- .15 (SEM) and increased to 2.61 +/- .17 after the bronchodilator. The mean morning FEV1 was 2.27 +/- .20. Mean preplacebo FEV1 was 2.07 +/- .12 and did not change significantly with placebo bronchodilator. Sleep analysis demonstrated no significant differences in total sleep time or duration of oxyhemoglobin desaturation between nights. The incidence of sleep disordered breathing was very low (0.14 apneas/hour). The frequency of apneas and hypopneas did not change significantly with treatment. Two of the 12 subjects experienced an asthma attack on placebo night which did not recur following active bronchodilator administration. We conclude that stable asthmatic patients with few nocturnal complaints have a low frequency of disordered breathing and desaturation events during sleep.