Long acting beta(2) agonists and theophylline in stable chronic obstructive pulmonary disease

Lack of Pharmacokinetic Interactions Between Cilomilast and Theophylline or Smoking in Healthy Volunteers

The pharmacokinetic profile of cilomilast (Ariflo), a selective phosphodiesterase 4 (PDE4) inhibitor, was investigated in three separate studies. Two of these studies explored the drug interaction potential of cilomilast with the nonselective PDE inhibitor, theophylline, and a third study compared the pharmacokinetic profile of cilomilast in smokers and nonsmokers. Repeated administration of cilomilast had no effect on the steady-state pharmacokinetics of theophylline in either a pilot dose-ranging or definitive therapeutic study. At therapeutic doses, the point estimate and 90% confidence interval for theophylline AUC(0-12) and C(max) were completely contained within the range (0.8, 1.25). Similarly, repeated administration of theophylline had little clinically relevant effect on the steady-state pharmacokinetics of cilomilast when compared to placebo, as only slight average increases in cilomilast AUC(0-12) and C(max) (6% and 3%, respectively) were observed. In addition, mean cilomilast exposure (AUC(0- infinity )) was found to be similar in both smokers and nonsmokers (8.47 +/- 2.20 microg*h/mL and 7.70 +/- 2.25 microg*h/mL, respectively). Throughout all three studies, cilomilast was well tolerated, and concomitant use of these selective and nonselective inhibitors, although unlikely in the clinic, is hypothetically feasible. Taken together, these studies clearly differentiate cilomilast from theophylline for drug-drug liability issues in a smoker and nonsmoker population, as well as highlight the potential to switch from one drug to another without undue clinical concern.

Pharmacology and therapeutics of bronchodilators

Bronchodilators are central in the treatment of of airways disorders. They are the mainstay of the current management of chronic obstructive pulmonary disease (COPD) and are critical in the symptomatic management of asthma, although controversies around the use of these drugs remain. Bronchodilators work through their direct relaxation effect on airway smooth muscle cells. at present, three major classes of bronchodilators, β(2)-adrenoceptor (AR) agonists, muscarinic receptor antagonists, and xanthines are available and can be used individually or in combination. The use of the inhaled route is currently preferred to minimize systemic effects. Fast- and short-acting agents are best used for rescue of symptoms, whereas long-acting agents are best used for maintenance therapy. It has proven difficult to discover novel classes of bronchodilator drugs, although potential new targets are emerging. Consequently, the logical approach has been to improve the existing bronchodilators, although several novel broncholytic classes are under development. An important step in simplifying asthma and COPD management and improving adherence with prescribed therapy is to reduce the dose frequency to the minimum necessary to maintain disease control. Therefore, the incorporation of once-daily dose administration is an important strategy to improve adherence. Several once-daily β(2)-AR agonists or ultra-long-acting β(2)-AR-agonists (LABAs), such as indacaterol, olodaterol, and vilanterol, are already in the market or under development for the treatment of COPD and asthma, but current recommendations suggest the use of LABAs only in combination with an inhaled corticosteroid. In addition, some new potentially long-acting antimuscarinic agents, such as glycopyrronium bromide (NVA-237), aclidinium bromide, and umeclidinium bromide (GSK573719), are under development, as well as combinations of several classes of long-acting bronchodilator drugs, in an attempt to simplify treatment regimens as much as possible. This review will describe the pharmacology and therapeutics of old, new, and emerging classes of bronchodilator.

The additive effect of theophylline on a combination of formoterol and tiotropium in stable COPD: A pilot study

We explored the additive effect of titrated oral theophylline in patients with stable chronic obstructive pulmonary disease (COPD) who received both tiotropium, 18mug od, and formoterol, 12mug bid. Thirty-six patients with moderate-to-severe COPD were enrolled in this two-period trial. They were initially treated with formoterol+tiotropium for 4 weeks. After this first period, they were divided in two groups of 18 patients. Both groups continued with the initial treatment for further 4 weeks, but the first group received also placebo whereas the second group received oral theophylline. The combination therapy with formoterol+tiotropium induced a significant improvement in mean predose FEV(1) and FVC at the end of the first period, and a significant reduction in dyspnea score as measure by a visual analogic scale and in use of rescue salbutamol. The second period of treatment elicited a significant further improvement in lung function and reduction in dyspnea score and salbutamol use in both groups. On the contrary, differences in improvements in FEV(1) and FVC and reduction in dyspnea score and salbutamol use between theophylline and placebo arms at the end of the second treatment period were not significant, although 5 patients reported an important relief in dyspnea during the theophylline administration period. These findings question the importance of adding theophylline in stable COPD patients already treated with two long-acting bronchodilators, but also indicate the possibility that some of them can benefit from theophylline because of a symptomatic improvement.

Phosphodiesterase-4 inhibitors as a novel approach for the treatment of respiratory disease: cilomilast

Phosphodiesterase-4 (PDE4) is an important cAMP-metabolising enzyme in immune and inflammatory cells, airway smooth muscle and pulmonary nerves. The phosphodiesterase 4 (PDE4) enzyme plays a significant role in modulating the activity of cAMP, an important second messenger that mediates the relaxation of airway smooth muscle and suppresses inflammatory cell function, thereby attenuating the inflammatory response. Selective inhibitors of this enzyme show a broad spectrum of activity in animal models of COPD and asthma. These drugs block the hydrolysis of cAMP via inhibition of PDE4 and are attractive candidates for novel anti-inflammatory drugs. At present, two second-generation PDE4 inhibitors for the treatment of COPD and asthma patients are being tested in clinical Phase III trials. The most advanced compound is the orally active, selective PDE4 inhibitor cilomilast (Ariflo, SB-207499, cis-4-cyano-4-[3-cyclopentyloxy-4-methoxyphenyl]-cyclohexanecarboxylic acid; GlaxoSmithKline). Cilomilast shows high selectivity for cAMP-specific PDE4, an isoenzyme that predominates in pro-inflammatory and immune cells and that is 10-fold more selective for PDE4D than for PDE4A, -B or -C. In vitro, cilomilast suppresses the activity of several pro-inflammatory and immune cells that have been implicated in the pathogenesis of asthma and COPD. Moreover, it is highly active in animal models of these diseases. Cilomilast has been shown to exert potent anti-inflammatory effects both in vitro and in vivo. It is orally active and may be effective in the treatment of asthma and COPD; however, complete assessment of the therapeutic value of this novel compound class must await the outcome of longer-term clinical trials. This review presents a summary of the preclinical and clinical profile of cilomilast in patients with COPD.

Outcomes in COPD patients receiving tiotropium or salmeterol plus treatment with inhaled corticosteroids

Patients with COPD are frequently prescribed inhaled corticosteroids (ICS); however, it is unclear whether the treatment with ICS might modify responses to inhaled bronchodilators. Two 6-month, randomized, placebo-controlled, double-blind, double-dummy, parallel-group studies of tiotropium 18 microg once daily, compared with salmeterol, 50 microg bid, had been conducted in patients with moderate-to-severe COPD. Efficacy was assessed by spirometry, transition dyspnea index (TDI), St. George's Respiratory Questionnaire (SGRQ), and exacerbations. Data from both studies were combined to form subgroups with regard to concurrent use of ICS. 796 patients receiving ICS were separately analyzed from 390 patients not receiving ICS. Mean age was 64 years, and pre-bronchodilator FEV1 was 1.06 L (ICS group) and 1.13 L (non-ICS group). Both bronchodilators increased morning mean +/- SE pre-dose FEV1 compared with placebo (ICS groups: tiotropium 110 +/- 20 mL, salmeterol 80 +/- 20 mL; non-ICS groups: tiotropium 150 +/- 30 mL, salmeterol 110 +/- 30 mL; p > 0.05 for tiotropium vs salmeterol). Improvements in TDI and SGRQ and frequency of exacerbations also tended to be more profound for tiotropium. Treatment with tiotropium in patients with moderate-to-severe COPD was superior to salmeterol in lung function, irrespective of concurrent use of ICS.

Salmeterol/fluticasone propionate in a Single Inhaler Device versus theophylline+fluticasone propionate in patients with COPD

STUDY OBJECTIVES

The aim of this study was to compare the relative efficacy in terms of improvement in symptoms and lung function of salmeterol/fluticasone propionate (SLM/FP) combination administered through the Diskus inhaler versus theophylline (THEO) added to FP Diskus in patients with stable chronic obstructive pulmonary disease (COPD).

METHODS AND MEASUREMENTS

Eighty patients were randomized to receive 4 months of treatment in one of two treatment groups: (1) fixed combination of SLM 50 microg and FP 500 microg Diskus, 1 inhalation twice daily; or (2) FP Diskus 500 microg, 1 inhalation twice daily, plus oral titrated THEO twice daily. Patients attended the clinic before and after 4, 8, 12 and 16 weeks of treatment for evaluations of pulmonary function, and dyspnea, which was assessed using an analogic visual scale. Also the supplemental salbutamol use was measured.

RESULTS

. Sixty-six patients completed the 4-month treatment period: 37 patients receiving SLM/FP and 29 patients receiving THEO+FP. Patients were withdrawn for various reasons, the most common of which were poor compliance with the protocol, exacerbation and GI events. A gradual increase in FEV(1) was observed with each treatment. Maximum significant increases in FEV(1) over baseline values that were observed after 4 months of treatment were as follows: SLM/FP 0.172 l (95% CI: 0.084-0.260) and THEO+FP 0.155 l (95% CI: 0.054-0.256). SLM/FP experienced significantly (p<0.05) greater improvements in dyspnea, and required significantly fewer supplemental salbutamol treatments than the THEO+FP group.

CONCLUSIONS

Our results suggest that SLM/FP combination may provide substantial benefits in both physiologic and clinical outcomes in symptomatic patients with COPD. It also causes a more effective control than THEO+FP.

PDE4 inhibitors in COPD—a more selective approach to treatment

Chronic obstructive pulmonary disease (COPD) is a serious and mounting global public health problem. Although its pathogenesis is incompletely understood, chronic inflammation plays an important part and so new therapies with a novel anti-inflammatory mechanism of action may be of benefit in the treatment of COPD. Cilomilast and roflumilast are potent and selective phosphodiesterase (PDE)4 inhibitors, with an improved therapeutic index compared with the weak, non-selective PDE inhibitor, theophylline. Unlike theophylline, which is limited by poor efficacy and an unfavourable safety and tolerability profile, the selective PDE4 inhibitors are generally well tolerated, with demonstrated efficacy in improving lung function, decreasing the rate of exacerbations and improving quality of life, with proven anti-inflammatory effects in patients with COPD. Theophylline is a difficult drug to use clinically, requiring careful titration and routine plasma monitoring due to the risk of toxic side effects, such as cardiovascular and central nervous system adverse events, with dose adjustments required in many patients, including smokers, the elderly and some patients on concomitant medications. In contrast, the selective PDE4 inhibitors are convenient medications for both patient and physician alike. Hence these agents represent a therapeutic advance in the treatment of COPD, due to their novel mechanism of action and potent anti-inflammatory effects, coupled with a good safety and tolerability profile.

Differential pharmacokinetics of theophylline in elderly patients

The clinical use of theophylline as a first-line bronchodilator has declined during the last two decades. However, in many clinical settings, such as an emergency bronchial asthma attack, theophylline may have a first-line role, in combination with beta(2)-adrenoreceptor agonists and corticosteroids, for improving the asthmatic status. Furthermore, many therapeutic mechanisms of theophylline for bronchial asthma have been reported, and recent studies have suggested that theophylline therapy may have a beneficial role in the management of chronic stable asthma as well as exacerbated disease. However, theophylline has a low therapeutic index because the bronchodilation it produces has a linear relationship with logarithmic increases in serum concentration for the therapeutic range of 5-20 mg/L. Thus, the knowledge of its basic pharmacokinetics and the factors that can alter its clearance is clinically relevant for physicians. Especially when used in elderly asthmatic patients, dosage adjustment of theophylline is a requisite since the elderly have several risk factors that may increase the plasma theophylline level, such as reduced clearance, various underlying diseases and multiple coadministered drugs. After theophylline treatment has been initiated, therapeutic drug monitoring is required.

Inhaled salmeterol: a review of its efficacy in chronic obstructive pulmonary disease

Inhaled salmeterol is a long-acting, selective beta2-adrenoceptor agonist bronchodilator. The drug has been compared with placebo, ipratropium bromide and oral theophylline in patients with chronic obstructive pulmonary disease (COPD) in randomised, clinical trials. Inhaled salmeterol 50 microg twice daily produced significant improvement in forced expiratory volume in 1 second (FEV1), equivalent to that obtained with inhaled ipratropium bromide 40 microg 4 times daily and greater than that obtained with placebo or oral theophylline in randomised trials. Use of as-needed salbutamol (albuterol) was significantly reduced during treatment with inhaled salmeterol or ipratropium bromide compared with placebo or oral theophylline. The time to first COPD exacerbation was significantly longer during 12 weeks of treatment with inhaled salmeterol 50 microg twice daily than ipratropium bromide 40 microg 4 times daily. Compared with baseline and placebo, patients treated for 16 weeks with salmeterol 50 microg (but not 100 microg) twice daily reported significant improvement in total St George's Respiratory Questionnaire (SGRQ) scores. Similarly, more patients treated with inhaled salmeterol 50 microg twice daily or ipratropium bromide 40 microg 4 times daily experienced an increase of > or = 10 points in Chronic Respiratory Disease Questionnaire (CRQ) scores, the minimum clinically significant increment. Compared with placebo, inhaled salmeterol 50 microg twice daily alone, or concurrent with ipratropium bromide 40 microg 4 times daily improved lung function and reduced symptoms in patients with stable COPD in a 12-week, randomised, double-blind study. Clinically meaningful improvement in CRQ scores was documented in significantly more patients treated with the combination of the 2 drugs than either salmeterol monotherapy or placebo. Inhaled salmeterol 50 microg twice daily plus oral theophylline had additive effects on lung function, increased the proportion of symptom-free days and decreased requirements for as-needed salbutamol compared with either agent alone according to a pooled analysis of 2 multicentre, randomised, double-blind studies.

CONCLUSION

When used at the optimal dosage, 50 microg twice daily, salmeterol provides symptomatic relief and improves lung function and health-related quality of life in patients with COPD. Available evidence suggests that the drug is as effective as ipratropium bromide and more effective than oral theophylline in patients with COPD. Moreover salmeterol has additive effects when used in combination with inhaled ipratropium bromide or oral theophylline. These qualities make the drug suitable for first-line use in patients with COPD who require regular bronchodilator therapy to manage symptoms.

Cilomilast, a selective phosphodiesterase-4 inhibitor for treatment of patients with chronic obstructive pulmonary disease: a randomised, dose-ranging study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a common, progressive respiratory disease that causes great morbidity and mortality despite treatment. There is evidence for airway inflammation in COPD. Cilomilast is an orally active, potent, selective phosphodiesterase type 4 inhibitor, which in vitro can affect cells thought to be of clinical importance in COPD. Our aim was to assess the safety, efficacy, and dose response of cilomilast in the treatment of patients with this disease.

METHODS

We did a 6-week, randomised, dose-ranging study in 424 patients with COPD (forced expiratory volume in 1 s [FEV(1)] 46.8% of predicted, FEV(1)/forced vital capacity [FVC] 54.6%, and postsalbutamol reversibility 5.4%). We randomly assigned individuals at 60 European centres to receive cilomilast 5 (n=109), 10 (n=102), or 15 (n=107) mg twice daily, or placebo (n=106). The main outcome measure was trough FEV(1) before and after use of a bronchodilator. Analyses were by intention to treat.

FINDINGS

Cilomilast 15 mg twice daily significantly improved FEV(1) compared with placebo (mean 130 mL vs -30 mL [95% CI 90-240] at week 6, p<0.0001). FVC and peak expiratory flow were also improved (p=0.001 and p<0.0001, respectively). Quality of life measures did not differ significantly between the groups. There were no significant differences in serious adverse events between the groups.

INTERPRETATION

Cilomilast 15 mg twice daily might be an effective maintenance treatment for COPD. Further clinical studies are underway.

Optimizing preoperative lung function

The exacerbation of chronic lung disease, bronchospasm, atelectasis, pneumonia, and respiratory failure with prolonged mechanical ventilation are considered to be clinically relevant postoperative pulmonary complications associated with increased morbidity and mortality. Careful history taking and a thorough physical examination are the most sensitive ways to identify patients at risk. Lung function tests serve as management tools for optimizing preoperative therapy and to assess postoperative lung function and individual risk in lung resection candidates. Additional cardiopulmonary exercise testing provides valuable information in borderline cases. The cessation of smoking, optimizing nutritional status and physiotherapy serve to prevent postoperative pulmonary complications. Moreover, medical therapy is recommended, especially for patients with obstructive airway diseases. In the absence of controlled clinical trials, medical therapy along the respective guidelines, with the primary goals of minimizing symptoms and improving lung function to the optimum seems to be a reasonable approach.

Additive effects of salmeterol and fluticasone or theophylline in COPD

BACKGROUND

ss(2)-Agonists and corticosteroids or theophylline can interact to produce beneficial effects on airway function in asthma, but this has not been established in COPD.

METHODS

Eighty patients with well-controlled COPD were randomized to receive 3 months of treatment in one of four treatment groups: (1) salmeterol, 50 microg bid; (2) salmeterol, 50 microg, plus fluticasone propionate, 250 microg bid; (3) salmeterol, 50 microg, plus fluticasone propionate, 500 microg bid; and (4) salmeterol, 50 microg, plus titrated theophylline bid. At each visit, a dose-response curve to inhaled salbutamol was constructed using a total cumulative dose of 800 microg.

RESULTS

A gradual increase in FEV(1) was observed with each of the four treatments. Maximum significant increases in FEV(1) over baseline values that were observed after 3 months of treatment were as follows: salmeterol, 50 microg bid, 0.163 L (95% confidence interval [CI], 0.080 to 0.245 L); salmeterol, 50 microg, plus fluticasone propionate, 250 microg bid, 0.188 L (95% CI, 0.089 to 0. 287 L); salmeterol, 50 microg, plus fluticasone propionate, 500 microg bid, 0.239 L (95% CI, 0.183 to 0.296 L); and salmeterol, 50 microg, plus titrated theophylline bid, 0.157 L (95% CI, 0.027 to 0. 288 L). Salbutamol always caused a significant dose-dependent increase in FEV(1) (p < 0.001), although the 800-microg dose never induced further significant benefit when compared with the 400-microg dose. The mean differences between the highest salbutamol FEV(1) after salmeterol, 50 microg, plus fluticasone propionate, 500 microg bid, and that after salmeterol, 50 microg, plus titrated theophylline bid or salmeterol, 50 microg bid, were statistically significant (p < 0.05).

CONCLUSION

These data show that both long-acting ss(2)-agonists and inhaled corticosteroids have a role in COPD. The data also show that fluticasone propionate and salmeterol given together are more effective than salmeterol alone. Moreover, it suggests that the addition of fluticasone propionate to salmeterol allows a greater improvement in lung function after salbutamol, although regular salmeterol is able to improve lung function in COPD patients without development of a true subsensitivity to its bronchodilator effect. In any case, patients must be treated for at least 3 months before a real improvement in lung function is achieved.

Long-acting beta2 agonists in the management of stable chronic obstructive pulmonary disease

Long-acting beta2 agonist bronchodilators (e.g. formoterol, salmeterol) are a new interesting therapeutic option for patients with chronic obstructive pulmonary disease (COPD). In the short term, both salmeterol and formoterol appear to be more effective than short-acting beta2 agonists, and in patients with stable COPD they are more effective than anticholinergic agents and theophylline. Regular treatment of patients with COPD with long-acting beta2 agonists can induce an improvement in the respiratory function and certain aspects of quality of life. Moreover, salmeterol seems to be better than ipratropium and theophylline in improving lung function at the recommended doses after a long term treatment. Use of combination therapy of a long-acting inhaled beta2 agonist and an anticholinergic agent or theophylline in patients with COPD has not been sufficiently studied. Combination of usual doses of ipratropium or oxitropium with usual doses of salmeterol or formoterol does not appear to improve pulmonary function, but this lack of improvement with the combination should not, in itself, prevent implementation of further therapeutic steps in patients responsive to an anticholinergic agent and/or salmeterol or formoterol administered singly. Neither formoterol nor salmeterol elicit significant cardiovascular effects in healthy individuals and patients with reversible airway obstruction. However, adverse cardiac events might occur in patients with COPD with pre-existing cardiac arrhythmias and hypoxaemia if they use long-acting 12 agonists, although the recommended single dose of salmeterol 50 microg or formoterol 12 microg ensures a relatively higher safety margin than formoterol 24 microg. The bronchodilatory effect of long-acting beta2 agonists seems to be fairly stable after regular treatment with these bronchodilators. Moreover, pre-treatment with a conventional dose of formoterol or salmeterol does not preclude the possibility of inducing further bronchodilation with salbutamol in patients with partially reversible COPD. All these findings support the use of long-acting beta2 agonist bronchodilators as first-line bronchodilator therapy for the long term treatment of airflow obstruction in patients with COPD. However, since physicians must always choose a drug that is highly efficacious, well tolerated and inexpensive, the cost-effectiveness analysis in relation to other bronchodilators will determine the proper place of long-acting beta2 agonists in the long term therapy of stable COPD.

Acute effect of pretreatment with single conventional dose of salmeterol on dose-response curve to oxitropium bromide in chronic obstructive pulmonary disease

BACKGROUND

An earlier study documented that, in patients with chronic obstructive pulmonary disease (COPD), addition of ipratropium bromide at the clinically recommended dose (40 microg) does not produce any further bronchodilation than that achieved with salmeterol 50 microg alone. However, the dose of ipratropium bromide needed to produce near maximal bronchodilation is several times higher than the customary dosage. The full therapeutic potential of combined salmeterol plus an anticholinergic drug can therefore only be established using doses higher than those currently recommended in the marketing of these agents. A study was undertaken to examine the possible acute effects of higher than conventional doses of an anticholinergic agent on the single dose salmeterol induced bronchodilation in patients with stable and partially reversible COPD.

METHODS

Thirty two outpatients received 50 microg salmeterol or placebo. Two hours after inhalation a dose-response curve to inhaled oxitropium bromide (100 microg/puff) or placebo was constructed using one puff, one puff, two puffs, and two puffs-that is, a total cumulative dose of 600 microg oxitropium bromide. Dose increments were given at 20 minute intervals with measurements being made 15 minutes after each dose. On four separate days all patients received one of the following: (1) 50 microg salmeterol + 600 microg oxitropium bromide; (2) 50 microg salmeterol + placebo; (3) placebo + 600 microg oxitropium bromide; (4) placebo + placebo.

RESULTS

Salmeterol induced a good bronchodilation (mean increase 0.272 l; 95% CI 0.207 to 0.337) two hours after its inhalation. Oxitropium bromide elicited an evident dose-dependent increase in forced expiratory volume in one second (FEV(1)) and this occurred also after pretreatment with salmeterol with a further mean maximum increase of 0.152 l (95% CI of differences 0.124 to 0.180).

CONCLUSIONS

This study shows that acute pretreatment with 50 microg salmeterol does not block the possibility of inducing more bronchodilation with an anticholinergic agent when a higher than normal dosage of the muscarinic antagonist is used.

Influence of higher than conventional doses of oxitropium bromide on formoterol-induced bronchodilation in COPD

We examined the influence of higher than conventional doses of oxitropium bromide on formoterol-induced bronchodilation in patients with partially reversible stable COPD. Twenty outpatients inhaled one or two puffs of formoterol (12 microg puff(-1)), or placebo. Two hours after inhalation, a dose-response curve to inhaled oxitropium bromide (100 microg puff(-1)) or placebo was constructed using one puff, one puff, two puffs and two puffs, for a total cumulative dose of 600 microg oxitropium bromide. Doses were given at 20-min intervals and measurements made 15 min after each dose. On six separate days, all patients received one of the following: (1) formoterol 12 microg + oxitropium bromide 600 microg, (2) formoterol 12 microg + placebo, (3) formoterol 24 microg + oxitropium bromide 600 microg, (4) formoterol 24 microg + placebo, (5) placebo + oxitropium bromide 600 microg, or (6) placebo + placebo. Both formoterol 12 microg and 24 microg induced a good bronchodilation (formoterol 12 microg, 0.19-0.20 l; formoterol 24 microg 0.22-0.24 l). The dose-response curve of oxitropium, but not placebo, showed an evident increase in FEV1, with a further significant increase of respectively 0.087 l and 0.082 l after the formoterol 12 microg and formoterol 24 microg pre-treatment. This study shows that improved pulmonary function in patients with stable COPD may be achieved by adding oxitropium 400-600 microg to formoterol. There is not much difference in bronchodilation between combining oxitropium with formoterol 12 microg or 24 microg. In any case, formoterol 24 microg alone seems sufficient to achieve the same bronchodilation induced by oxitropium 600 microg alone in most patients.