Fenoterol: a beta2-adrenergic agonist for use in asthma. Pharmacology, pharmacokinetics, clinical efficacy and adverse effects

A burst of fenoterol excretion during the recovery of a weight loss protocol

Fenoterol is a sympathomimetic β2 receptor agonist primarily used as a bronchodilator. Due to its sympathomimetic actions, the World Anti-Doping Agency (WADA) has banned it. Multiple acute weight loss protocols (WLP) are used by Olympic athletes for sports that segregate athletes by weight; these generally involve caloric and water deprivation combined with heat exposure. Athletes use WLP before weigh-in, then transition to different body acute weight regain protocols (WRP) before competitions. Here, we studied the pharmacokinetics of fenoterol under WLP conditions: energetic dietary restriction, decreased water intake, and exposure to a dry sauna (80 ± 2 °C), followed by a WRP. Five elite-level female judo athletes participated in the study. Four received fenoterol (200 μg; n = 2 or 400 μg; n = 2), while one was a control receiving placebo under identical conditions. We measured excretion of the fenoterol parent molecule and presented qualitative data of its sulfated metabolite using QqQ tandem quadrupole mass spectrometry for 118 h. The fenoterol parent appeared earlier in urine than did its conjugated metabolite; excretion profiles were similar among all subjects. The centers of mass for fenoterol parent curves were (time, fenoterol): athlete A (10.9, 7.3); athlete B (9.2, 27.3); athlete C (8.5, 6.9); athlete D (9.7, 5.0). After initiating WRP, we observed a burst in urinary fenoterol excretion once in complete decay. This trend was observed for all four athletes who received fenoterol. Our results suggest that during hypohydration, some of the unmetabolized fenoterol accumulates in tissues, then is released during rehydration. These findings can be important for detecting fenoterol use in athletes.

Molecular mechanism of inhibition of COVID-19 main protease by β-adrenoceptor agonists and adenosine deaminase inhibitors using in silico methods

Novel coronavirus (COVID-19) responsible for viral pneumonia which emerged in late 2019 has badly affected the world. No clinically proven drugs are available yet as the targeted therapeutic agents for the treatment of this disease. The viral main protease which helps in replication and transcription inside the host can be an effective drug target. In the present study, we aimed to discover the potential of β-adrenoceptor agonists and adenosine deaminase inhibitors which are used in asthma and cancer/inflammatory disorders, respectively, as repurposing drugs against protease inhibitor by ligand-based and structure-based virtual screening using COVID-19 protease-N3 complex. The AARRR pharmacophore model was used to screen a set of 22,621 molecules to obtain hits, which were subjected to high-throughput virtual screening. Extra precision docking identified four top-scored molecules such as +/--fenoterol, FR236913 and FR230513 with lower binding energy from both categories. Docking identified three major hydrogen bonds with Gly143, Glu166 and Gln189 residues. 100 ns MD simulation was performed for four top-scored molecules to analyze the stability, molecular mechanism and energy requirements. MM/PBSA energy calculation suggested that van der Waals and electrostatic energy components are the main reasons for the stability of complexes. Water-mediated hydrogen bonds between protein-ligand and flexibility of the ligand are found to be responsible for providing extra stability to the complexes. The insights gained from this combinatorial approach can be used to design more potent and bio-available protease inhibitors against novel coronavirus.Communicated by Ramaswamy H. Sarma.

A randomized clinical trial on inhaled ciclesonide for managing acute asthma in the emergency room

BACKGROUND

Use of inhaled corticosteroids for managing acute asthma exacerbations has been tested since the 1990s.

OBJECTIVE

To compare high doses of inhaled ciclesonide with systemic hydrocortisone for managing acute asthma exacerbations in the emergency department.

DESIGN AND SETTING

Double-blind, randomized clinical trial in the public healthcare system of the city of São Paulo.

METHODS

Fifty-eight patients with moderate or severe asthma with peak flow < 50% of predicted were randomized into two groups. Over the course of four hours, one group received 1440 mcg of inhaled ciclesonide plus hydrocortisone-identical placebo (ciclesonide + placebo), while the other received 500 mg of intravenous hydrocortisone plus ciclesonide-identical placebo (hydrocortisone + placebo). Both groups received short-acting bronchodilators (fenoterol hydrobromide and ipratropium bromide). The research protocol included spirometry, clinical evaluation, vital signs and electrocardiogram monitoring. Data were obtained at 30 (baseline), 60, 90, 120, 180, and 240 minutes. We compared data from baseline to hour 4, between and within groups.

RESULTS

Overall, 31 patients received ciclesonide + placebo and 27 received hydrocortisone + placebo. Inhaled ciclesonide was as effective as intravenous hydrocortisone for improving clinical parameters (Borg-scored dyspnea, P = 0.95; sternocleidomastoid muscle use, P = 0.55; wheezing, P = 0.55; respiratory effort, P = 0.95); and spirometric parameters (forced vital capacity, P = 0.50; forced expiratory volume in the first second, P = 0.83; peak expiratory flow, P = 0.51).

CONCLUSIONS

Inhaled ciclesonide was not inferior to systemic hydrocortisone for managing acute asthma exacerbations, and it improved both clinical and spirometric parameters.

TRIAL REGISTRATION

RBR-6XWC26 - Registro Brasileiro de Ensaios Clínicos (http://www.ensaiosclinicos.gov.br/rg/RBR-6xwc26/).

Molecular basis for stereoselective transport of fenoterol by the organic cation transporters 1 and 2

Stereoselectivity is important in many pharmacological processes but its impact on drug membrane transport is scarcely understood. Recent studies showed strong stereoselective effects in the cellular uptake of fenoterol by the organic cation transporters OCT1 and OCT2. To provide possible molecular explanations, homology models were developed and the putative interactions between fenoterol enantiomers and key residues explored in silico through computational docking, molecular dynamics simulations, and binding free energy calculations as well as in vitro by site-directed mutagenesis and cellular uptake assays. Our results suggest that the observed 1.9-fold higher maximum transport velocity (v_max) for (R,R)- over (S,S)-fenoterol in OCT1 is because the enantiomers bind to two distinct binding sites. Mutating PHE355 and ILE442, predicted to interact with (R,R)-fenoterol, reduced the v_max ratio to 1.5 and 1.3, respectively, and to 1.2 in combination. Mutating THR272, predicted to interact with (S,S)-fenoterol, slightly increased stereoselectivity (v_max ratio of 2.2), while F244A resulted in a 35-fold increase in v_max and a lower affinity (29-fold higher K_m) for (S,S)-fenoterol. Both enantiomers of salbutamol, for which almost no stereoselectivity was observed, were predicted to occupy the same binding pocket as (R,R)-fenoterol. Unlike for OCT1, both fenoterol enantiomers bind in the same region in OCT2 but in different conformations. Mutating THR246, predicted to interact with (S,S)-fenoterol in OCT2, led to an 11-fold decreased v_max. Altogether, our mutagenesis results correlate relatively well with our computational predictions and thereby provide an experimentally-corroborated hypothesis for the strong and contrasting enantiopreference in fenoterol uptake by OCT1 and OCT2.

Drivers of absolute systemic bioavailability after oral pulmonary inhalation in humans

There are few studies in humans dealing with the relationship between physico-chemical properties of drugs and their systemic bioavailability after administration via oral inhalation route (Fpulm). Getting further insight in the determinants of Fpulm after oral pulmonary inhalation could be of value for drugs considered for a systemic delivery as a result of poor oral bioavailability, as well as for drugs considered for a local delivery to anticipate their undesirable systemic effects. To better delineate the parameters influencing the systemic delivery after oral pulmonary inhalation in humans, we studied the influence of physico-chemical and permeability properties obtained in silico on the rate and extent of Fpulm in a series of 77 compounds with or without marketing approval for pulmonary delivery, and intended either for local or for systemic delivery. Principal component analysis (PCA) showed mainly that Fpulm was positively correlated with Papp and negatively correlated with %TPSA, without a significant influence of solubility and ionization fraction, and no apparent link with lipophilicity and drug size parameters. As a result of the small sample set, the performance of the different models as predictive of Fpulm were quite average with random forest algorithm displaying the best performance. As a whole, the different models captured between 50 and 60% of the variability with a prediction error of less than 20%. Tmax data suggested a significant positive influence of lipophilicity on absorption rate while charge apparently had no influence. A significant linear relationship between Cmax and dose (R² = "0.79) highlighted that Cmax was primarily dependent on dose and absorption rate and could be used to estimate Cmax in humans for new inhaled drugs.

Protective effects of total flavonoids from Qu Zhi Qiao (fruit of Citrus paradisi cv. Changshanhuyou) on OVA-induced allergic airway inflammation and remodeling through MAPKs and Smad2/3 signaling pathway

Allergic asthma is one of the inflammatory diseases, which has become a major public health problem. Qu zhi qiao (QZQ), a dry and immature fruit of Citrus paradisi cv. Changshanhuyou, has various flavonoids with pharmacological properties. However, there is a knowledge gap on the pharmacological properties of QZQ on allergic asthma. Therefore, here, we explored the efficacy and mechanism of total flavonoids from QZQ (TFCH) on allergic asthma. We extracted and purified TFCH and conducted animal experiments using an Ovalbumin (OVA)-induced mice model. Bronchoalveolar lavage fluid and Swiss-Giemsa staining were used to count different inflammatory cells in allergic asthma mice. We conducted histopathology and immunohistochemistry to evaluate the changes in the lungs of allergic asthma mice. Moreover, we used ELISA assays to analyze chemokines and inflammatory cytokines. Furthermore, western blot analyses were conducted to elucidate the mechanism of TFCH on allergic asthma. We established that TFCH has anti-inflammatory effects and inhibits airway remodeling, providing a potential therapeutic strategy for allergic asthma.

Bisindolylmaleimide IX: A novel anti-SARS-CoV2 agent targeting viral main protease 3CLpro demonstrated by virtual screening pipeline and in-vitro validation assays

SARS-CoV-2, the virus that causes COVID-19 consists of several enzymes with essential functions within its proteome. Here, we focused on repurposing approved and investigational drugs/compounds. We targeted seven proteins with enzymatic activities known to be essential at different stages of the viral cycle including PLpro, 3CLpro, RdRP, Helicase, ExoN, NendoU, and 2'-O-MT. For virtual screening, energy minimization of a crystal structure of the modeled protein was carried out using the Protein Preparation Wizard (Schrodinger LLC 2020-1). Following active site selection based on data mining and COACH predictions, we performed a high-throughput virtual screen of drugs and investigational molecules (n = 5903). The screening was performed against viral targets using three sequential docking modes (i.e., HTVS, SP, and XP). Virtual screening identified ∼290 potential inhibitors based on the criteria of energy, docking parameters, ligand, and binding site strain and score. Drugs specific to each target protein were further analyzed for binding free energy perturbation by molecular mechanics (prime MM-GBSA) and pruning the hits to the top 32 candidates. The top lead from each target pool was further subjected to molecular dynamics simulation using the Desmond module. The resulting top eight hits were tested for their SARS-CoV-2 anti-viral activity in-vitro. Among these, a known inhibitor of protein kinase C isoforms, Bisindolylmaleimide IX (BIM IX), was found to be a potent inhibitor of SARS-CoV-2. Further, target validation through enzymatic assays confirmed 3CLpro to be the target. This is the first study that has showcased BIM IX as a COVID-19 inhibitor thereby validating our pipeline.

Experimental research in rats on the reactivity of new corneal blood vessels to adrenaline

Aim: The purpose of this experimental study was to evaluate the existence of adrenergic receptors in ketamine-induced corneal blood vessels in rat pups. Methods: The study of corneal neovascularization motricity was performed on 45-day-old Wistar rats in which, starting from the 15th day of life, corneal blood vessels were obtained by injecting intraperitoneal ketamine at a dose of 150 mg/ kg body weight, a total of 5 successive doses. The examination of the neovascularization was done with the help of a Nikon stereomicroscope connected to a video camera and a computer, the total magnification being 400X. The reactivity of the new corneal blood vessels to the administration in conjunctival instillations of a 1.5 mmol/L adrenaline solution was tested. The parameters followed were represented by variations in the caliber of corneal blood vessels. The data were analyzed using Microsoft Office Excel. Results: Administration of distilled water did not produce statistically significant changes in corneal blood vessels, while adrenaline produced a statistically significant constriction of vascular diameter (p=0.01 at T9, p=0.004 at T10, p=0.019 at time T11 of examinations). Conclusions: The results showed that adrenaline produces vasoconstriction in the new corneal blood vessels, which allows us to assume that they contain α-adrenergic receptors. However, we cannot say that corneal pathological vessels do not contain β2-type adrenergic receptors, because the effect of adrenaline may be an algebraic sum between vasoconstriction produced by stimulating α-adrenergic receptors and vasodilation produced by stimulating β2-adrenergic receptors, but in which the vasodilating effect may be masked by the vasoconstrictor effect given by a higher density of α-adrenergic receptors. Abbreviations: A= adrenaline, DNM = non-measurable diameter, NA= noradrenaline, Std.Er.= Standard error.

Targeting SARS-CoV-2 Nsp12/Nsp8 interaction interface with approved and investigational drugs: an in silico structure-based approach

In this study, the Nsp12–Nsp8 complex of SARS-CoV-2 was targeted with structure-based and computer-aided drug design approach because of its vital role in viral replication. Sequence analysis of RNA-dependent RNA polymerase (Nsp12) sequences from 30,366 different isolates were analysed for possible mutations. FDA-approved and investigational drugs were screened for interaction with both mutant and wild-type Nsp12–Nsp8 interfaces. Sequence analysis revealed that 70.42% of Nsp12 sequences showed conserved P323L mutation, located in the Nsp8 binding cleft. Compounds were screened for interface interaction, any with XP GScores lower than −7.0 kcal/mol were considered as possible interface inhibitors. RX-3117 (fluorocyclopentenyl cytosine) and Nebivolol had the highest binding affinities in both mutant and wild-type enzymes, therefore they were selected and resultant protein–ligand complexes were simulated for analysis of stability over 100 ns. Although the selected ligands had partial mobility in the binding cavity, they were not removed from the binding pocket after 100 ns. The ligand RX-3117 remained in the same position in the binding pocket of the mutant and wild-type enzyme after 100 ns MD simulation. However, the ligand Nebivolol folded and embedded in the binding pocket of mutant Nsp12 protein. Overall, FDA-approved and investigational drugs are able to bind to the Nsp12–Nsp8 interaction interface and prevent the formation of the Nsp12–Nsp8 complex. Interruption of viral replication by drugs proposed in this study should be further tested to pave the way for in vivo studies towards the treatment of COVID-19.

Communicated by Ramaswamy H. Sarma

Minute-scale persistence of a GPCR conformation state triggered by non-cognate G protein interactions primes signaling

Despite the crowded nature of the cellular milieu, ligand-GPCR-G protein interactions are traditionally viewed as spatially and temporally isolated events. In contrast, recent reports suggest the spatial and temporal coupling of receptor-effector interactions, with the potential to diversify downstream responses. In this study, we combine protein engineering of GPCR-G protein interactions with affinity sequestration and photo-manipulation of the crucial Gα C terminus, to demonstrate the temporal coupling of cognate and non-cognate G protein interactions through priming of the GPCR conformation. We find that interactions of the Gαs and Gαq C termini with the β₂-adrenergic receptor (β₂-AR), targeted at the G-protein-binding site, enhance Gs activation and cyclic AMP levels. β₂-AR-Gα C termini interactions alter receptor conformation, which persists for ~90 s following Gα C terminus dissociation. Non-cognate G-protein expression levels impact cognate signaling in cells. Our study demonstrates temporal allostery in GPCRs, with implications for the modulation of downstream responses through the canonical G-protein-binding interface.

In utero Exposure to β-2-Adrenergic Receptor Agonist Drugs and Risk for Autism Spectrum Disorders

OBJECTIVES

The purpose of this study was to investigate associations between use of β-2-adrenergic receptor (B2AR) agonist drugs during pregnancy and risk for autism spectrum disorders (ASD).

METHODS

A case-control study was conducted by using Denmark's health and population registers. Among children born between 1997 and 2006, 5200 cases with ASD admission diagnoses and 52 000 controls without ASD were identified and individually matched on month and year of birth. Conditional logistic regression models were used to estimate odds ratios (OR) and confidence intervals (CI) for any B2AR agonist exposure during pregnancy, preconception, and by trimester.

RESULTS

In total, 3.7% of cases and 2.9% of controls were exposed to B2ARs during pregnancy. Use of B2ARs during pregnancy was associated with increased risk of ASD, even after adjustment for maternal asthma and other covariates (OR: 1.3, 95% CI: 1.1-1.5). The elevated risk was observed with use of B2AR during preconception (OR: 1.3, 95% CI: 1.0-1.6), first trimester (OR: 1.3, 95% CI: 1.1-1.5), second trimester (OR: 1.5, 95% CI: 1.1-1.7), and the third trimester (OR: 1.4, 95% CI: 1.1-1.7). There was some evidence that longer B2AR within-pregnancy use was associated with the increased risk.

CONCLUSIONS

B2AR agonist exposure during pregnancy may be associated with an increased risk for ASD. If the effect is real, any intervention must be balanced against benefits of indicated medication use by pregnant women.

Inhaled anticholinergics and short-acting beta(2)-agonists versus short-acting beta2-agonists alone for children with acute asthma in hospital

BACKGROUND

Inhaled anticholinergics given in addition to β2-agonists are effective in reducing hospital admissions in children presenting to the emergency department with a moderate to severe asthma exacerbation. It seems logical to assume a similar beneficial effect in children hospitalised for an acute asthma exacerbation.

OBJECTIVES

To assess the efficacy and safety of anticholinergics added to β2-agonists as inhaled or nebulised therapy in children hospitalised for an acute asthma exacerbation. To investigate the characteristics of patients or therapy, if any, that would influence the magnitude of response attributable to the addition of anticholinergics.

SEARCH METHODS

We identified trials from the Cochrane Airways Group Specialised Register of trials (CAGR), which is derived through systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, AMED and PsycINFO and through handsearching of respiratory journals and meeting abstracts. The search is current to November 2013.

SELECTION CRITERIA

Randomised trials comparing the combination of inhaled or nebulised anticholinergics and short-acting β2-agonists versus short-acting β2-agonists alone in children one to 18 years of age hospitalised for an acute asthma exacerbation were eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the methodological quality of trials and extracted data; disagreement was resolved by consensus or with the input of a third review author, when needed. Primary outcomes were duration of hospital stay and serious adverse events. Secondary outcomes included admission and duration of stay in the intensive care unit (ICU), ventilation assistance, time to short-acting β2-agonists spaced at four hours or longer, supplemental asthma therapy, duration of supplemental oxygen, change from baseline in asthma severity, relapse after discharge, adverse health effects and withdrawals.

MAIN RESULTS

Seven randomised trials were included, four of which reported usable data on 472 children with asthma one to 18 years of age who were admitted to paediatric wards. No trials included patients admitted to the ICU. The anticholinergic used, ipratropium bromide 250 μg, was given every one to eight hours over a period from four hours to the entire length of the hospital stay. Two of four trials (50%) contributing data were deemed of high methodological quality. The addition of anticholinergics to β2-agonists showed no evidence of effect on the duration of hospital admission (mean difference (MD) -0.28 hours, 95% confidence interval (CI) -5.07 to 4.52, 3 studies, 327 participants, moderate quality evidence) and no serious or non-serious adverse events were reported in any included trials. As a result of the similarity of trials, we could not explore the influence of age, admission site, intensity of anticholinergic treatment and co-interventions on primary outcomes. No statistically significant group difference was noted in other secondary outcomes, including the need for supplemental asthma therapy, time to short-acting β2-agonists spaced at four hours or longer, asthma clinical scores, lung function and overall withdrawals for any reason.

AUTHORS' CONCLUSIONS

In children hospitalised for an acute asthma exacerbation, no evidence of benefit for length of hospital stay and other markers of response to therapy was noted when nebulised anticholinergics were added to short-acting β2-agonists. No adverse health effects were reported, yet the small number of trials combined with inadequate reporting prevent firm reassurance regarding the safety of anticholinergics. In the absence of trials conducted in ICUs, no conclusion can be drawn regarding children with impending respiratory failure. These findings support current national and international recommendations indicating that healthcare practitioners should refrain from using anticholinergics in children hospitalised for acute asthma.

Combined inhaled anticholinergics and short-acting beta2-agonists for initial treatment of acute asthma in children

BACKGROUND

There are several treatment options for managing acute asthma exacerbations (sustained worsening of symptoms that do not subside with regular treatment and require a change in management). Guidelines advocate the use of inhaled short acting beta2-agonists (SABAs) in children experiencing an asthma exacerbation. Anticholinergic agents, such as ipratropium bromide and atropine sulfate, have a slower onset of action and weaker bronchodilating effect, but may specifically relieve cholinergic bronchomotor tone and decrease mucosal edema and secretions. Therefore, the combination of inhaled anticholinergics with SABAs may yield enhanced and prolonged bronchodilation.

OBJECTIVES

To determine whether the addition of inhaled anticholinergics to SABAs provides clinical improvement and affects the incidence of adverse effects in children with acute asthma exacerbations.

SEARCH METHODS

We searched MEDLINE (1966 to April 2000), EMBASE (1980 to April 2000), CINAHL (1982 to April 2000) and reference lists of studies of previous versions of this review. We also contacted drug manufacturers and trialists. For the 2012 review update, we undertook an 'all years' search of the Cochrane Airways Group's register on the 18 April 2012.

SELECTION CRITERIA

Randomized parallel trials comparing the combination of inhaled anticholinergics and SABAs with SABAs alone in children (aged 18 months to 18 years) with an acute asthma exacerbation.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We used the GRADE rating system to assess the quality of evidence for our primary outcome (hospital admission).

MAIN RESULTS

Twenty trials met the review eligibility criteria, generated 24 study comparisons and comprised 2697 randomised children aged one to 18 years, presenting predominantly with moderate or severe exacerbations. Most studies involved both preschool-aged children and school-aged children; three studies also included a small proportion of infants less than 18 months of age. Nine trials (45%) were at a low risk of bias. Most trials used a fixed-dose protocol of three doses of 250 mcg or two doses of 500 mcg of nebulized ipratropium bromide in combination with a SABA over 30 to 90 minutes while three trials used a single dose and two used a flexible-dose protocol according to the need for SABA.The addition of an anticholinergic to a SABA significantly reduced the risk of hospital admission (risk ratio (RR) 0.73; 95% confidence interval (CI) 0.63 to 0.85; 15 studies, 2497 children, high-quality evidence). In the group receiving only SABAs, 23 out of 100 children with acute asthma were admitted to hospital compared with 17 (95% CI 15 to 20) out of 100 children treated with SABAs plus anticholinergics. This represents an overall number needed to treat for an additional beneficial outcome (NNTB) of 16 (95% CI 12 to 29).Trends towards a greater effect with increased treatment intensity and with increased asthma severity were observed, but did not reach statistical significance. There was no effect modification due to concomitant use of oral corticosteroids and the effect of age could not be explored. However, exclusion of the one trial that included infants (< 18 months) and contributed data to the main outcome, did not affect the results. Statistically significant group differences favoring anticholinergic use were observed for lung function, clinical score at 120 minutes, oxygen saturation at 60 minutes, and the need for repeat use of bronchodilators prior to discharge from the emergency department. No significant group difference was seen in relapse rates.Fewer children treated with anticholinergics plus SABA reported nausea and tremor compared with SABA alone; no significant group difference was observed for vomiting.

AUTHORS' CONCLUSIONS

Children with an asthma exacerbation experience a lower risk of admission to hospital if they are treated with the combination of inhaled SABAs plus anticholinergic versus SABA alone. They also experience a greater improvement in lung function and less risk of nausea and tremor. Within this group, the findings suggested, but did not prove, the possibility of an effect modification, where intensity of anticholinergic treatment and asthma severity, could be associated with greater benefit.Further research is required to identify the characteristics of children that may benefit from anticholinergic use (e.g. age and asthma severity including mild exacerbation and impending respiratory failure) and the treatment modalities (dose, intensity, and duration) associated with most benefit from anticholinergic use better.

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.

Modeling GPCR active state conformations: the β(2)-adrenergic receptor

The recent publication of several G protein-coupled receptor (GPCR) structures has increased the information available for homology modeling inactive class A GPCRs. Moreover, the opsin crystal structure shows some active features. We have therefore combined information from these two sources to generate an extensively validated model of the active conformation of the β(2)-adrenergic receptor. Experimental information on fully active GPCRs from zinc binding studies, site-directed spin labeling, and other spectroscopic techniques has been used in molecular dynamics simulations. The observed conformational changes reside mainly in transmembrane helix 6 (TM6), with additional small but significant changes in TM5 and TM7. The active model has been validated by manual docking and is in agreement with a large amount of experimental work, including site-directed mutagenesis information. Virtual screening experiments show that the models are selective for β-adrenergic agonists over other GPCR ligands, for (R)- over (S)-β-hydroxy agonists and for β(2)-selective agonists over β(1)-selective agonists. The virtual screens reproduce interactions similar to those generated by manual docking. The C-terminal peptide from a model of the stimulatory G protein, readily docks into the active model in a similar manner to which the C-terminal peptide from transducin, docks into opsin, as shown in a recent opsin crystal structure. This GPCR-G protein model has been used to explain site-directed mutagenesis data on activation. The agreement with experiment suggests a robust model of an active state of the β(2)-adrenergic receptor has been produced. The methodology used here should be transferable to modeling the active state of other GPCRs.

Management of acute asthma exacerbations in children

The management of acute asthma exacerbations in children remains controversial and the latest guidelines (Expert Panel Report [EPR]-3 2007 and the Global Initiative of Asthma 2008) leave several questions unanswered. This review summarizes the most up-to-date information on the practical prevention and control of asthma attacks in children, and describes the 20-year experience of a major tertiary asthma clinic with the administration of inhaled corticosteroids in this setting. The following subjects are discussed: the knowledge and skills required by the parents regarding asthma and its treatment, how to prevent or minimize exacerbations in asthmatic children, the drugs used in the treatment of exacerbations and their order of administration, and the steps to follow after discharge from the emergency department or after a severe asthma exacerbation. The efficacy of inhaled corticosteroids in the management of acute asthma exacerbations in children, both at home and in the emergency department, is discussed in detail. The goal of asthma-management programs is to arm parents with the skills and knowledge to prevent, detect and successfully control most exacerbations of asthma in children at home.

DEVELOPMENT AND INNOVATION IN CARDIOVASCULAR MEDICINE

The last century has witnessed groundbreaking advances in clinical medicine across the entire diagnostic and therapeutic range, but inequities in access to these advances and innovations continue to be a major challenge to our societies.

Innovations are often initiated by "eureka" moments of discovery, but realising their full potential depend on a process of continuous incremental innovation and interaction involving complex networks. When developing systems that reward, encourage, and sustain medical advances, policy makers must recognise four important factors. First, "incremental" and "continuous" innovation is as important as "breakthrough" innovation. Second, investment across the entire innovation process is needed. Third, the ability of physicians to work across a wide range of scientific fields at "the bench and bedside" is critical to continuous innovation. And fourth, final medical advance that can result from an initial discovery may not be obvious and only occur following interaction with experts and innovations in other fields.

The impact of therapeutic reference pricing on innovation in cardiovascular medicine

Therapeutic reference pricing (TRP) places medicines to treat the same medical condition into groups or 'clusters' with a single common reimbursed price. Underpinning this economic measure is an implicit assumption that the products included in the cluster have an equivalent effect on a typical patient with this disease. 'Truly innovative' products can be exempt from inclusion in the cluster. This increasingly common approach to cost containment allocates products into one of two categories - truly innovative or therapeutically equivalent. This study examines the implications of TRP against the step-wise evolution of drugs for cardiovascular conditions over the past 50 years. It illustrates the complex interactions between advances in understanding of cellular and molecular disease mechanisms, diagnostic techniques, treatment concepts, and the synthesis, testing and commercialisation of products. It confirms the highly unpredictable and incremental nature of the innovation process. Medical progress in terms of improvement in patient outcomes over the long-term depends on the cumulative effect of year after year of painstaking incremental advances. It shows that the parallel processes of advances in scientific knowledge and the industrial 'investment-innovative cycle' involve highly developed sets of complementary capabilities and resources. A framework is developed to assess the impact of TRP upon research and development investment decisions and the development of therapeutic classes. We conclude that a simple categorisation of products as either 'truly innovative' or 'therapeutically equivalent' is inconsistent with the incremental processes of innovation and the resulting differentiated product streams revealed by our analysis. Widespread introduction of TRP would probably have prematurely curtailed development of many incremental innovations that became the preferred 'product of choice' by physicians for some indications and patients in managing the incidence of cardiovascular disease.

Enhanced G(i) signaling selectively negates beta2-adrenergic receptor (AR)--but not beta1-AR-mediated positive inotropic effect in myocytes from failing rat hearts

BACKGROUND

Myocardial contractile response to beta1- and beta2-adrenergic receptor (AR) stimulation is severely impaired in chronic heart failure, in which G(i) signaling and the ratio of beta2/beta1 are often increased. Because beta2-AR but not beta1-AR couples to G(s) and G(i) with the G(i) coupling negating the G(s)-mediated contractile response, we determined whether the heart failure-associated augmentation of G(i) signaling contributes differentially to the defects of these beta-AR subtypes and, if so, whether inhibition of G(i) or selective activation of beta2-AR/G(s) by ligands restores beta2-AR contractile response in the failing heart.

METHODS AND RESULTS

Cardiomyocytes were isolated from 18- to 24-month-old failing spontaneously hypertensive (SHR) or age-matched Wistar-Kyoto (WKY) rat hearts. In SHR cardiomyocytes, either beta-AR subtype-mediated inotropic effect was markedly diminished, whereas G(i) proteins and the beta2/beta1 ratio were increased. Disruption of G(i) signaling by pertussis toxin (PTX) enabled beta2- but not beta1-AR to induce a full positive inotropic response in SHR myocytes. Furthermore, screening of a panel of beta2-AR ligands revealed that the contractile response mediated by most beta2-AR agonists, including zinterol, salbutamol, and procaterol, was potentiated by PTX, indicating concurrent G(s) and G(i) activation. In contrast, fenoterol, another beta2-AR agonist, induced a full positive inotropic effect in SHR myocytes even in the absence of PTX.

CONCLUSIONS

We conclude that enhanced G(i) signaling is selectively involved in the dysfunction of beta2- but not beta1-AR in failing SHR hearts and that disruption of G(i) signaling by PTX or selective activation of beta2-AR/G(s) signaling by fenoterol restores the blunted beta2-AR contractile response in the failing heart.

A proposal for a practical treatment guideline designed for the initial two-hours of the management of patients with acute severe asthma and COPD using the principles of evidence-based medicine

We have proposed a clinical treatment guideline for the management of acute, severe asthma and chronic obstructive pulmonarydisease (COPD) using the principles of evidence-based medicine. The content is based upon practical clinical issues in need of consensus. A previous study has shown that this particular area is in serious need of quality control. Based on a strict 2 h time schedule with a unified treatment plan for both asthma and COPD, it is possible to secure for the patients a well-documented medical therapy promoting decision-making and clarification of the patient within this time limit. A summary of the statements is presented in a one-page, user-friendly format in order to cope with the clinician's need of having access to published evidence quickly and easily. A website (www.phanareth.dk or a website provided by Respiratory Medicine) has been established providing regular updates. A strategy for the implementation and the evaluation process has been planned after the publication of this paper. We believe this approach to be an important step towards an increase in the quality of guidelines and also a tool to make "guideline writers" aware of the responsibility of making their recommendations work.

Management of children with severe asthma exacerbation in the emergency department

Although acute asthma is a very common cause of emergency department visits in children, there is as yet insufficient evidence for the establishment of a standardized treatment protocol. The aim of this review is to describe updated information on the management of asthma exacerbations in the pediatric emergency department. Oxygen is the first-line treatment of acute asthma exacerbations in the emergency department to control hypoxemia. It is accompanied by the administration of beta(2)-adrenoceptor agonists followed by corticosteroids. beta(2)-Adrenoceptor agonists have traditionally been administered by nebulization, although spacers have recently been introduced and proven, in many cases, to be as effective as nebulization. Oral prednisolone, with its reliability, simplicity, convenience and low cost, should remain the treatment of choice for the most severe asthma exacerbations, when the lung airways are extremely contracted and filled with secretions. Recently, several studies have shown that high-dose inhaled corticosteroids are at least as effective as oral corticosteroids in controlling moderate to severe asthma attacks in children and therefore should be considered an alternative treatment to oral corticosteroids in moderate to severe asthma attacks. Studies of other drugs have shown that ipratropium bromide may be given only in addition to beta(2)-adrenoceptor agonists; theophylline has no additional benefit, and magnesium sulfate has no clear advantage. Comprehensive asthma management should also include asthma education, measures to prevent asthma triggers, and training in the use of inhalers and spacers. Proper management will avoid most asthma attacks and reduce admission and readmission to emergency departments.

Determination of fenoterol in human plasma by HPLC with fluorescence detection after derivatization

A new method for the determination of fenoterol is described, which uses HPLC separation with fluorescence detection. Dobutamine is employed as an internal standard. The separation was achieved on a short reversed phase column with a mobile phase consisting of water, acetonitrile and methanol. Prior to chromatography both analytes are derivatized with 9-chloroformyl-carbazole. Isolation of the analytes from plasma is carried out by liquid-liquid extraction into 2-butanol after protein precipitation with acetonitrile. The method is capable of estimating fenoterol concentrations in the sub-nanogram per ml range with sufficient accuracy and precision. The determination of fenoterol can now be carried out in the average laboratory without radiolabelled material.

Fenoterol hydrobromide delivered via HFA-MDI or CFC-MDI in patients with asthma: a safety and efficacy comparison

The main objective of the study was to compare the long-term safety and tolerability of fenoterol hydrobromide delivered using a metered-dose inhaler formulated with the alternative propellant, hydrofluoroalkane 134a (HFA-MDI), with delivery using the currently available chlorofluorocarbon MDI (CFC-MDI; Berotec 100). A further objective was to compare the efficacy of fenoterol HFA-MDI with fenoterol CFC-MDI, using the pulmonary function parameters of forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF). Following a 2-week run-in phase, a 12-week, double-blind parallel group comparison was undertaken in 290 patients randomized on a 2:1 basis to two puffs of 100 microg fenoterol four times a day (HFA-MDI=197 patients; CFC-MDI=93 patients). A total of 236 patients in this multi-centre study completed the trial as planned. The overall incidence of adverse events (AEs) was similar in both groups (29.9% of HFA-MDI patients and 28% of CFC-MDI patients). Reports of respiratory disorder AEs were also comparable (21.8% HFA-MDI; 22.6% CFCMDI). End of study laboratory tests, ECG, pulse, blood pressure and physical examination showed no significant differences from pre-study baselines in either group and both treatments appeared to be well tolerated. Pre-dose FEV1 measurements taken at the three clinic visits were constant and increase in FEV1 at 5 and 30 min post-dose demonstrated equivalent efficacy for the two formulations. No difference between the two groups was observed in PEF or in the use of rescue medication. We conclude from these findings that the long-term safety and efficacy profile of fenoterol HFA-MDI is comparable to that of the fenoterol CFC-MDI.

Combined inhaled anticholinergic agents and beta-2-agonists for initial treatment of acute asthma in children

BACKGROUND

Anti-cholinergic agents and beta2-agonist drugs are both bronchodilators used to reverse acute bronchospasm in children with asthma. These drugs have different modes of action, so may have complementary or additive effects.

OBJECTIVES

The objective of this review was to assess the effects of adding inhaled anti-cholinergics to beta2-agonists in acute paediatric asthma.

SEARCH STRATEGY

We searched Medline (1966 to 1996), Embase (1980 to 1995), Cinahl (1982 to 1995) and reference lists of studies. We also contacted drug manufacturers and researchers.

SELECTION CRITERIA

Randomised trials comparing the combination of inhaled anti-cholinergics and beta2-agonists with beta2-agonists alone in children aged 18 months to 17 years with acute asthma.

DATA COLLECTION AND ANALYSIS

Assessments of trial quality and data extraction were done by two reviewers independently.

MAIN RESULTS

Ten trials involving a total of 836 children were included. Most trials were of high quality. When only one dose of anti-cholinergic inhalation was added to beta2-agonist therapy, there was an improvement in forced expiratory volume in one second after 60 minutes with combination therapy (weighted mean difference 16.1%, 95% confidence interval 5.5 to 26. 7% reduction). There was no reduction in hospital admission (odds ratio 0.80, 95% confidence interval 0.35 to 1.82, using a random effects model). For multiple doses in children with severe asthma, there was a reduction in forced expiratory volume in 1 second (weighted mean difference 9.8% predicted, 95% confidence interval 6. 5 to 13.1% predicted). There may also be a reduction in hospital admission (odds ratio 0.62, 95% confidence interval 0.38 to 0.99). Eleven children would need to be given multiple doses of anti-cholinergics in combination with beta2-agonists to avoid one hospital admission compared to children given beta2-agonists alone.

REVIEWER'S CONCLUSIONS

In children with acute asthma, the addition of multiple doses of anti-cholinergics to inhaled beta2-agonists appears to improve lung function modestly and may decrease hospital admission. There is no associated increase in adverse effects. Single doses of anti-cholinergics may improve lung function in children with severe asthma, but do not appear to reduce hospital admissions.

Should inhaled anticholinergics be added to beta2 agonists for treating acute childhood and adolescent asthma? A systematic review

OBJECTIVES

To estimate the therapeutic and adverse effects of addition of inhaled anticholinergics to beta2 agonists in acute asthma in children and adolescents.

DESIGN

Systematic review of randomised controlled trials of children and adolescents taking beta2 agonists for acute asthma with or without the addition of inhaled anticholinergics.

MAIN OUTCOME MEASURES

Hospital admission, pulmonary function tests, number of nebulised treatments, relapse, and adverse effects.

RESULTS

Of 37 identified trials, 10 were relevant and six of these were of high quality. The addition of a single dose of anticholinergic to beta2 agonist did not reduce hospital admission (relative risk 0.93, 95% confidence interval 0.65 to 1.32). However, significant group differences in lung function supporting the combination treatment were observed 60 minutes (standardised mean difference -0.57, -0.93 to -0.21) and 120 minutes (-0.53, -0.90 to -0.17) after the dose of anticholinergic. In contrast, the addition of multiple doses of anticholinergics to beta2 agonists, mainly in children and adolescents with severe exacerbations, reduced the risk of hospital admission by 30% (relative risk 0.72, 0.53 to 0.99). Eleven (95% confidence interval 5 to 250) children would need to be treated to avoid one admission. A parallel improvement in lung function (standardised mean difference -0.66, -0.95 to -0.37) was noted 60 minutes after the last combined inhalation. In the single study where anticholinergics were systematically added to every beta2 agonist inhalation, irrespective of asthma severity, no group differences were observed for the few available outcomes. There was no increase in the amount of nausea, vomiting, or tremor in patients treated with anticholinergics.

CONCLUSIONS

Adding multiple doses of anticholinergics to beta2 agonists seems safe, improves lung function, and may avoid hospital admission in 1 of 11 such treated patients. Although multiple doses should be preferred to single doses of anticholinergics, the available evidence only supports their use in school aged children and adolescents with severe asthma exacerbation.

Dose-effect relationship of the beta-agonists fenoterol and salbutamol in patients with asthma

QUESTION

What is the relative per microgram potency and side effect profile of the beta-agonists salbutamol and fenoterol?

METHOD

The relative bronchodilator (delta FEV1, V25, V50) potency and side effect profile (delta tremor, heart rate, breathlessness, BP) of nebulized salbutamol and fenoterol were evaluated by means of a randomized, double-blind, crossover, cumulative (50 to 2,500 micrograms) dose-response study. Both beta-agonists were administered to 12 patients with stable asthma over age 18 years with baseline FEV1 between 35 to 70 percent predicted.

RESULTS

(1) Salbutamol and fenoterol both provided significant bronchodilatation compared with baseline. (2) There was no dose-effect difference between the two beta-agonists with respect to bronchodilator response. (3) Overall there was no significant difference between the side effect profiles of the two beta-agonists, although at the highest dose of fenoterol, there was marginally greater tremor when measured by accelerometry. (4) There was no difference in the vital signs or subjective patient evaluations of tremor, palpitations, or breathlessness as estimated by a visual analogue scale. (5) No significant adverse reactions occurred.

SUMMARY AND CONCLUSION

Equivalent bronchodilatation and similar side effect profiles were measured in a group of patients with stable asthma after treatment with nebulized salbutamol or fenoterol in the dose range 50 to 1,250 micrograms (cumulative, 2,500 micrograms). This indicates that both beta-agonists have similar per microgram potency and side effect profiles. Observed clinical differences in response or side effects associated with fenoterol metered-dose inhaler administration may be a result of its higher dose per puff metered-dose inhaler formulation.

Twelve month comparison of salmeterol and salbutamol as dry powder formulations in asthmatic patients. European Study Group

BACKGROUND

Salmeterol is a potent selective beta 2 agonist that has been shown to have a duration of action in excess of 12 hours. In this study salmeterol and salbutamol were compared over a three month period with a further extension of nine months.

METHODS

Three hundred and eighty eight patients with mild to moderate reversible airways obstruction (forced expiratory volume in one second (FEV1) > 50% predicted) were randomised to receive salmeterol (50 micrograms) twice daily or salbutamol (400 micrograms) four times daily, both by dry powder, in a double blind parallel group study. During the first three months detailed assessment of efficacy was made with recording of morning and evening peak expiratory flow rates (PEF), asthma symptoms, and bronchodilator use when necessary for the relief of symptoms. Patients continued in the study for a further nine months with the salbutamol dose reduced to 400 micrograms twice daily. Lung function was measured at the clinic and safety data were collected during this period.

RESULTS

Salmeterol produced a significantly higher mean morning PEF (mean difference compared with salbutamol 21 (95% CI 12-31) l/min), and a significant reduction in mean diurnal variation in PEF (from 30 l/min at baseline to 11 34 l/min at baseline to 32 l/min during salbutamol treatment). Salmeterol also reduced day and night symptoms and use of rescue bronchodilator. FEV1 increased with both salmeterol and salbutamol treatment over the 12 month treatment period. For both treatments the number of patients reporting exacerbations of asthma and the frequency of these exacerbations remained constant during the study. Thirty six patients in the salmeterol and 49 in the salbutamol group withdrew during the 12 months of the study.

CONCLUSIONS

In this study salmeterol (50 micrograms twice daily) was more effective than salbutamol (400 micrograms four times daily) in the control of asthma over three months, and more effective than salbutamol (400 micrograms twice daily) over a further nine months. Neither salmeterol nor salbutamol was associated with any worsening of control of asthma.

Low dose fenoterol aerosol protects against histamine-induced bronchoconstriction in mild asthmatics: a dose response study

Sixteen subjects with mild stable asthma participated in a randomized double blind study on the effects of low dose fenoterol against histamine induced bronchoconstriction. Fenoterol aerosol at concentrations of 10, 50 and 200 micrograms and placebo were delivered at random through a metered dose inhaler as a single dose 30 min before histamine challenges on four separate occasions. Compared to placebo a fenoterol dose of 10 micrograms provided significant bronchodilatation (sRaw [s.d.] 8.3 [2.73] vs 6.3 [1.74] cm H2O* s [P less than 0.05]) and protection (PC100 sRaw [s.e.m.] 0.72 (1.31) vs 1.45 (1.39) mg/ml). The bronchodilatory and protective actions of fenoterol were more pronounced after the inhalation of 200 micrograms (P less than 0.05) with no difference between 10 and 50 micrograms fenoterol aerosol. The magnitude of bronchodilatation and protection was not correlated (r = 0.15). The results from this acute study may suggest that fenoterol at doses up to 20 times lower than routinely recommended may be an effective treatment in mild asthmatics.

Salmeterol, a novel, long-acting beta 2-adrenoceptor agonist: characterization of pharmacological activity in vitro and in vivo

1. Salmeterol, a novel, long-acting beta-adrenoceptor agonist, has been compared with isoprenaline and salbutamol for activity in vitro on a range of beta-adrenoceptor containing preparations from laboratory animals and man, and in vivo for bronchodilator activity in the conscious guinea-pig. 2. Salmeterol, like isoprenaline and salbutamol, relaxed preparations of both guinea-pig trachea (contracted by prostaglandin (PG)F2alpha or electrical stimulation) and human bronchus (contracted by PGF 2 alpha) in a concentration-related fashion. Salmeterol was of similar potency to isoprenaline and more potent than salbutamol on both airway preparations. 3. Relaxant responses of superfused guinea-pig trachea and human bronchus to isoprenaline and salbutamol declined rapidly when the agonists were washed from the tissues, with complete recovery within 10 min, whereas responses to salmeterol were more persistent. In electrically-stimulated guinea-pig trachea preparations, inhibition by salmeterol persisted for periods of up to 12h, despite continuous superfusion with agonist-free medium. However, these persistent responses were rapidly and fully reversed by the beta-adrenoceptor blocking drug, propranolol (0.1 microM). In further studies on guinea-pig trachea, propranolol caused concentration-related parallel, rightward shifts of salmeterol concentration-effect curves, yielding a pA2 of 9.0. The slope of the Schild plot was 1.02. 4. Another beta-adrenoceptor blocking drug, sotalol (10 microM), also fully and rapidly reversed established submaximal responses to salmeterol in superfused guinea-pig trachea. However, after administration of sotalol was stopped, the antagonism waned, and salmeterol responses were reasserted without the addition of further agonist. 5. In the beta 1-adrenoceptor containing preparation, rat left atria, isoprenaline exhibited potent, concentration-related, positive inotropic activity, whereas salbutamol and salmeterol were at least 2000-5000 fold less potent, and appeared to be partial agonists. At a concentration of 72 microM, salmeterol exhibited weak antagonism of isoprenaline-induced increases in atrial force of contraction. This antagonism was less marked than that caused by salbutamol (42 microM).6. On the guinea-pig isolated gastric fundus strip, a putative beta3-adrenoceptor containing preparation, salbutamol and salmeterol had only modest agonist activity, being 20-30 fold less potent than isoprenaline and the selective ,beta3-adrenoceptor agonist, BRL 35135.7. In conscious guinea-pigs, inhaled salmeterol and salbutamol were approximately equipotent in causing dose-related bronchodilatation. Whereas the duration of action of salbutamol at its threshold-effective dose was less than 90min, the responses to a similarly effective dose of salmeterol were well-maintained for at least 6 h.8. Salmeterol is therefore a potent and selective beta2-adrenoceptor agonist with a remarkably long duration of action in isolated superfused airways smooth muscle. It also causes persistent bronchodilatation in vivo, in the guinea-pig, when administered by the inhaled route.

Bronchodilator, cardiovascular, and hypokalaemic effects of fenoterol, salbutamol, and terbutaline in asthma

The airway response and cardiovascular and hypokalaemic effects of fenoterol, salbutamol, and terbutaline given in multiples of standard doses from metered-dose inhalers were studied in ten patients with mild asthma. In a double-blind, crossover, placebo-controlled study the subjects received 2, 6, and 18 puffs of each drug with intervals of 90 min, and forced expiratory volume in 1 s, heart rate, QTc interval, plasma potassium concentration, tremor, and bronchial reactivity to histamine were measured. All three drugs produced similar bronchodilatation. However, the rises in heart rate, QTc interval, and tremor and the fall in plasma potassium were greater after fenoterol than after salbutamol or terbutaline. The maximum mean (SD) increases in heart rate for fenoterol, salbutamol, and terbutaline were 29 (24) bpm, 8 (9) bpm, and 8 (14) bpm, respectively; falls in plasma potassium were 0.76 (0.62) mmol/l, 0.46 (0.32) mmol/l, and 0.52 (0.39) mmol/l, respectively. Fenoterol afforded no additional protection against histamine compared with salbutamol. These findings suggest that at doses based on those used in clinical practice fenoterol causes more adverse effects than salbutamol or terbutaline. The most likely explanation for these effects is that fenoterol has been marketed at a higher dose than the other beta 2-agonists; fenoterol may in addition be less selective for beta 2 receptors.

The effect of inhaled fenoterol and ipratropium bromide on propranolol induced bronchoconstriction in the asthmatic airways

1. The provocative dose of inhaled propranolol, (PC20P, mg/mL) needed to induce a 20% reduction in the forced expired volume in 1 s (FEV1, L) was determined for 15 adult asthmatics following randomized pre-treatment with placebo, ipratropium bromide (40, 160 micrograms) and fenoterol (200, 800 micrograms) aerosols using a double-blind protocol. 2. Fenoterol 200 micrograms, 800 micrograms increased the baseline FEV1 0.28 +/- 0.16, 0.32 +/- 0.16 L (P = 0.04, P = 0.008 respectively). Fenoterol 800 micrograms moved the PC20 P rightwards from placebo geometric mean 10.95, 95% Confidence Intervals (95% CI) 4.43-27.22 mg/mL to mean 20.41, 95% CI 10.13 to 40.64 mg/mL (P = 0.01). Fenoterol 200 micrograms was not protective; mean PC20 16.22, 95% CI 7.83-34.35 mg/mL (P = 0.08). Neither 40 or 160 micrograms ipratropium changed the FEV1 or PC20P values compared with placebo; increase in FEV1 0.15 +/- 0.27 L (P = 0.22), 0.24 +/- 0.12 L (P = 0.14) and geometric mean PC20P 16.59 +/- 0.57 mg/mL, 95% CI 8.01-34.51 mg/mL (P = 0.90), 15.58 +/- 0.66 mg/mL, 95% CI 6.72-36.05 mg/mL (P = 0.34) respectively after ipratropium treatments. 3. Bronchoconstriction induced by inhaled propranolol (P) appears to be only weakly antagonized by inhaled beta-agonist and not reduced by antimuscarinic anticholinergic aerosol. This finding argues against the activation of a cholinergic reflex to explain propranolol induced bronchoconstriction (PIB).

Oxitropium bromide: an acute dose response study of a new anticholinergic drug in combination with fenoterol in asthma and chronic bronchitis

The aim of this study was to compare the bronchodilator response of patients with either stable asthma or stable chronic bronchitis to the acute administration of oxitropium bromide and a beta agonist (fenoterol) when given both separately and together in order to determine the responses of these two groups of patients and the optimal doses of these agents when given in combination. The responses of 23 patients with asthma and 25 patients with chronic bronchitis to 400 micrograms of fenoterol, and 200 micrograms of oxitropium given either alone or together with 100, 200 or 400 micrograms of fenoterol was studied. The peak bronchodilator response to oxitropium bromide of the patients with chronic bronchitis was equivalent to the fenoterol response while, in the patients with asthma, the response to oxitropium bromide was approximately 30% of the response to fenoterol. In both groups of subjects the addition of oxitropium bromide to fenoterol significantly increased both the magnitude and the duration of the bronchodilator response without a significant increase in side effects. In both groups of subjects 200 micrograms of oxitropium bromide and 200 micrograms or more of fenoterol gave the optimal response.

Antiasthmatic therapy in children

The availability of more and better medications for asthma contrasts with reports of an increasing frequency of hospitalization and fatalities. An understanding of the pathophysiology of the disease, its variations in clinical patterns, and the therapeutic potential of the available options for treatment in this overview of asthma management provides a basis for addressing this paradox. A scheme for matching the therapeutic options to the clinical pattern of the disease is presented with comments on the delivery of health care to asthmatic patients. Results of outcome from comprehensive asthma management programs are described.

Comparison of ipratropium solution, fenoterol solution, and their combination administered by nebulizer and face mask to children with acute asthma

In a randomized, double-blind, parallel-group trial, 47 children with acute asthma received a combination of ipratropium bromide solution (250 micrograms) and fenoterol hydrobromide solution (625 micrograms), fenoterol solution (625 micrograms) alone, or ipratropium solution (250 micrograms) alone, administered by face mask and nebulizer, with the dose repeated 60 minutes later. The groups did not differ significantly with regard to age, pulmonary function at baseline, or any other variable. They were monitored at 30, 60, 90, and 120 minutes by use of a clinical score, oxygen saturation, and pulmonary function tests. At the end of the study, albuterol was administered to assess residual bronchoconstriction. Clinical scores improved significantly after treatment in all groups at all times compared with baseline. The greatest improvement in FEV1 was seen in the patients treated with ipratropium/fenoterol, whether considered as absolute change, change in percent predicted, or percent change from baseline. Ipratropium/fenoterol was significantly better than fenoterol alone only when considered as percent change from baseline. Improvement in flow at mid and low lung volumes was significantly greater for the ipratropium/fenoterol combination than for ipratropium alone; no significant differences were noted between ipratropium/fenoterol and fenoterol for flow at mid and low lung volumes. Treatment with albuterol did not significantly improve pulmonary function in the groups receiving ipratropium/fenoterol or fenoterol alone, but it did increase flow at all lung volumes in the group receiving ipratropium alone. No patient complained spontaneously of any adverse reactions, and no clinically significant changes in heart rate or systolic or diastolic blood pressures occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Salmeterol, a new long acting inhaled beta 2 adrenoceptor agonist: comparison with salbutamol in adult asthmatic patients

Salmeterol is a new inhaled beta 2 adrenoceptor agonist, which has been shown in animal experiments to produce a more prolonged bronchodilator effect than currently available beta 2 adrenoceptor agonists. It was studied in eight adult asthmatic patients. Each patient received on separate test days salbutamol 200 micrograms and salmeterol 50, 100, and 200 micrograms according to a randomised, double blind, crossover design. FEV1, peak expiratory flow (PEF), heart rate, blood pressure, and tremor were recorded in the clinic for six hours after drug inhalation; PEF was recorded for a further six hours at home. All three doses of salmeterol produced peak increases in FEV1 (mean 0.5-0.8 l) and PEF (71-100 l/min) similar to those produced by salbutamol 200 micrograms (0.5 l and 74 l/min). After salbutamol FEV1 and PEF had returned to baseline within six hours, but after all three doses of salmeterol more than half of the maximum bronchodilator effect remained after 12 hours. The effects of salbutamol and the two lower doses of salmeterol (50 and 100 micrograms) on cardiovascular measurements and on tremor were similar, whereas after salmeterol 200 micrograms there was a small decrease in diastolic blood pressure and an increase in heart rate and tremor. Thus inhaled salmeterol has a long acting bronchodilator action in asthmatic patients. This effect may be of value in the treatment of asthma, particularly in patients with nocturnal symptoms.

Decrease of plasma potassium due to inhalation of beta-2-agonists: absence of an additional effect of intravenous theophylline

The effect on the plasma potassium concentration of inhalation of the beta-2-agonists fenoterol, salbutamol (albuterol), and terbutaline from metered-dose inhalers was studied in normal volunteers. All three drugs caused a significant, dose-dependent decrease, more pronounced for fenoterol and salbutamol than for terbutaline. Relative to the bronchodilating potency (one puff of fenoterol 0.2 mg is considered to be equivalent to two puffs of salbutamol 2 x 0.1 mg, or two puffs of terbutaline 2 x 0.25 mg), fenoterol had a more pronounced effect on plasma potassium than salbutamol or terbutaline. The systemic effect on plasma potassium seems to be related to the structure of the drugs: the more lipophilic the drug (fenoterol) the sooner the systemic symptoms appear and the more pronounced they are. The effects of theophylline alone, and combined with fenoterol, were also studied. The intravenous infusion of theophylline (after placebo inhalation; maximal mean plasma concentration 14.9 +/- 2.2 mg l-1) caused a small but significant decrease of plasma potassium. There was no additive or synergistic effect when theophylline was added to fenoterol. It is concluded that inhalation of beta-agonists induces a decrease of plasma potassium, that this effect is relatively more pronounced for fenoterol than either salbutamol or terbutaline, and that it is not enhanced by the concomitant use of theophylline. Theophylline by itself causes a slight decrease in plasma potassium concentration.

Hypokalaemia and other non-bronchial effects of inhaled fenoterol and salbutamol: a placebo-controlled dose-response study in healthy volunteers

1. The hypokalaemia-inducing effects of two widely used inhaled antiasthmatic beta 2-adrenoceptor agonists, fenoterol and salbutamol, were compared in six healthy male volunteers. 2. Each drug was administered in three different doses, 400, 600 and 800 micrograms, which were repeated three times with 30 min intervals (total doses 1200, 1800 and 2400 micrograms in 1 h). The treatments were given at 1 week intervals in random order in a single-blind fashion. 3. The concentration of potassium in plasma was dose-dependently reduced by both drugs with peak effects 75-90 min after the first inhalations. The hypokalaemic effect of fenoterol was significantly greater than that of equal doses of salbutamol (average +/- s.d. reductions of 1.13 +/- 0.32 and 0.67 +/- 0.25 mEq l-1, respectively, after the highest doses, P less than 0.05). Concomitantly, decreases were noted in the amplitude of the T-wave on the ECG. 4. The concentration of cyclic AMP in plasma was measured and used as an indicator of systemic beta 2-adrenoceptor agonistic effects of the drugs. Increases in cAMP were a close mirror image of the drugs' effects on potassium in plasma. 5. Plasma renin activity, noradrenaline in plasma and heart rate were also dose-dependently increased by the treatments, whereas blood pressure remained unaltered. 6. While the clinical significance of hypokalaemia induced by inhaled beta 2-adrenoceptor sympathomimetics still is a matter of debate, our results point to possible differences between therapeutically equipotent doses of fenoterol and salbutamol in their propensity to cause hypokalaemia and other acute non-bronchial effects.

Liquid chromatographic separation of enantiomers of adrenergic agonists

Many established and experimental adrenergic agonists are derivatives of 2-aminoethanol with a phenol or catechol moiety in the 1-position. There is considerable interest in the stereochemical aspects of the actions of such chiral drugs. Surprisingly, however, little has been published on the chromatographic separation of the enantiomers of these compounds, and what has been published involved nearly exclusively capillary gas-liquid chromatography. In this report, the resolution of the racemates of ten adrenergic agents using reversed-phase liquid chromatography is described. The procedure is based on derivatizing the racemic mixture of each agent with the chiral reagent 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate, followed by separation of the resulting diastereomers on octadecylsilane columns using methanol-aqueous ammonium acetate mixtures as mobile phase. Detection was at 254 nm. The separation of the enantiomers of norphenylephrine and of octopamine was less than complete; the resolution of the other agents, i.e., synephrine, N-ethylnorphenylephrine, p-hydroxyephedrine, p-hydroxynorephedrine, metanephrine, normetanephrine, isoproterenol, and nordefrin, was complete. The derivative of (-)-isoproterenol eluted before that of its antipode. The procedure may be applicable to other similar agents.