Bambuterol in the treatment of asthma. A placebo-controlled comparison of once-daily morning vs evening administration

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

Recommended timing of medications that impact sleep and wakefulness: A review of the American Prescribers' Digital Reference

An appreciable number of medicines have a recommended unique single time-of-day or asymmetrical or unequal-interval multiple-daily administration schedule. Many prescription and over-the-counter (OTC) products, according to administration time, can exert positive or negative impact on nighttime sleep and daytime wakefulness. Intuitively, medicines used to manage nighttime sleep and daytime wake disorders should be taken, respectively, at night before bedtime and morning after arising. However, some utilized for other medical conditions, if improperly timed, may compromise nocturnal sleep and diurnal attentiveness. We conducted a comprehensive review of the American Prescribers' Digital Reference, internet version of the Physician's Desk Reference, for the recommended scheduling of medications and OTC remedies that can impact sleep and wakefulness. The search revealed several hundred therapies of various classes -- α₂-receptor agonists, antidepressants, barbiturates, central nervous system stimulants, benzodiazepines, dopamine agonists, dopamine norepinephrine reuptake inhibitors, selective norepinephrine reuptake inhibitors, eugeroics, γ-aminobutyric acid modulators, H₁ and H₃-receptor antagonists, melatonin analogues, OTC melatonin-containing products, non-benzodiazepine benzodiazepine-receptor agonists, dual orexin-receptor antagonists, and serotonin modulators -- that have a recommended unique dosing schedule. The tables and text of this article are intended to guide the proper scheduling of these medicines to optimize desired and/or minimize undesired effects.

Circadian clock synchrony and chronotherapy opportunities in cancer treatment

Cell-autonomous, tissue-specific circadian rhythms in gene expression and cellular processes have been observed throughout the human body. Disruption of daily rhythms by mistimed exposure to light, food intake, or genetic mutation has been linked to cancer development. Some medications are also more effective at certain times of day. However, a limited number of clinical studies have examined daily rhythms in the patient or drug timing as treatment strategies. This review highlights advances and challenges in cancer biology as a function of time of day. Recent evidence for daily rhythms and their entrainment in tumors indicate that personalized medicine should include understanding and accounting for daily rhythms in cancer patients.

Circadian Variation in Efficacy of Medications

Although much has been learned about circadian clocks and rhythms over the past few decades, translation of this foundational science underlying the temporal regulation of physiology and behavior to clinical applications has been slow. Indeed, acceptance of the modern study of circadian rhythms has been blunted because the phenomenology of cyclic changes had to counteract the 20th century dogma of homeostasis in the biological sciences and medicine. We are providing this review of clinical data to highlight the emerging awareness of circadian variation in efficacy of medications for physicians, clinicians, and pharmacists. We are suggesting that gold-standard double-blind clinical studies should be conducted to determine the best time of day for optimal effectiveness of medications; also, we suggest that time of day should be tracked and reported as an important biological variable in ongoing clinical studies hereafter. Furthermore, we emphasize that time of day is, and should be considered, a key biological variable in research design similar to sex. In common with biomedical research data that have been historically strongly skewed toward the male sex, most pharmaceutical data have been skewed toward morning dosing without strong evidence that this is the optimal time of efficacy.

Dosing time matters

Circadian precision medicine may supplement genetic precision to improve drug action

The novel combination of theophylline and bambuterol as a potential treatment of hypoxemia in humans

Hypoxemia can be life-threatening, both acutely and chronically. Because hypoxemia causes vascular dysregulation that further restricts oxygen availability to tissue, it can be pharmacologically addressed. We hypothesized that theophylline can be safely combined with the β2-adrenergic vasodilator bambuterol to improve oxygen availability in hypoxemic patients. Ergogenicity and hemodynamic effects of bambuterol and theophylline were measured in rats under hypobaric and normobaric hypoxia (12% O₂). Feasibility in humans was assessed using randomized, double-blind testing of the influence of combined slow-release theophylline (300 mg) and bambuterol (20 mg) on adverse events (AEs), plasma K⁺, pulse, blood pressure, and drug interaction. Both drugs and their combination significantly improved hypoxic endurance in rats. In humans, common AEs were low K⁺ (<3.5 mmol/L; bambuterol: 12, theophylline: 4, combination: 13 episodes) and tremors (10, 0, 14 episodes). No exacerbation or serious AE occurred when drugs were combined. A drop in plasma K⁺ coincided with peak bambuterol plasma concentrations. Bambuterol increased heart rate by approximately 13 bpm. Drug interaction was present but small. We report promise, feasibility, and relative safety of combined theophylline and bambuterol as a treatment of hypoxemia in humans. Cardiac safety and blood K⁺ will be important safety endpoints when testing these drugs in hypoxemic subjects.

Objective measurement of frequency and pattern of nocturnal cough in children with asthma exacerbation

BACKGROUND

Although a number of patients with asthma report experiencing persistent cough during sleep, it has not yet been objectively investigated.

OBJECTIVE

To classify cough severity and evaluate a characteristic pattern of cough frequency in children with asthma using an objective cough monitoring system.

METHODS

An objective cough monitoring system that specialized in children was used to measure cough frequency and nocturnal cough patterns. Coughs were recorded with microphone and accelerometer and analyzed using a customized software program. The number of nocturnal coughs and the pattern of cough frequency in 30-minute intervals were measured along with the severity of each asthma exacerbation, and the results were compared with children without asthma.

RESULTS

The total overnight cough count of 34 children with asthma was higher than that of 15 children without asthma (P < .001). The total overnight cough count in children with severe asthma exacerbation was higher than that in children with moderate asthma exacerbation (P < .05). The cough counts were significantly increased at the time of falling asleep and waking. This pattern was not observed in children without asthma. The total cough counts and cough patterns in children with asthma were not affected by sex, age, cause of asthma exacerbation, or therapy.

CONCLUSION

Our data indicate huge cough counts and characteristic nocturnal cough patterns in children with asthma. Objective and precise cough monitoring is useful for the management of childhood asthma.

The Lipid-lowering Effects of R-bambuterol in Healthy Chinese Volunteers: A Randomized Phase I Clinical Study

Background

Existing treatments are inadequate for patients at high risk of coronary heart disease caused by elevated levels of plasma low-density lipoprotein cholesterol (LDL-C). Bambuterol is a prodrug of β2-agonist commonly used for the treatment of asthma and chronic obstructive pulmonary disease (COPD) with the advantage of once daily dosing and favorable side effect profile. The potential lipid-lowering effects of bambuterol were unclear, possibly due to the racemic bambuterol (rac-bambuterol) that was used in previous studies.

Methods

The lipid-lowering effects of R-bambuterol were examined in a randomized phase I trial in 48 healthy Chinese volunteers aged 18–45 years. Participants were randomly assigned to five groups to receive a single dose (2.5 mg, 5 mg or 10 mg) or multiple doses (5 mg) of oral medications of R-bambuterol, or a single dose of rac-bambuterol (10 mg). Plasma lipid levels were measured at baseline, time to peak concentration (T_max) and 24 h after the treatment.

Findings

Administration of a single-dose of R-bambuterol resulted in dose-dependent reductions in the levels of plasma LDL-C, high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), apolipoprotein B (ApoB) and apolipoprotein A1 (ApoA1) at T_max. Levels of LDL-C exhibited the most reductions, which were statistically significant in all three single-dose R-bambuterol groups (all P values < 0.05). R-bambuterol was more potent in LDL-C lowering compared to rac-bambuterol at T_max (P = 0.08). At 24 h after dosing, the significant lipid lowering effects of R-bambuterol sustained for LDL-C (P = 0.01), ApoB (P = 0.001) and ApoA1 (P = 0.03), but not for HDL-C. The ratio of ApoA1/ApoB was marginally increased (P = 0.06). In the multiple-dose group, LDL-C levels again were significantly reduced (all P values < 0.05), whereas the ratios of ApoA1/ApoB were marginally increased.

Interpretation

R-bambuterol can lower the plasma levels of LDL-C, and marginally raise the ratio of ApoA1/ApoB (indicator of HDL-C/LDL-C) with both a single dose and multiple doses. R-bambuterol was more potent in LDL-C lowering than rac-bambuterol.

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Oral administration of R-bambuterol, a long-acting bronchodilator, can significantly lower LDL cholesterol in healthy Chinese volunteers.

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R-bambuterol was more potent than rac-bambuterol in lowering LDL-C and raising the ratio of ApoA1/ApoB.

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It may provide an alternative for treating high cholesterol, especially for those also suffering from COPD.

Design and mechanism of on-off pulsed drug release using nonenteric polymeric systems via pH modulation

The aim was to design a pH-sensitive pulsatile drug delivery system that allows for an on-off pulsed release of a drug using polyacrylic acid (PAA) blended with ethyl cellulose (EC) in different ratios. PAA, a polyelectrolyte polymer, exhibits a highly coiled conformation at low pH but a highly extended structure at high pH. Fumaric acid, which is an internal acidifying agent, was incorporated into the hydroxypropyl methylcellulose-based core tablets to create an acidic microenvironmental pH (pH(M)). The concentration of fumaric acid inside the core tablet and the ratio of PAA/EC in the coating layer were very crucial in modulating drug release behaviors. When the fumaric acid was retained in the core tablet, it gave a more acidic pH(M), so that the PAA was kept in a highly coiled state in the coated film, which hindered drug release ("off" release pattern). Interestingly, the release profiles of the drug and fumaric acid from coated tablets showed the on-off pulsed pattern upon dissolution. Imaging analyses using scanning electron microscopy, near-infrared imaging, confocal laser scanning microscopy, and Fourier transform infrared spectroscopy confirmed this on-off release behavior of the drug and fumaric acid from coated tablets.

Influence of the Circadian System on Disease Severity

The severity of many diseases varies across the day and night. For example, adverse cardiovascular incidents peak in the morning, asthma is often worse at night and temporal lobe epileptic seizures are most prevalent in the afternoon. These patterns may be due to the day/night rhythm in environment and behavior, and/or endogenous circadian rhythms in physiology. Furthermore, chronic misalignment between the endogenous circadian timing system and the behavioral cycles could be a cause of increased risk of diabetes, obesity, cardiovascular disease and certain cancers in shift workers. Here we describe the magnitude, relevance and potential biological basis of such daily changes in disease severity and of circadian/behavioral misalignment, and present how these insights may help in the development of appropriate chronotherapy.

Optimal time to take once-daily oral medications in clinical practice

Currently only a few package inserts of once-daily medications specially define the dosing time, although sporadic studies have demonstrated administration time-dependent effects on the therapeutic outcome. Some chronotherapeutic approaches aim to diminish the occurrence of adverse drug reactions (ADRs) and hence better tolerance and medication compliance whereas most of the chronotherapies are recommended to improve therapeutic efficacy. The administration time-dependent efficacy seems not a common feature of drugs within the similar therapeutic or structural class and it is related to kinds of drugs, pathophysiologic status, clinical symptoms and feedback from patients. Doctors, pharmacists and nurses should know what kind of drug has requirement for optimal dosing time, and realize that better efficacy and lower incidence of ADRs may be achieved by rational arrangement of administration schedule. In order to promote medication compliance, it is essential to provide patient education regarding differences between conventional and chronotherapeutic approaches and pathophysiologic benefits of chronotherapy.

Chronobiology and chronotherapy of allergic rhinitis and bronchial asthma

Study of the chronobiology of allergic rhinitis (AR) and bronchial asthma (BA) and the chronopharmacology and chronotherapy of the medications used in their treatment began five decades ago. AR is an inflammatory disease of the upper airway tissue with hypersensitivity to specific environmental antigens, resulting in further local inflammation, vasomotor changes, and mucus hypersecretion. Symptoms include sneezing, nasal congestion, and runny and itchy nose. Approximately 25% of children and 40% of adults in USA are affected by AR during one or more seasons of the year. The manifestation and severity of AR symptoms exhibit prominent 24-h variation; in most persons they are worse overnight or early in the morning and often comprise nighttime sleep, resulting in poor daytime quality of life, compromised school and work performance, and irritability and moodiness. BA is also an inflammatory medical condition of the lower airways characterized by hypersensitivity to specific environmental antigens, resulting in greater local inflammation as well as bronchoconstriction, vasomotor change, and mucus hypersecretion. In USA an estimated 6.5 million children and 15.7 million adults have BA. The onset and worsening of BA are signaled by chest wheeze and/or croupy cough and difficult and labored breathing. Like AR, BA is primarily a nighttime medical condition. AR is treated with H1-antagonist, decongestant, and anti-inflammatory (glucocorticoid and leukotriene receptor antagonist and modifier) medications. Only H1-antagonist AR medications have been studied for their chronopharmacology and potential chronotherapy. BA is treated with some of the same medications and also theophylline and beta2-agonists. The chronopharmacology and chronotherapy of many classes of BA medications have been explored. This article reviews the rather extensive knowledge of the chronobiology of AR and BA and the chronopharmacology and chronotherapy of the various medications used in their treatment.

Beta-adrenoceptor agonists and asthma--100 years of development

Inhaled beta(2)-adrenoceptor agonists are by far the most effective and safe bronchodilators currently available. They have not been surpassed by any other bronchodilating principle. The way to this position has been long and started with the first successful treatment of acute, severe asthma with s.c. injections of adrenaline 100 years ago. Over the years, synthetic congeners of adrenaline have been produced and tested for their pharmacological properties. During the first decades, little attention was given airway smooth muscle. The discovery of isoprenaline in 1940 was the first major step towards selective bronchodilation. This compound became a key tool for the classification of adrenoceptors into alpha and beta. Salbutamol and terbutaline were the first to show a significant attenuation of the cardiostimulant effect and confirmed the subdivision of beta-adrenoceptors into beta(1) and beta(2). Much effort was made to eliminate the next dose-limiting side effect, skeletal muscle tremor but in vain. Prolonged duration of action was achieved in three ways: with bambuterol, an orally active carbamate ester prodrug of terbutaline, salmeterol, an inhaled beta(2)-adrenoceptor agonist emerging from a purposeful research project, and formoterol which was found, accidentally, to have a long duration of action when inhaled. Throughout the 20th century, beta-adrenoceptor agonists have been developed and marketed as racemates. The pharmacological activity usually resides in the (R)-enantiomer. Despite claims for the opposite, there is so far no compelling evidence that the presence of the less active (S)-enantiomer is of any harm to the patient. One hundred years of experience of structural modifications of adrenaline has shown that the possibilities to modify the properties of this endogenous prototype appear to be unlimited.

Long-acting beta-agonist treatment in patients with persistent asthma already receiving inhaled corticosteroids

International guidelines recommend that long-acting beta-agonists should be considered in patients who are symptomatic despite moderate doses of inhaled corticosteroids. When combined with inhaled corticosteroids they improve asthma symptoms and lung function and reduce exacerbations. The evidence suggests that they are well tolerated. However, they are less effective than inhaled corticosteroids as monotherapy and should not be used alone, although the addition of a long-acting beta-agonist may permit a small reduction in the corticosteroid dose. Both salmeterol and formoterol appear equally effective in improving asthma control. Formoterol, however, has a rapid onset of action and is now being promoted for the relief of acute asthma symptoms. Both drugs provide prolonged protection against exercise-induced bronchospasm. However, this effect rapidly diminishes with continuous therapy and if this is the main aim of treatment, intermittent use may be preferable. When compared with alternative treatments, inhaled long-acting beta-agonists are more effective in controlling asthma symptoms than either theophylline or antileukotriene agents. Bambuterol, an oral prodrug of terbutaline, appears to be as effective as the inhaled long-acting beta-agonists and has the advantage of once daily oral administration. However, the inhaled long-acting beta-agonists are less likely to have systemic adverse effects. There are theoretical concerns that regular beta-agonist treatment may lead to tolerance and a failure to respond to emergency asthma treatment. While there is no doubt that tolerance occurs, there is currently little evidence that this is a clinical problem. Insights into pharmacological as well as therapeutic interactions between inhaled corticosteroids and beta-agonists are providing justification for their use in combination. Guidelines for the management of patients with chronic persistent asthma are likely to require modification to reflect these developments.

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.

Comparative study using oral solutions of bambuterol once daily or terbutaline three times daily in 2-5-year-old children with asthma. Bambuterol Multicentre Study Group

The aim of this study was to compare safety and efficacy of bambuterol hydrochloride (10 mg) oral solution administered once daily in the evening with terbutaline sulphate (0.075 mg/kg body weight) oral solution administered three times daily in 2-5-year-old children with asthma. There were two treatment groups: (2/3) of the patients received bambuterol and (1/3) received terbutaline. The study was double-blind, randomized, and of a parallel group design, and it lasted for 3 months after a 2-week run-in period. The primary objective was to evaluate safety (adverse events, and changes in blood pressure, pulse rate, hematology, and clinical chemistry parameters). Plasma concentrations of terbutaline and/or bambuterol were also measured. Evaluation of efficacy (diary card data) was a secondary objective. A total of 155 patients (range, 2-6 years; 3 patients were 6 years old at randomization) were treated with the study drugs; 104 patients received bambuterol and 51 patients received terbutaline. Both treatments showed a good safety profile with respect to clinical and laboratory tests, and they were generally well tolerated. Reported adverse events were mild to moderate. There were no statistically significant differences between treatment groups in any of the efficacy variables (diary variables: peak expiratory flow (PEF), asthma symptoms, restlessness, other reported symptoms, use of inhaled bronchodilators, and nighttime awakenings). For morning PEF, the mean increase from run-in to treatment was 16.9 L/min in the terbutaline group and 23.3 L/min in the bambuterol group. For evening PEF, the mean increase was 20.2 L/min in the terbutaline group and 20.6 L/min in the bambuterol group. In conclusion, once-daily bambuterol is as safe and effective as terbutaline given three times daily. The study also confirmed that bambuterol has a 24-hr duration of action, and therefore its once daily administration, makes it a preferred bronchodilator agent. Pediatr Pulmonol. 2000:29:194-201.

Circadian rhythms in the pharmacokinetics and clinical effects of beta-agonist, theophylline, and anticholinergic medications in the treatment of nocturnal asthma

Published asthma consensus reports now acknowledge that asthma is a nocturnal disease in as many as 75% of those afflicted by this medical condition. Nonetheless, the treatment of this chronic obstructive pulmonary disease in the clinic continues to be based primarily on homeostatic considerations in that it relies on long-acting bronchodilator and other therapies formulated and scheduled to ensure constant or near-constant levels of medication during the 24h. The need of asthma patients prone to nighttime attacks is not the same during the day and night; the therapeutic requirements of patients who experience nocturnal asthma, especially ones with the more severe forms of the disease, are often not satisfied by conventional medications. The therapeutic response and patient tolerance to bronchodilator medications can be improved markedly when the medications are proportioned during the 24h as a chronotherapy, that is, when more medication is delivered during nighttime sleep than daytime activity, as verified by numerous studies. This article reviews how the body's circadian rhythms influence the pharmacokinetics and effects of commonly prescribed asthma therapies and addresses why and how they must be taken into consideration to increase the effectiveness of asthma treatment.

Pharmacokinetics of bambuterol during oral administration to asthmatic children

AIMS

To investigate dose proportionality, dosing frequency, and ethnic aspects of the pharmacokinetics of bambuterol in asthmatic children, and to discuss the relationship with previous observations in adults.

METHODS

Forty-eight children in four different studies completed two double-blind bambuterol treatments each (daily doses of bambuterol hydrochloride): 12 preschool (5 mg x 2 vs 10 mg) and 12 school (10 mg vs 20 mg) Caucasians, 12 preschool (2.5 mg vs 5 mg), and 12 school (10 mg vs 20 mg) Orientals. Peak plasma concentrations and dosing interval area under curve (AUC) of bambuterol and the active metabolite terbutaline were assessed at steady state. Treatment differences were analysed statistically within each study. Differences between the studies and the relation to steady-state AUC in adults were described.

RESULTS

Dose proportionality was seen for terbutaline but not for bambuterol. Twice-daily dosing (2 x AUC(0,12 h)) could not be shown to differ from once-daily dosing (AUC(0,24 h)) in the preschool Caucasians. Mean AUC of terbutaline was 128 and 242 nmol l-1 h in the preschool Caucasians (5 mg/12 h; 10 mg/24 h), 213 and 406 nmol l-1 h in the Caucasian school children (10 mg; 20 mg), 87.4 and 202 nmol l-1 h in the Oriental preschool children (2.5 mg; 5 mg), and 356 and 640 nmol l-1 h in the Oriental school children (10 mg; 20 mg). Oriental school children had higher plasma concentrations of bambuterol and terbutaline than Caucasian school children. The strict ethnic implication of the difference could not be elucidated, because demographic data were not perfectly matched. Terbutaline AUC was only moderately increased in the Caucasian school children compared with Caucasian adults. The increase was more pronounced in Oriental children and in some preschool Caucasians. The highest concentration of terbutaline, 58 nmol l-1, was seen in an Oriental school child after a 20 mg dose.

CONCLUSIONS

Caucasian school children can be given bambuterol hydrochloride very much as Caucasian adults, 10 or 20 mg once daily, but Oriental preschool and school children plus preschool Caucasians should be given lower doses.

Comparison of oral bambuterol and inhaled salmeterol in patients with symptomatic asthma and using inhaled corticosteroids

Salmeterol inhaled twice-daily is now being used more frequently as additional treatment in asthma insufficiently controlled by inhaled corticosteroids. We compared oral bambuterol in a dose of 20 mg taken once daily in the evening with inhaled salmeterol at 50 microgram taken twice daily in 126 asthmatic patients (60 bambuterol, 66 salmeterol) aged 18 to 74 yr who were treated for at least 4 wk with inhaled corticosteroids at a constant dose of 400 to 2,000 microgram/d or with oral corticosteroids at </= 20 mg/d. The patients were able to use a pressurized metered dose inhaler (pMDI) efficiently, and had an FEV1 of 40 to 85% of the predicted normal value. During a run-in period, patients had to show at least one nocturnal or early awakening caused by asthma symptoms that required rescue medication, and a >/= 15% overnight decrease in peak expiratory flow (PEF) on 3 of the preceding 7 d, in order to be randomized into this double-blind, double dummy, multicenter parallel group study (2-wk run-in period and 6 wk of treatment). There was no significant difference between bambuterol and salmeterol in morning change from baseline in PEF (p = 0.53). The median increases in morning PEF were 50 L/min for bambuterol and 55 L/min for salmeterol. Other variables (evening PEF, percent of overnight decrease in PEF, number of awakenings, percent of nights with an awakening, number of puffs of rescue medication, asthma symptoms during the day and night, and mean tremor score) also showed no significant difference between bambuterol and salmeterol. Both treatments, at the doses given, were well tolerated. Once-daily oral bambuterol is a convenient, effective, and less expensive alternative to twice-daily inhaled salmeterol for treating nocturnal asthma.

A comparison of two long-acting beta-agonists, oral bambuterol and inhaled salmeterol, in the treatment of moderate to severe asthmatic patients with nocturnal symptoms. The French Bambuterol Study Group

This multicentre study was set up to compare the efficacies of two long-acting beta 2-agonists, oral bambuterol (20 mg nocte) and inhaled salmeterol (50 micrograms b.i.d.), for the treatment of moderate to severe asthmatics who were considered to be on optimal steroid/bronchodilator therapy, but continued to have troublesome nocturnal symptoms. The study was of double-blind, parallel-group design and comprised a 2-week run-in on previous maintenance therapy followed by a 6-week study treatment period. There were 117 randomized asthmatic patients aged 20-70 years (65 women and 52 men with a mean age of 45 and predicted FEV1 of 64%), who had been taking 800-2000 micrograms inhaled steroid and/or up to 20 mg oral steroid per day for at least 4 weeks. They were asked to complete daily diary cards, recording morning and evening PEF, daily symptoms, nocturnal awakenings, rescue medication and subjective tremor. There was a significant increase in both morning and evening PEF respectively, on bambuterol (28 l min-1, 20 l min-1, P < 0.05) and salmeterol (29 l min-1, P < 0.001; 23 l min-1, P < 0.01) when compared with run-in. The mean percentage fall in overnight PEF was reduced by 8.3% (P < 0.001) on bambuterol and by 6.8% (P < 0.001) on salmeterol. Nocturnal awakenings and daytime symptoms due to asthma were significantly lowered by both treatments, as was the consumption of rescue bronchodilator. Tremor scores were very low during both run-in and study treatments. No significant treatment difference between bambuterol and salmeterol was detected for any of the above variables. Once-daily oral bambuterol provides a highly effective alternative to twice-daily inhaled salmeterol for relief of nocturnal symptoms in patients with moderate to severe asthma.

Rationale and design for the Controlled ONset Verapamil INvestigation of Cardiovascular Endpoints (CONVINCE) Trial

The Controlled ONset Verapamil INvestigation of Cardiovascular Endpoints (CONVINCE) Trial is a randomized, prospective, double-blind, parallel-group, two-arm, actively controlled, multicenter, international 5-year clinical trial involving 15,000 patients. CONVINCE will compare the incidence of fatal or nonfatal myocardial infarction (MI), fatal or nonfatal stroke, or cardiovascular-disease-related death in two antihypertensive treatment regimens. One treatment arm begins with controlled onset-extended release (COER)-verapamil, which has its major antihypertensive effect 6-12 hours after administration. The other arm (standard of care (SOC)) begins with either hydrochlorothiazide (HCTZ) or atenolol, one of which is preselected by the investigator for an individual patient prior to randomization. Secondary objectives include comparisons of the regimens for each of the components of the primary endpoint (separately), death or hospitalization related to cardiovascular disease, efficacy in lowering blood pressure to goal, primary events occurring between 6 am and noon, all-cause mortality, withdrawals from blinded therapy, cancer, and hospitalizations due to bleeding. Patients may be enrolled if they are hypertensive and at least 55 years of age and have an established second risk factor for cardiovascular disease. Initial medications include COER-verapamil (180 mg/d), HCTZ (12.5 mg/d), or atenolol (50 mg/d). Initial doses are doubled if blood pressure (BP) does not reach goal (systolic BP < 140 mm and diastolic BP < 90 mm Hg). If BP is not controlled by the higher dose of the initial medication, HCTZ is added to COER-verapamil, or the SOC choice not initially selected is added in the SOC arm. An ACE-inhibitor is recommended (although nearly any open-label medication is allowed) as the third step for patients whose BP is not adequately controlled or who have a contraindication to one of the two SOC medications. Patients take two sets of tablets daily, one in the morning and one in the evening. Although most patients switch from an established antihypertensive medication to randomized treatment, untreated patients with stages I-III hypertension (SBP between 140 and 190 or DBP between 90 and 110 mm Hg) are eligible. Outcomes are monitored by an independent Data and Safety Monitoring Board. Enrollment began during the third quarter of 1996, and follow-up is to be completed in the third quarter of 2002.

Pharmacokinetics of bambuterol in healthy subjects

AIMS

To study the pharmacokinetics and bioavailability of the prodrug bambuterol and its bronchodilator moiety terbutaline in healthy subjects.

METHODS

Eight healthy subjects (four women) received intravenous doses of bambuterol and terbutaline. On a third occasion, they, plus another four subjects, ingested oral bambuterol as a single dose followed by repeated doses once daily for 7 days. Plasma concentrations and urinary excretion of bambuterol and terbutaline were measured.

RESULTS

After intravenous administration, renal clearances of bambuterol and terbutaline were similar (about 140 ml min(-1)), but there was a five-fold difference in total clearance (bambuterol 1.25 l min(-1), terbutaline 0.23 l min(-1)). Volume of distribution (Vss) was 1.6 l kg(-1) b.w. for both substances. A similar renal clearance of bambuterol was found during oral administration but that of terbutaline decreased (to about 120 ml min(-1)). Mean terminal half-life of bambuterol was 2.6 h after intravenous and 12 h after oral administration, implying that uptake was rate-limiting. Mean residence time of terbutaline generated from oral bambuterol was 34 h compared with 8.0 h when terbutaline as such was infused. Generated terbutaline had a bioavailability of 36% (28-46) after intravenous and 10.2% (6.1-13.2) after oral administration of the prodrug. Bambuterol was well tolerated. The mean activity of plasma cholinesterase, an enzyme catalyzing bambuterol metabolism, was inhibited between 30-60% during repeated oral dosing. It virtually regained original activity within 48 h after the last dose.

CONCLUSIONS

The plasma concentration ofterbutaline fluctuated little during repeated oral administration (mean peak: trough ratio 1.9), as a result of prolonged absorption of bambuterol and slow formation of terbutaline. Thus, the pharmacokinetic properties of bambuterol make it suitable for oral once-daily dosage.

Clinical pharmacokinetics of bambuterol

Bambuterol, a biscarbamate ester prodrug of the beta 2 adrenergic agonist terbutaline, has been approved for the treatment of asthma in 28 countries. It is available in 10 and 20mg (25 and 50 mumol) tablets as the hydrochloride salt. Bambuterol is stable to presystemic elimination and is concentrated by lung tissue after absorption from the gastrointestinal tract. The prodrug is hydrolysed to terbutaline primarily by butyrylcholinesterase, and lung tissue is capable of this metabolic pathway. It is also oxidatively metabolised to products which can be hydrolysed to terbutaline. Peak terbutaline plasma concentrations occur 3.9 to 6.8 hours after bambuterol ingestion, and the peak: trough terbutaline concentration ratio is lower than that after ingestion of terbutaline. Older patients have a greater area under the plasma concentration-time curve for terbutaline over a dose interval at steady-state. Whether genetic variations in the expression of butyrylcholinesterase alter therapeutic response remains to be determined. The efficacy of bambuterol has been demonstrated to last for 24 hours after ingestion; once-daily administration in the evening is recommended. Maximum therapeutic benefit requires more than 1 week of treatment. Except for the suppression of plasma butyrylcholinesterase, the adverse effect profile of bambuterol is essentially that of a beta 2 agonist and is best correlated with circulating terbutaline concentration in plasma. Plasma butyrylcholinesterase activity returns to control values approximately 2 weeks after discontinuation of treatment with bambuterol. This new drug provides oral beta 2 agonist therapy in a more convenient form than was available previously, and may have a better therapeutic: toxic ratio than terbutaline.