Combined treatment with sustained-release theophylline and beta2-adrenoceptor-stimulating agents in chronic childhood 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.

Is combined therapy of sympathomimetics and theophylline indicated?

Bronchodilator effect and toxicity of theophylline 300 mg twice a day (R1), salbutamol 4 mg tid (R2), their combination in higher (200/4mg, R3), and lower doses (100/2mg R4), and placebo (calcium lactate 300 mg) tid (R5) were compared in 25 patients with bronchial asthma in a randomized crossover trial. Statistically significant improvement in forced expiratory volume in one second (FEV1) was observed in all the active treatment groups (R1 to R4) compared with placebo (R5). The mean improvement in FEV1 was 29.0%, 22.0%, 28.0%, 30.0%, and 0.73% in regimen R1, R2, R3, R4, and R5, respectively day 1, and corresponding improvement was 30.0%, 24.0%, 29.0%, 34.0%, and 4.4% on completion of one week therapy. On intergroup statistical comparison, mean improvement in pulmonary function test values were statistically significant or highly significant in regimens R1 to R4, as compared with placebo. However, improvement between any two regimens was not statistically significant in any of the regimens (R1-R4). Almost all the regimens were tolerated well and no patient showed major adverse reactions or cardiotoxicity necessitating withdrawal of the drug. On the other hand, minor adverse reactions were common and the high dose combination (R3) was found to have more adverse reactions than the low dose combination and either drug used alone.

Management of asthma and chronic airflow limitation. Are methylxanthines obsolete?

After almost 50 years as first-line drugs in the management of asthma and COPD, methylxanthines have been largely superceded by inhaled adrenoceptor agonist and anticholinergic bronchodilators which are more potent and far less toxic. Accumulating evidence indicates that intravenous theophylline contributes side effects, but is rarely of benefit in acute exacerbations of asthma or COPD. In the maintenance therapy of asthma, first-line therapy is dose-optimized inhaled steroids, reducing the need for bronchodilators. Inhaled adrenoceptor agonists are second line medications, anticholinergic aerosols third line, and theophylline, if needed at all, may fulfill a minor systemic steroid-sparing function in severe asthmatics on maximum doses of the inhaled medications. In the maintenance therapy of some patients with COPD, theophylline sometimes may be useful but these responders should be identified by objectively establishing therapeutic benefit. Since many patients have side effects from the methylxanthines, while their therapeutic benefit over and above dose-optimized inhaled therapy is marginal, their continued almost routine use in the management of reversible airflow obstruction is hard to justify, although this class of drugs may be useful in selected patients in whom both subjective and objective benefit can be demonstrated. In COPD, theophylline may improve exercise capacity in some patients by still incompletely understood mechanisms probably unrelated to bronchodilation.

Theophylline-terbutaline, a steady state study on possible pharmacokinetic interactions with special reference to chronopharmacokinetic aspects

1. The pharmacokinetic interaction of terbutaline and theophylline and chronopharmacokinetics of both drugs were studied in a three-way crossover study with repeated administration of terbutaline (Bricanyl Depot) 7.5 mg twice daily, theophylline (Theo-Dur) 300 mg twice daily alone or the combination of both for 7 days to 12 healthy volunteers (six male and six female). 2. After the morning dose on day 7, blood and urine were sampled for 12 h, and after the evening dose on day 7, blood and urine were sampled for 48 h. Theophylline concentrations in plasma and concentrations of unchanged drug and metabolites in urine were determined by two selective high performance liquid chromatography methods. Terbutaline concentrations in plasma and urine were measured with a gas chromatography-mass spectrometry method. Area under the plasma concentration-time curve, fluctuations in plasma concentration, mean residence time, elimination half-life, renal clearance as well as maximal, minimal and average plasma concentration at steady state were evaluated. 3. The addition of terbutaline to the repeated administration of theophylline lowered the relative bioavailability of theophylline by approximately 11% during the night interval. The rate of elimination of theophylline and mean residence time were influenced accordingly. No significant changes in excretion of the theophylline metabolites were observed, but the excretion of 3-methylxanthine was slightly reduced by the concomitant terbutaline administration. None of the observed changes should be of any clinical importance. 4. The addition of theophylline did not influence any of the calculated pharmacokinetic parameters of terbutaline. 5. It can be concluded that no dosage adjustment is necessary when terbutaline and theophylline are given together.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effect of excipients on tablet properties and dissolution behavior of theophylline-tableted microcapsules under different compression forces

Theophylline ethylcellulose microcapsules were tableted by compression with or without excipients [lactose or hydroxypropyl cellulose (HPC-H)]. Tablets without excipients had a crushing strength that was independent of the applied compression force and the particle size of the microcapsules used, but tablet thickness decreased with an increase in the particle size of the microcapsules. The dissolution characteristics of theophylline from tableted microcapsules without excipients were almost independent of the applied compression force, but showed a sustained-release behavior. However, the thickness, crushing strength, and dissolution properties of tablets containing excipients were found to be affected by the type of excipient. Tableted microcapsules containing lactose showed an increase in tablet crushing strength that correlated with an increase in the applied compression pressure, but the tablet thickness did not change. In contrast, tableted microcapsules containing HPC-H showed a decrease in tablet thickness with an increase in the applied compression pressure, but the tablet crushing strength was initially reduced and then increased with an increase in the compression force. There was a rapid release rate for theophylline from tableted microcapsules containing lactose; a zero-order release rate for theophylline was found in tableted microcapsules containing HPC-H. The insoluble compacted matrix formation, disintegration of tablet, rupture of microcapsules, and gel matrix formation may be responsible for the release behavior of theophylline-tableted microcapsules with or without excipients. The reduced surface area and porosity resulted in a prolongation of the release from tableted microcapsules compared with untableted microcapsules.

Aminophylline in acute asthma

It is widely believed that theophylline is a valuable addition to beta-agonists in the treatment of asthma. This is true when beta-agonists are given in low doses, but available evidence suggests that theophylline adds little or nothing to the effect of maximal doses of beta-agonists. Clinical trials, albeit some with limitations, in acute asthma support the view that theophylline confers no benefit on patients treated with high-dose beta-agonists. As theophylline is a difficult drug to use safely, and its toxicity is serious, its use should be confined to unusual circumstances, and the dose should be small.

Terbutaline slow-release tablets in children with bronchial asthma. Effect and pharmacokinetics compared with plain terbutaline tablets

The effect of terbutaline sulphate in slow-release (SR) tablets (Bricanyl Depot), 5 mg twice daily, was compared with that of terbutaline sulphate in ordinary tablets (Bricanyl), 2.5 mg three times daily, in a double-blind, randomized, cross-over study during 2 consecutive weeks in 10 asthmatic children. Plasma concentrations and urinary excretion of terbutaline were measured at various times during both treatment periods. The SR tablets produced a higher mean plasma concentration in the morning and a smaller peak-trough variation over the day than the ordinary ones. No differences between the two treatments were observed concerning FEV1 (forced expiratory volume in 1 s). Tremor, measured with an opto-electronic tremorgraph, was about the same for two treatments and not significantly different from tremor seen in healthy children. The reported side effects were less frequent in the SR tablet period.

Bioavailability and pharmacological effects of two slow-release theophylline preparations: intrasubject tablet-to-tablet variability

The bioavailability and pharmacological effects of slow-release preparations oxtriphylline (Choledyl SA) and anhydrous theophylline (Theo-Dur) were compared in a single-blind, randomized, crossover study in 10 normal men. Subjects were administered three doses from the same lot of each preparation at weekly intervals. Plasma concentration of theophylline was measured at timed intervals for 33 hr by high-pressure liquid chromatography. Pharmacokinetic analysis showed that Choledyl SA peaked earlier (4.7 +/- 1.0 hr) than did Theo-Dur (9.6 +/- 8.2 hr), with higher peak concentrations, 6.4 +/- 0.7 micrograms/ml versus 4.1 +/- 0.5 micrograms/ml for Theo-Dur, and greater are under the curve, 102.4 +/- 15.7 micrograms/ml X hr versus 75.3 +/- 9.1 micrograms/ml X hr for Theo-Dur. 88% absorption was achieved in 6 hr with Choledyl SA versus 10 hr with Theo-Dur. Wide intra- and intersubject variations were observed with both preparations. Likewise, variable effects on systolic and diastolic blood pressure and pulse were observed with both preparations. The effects of both theophylline preparations on urine flow, osmolar clearance, and glomerular filtration rate were compared. Osmotic diuresis without detectable changes in the glomerular filtration rate was observed in subjects who received Choledyl SA versus Theo-Dur. Differences in the bioavailability and renal effects were observed between Choledyl SA and Theo-Dur. Wide intra- and intersubject tablet-to-tablet variability were observed with both preparations.

Advantages and disadvantages of 24-hour theophylline

The general trend in medical therapy toward once-daily administration has not escaped theophylline preparations. Rapid metabolizers, as are found especially among children and smoking adults, may require a more frequent interval than once-a-day dosing, and greater fluctuations in theophylline levels should be expected. An interaction with food has been seen with once- and twice-daily theophylline preparations. Some products release their contents more rapidly while others do so more slowly in association with a high-fat diet. The food effect is of little concern if the theophylline is taken 1 hour before the meal. The greatest anticipated value of once-daily theophylline medications would be improved patient compliance.

Coexistence of hypocalciuric hypercalcaemia and interstitial lung disease in a family: a cross-sectional study

In a prospective investigation, a large kindred (twenty-one subjects) with unexplained association of familial hypocalciuric hypercalcaemia and idiopathic interstitial lung disease was studied. Serum calcium was increased in fifteen patients (the youngest being 7 years old) and was associated with hypo- or normocalciuria. The abnormalities were not age-dependent. The serum concentrations of parathyroid hormone, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and calcitonin were normal. In twelve patients the diffusing capacity (DLCO) and/or DLCO per unit lung volume was less than 75% predicted. This was often accompanied by a vital capacity of less than 80% predicted, and increased Tiffeneau index, and a reticulo-micronodular pattern with high diaphragm on chest X-ray. The decrease in DLCO was more pronounced in older non-smoking as well as smoking subjects (P less than 0.02) suggesting a progressing interstitial disease with age. The fibrosing alveolitis, which had been confirmed by open lung biopsy in three subjects, could not be attributed to sarcoidosis, collagen-vascular disease, or exogenous causes. The disturbances in the calcium homeostasis and in the diffusing capacity of the lung coexisted in seven of the twenty-one patients. Apparently, both abnormalities were inherited following an autosomal-dominant pattern but with a different penetration in each person, and seemed not be causally related to each other.

Concomitant bitolterol mesylate aerosol and theophylline for asthma therapy, with 24 hr electrocardiographic monitoring

A higher incidence of fatal asthma after increased use of combined inhaled beta 2-agonists and theophylline has been attributed to additive cardiac toxicity of these agents. This study had three major objectives: first, to evaluate the efficacy and safety of a new long-acting beta 2-agonist, bitolterol mesylate, given as metered-dose aerosol in a regular "round-the-clock" asthma medication regimen; second, to compare the efficacy and safety of bitolterol with those of sustained-release theophylline alone and of the combination of bitolterol and theophylline; third, to use 24 hr Holter monitoring to evaluate cardiac toxicity of the three medication regimens. This was a 6 wk double-blind study of regular, daily medication in 36 young non-steroid-dependent and 37 older steroid-dependent stable asthmatic patients. All patients had two 24 hr Holter ECG monitorings during the 2 wk baseline period when all patients received theophylline only and four further 24 hr Holter monitorings during the double-blind period. All Holter recordings from the study groups showed no significant abnormalities in any treatment group. Pulmonary function studies were performed on 4 study days in the 6 wk double-blind period. The largest increase in bronchodilator effect was obtained with combined medication and the smallest with theophylline alone. Mean duration of action was markedly longer in the combined treatment group (greater than 7 hr) than with bitolterol mesylate aerosol or theophylline alone (greater than 5 and greater than 4 hr, respectively) in the non-steroid-dependent patients. Degree of bronchodilation and duration of action was less in the steroid-dependent patients in all treatment groups. There is no evidence from cardiac monitoring that therapeutic doses of bitolterol mesylate or theophylline alone or in combination have cardiotoxic effects.

Comparison of a sustained-release preparation (Theo-Dur) with a conventional preparation (Nuelin) in the treatment of chronic asthma

In a double-blind, cross-over trial comprising 19 adult asthmatic patients a sustained-release preparation of theophylline (Theo-Dur), given twice daily, was compared with a conventional fast-release preparation (Nuelin), given three times daily. The theophylline doses were individually titrated to give plasma concentrations in the lower region of the therapeutic interval. The sustained-release preparation gave higher morning theophylline concentrations than the fast-release preparation (9.2 vs 5.9 mg/l). This resulted in somewhat higher morning peak flow values during Theo-Dur treatment. However, the difference in asthma symptoms was not significant and the patients showed no preference for either preparation. We conclude that the advantage of a sustained-release preparation over a conventional fast-release theophylline preparation is the lower dosing frequency rather than the better clinical effect in patients who suffer from chronic asthma, but whose disease is in a relatively stable phase.

Combination bronchodilator therapy

Bronchodilators may be classified into 3 groups: anticholinergics, beta-adrenoceptor agonists and methylxanthines. These drugs act through related biochemical pathways and there are theoretical reasons for expecting beneficial additive or synergistic interactions between them. While there is in vitro evidence of synergistic interactions producing bronchodilatation, in vivo studies indicate that the interactions are additive rather than synergistic but still of therapeutic value. There have been no clinical studies on methylxanthines combined with anticholinergic drugs, but there is an extensive and growing literature on the other combinations. The majority show clear evidence of an additive bronchodilator effect when anticholinergics are combined with beta 2-adrenoceptor agonists, although atropine sulphate is less effective in this regard than atropine methylnitrate or ipratropium bromide. This type of combination has only been tested by inhalation and, because of the slower onset of action of the anticholinergic group, it is preferable that the beta 2-adrenoceptor agonist be inhaled first. There is no evidence for an additive interaction of the side effects of these drugs. In general, bronchitics respond better than asthmatics to anticholinergic drugs. Studies on methylxanthines (usually theophylline) and adrenoceptor agonists may be divided into 2 groups: those using ephedrine and those using more selective beta-adrenoceptor agonists. Ephedrine is a relatively ineffective bronchodilator and often fails to add any useful bronchodilatation to theophylline. Also, there does seem to be a synergistic increase in side effects of the two drugs and this combination is therefore undesirable. Ephedrine has now been superseded by the more selective beta 2-adrenoceptor agonist drugs all of which, whether given orally, intravenously or by inhalation, appear to have an additive effect with the methylxanthines. It is often possible to achieve the same therapeutic effect with half doses of drugs from 2 different groups as with a full dose of 1 drug. This may sometimes, but not always, reduce side effects. There is evidence that giving 2 drugs by different routes is a useful therapeutic procedure; for example, the addition of an inhaled beta 2-adrenoceptor agonist may improve upon the maximal bronchodilatation achieved with intravenous theophylline. When theophylline is administered plasma levels of the drug should be monitored and it is possible that, when used in combination with a beta 2-adrenoceptor agonist, a therapeutic range lower than that normally recommended may apply. There is no longer any place for fixed combination bronchodilators and, in spite of recent suggestions, there is no evidence that bronchodilator combinations are responsible for an increase in asthma mortality. Further studies to clarify some aspects of bronchodilator combinations are needed. The therapeutic use of various combinations is briefly discussed.

Pharmacokinetics and dose regimen of oral theophylline in children

The pharmacokinetics of theophylline after oral administration in tablet (Oxyphyllin) or solution (Teovent) form was determined in 22 children 0.6-16 years of age. Four of these children also received intravenous theophylline. The absorption of theophylline both from the tablets and from the solution was rapid (mean half-time 14.3 and 16.1 min., respectively) and almost complete. The youngest children (2-8 years) given tablets had a significantly shorter half-time of elimination and a higher total plasma clearance than children aged 9-16 years. Adverse effects during treatment with the oral solution were studied in another 19 children. Medication was stopped by the parents of two children because of the unpleasant taste. Gastrointestinal disturbances were frequent but not serious enough to cause discontinuation of treatment. Simulations based on obtained pharmacokinetic data showed that in the average child below nine years of age oral theophylline, 6-8 mg/kg three times daily, would give plasma levels between 10 and 20 micrograms/ml (55-110 mumol/l) for about 60-70% of the day. A dose of 6 mg/kg four times daily would achieve such concentrations during almost 24 hrs of the day. In the average child aged 9-16 years a reduced dose of about 5-6 mg/kg three times daily would suffice to produce plasma levels of 10-20 micrograms/ml owing to the slower elimination of the drug in this age group. Individual titration of the dose is necessary for optimal treatment with theophylline in all age groups.

Effects of oral theophylline and oral salbutamol in the treatment of asthma

A double-blind randomised controlled trial was conducted to study the effects of oral theophylline alone compared with oral theophylline and salbutamol in a sample of asthmatic children. Each treatment was administered at maximum recommended dosage. Children treated with the theophylline and salbutamol combination had higher pulse rates, lower peak flow measurements, and depressed blood theophylline levels. These results suggest that when given at maximum oral dosage, theophylline and salbutamol in combination, tend to interact negatively producing tachycardia and reduced therapeutic function.

Effects of oral theophylline combined with oral and inhaled beta-2-adrenostimulants in asthmatics

The acute ventilatory, cardiovascular and tremorogenic effect of a high oral dose of terbutaline (5 mg) was compared with that of half the dose (2.5 mg) combined with 280 mg anhydrous theophylline orally in the randomized, double-blind, cross-over study in eight asthmatics. After 120 min, when steady-state bronchodilation was achieved, five terbutaline inhalations (1.25 mg terbutaline sulphate) were added to both treatment regimens. The mean maximum plasma concentration of theophylline was then 7 micrograms/ml (39 mumol/l). Inhalation of a beta 2-adrenostimulant had a very good additional effect without increasing side effects in these patients with good inhalation technique. The oral low-dose combination gave significantly better bronchodilation than the high dose of terbutaline alone and caused significantly less tremor. Although the combination only had an additive bronchodilating effect, it may offer important clinical advantages. If the patient cannot use the metered dose aerosol, an oral low dose combination should be preferred to a single high dose of either theophylline or beta 2-adrenostimulants. In patients with good inhalation technique but not controlled by inhalation from a metered dose aerosol alone, a combination of oral theophylline and terbutaline in "sub-optimal" dose and an inhaled beta 2-agonist in individually titrated optimal dose gave a maximal bronchodilating effect with minimum side effects.