Formoterol: pharmacology, molecular basis of agonism, and mechanism of long duration of a highly potent and selective beta 2-adrenoceptor agonist bronchodilator

Long-lasting target binding and rebinding as mechanisms to prolong in vivo drug action

An increasing number of examples in the literature suggest that the in vivo duration of drug action not only depends on macroscopic pharmacokinetic properties like plasma half-life and the time needed to equilibrate between the plasma and the effect compartments, but is also influenced by long-lasting target binding and rebinding. The present review combines information from different research areas and simulations to explore the nature of these mechanisms and the conditions in which they are most prevalent. Simulations reveal that these latter phenomena become especially influential when there is no longer sufficient free drug around to maintain high levels of receptor occupancy. There is not always a direct link between slow dissociation and long-lasting in vivo target protection, as the rate of free drug elimination from the effect compartment is also a key influencing factor. Local phenomena that hinder the diffusion of free drug molecules away from their target may allow them to consecutively bind to the same target and/or targets nearby (denoted as 'rebinding') even when their concentration in the bulk phase has already dropped to insignificant levels. The micro-anatomic properties of many effect compartments are likely to intensify this phenomenon. By mimicking the complexity of tissues, intact cells offer the opportunity to investigate both mechanisms under the same, physiologically relevant conditions.

Rebinding: or why drugs may act longer in vivo than expected from their in vitro target residence time

IMPORTANCE OF THE FIELD

It is well established that the in vivo duration of drug action not only depends on macroscopic pharmacokinetic properties like its plasma half-life, but also on the residence time of the drug-target complexes. However, drug 'rebinding' (i.e., the consecutive binding of dissociated drug molecules to the original target and/or targets nearby) can be influential in vivo as well.

AREAS COVERED IN THIS REVIEW

Information about rebinding is available since the 1980s but it is dispersed in the life sciences literature. This review compiles this information. In this respect, neurochemists and biopohysicians advance the same equations to describe drug rebinding.

WHAT THE READER WILL GAIN

The rebinding mechanism is explained according to the prevailing viewpoint in different life science disciplines. There is a general consensus that high target densities, high association rates and local phenomena that hinder the diffusion of free drug molecules away from their target all promote rebinding.

TAKE HOME MESSAGE

Simulations presented here for the first time suggest that rebinding may increase the duration and even the constancy of the drug's clinical action. Intact cell radioligand dissociation and related ex vivo experiments offer useful indications about a drug's aptitude to experience target rebinding.

Prolonged bronchoprotection against inhaled methacholine by inhaled BI 1744, a long-acting beta(2)-agonist, in patients with mild asthma

BACKGROUND

Long-acting ss(2)-agonists are an established controller medication in asthma. BI 1744 is a novel L\long-acting ss(2)-agonist with a preclinical profile that suggests 24-hour bronchodilation and bronchoprotection may be achieved.

OBJECTIVE

To examine the bronchoprotective effects of single doses of BI 1744 against methacholine provocation in subjects with mild asthma.

METHODS

Thirty-one subjects with mild asthma were randomized to receive single doses of BI 1744 (2, 5, 10, 20 microg) or placebo on separate days according to a double-blind, 5-way crossover design. Methacholine challenges were performed at 30 minutes and at 4, 8, 24, and 32 hours after each single dose of medication, and the results were expressed as PC(20) FEV(1).

RESULTS

All doses of BI 1744 produced statistically significant increases in the methacholine PC(20) compared with placebo as long as 32 hours. The mean (geometric SEM) methacholine PC(20) 24 hours after dosing with placebo was 1.73 (1.13) mg/mL, which increased after 2 microg to 3.86 (1.14) mg/mL, after 5 microg to 5.67 (1.14) mg/mL, after 10 microg to 9.42 (1.13) mg/mL, and after 20 microg to 13.71 (1.14) mg/mL (all P < .0001). After 32 hours, the methacholine PC(20) value remained significantly increased for all doses. No safety or tolerability concerns were identified.

CONCLUSION

BI 1744 provides significant bronchoprotection against inhaled methacholine for up to 32 hours after single-dose administration.

Ligands, their receptors and ... plasma membranes

Ligand-receptor interactions are customarily described by equations that apply to solutes. Yet, most receptors are present in cell membranes so that sufficiently lipophilic ligands could reach the receptor by a two-dimensional approach within the membrane. As summarized in this review, this may affect the ligand-receptor interaction in many ways. Biophysicians calculated that, compared to a three-dimensional approach from the liquid phase, such approach could alter the time the ligands need to find a receptor. Biochemists found that ligand incorporation in lipid bilayers modifies their conformation. This, along with the depth at which the ligands reside in the bilayer, will affect the probability of successful receptor interaction. Novel mechanisms were also introduced, including "exosite" binding and ligand translocation between the receptor's alpha-helical transmembrane domains. Pharmacologists focused attention at ligand concentrations in membrane, their adsorption and release rates and the effects thereof on ligand potency and residence time at the receptor.

Evaluation of combination long-acting beta-2 agonists and inhaled glucocorticosteroids for treatment of asthma

BACKGROUND

Treating asthma with a combination of inhaled corticosteroid and a long-acting beta-2-agonist is often preferred when asthma is not controlled when using a low-medium dose of an inhaled corticosteroid.

OBJECTIVE

To review the pharmacology, efficacy and safety of inhalers containing combinations of long-acting bronchodilators and inhaled corticosteroids to treat moderate-to-severe, persistent asthma.

METHODS

Using a list of keywords, we conducted a PubMed search of the literature. Data provided by the manufacturer were also reviewed.

RESULTS

Fluticasone propionate with salmeterol and budesonide with formoterol are both well tolerated, have equal clinical efficacy and have recent data affirming their safe use in diverse patient populations.

CONCLUSIONS

Combination inhalers improve asthma control in patients previously uncontrolled on inhaled corticosteroids.

Molecular mechanisms for the persistent bronchodilatory effect of the beta 2-adrenoceptor agonist salmeterol

BACKGROUND

Beta(2)-adrenoceptor agonists are effective bronchodilators. In vitro studies demonstrated long-lasting airway smooth muscle relaxation by salmeterol after washout, the quick disappearance of this effect in presence of antagonists and its recovery after antagonist removal. Current explanations invoke salmeterol accumulation in the membrane ('diffusion microkinetic' model) or the existence of salmeterol-binding 'exosites'. An alternative model based on 'rebinding' of a dissociated ligand to the receptor molecules also produces an apparent decrease in the ligand's dissociation rate in the absence of competing ligands. PURPOSE AND APPROACH: Computer-assisted simulations were performed to follow the receptor-occupation by a salmeterol-like ligand and a competing ligand as a function of time. The aptness of the models to describe the above in vitro findings was evaluated.

KEY RESULTS

The 'diffusion microkinetic' model is sufficient to explain a long-lasting beta(2)-adrenoceptor stimulation and reassertion as long as the membrane harbors a high concentration of the agonist. At lower concentration, 'rebinding' and, in second place, 'exosite' binding are likely to become operational.

CONCLUSIONS AND IMPLICATIONS

The 'rebinding' and 'exosite' binding mechanisms take place at a sub-cellular/molecular scale. Pending their demonstration by experiments on appropriate, simple models such as intact cells or membranes thereof, these mechanisms remain hypothetical in the case of salmeterol. Airway smooth muscle contraction could also be governed by additional mechanisms that are particular to this macroscopic approach.

An estimation of beta 2-adrenoceptor reserve on human bronchial smooth muscle for some sympathomimetic bronchodilators

BACKGROUND AND PURPOSE

The beta(2)-adrenoceptor on human pro-inflammatory cells is exquisitely sensitive to desensitization, whereas beta(2)-adrenoceptor-mediated relaxation of human airways smooth muscle (HASM) is relatively resistant to this phenomenon. An explanation for this discrepancy is that a large beta(2)-adrenoceptor 'reserve' exists on HASM cells for sympathomimetic bronchodilators, which protects against desensitization.

EXPERIMENTAL APPROACH

The operational model of agonism was used to estimate the affinity of salbutamol, terbutaline, formoterol and procaterol for the beta(2)-adrenoceptors in methacholine (MCh)-contracted HASM from which the relationship between fractional receptor occupancy and relaxation was determined. This analysis was performed under conditions of fractional, irreversible, beta(2)-adrenoceptor inactivation and, for salbutamol and terbutaline only, by the comparative method of Barlow et al. The affinity of salbutamol for the beta(2)-adrenoceptor guinea-pig eosinophils and the receptor/occupancy-response relationship for the suppression of the respiratory burst (an index of pro-inflammatory cell function) was also determined.

KEY RESULTS

For salbutamol and terbutaline, both pharmacological approaches yielded in HASM discrepant affinity estimates (values differed, maximally, by 0.67 log(10) unit). However, affinity values more closely agreed (difference <0.47 log(10) unit), when operational analysis was performed on data corrected for 'fade' of the MCh-induced contraction. Plots of fractional beta(2)-adrenoceptor occupancy versus relaxation indicated a receptor 'reserve' for all agonists tested at all levels of response. In contrast, minimal receptor reserve was detected for the ability of salbutamol to suppress respiratory burst activity in eosinophils.

CONCLUSIONS AND IMPLICATIONS

These data may help explain the relative inability of sympathomimetic bronchodilators to render HASM tolerant to beta(2)-adrenoceptor-mediated relaxation.

Differences in the pharmacodynamics of budesonide/formoterol and salmeterol/fluticasone reflect differences in their therapeutic usefulness in asthma

Although the available inhaled corticosteroid (ICS)/long-acting beta( 2)-agonist (LABA) combinations principally work in a similar fashion, they differ in several important ways, leading to different efficacy. The ICS/LABA combination product budesonide/formoterol can be used as both maintenance and reliever therapy, providing a fixed maintenance dose, which does not change, and replacing short-acting beta(2)-agonists as relievers thereby allowing intervention to address the underlying inflammation at the earliest sign of symptomatic worsening. This approach is not suitable for other combination products such as salmeterol/fluticasone. Here we review the pharmacological differences of budesonide/ formoterol and salmeterol/fluticasone that permit the use of budesonide/formoterol as both maintenance and reliever therapy.

Efficacy and safety of formoterol fumarate delivered by nebulization to COPD patients

Nebulized solutions of long-acting bronchodilators provide an alternative to DPI and MDI delivery, particularly for COPD patients unable to use hand-held devices easily or correctly. The long-acting beta2-agonist, formoterol fumarate, is differentiated by its onset of significant bronchodilation within 5 min of administration. In a randomized, double-blind, double-dummy trial, COPD subjects (n=351, mean forced expiratory volume FEV1=1.3 L, 44% predicted) received nebulized formoterol fumarate (Perforomist inhalation solution; FFIS 20 microg) or DPI (Foradil Aerolizer; FA 12 microg), or placebo twice daily for 12 weeks. Efficacy was assessed with 12-h pulmonary function tests, and quality of life was assessed before and after treatment with the St. George's Respiratory Questionnaire (SGRQ). At the 12-week endpoint, FFIS significantly increased FEV1 AUC0-12h relative to placebo (p<0.0001). No evidence of tachyphylaxis was observed as indicated by maintained FEV1 AUC and reduced rescue albuterol use throughout treatment. FFIS also significantly increased peak FEV1, trough FEV1, and standardized FVC AUC0-12h compared with placebo. SGRQ assessment at Week 12 demonstrated significant and clinically meaningful improvements in total score (FFIS vs placebo, -4.9, p=0.0067), symptom, and impact scores. No significant differences in efficacy were observed between the two active treatments. Drug related AEs in the FFIS arm with a frequency > or = 1% and exceeding placebo were dry mouth, nausea, and insomnia. Nebulized FFIS provided significant improvement in respiratory status and quality of life in subjects with COPD relative to placebo and was well tolerated. The efficacy and safety profile of FFIS was comparable to FA DPI.

Relaxations to beta-adrenoceptor subtype selective agonists in wild-type and NOS-3-KO mouse mesenteric arteries

We have investigated the role of nitric oxide (NO) in relaxations to beta-adrenoceptor agonists in mesenteric artery from wild-type (WT) and NO synthase-3 knockout (NOS-3-KO) mice. Isoprenaline, formoterol and BRL 37344 ((R(),R())-(+/-)-4-[2-[(2-(3-chlorophenyl)-2-hydroxyethyl)amino]propyl]phenoxyacetic acid) were chosen as non-selective and beta(2)- and beta(3)-adrenoceptor agonists, respectively. Atenolol, ICI 118,551 ((+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride) and SR59230A (1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride) were chosen as selective beta(1)-, beta(2)- and beta(3)-adrenoceptor antagonists, respectively. Experiments employing isoprenaline were carried out in the presence of prazosin (0.1 microM). Isoprenaline produced relaxations with a potency of 5.68+/-0.36 (-log M, n=6) in WT mice. Relaxations to isoprenaline were blocked by atenolol (10 microM) and were absent in vessels from NOS-3-KO animals. Formoterol produced relaxations with two components. ICI 118,551 (1 microM) abolished relaxations to low concentrations of formoterol (0.1-10 microM), but failed to affect relaxations to formoterol (100 microM). In NOS-3-KO mice only the highest concentration of formoterol (100 microM) produced relaxations: the relaxation was resistant to all of the beta-adrenoceptor antagonists employed. BRL 37344 (5.75+/-0.28, n=9) was approximately equipotent with isoprenaline but produced a smaller degree of relaxation, in WT mice. SR59230A (1 microM) abolished relaxations to BRL 37344 in WT mice. In NOS-3-KO mice, BRL 37344 produced concentration-dependent relaxations which were abolished by SR59230A. It is concluded that the predominant beta-adrenoceptor mediating relaxations in mouse mesenteric artery is beta(1), and relaxations involve NOS-3. In addition, beta(3)-adrenoceptors mediate smaller relaxations at least partly independent of NOS-3, and beta(2)-adrenoceptors may mediate smaller relaxations dependent on NOS-3.

Role of arformoterol in the management of COPD

Formoterol is a beta2-agonist that has both short and long acting bronchodilator effects. Beta2-agonists used as bronchodilators have been synthesized as racemates that comprise (R,R) and (S,S)-enantiomers. Compounds that are beta2-selective derive their bronchodilator effect from an interaction between the (R,R)-enantiomer and the beta2-adrenoceptor. Arformoterol is the (R,R)-enantiomer and is distinguished from the more commonly used racemic (RR/S,S)-diasteriomer of formoterol. Overall literature on the use of arformoterol in COPD is very preliminary. There is some in vitro data that demonstrate significant bronchodilation and inhibition of inflammation with arformoterol, and these effects may be more pronounced than those caused by racemic formoterol. There are limited clinical trial data that demonstrate that arformoterol produces significant improvement in lung function in COPD; however, many of the subjects involved had marked baseline airway reversibility. Arformoterol has been very well tolerated in clinical trials and could potentially be used only once every 24 hours (due to its prolonged effect). It can only be given in nebulized form. Arformoterol can potentially be given with other inhaled medications.

Formoterol dry-powder inhaler for the treatment of asthma and chronic obstructive pulmonary disease

Formoterol, a long-acting beta2-adrenergic agonist, is used as an inhaled bronchodilator therapy for patients with asthma or for the prevention of exercise-induced bronchospasm in children and in chronic obstructive pulmonary disease. Formoterol has unique characteristics of rapid onset and sustained duration of action compared with other bronchodilators. In addition to its effectiveness as regular maintenance therapy in asthma and chronic obstructive pulmonary disease, formoterol is also reported to be effective as an as-needed reliever therapy in patients with asthma. Formoterol is available in several different types of dry-powder inhalers and pressurized metered-dose inhalers.

Long duration of airway but not systemic effects of inhaled formoterol in asthmatic patients

RATIONALE

Formoterol is approved as asthma rescue medication in many countries. The exact duration of the airway vs. systemic effects of formoterol compared with another rescue medication, salbutamol, has not been evaluated.

OBJECTIVE

To assess the duration of airway bronchodilatory effects vs. systemic effects of inhaled formoterol and salbutamol in asthmatic patients.

METHODS

Twenty-six patients with stable and reversible asthma were given single doses of formoterol dry-powder inhaler (OxisTurbuhaler) 2x9 microg (lower dose; LD) and 6x9 microg (higher dose; HD), salbutamol (VentolinDiskhaler) 3x400 microg (LD) and 9x400 microg (HD), and placebo in a randomized, double-blind, crossover trial. Airway and systemic effects were assessed by forced expiratory volume in 1s (FEV1), serum potassium, blood pressure, corrected QT-interval (QTc), and palpitation and tremor scores. Time with clinically relevant bronchodilation (FEV1 increase 12%) without clinically relevant markers of systemic effects (serum potassium suppression 0.2 mmol/L, QTc-prolongation 20 ms, or heart rate increase 8 beats per minute) was evaluated.

RESULTS

Bronchodilation was maintained for 24h with both formoterol doses and for 7-11h with salbutamol. Maximum bronchodilation and systemic effects were similar after formoterol and salbutamol, except for statistically significantly larger maximum heart rate and palpitation and tremor scores after salbutamol. Systemic responses were similarly brief for formoterol and salbutamol (7 h).

CONCLUSIONS

The airway effects of inhaled formoterol are of long duration, whereas the systemic effects are of a similarly short duration as salbutamol. Thus, the time with clinically relevant bronchodilation without systemic effects is substantially longer after formoterol than after salbutamol.

Efficacy and safety of formoterol for the treatment of chronic obstructive pulmonary disease

Formoterol is a selective long-acting beta2-adrenergic receptor agonist (LABA) that provides significant and sustained bronchodilatory effect for up to 12h following a single dose. The onset of effect is significantly faster with formoterol compared with an alternative LABA, salmeterol, although both have a similar duration of action. The overall efficacy of formoterol in improving lung function and controlling symptoms of chronic obstructive pulmonary disease (COPD) is comparable to that of salmeterol and potentially superior to that of ipratropium or theophylline. Formoterol provides additional benefit when administered in combination with other bronchodilators or inhaled corticosteroids. In clinical studies, formoterol was well tolerated and had an adverse-event profile similar to that of other beta2-adrenergic receptor agonists. Formoterol is a rapidly acting, well-tolerated, effective beta2-adrenergic receptor agonist that can be regularly used as a long-acting bronchodilator for patients with moderate to severe COPD, as per recommendations of the current treatment guidelines.

The discovery of indole-derived long acting beta2-adrenoceptor agonists for the treatment of asthma and COPD

The design and profile of a series of indole containing long acting beta(2)-adrenoceptor agonists is described. Evaluation of these analogues using an in vitro guinea pig trachea tissue model demonstrates that analogues within this series have salmeterol-like duration of action with potential for long duration of action in humans.

Effects of formoterol on exercise tolerance in severely disabled patients with COPD

OBJECTIVE

We wished to evaluate the effects of inhaled formoterol, a long-acting beta(2)-adrenergic agonist, on exercise tolerance and dynamic hyperinflation (DH) in severely disabled chronic obstructive pulmonary disease (COPD) patients.

DESIGN

In a two-period, crossover study, 21 patients with advanced COPD (FEV(1)=38.8+/-11.7% predicted, 16 patients GOLD stages III-IV) were randomly allocated to receive inhaled formoterol fumarate 12 microg twice daily for 14 days followed by placebo for 14 days, or vice versa. Patients performed constant work-rate cardiopulmonary exercise tests to the limit of tolerance (Tlim) on a cycle ergometer: inspiratory capacity (IC) was obtained at rest and each minute during exercise. Baseline and transitional dyspnoea indices (BDI and TDI) were also recorded.

RESULTS

Eighteen patients completed both treatment periods. Formoterol treatment was associated with an estimated increase of 130 s in Tlim compared with placebo (P=0.052): this corresponded to a 37.8% improvement over placebo (P=0.012). Enhanced exercise tolerance after bronchodilator was associated with diminished DH marked by higher inspiratory reserve and tidal volumes at isotime and exercise cessation (P<0.05). There was no significant difference between formoterol and placebo on exercise dyspnoea ratings; however, all domains of the TDI improved (P<or=0.02) following formoterol, compared with placebo.

CONCLUSION

Inhaled formoterol 12 microg twice daily is effective in ameliorating DH, daily dyspnoea and exercise intolerance even in patients with advanced COPD.

The discovery of long acting β2-adrenoreceptor agonists

The design and profile of a series of saligenin containing long acting beta(2)-adrenoreceptor agonists is described. Evaluation of these analogues using a guinea-pig tissue model demonstrates that analogues within this series have significantly longer durations of action than salmeterol and have the potential for a once daily profile in human.

Acute asthma intervention: insights from the STAY study

In some patients, asthma control is improved by combining inhaled corticosteroids with long-acting beta(2)-agonists. However, fluctuating asthma control and exacerbations can still occur. The STAY study evaluated whether, in patients with moderate to severe asthma, replacing a short-acting beta(2)-agonist reliever with the combination of budesonide/formoterol as reliever would both provide rapid symptom relief and reduce asthma exacerbations. The study evaluated 2760 patients with asthma (4-80 years) randomized to budesonide 400 microg twice daily (bid) and terbutaline as reliever, budesonide/formoterol 100/6 microg bid and terbutaline as reliever, or budesonide/formoterol 100/6 microg bid both as maintenance and reliever. Children (age 4-11 years) used a once-daily maintenance dose. Budesonide/formoterol as maintenance and reliever significantly reduced severe exacerbation risk by 45% to 47% compared with the other 2 treatments and improved symptoms, awakenings, and lung function. The benefit was seen in patients of all ages. Subsequent studies have revealed that this beneficial effect of budesonide/formoterol as maintenance and reliever requires both components of the combination.

Current issues with beta2-adrenoceptor agonists: pharmacology and molecular and cellular mechanisms

Beta2-adrenoceptors are widely, almost ubiquitously, expressed. Activation of these receptors on bronchial smooth muscle by short- and long-acting beta2-adrenoceptor agonists causes bronchodilation. Here, the beta2-adrenoceptor is linked by the G protein, Gs, to adenylyl cyclase, which increases cyclic adenosine monophosphate (cAMP), thus activating protein kinase A, which affects calcium levels and reduces the efficiency of myosin light-chain kinase, causing relaxation. Activation also entrains numerous acute and longer term downregulation responses affecting the number, location, and net efficiency of signaling of the receptor. Synthetic beta2-agonists are all "partial agonists," incompletely able to optimally stimulate cAMP signal transduction. However, compared with some cells (such as mast cells) involved in exercise- induced asthma induction, airway smooth muscle is privileged in that transduction efficiency is intrinsically high and the tissue is very resistant to complete downregulation. Glucocorticosteroids have broadly beneficial interactions with beta2-adrenoceptors. Researchers have recently discovered that the beta2-adrenoceptor may function as a homodimer and that it can form heterodimers with both the beta1- and beta3-adrenoceptors, and possibly other receptors. This further complicates interpretation of the effect of beta2-adrenoceptor polymorphisms, but it is unknown whether this occurs in humans in vivo. Researchers have known for some time that strong contraction involving receptors coupled to the Gq G protein (e.g., cholinergic and leukotriene receptors via negative biochemical crosstalk), virus infection (via uncoupling), and inflammation (via kinases) can impair relaxation. Most recently, researchers have discovered that the beta2-adrenoceptor can also send potentially adverse signals after "atypical coupling" to Gq rather than Gs. The clinical implications of these uncouplings, crosstalk, and atypical coupling possibilities are not well-understood.

Low dose formoterol administration improves muscle function in dystrophic mdx mice without increasing fatigue

The beta(2)-adrenoceptor agonist (beta(2)-agonist), formoterol, has been shown to cause muscle hypertrophy in rats even when administered at the micromolar dose of 25 micro g/kg/day. We investigated whether a similar low dose of formoterol could improve muscle function in the dystrophic mdx mouse. Ten-week-old male mdx and wild-type (C57BL/10) mice were administered formoterol (25 micro g/kg/day, i.p.) for 4 weeks. Formoterol treatment increased extensor digitorum longus (EDL) and soleus muscle mass, increased median muscle fibre size in diaphragm, EDL, and soleus muscles, and increased maximum force producing capacity in skeletal muscles of both wild-type and mdx mice. In contrast to other studies where beta(2)-agonists have been administered to mice and rats, generally at higher doses, low dose formoterol treatment did not increase the fatiguability of EDL, soleus or diaphragm muscles. Although others have found formoterol can decrease ubiquitin mRNA and proteasome activity when administered to tumour bearing rats at high doses (2mg/kg/day), in the present study low dose formoterol treatment did not alter ubiquitin or the E1 and E3 ubiquitin ligases in diaphragm muscles of wild-type or mdx mice, but it did reduce the level of ubiquitinated proteins in diaphragm of wild-type mice. The findings indicate that formoterol has considerably more powerful anabolic effects on skeletal muscle than older generation beta(2)-agonists (like clenbuterol and albuterol), and has considerable therapeutic potential for muscular dystrophies and other neuromuscular disorders where muscle wasting is indicated.

Bioluminescence resonance energy transfer as a screening assay: Focus on partial and inverse agonism

The reported data for compound screening with the bioluminescence resonance energy transfer (BRET2) assay is very limited, and several questions remain unaddressed, such as the behavior of agonists. Eleven beta2 adrenergic receptor (beta2-AR) agonists were tested for full or partial agonism in an improved version of the receptor/beta-arrestin2 BRET2 assay and in 2 cyclic adenosine monophosphate (cAMP) assays (column cAMP assay and ALPHAscreen cAMP assay). Tested in the highly sensitive ALPHAscreen cAMP assay, all selected agonists behaved as full agonists, using isoproterenol as a reference compound. In the less sensitive column cAMP assay, ephedrine and dopamine had a clear partial response. For the BRET2 assay, a highly graded picture was obtained. Moreover, beta2-AR antagonists were tested for inverse agonism. Pronounced inverse agonism was detected in the ALPHAscreen cAMP assay. Only marginal inverse agonistic responses were seen for alprenolol and pindolol in the column cAMP assay, and no inverse agonism was seen in the BRET2 assay. For the beta2-AR, the BRET2 assay may be superior for secondary screening of agonists where a separation of full and partial agonists is needed and the ALPHAscreen cAMP assay may be preferred for primary screening of agonists where all receptor activating compounds are desired.

Systemic administration of beta2-adrenoceptor agonists, formoterol and salmeterol, elicit skeletal muscle hypertrophy in rats at micromolar doses

beta(2)-Adrenoceptor agonists provide a potential therapy for muscle wasting and weakness, but their use may be limited by adverse effects on the heart, mediated in part, by beta(1)-adrenoceptor activation. Two beta(2)-agonists, formoterol and salmeterol, are approved for treating asthma and have an extended duration of action and increased safety, associated with greater beta(2)-adrenoceptor selectivity. The pharmacological profiles of formoterol and salmeterol and their effects on skeletal and cardiac muscle mass were investigated in 12-week-old, male F344 rats. Formoterol and salmeterol were each administered via daily i.p. injection at one of seven doses (ranging from 1 to 2,000 microg kg(-1) day(-1)), for 4 weeks. Rats were anaesthetised and the EDL and soleus muscles and the heart were excised and weighed. Dose-response curves were constructed based on skeletal and cardiac muscle hypertrophy. Formoterol was more potent than salmeterol, with a significantly lower ED(50) in EDL muscles (1 and 130 microg kg(-1) day(-1), P <0.05), whereas salmeterol had greater intrinsic activity than formoterol in both EDL and soleus muscles (12% greater hypertrophy than formoterol). The drugs had similar potency and intrinsic activity in the heart, with a smaller leftward shift for formoterol than seen in skeletal muscle. A dose of 25 microg kg(-1) day(-1) of formoterol elicited greater EDL and soleus hypertrophy than salmeterol, but resulted in similar beta-adrenoceptor downregulation. These results show that doses as low as 1 microg kg(-1) day(-1) of formoterol can elicit significant muscle hypertrophy with minimal cardiac hypertrophy and provide important information regarding the potential therapeutic use of formoterol and salmeterol for muscle wasting.

Pharmacological management of mild or moderate persistent asthma

Patients with mild persistent asthma rarely see their doctor with symptoms of the disease. Partly as a result of this situation, mild asthma is generally undertreated. Findings of several large randomised clinical trials have shown benefits for this population of regular treatment with low doses of inhaled corticosteroids. Additional drugs are rarely needed, and although leukotriene modifiers are effective, they are less so than inhaled corticosteroids. People with moderate persistent asthma are not well controlled on low doses of inhaled corticosteroids. A combination of this drug and long-acting inhaled beta2 agonists provides improved control compared with doubling of the maintenance dose of inhaled corticosteroids. The combination of budesonide and formoterol has been assessed as both maintenance and reliever treatment. This approach further reduces the risk for severe exacerbations. With these strategies, most individuals can achieve good control of their asthma. For patients who do not achieve asthma control despite taking drugs, measurement of the inflammatory response in the airway in induced sputum could provide further information to guide treatment.

Comparative Effects of Salmeterol, Albuterol, and Ipratropium on Normal and Impaired Mucociliary Function in Sheep

STUDY OBJECTIVE

We measured tracheal mucus velocity (TMV), a marker of mucociliary clearance (MCC), in sheep before and for 12 h after treatment with salmeterol, albuterol, ipratropium, or vehicle to determine the effects on normal MCC. We also determined if these agents could reverse the depression in TMV caused by inhaled human neutrophil elastase (HNE), a model of abnormal MCC.

METHODS

Study 1: TMV was measured initially and then for 6 h after metered-dose inhaler treatment with salmeterol (42 microg), albuterol (180 microg), ipratropium bromide (36 microg), or vehicle. After 6 h, the sheep in the albuterol and ipratropium treatment arms were administered a second dose of drug, whereas the salmeterol and vehicle treatment arms received vehicle. TMV was measured for another 6 h. Study 2: Six sheep inhaled HNE aerosol, which significantly reduced TMV by 2 h. At this point, the sheep were treated with either salmeterol, albuterol, ipratropium, or vehicle, and the effects on TMV were measured for another 6 h. This experiment was repeated in four sheep using only salmeterol and albuterol, but the posttreatment measurements were extended to 12 h.

RESULTS

Study 1: Only salmeterol and albuterol increased TMV (p < 0.05) during the initial 6-h period. From 6 to 12 h only, the salmeterol-treated sheep had TMV that remained at or above the initial TMV for the entire time, although both albuterol and ipratropium showed enhancement of TMV compared to vehicle. Study 2: Salmeterol and albuterol reversed the HNE-induced depression in TMV to a similar degree over the 6-h time course. However, the protection afforded by salmeterol was more prolonged than that seen with albuterol if the posttreatment interval was extended to 12 h. Ipratropium and vehicle had no effect.

CONCLUSION

We conclude that salmeterol and albuterol can stimulate normal MCC and reverse HNE-induced mucociliary dysfunction and that salmeterol has a longer duration of action in these models of normal and abnormal MCC.

Past, present and future--beta2-adrenoceptor agonists in asthma management

The beta-adrenoceptor agonists (beta-agonists) have been used to relieve bronchoconstriction for at least 5000 years. beta-agonists are based on adrenaline and early forms, such as isoprenaline, Lacked bronchial selectivity and had unpleasant side effects. Modern beta-agonists are more selective for the beta2-adrenoceptors (beta2-receptors) located in bronchial smooth muscle and have less cardiotoxicity. Traditional beta2-adrenoceptor agonists (beta2-agonists), such as salbutamol, terbutaline and fenoterol, were characterised by a rapid onset but relatively short duration of action. While valuable as reliever medication, their short duration gave inadequate night-time relief and limited protection from exercise-induced bronchoconstriction. beta2-agonists with longer durations of action, formoterol and salmeterol, were subsequently discovered or developed. When combined with inhaled corticosteroids they improved lung function, and reduced symptoms and exacerbations more than an increased dose of corticosteroids. However, tolerance to the bronchprotective effects of long-acting beta2-agonists and cross-tolerance to the bronchodilator effects of short-acting beta2-agonists is apparent despite use of inhaled corticosteroids. The role of beta2-receptor polymorphisms in the development of tolerance has yet to be fully determined. Formoterol is unique in having both a long-lasting bronchodilator effect (> 12 h) and a fast onset of action (1-3min from inhalation), making it effective both as maintenance and reliever medication. The recent change in classification from short- and long-acting beta2-agonists to rapid-acting and/or long-acting agents reflects the ongoing evolution of beta2-agonist therapy.

Combination therapy of long-acting beta agonists and inhaled corticosteroids in the management of chronic asthma

Both the Global Initiative for Asthma (GINA) and the National Heart, Lung and Blood Institute (NHLBI) Expert Panel guidelines recommend combination treatment with inhaled corticosteroids (ICSs) and inhaled long-acting beta-agonists (LABAs) for patients whose asthma is not adequately controlled by low doses of ICSs alone. Not only is this combination more effective than the combination of either theophylline or leukotriene modifiers with ICSs, there is suggestive evidence that the results with LABAs and ICSs may be more than additive. Through the effect of each one on the receptor for the other, they may have a synergistic action. This marked effectiveness of the combination, particularly when combined in the same device, has led to new objectives and novel applications. Therefore, for the first time, it appears that the Goals of Asthma Therapy, as outlined in the guidelines, are achievable for many patients with asthma. Also, at least for combination therapies including formoterol, adjustable dosing and perhaps even use as a rescue as well as a maintenance therapy may be possible.

A respiratory therapist-directed protocol for managing inpatients with asthma and COPD incorporating a long-acting bronchodilator

This prospective study was designed to determine whether incorporating formoterol into a standardized respiratory therapist-directed protocol for administering bronchodilators to hospitalized patients with obstructive airway disease would reduce health care resource use and provide a safety advantage. All patients admitted to Washington Hospital Center with asthma and chronic obstructive pulmonary disease (CODP) are administered bronchodilators under a standardized respiratory therapist-directed protocol. Formoterol was the primary bronchodilator for the intervention period from January through March 2002, with levalbuterol, albuterol, and ipratropium available as needed. Results for the intervention period were compared against two historical control periods. From January through March 2000, the bronchodilators in the protocol were albuterol and ipratropium, and from January through March 2001 levalbuterol, albuterol, and ipratropium were available. Health care resource use was determined by the number of bronchodilator treatments administered per admission. Costs (adjusted to 2002 dollars) for supplies, therapist time, and drugs were calculated for the three time periods. Adverse events related to bronchodilator administration were recorded in a standardized manner for all three time periods. Bronchodilator treatments per admission, respiratory therapist visits per admission, and time spent per admission, and cost per bronchodilator treatment significantly decreased in 2002. Significantly fewer adverse events related to bronchodilator treatments were reported in 2002 than 2000. The addition of formoterol to a respiratory therapist-directed protocol for administering bronchodilators reduced health care resource use and adverse events for patients with asthma and COPD.

Long-acting beta(2)-agonists in the management of asthma exacerbations

PURPOSE OF REVIEW

Asthma exacerbations are a major cause of morbidity in the United States. Although long-acting beta2-agonists have a defined role in maintenance therapy, their potential use in exacerbations remains largely undetermined. This paper reviews recent literature on long-acting beta2-agonists in the context of the management of acute asthma.

RECENT FINDINGS

Although clinical experience with long-acting beta2-agonists now approaches 20 years, their applicability in asthma exacerbations has only recently been explored. Formoterol, with a rapid onset of action similar to albuterol, has already been approved in Europe as a reliever medication and there are emerging data to support its use in the outpatient management of mild exacerbations of asthma. Salmeterol added to conventional therapy has been found to be safe and potentially beneficial in patients hospitalized for an exacerbation.

SUMMARY

Long-acting beta2-agonists have proved to be useful in the chronic management of asthma and the prevention of exacerbations. Recent data suggest a role for patient-guided management using adjustable dosing of long-acting beta2-agonists with inhaled corticosteroids during periods of worsening asthma. Further research to evaluate the potential role of long-acting beta2-agonists in the management of acute asthma is needed.

Combination therapy in asthma--fixed or variable dosing in different patients?

The introduction of combination products, for the coadministration of an inhaled corticosteroid (ICS) with a long-acting beta2-agonist in a single inhaler, has greatly simplified asthma therapy. The two combination inhalers currently available, Symbicort (budesonide/formoterol in a single inhaler) and Seretide (salmeterol/fluticasone), comply with Step 3 of international guidelines that recommend the addition of a long-acting beta2-agonist to ICS in patients who are inadequately controlled on ICS alone. Importantly, combination inhalers ensure that patients cannot neglect their ICS maintenance therapy in favour of the long-acting beta2-agonist--which may improve adherence and overall asthma control. In vitro experiments suggest that ICS and long-acting beta2-agonists may interact beneficially when they are administered via one inhaler. The efficacy and tolerability of budesonide/formoterol and salmeterol/fluticasone have been demonstrated. There are currently two approaches for treating asthma using combination therapy--fixed and adjustable dosing. Fixed dosing with budesonide/formoterol or salmeterol/fluticasone provides effective asthma control in line with guideline goals. However, given the inherent variability of asthma, there is increasing evidence that adjusting the dose of ICS according to fluctuations in symptoms is beneficial. Findings from a series of studies comparing fixed and adjustable symptom-guided dosing regimens demonstrate that adjustable dosing may improve asthma control at an overall lower steroid dose. Ultimately, if adjustable dosing proves to be an effective treatment option, it may be possible to use budesonide/formoterol for both maintenance therapy and symptom relief, thereby overcoming the need for a separate reliever inhaler. This is because formoterol has a more rapid onset and greater dose-related effects than salmeterol in salmeterol/fluticasone. Given that all patients are different, with different disease severities and treatment preferences, both fixed and adjustable dosing strategies are likely to be important in the long-term management of asthma. It is possible that different treatment options will be used for different patients, depending on their disease severity, personality and ability to adhere to therapy.

Synthetic responses in airway smooth muscle

Human airway smooth muscle (ASM) has several properties and functions that contribute to asthma pathogenesis, and increasing attention is being paid to its synthetic capabilities. ASM can promote the formation of the interstitial extracellular matrix, and in this respect, ASM from asthmatic subjects compared with normal subjects responds differently, both qualitatively and quantitatively. Thus, ASM cells are important regulating cells that potentially contribute to the known alterations within the extracellular matrix in asthma. In addition, through integrin-directed signaling, extracellular matrix components can alter the proliferative, survival, and cytoskeletal synthetic function of ASM cells. ASM also functions as a rich source of biologically active chemokines and cytokines that are capable of perpetuating airway inflammation in asthma and chronic obstructive pulmonary disease by promoting recruitment, activation, and trafficking of inflammatory cells in the airway milieu. Emerging evidence shows that airway remodeling may also be a result of the autocrine action of secreted inflammatory mediators, including T(H)2 cytokines, growth factors, and COX-2-dependent prostanoids. Finally, ASM cells contain both beta(2)-adrenergic receptors and glucocorticoid receptors and may represent a key target for beta(2)-adrenergic receptor agonist/corticosteroid interactions. Combinations of long-acting beta(2)-agonists and corticosteroids appear to have additive and/or synergistic effects in inhibiting inflammatory mediator release and the migration and proliferation of ASM cells.

Formoterol vs. albuterol administered via Turbuhaler system in the emergency treatment of acute asthma in children

BACKGROUND

Formoterol is a new beta 2 agonist with a duration of 8-12 hours. Albuterol is a beta 2-agonist with rapid onset of action and a duration of approximately 6 hours.

OBJECTIVE

The aim of the present study was to compare the onset of action between formoterol and albuterol, both administered through a Turbohaler.

MATERIAL AND METHOD

In a double-blind, parallel-group study design 36 patients were randomly allocated to receive either formoterol 12 microg or salbutamol 200 microg. The two drugs were administered through a Turbohaler system. Response (% forced expiratory volume in one second [FEV1]) was evaluated 3, 30 and 60 minutes after drug administration.

RESULTS

The %FEV1 values at 3, 30 and 60 minutes were similar in both groups: 82 15.0 for formoterol and 82 14.4 for albuterol at 60 minutes (p > 0.05).

CONCLUSIONS

Formoterol 12 microg has a similar onset of action and potency to albuterol 200 microg when administered via a Turbuhaler in children with a mild acute asthma crisis.

FEV1 reversibility does not adequately predict effect of formoterol via Aerolizer in chronic obstructive pulmonary disease

Evaluation of patients with chronic obstructive pulmonary disease (COPD) often includes the use of post-bronchodilator reversibility testing to guide treatment decisions. Recommendations for reversibility testing differ and there is no universally accepted method or outcome criterion. A survey of recent clinical trials with beta2-agonists in COPD illustrates the diversity of methods used to assess reversibility and highlights the difficulty of comparing data from such trials. Two recent studies demonstrated the benefits of treatment with the long-acting beta2-agonist bronchodilator formoterol (Foradil Aerolizer) in patients with COPD. When patients were classified according to their degree of reversibility as partially or poorly reversible, improvements were observed in both groups irrespective of the definition applied. These results suggest that bronchodilator reversibility testing should not be used as a rigid basis for treatment decisions with beta2-agonists in COPD patients. There is a pressing need for the role of reversibility testing to be clearly defined.

Dose-related efficacy and safety of formoterol (Oxis) Turbuhaler compared with salmeterol Diskhaler in children with asthma

To compare the dose-related bronchodilator efficacy and tolerability of formoterol (Oxis) Turbuhaler with salmeterol Diskhaler and placebo in children with asthma. A single-dose, randomized, double-blind, incomplete crossover study of 68 children (7-17 years), with moderate-to-severe asthma, 82% receiving inhaled corticosteroids. Patients received four of six treatments [4.5, 9, 18, or 36 microg formoterol (6, 12, 24 or 48 microg metered doses), 50 microg salmeterol (metered dose) or placebo] at 12-h visits, separated by > or =3 days. Forced expiratory volume in 1 s (FEV1), pulse, blood pressure, electrocardiogram, adverse events and urine formoterol were assessed. The therapeutic ratio of formoterol vs. salmeterol was estimated from the efficacy and systemic effects results. All active treatments significantly improved FEV1 compared with placebo. Formoterol 9-36 microg provided dose-related increases over salmeterol in lung function: average 12-h FEV1 (increases of 4.9-8.7%, p < 0.001) and FEV1 at 12 h post-dose (7.0-12.2%, p < 0.001). The onset of effect of formoterol was also significantly faster than salmeterol for doses > or =9 microg. Salmeterol 50 microg was estimated to be equieffective to 3.3 microg formoterol for 12-h average FEV1 and the estimated equieffective dose for a variety of systemic effects was 7.8-13.5 microg formoterol. All treatments were well tolerated. Formoterol (Oxis) Turbuhaler 4.5-36 microg provided dose-related improvements in bronchodilator efficacy in children with asthma. Formoterol > or =9 microg provided superior bronchodilator efficacy over 12 h compared with salmeterol Diskhaler 50 microg with no increase in systemic effects.

Formoterol delivered via the dry powder Aerolizer inhaler versus albuterol MDI and placebo in mild-to-moderate asthma: a randomized, double-blind, double-dummy trial

The objectives of this study were to compare the efficacy and tolerability of twice-daily formoterol dry powder 12 microg and 24 microg (Foradil) delivered via Aerolizer inhaler with four times daily albuterol (salbutamol) 180 microg delivered via metered dose inhaler (MDI) and placebo. A total of 554 adolescents and adults (ages 12-75 years) with mild-to-moderate asthma were randomized to this 12-week, multicenter, double-blind, double-dummy, placebo-controlled, parallel-group study. Twelve-hour spirometry measurements were taken at weeks 0, 4, 8, and 12. A total of 484 patients completed the study (122, 116, 127, and 119 given formoterol 12 microg, formoterol 24 microg, albuterol, and placebo, respectively). For the primary efficacy variable, the forced expiratory volume in 1 second (FEV1), both formoterol 12 microg and 24 microg were statistically superior to placebo at all time points on all test days (p < or = 0.017) and to albuterol at most time points on all test days (p < or = 0.001). The onset of improvement in FEV1 was rapid, with 15% increase within 5 min in 57%, 71%, and 65% of formoterol 12 microg, formoterol 24 microg, and albuterol patients, respectively. Formoterol was also superior to placebo and albuterol in terms of secondary efficacy variables: FEV1 area under the curve, percentage of predicted FEV1, forced vital capacity and forced expiratory flow, asthma symptom scores, and peak expiratory flows. In conclusion, both formoterol doses were superior to placebo in all lung function measurements. Overall, compared with albuterol, both formoterol doses produced superior bronchodilation. Formoterol and albuterol were safe and well-tolerated.

Long-acting inhaled beta 2-agonists for stable COPD

OBJECTIVE

To describe the pathogenesis of chronic obstructive pulmonary disease (COPD) and mechanisms of benefit, formulations available, drug costs, pharmacokinetic profiles, and pertinent clinical studies for long-acting beta(2)-agonists.

DATA SOURCES

A MEDLINE search was conducted from July 1966 through October 2002.

STUDY SELECTION AND DATA EXTRACTION

Pertinent articles related to COPD and long-acting beta(2)-agonists.

DATA SYNTHESIS

The incidence and subsequent morbidity and mortality of COPD have increased during the last 4 decades, prompting worldwide initiatives to formulate guidelines to decrease the burden of this disease. COPD is a progressive, irreversible disease state characterized by chronic cough, dyspnea, sputum production, and wheezing, in which no medication has been shown to decrease mortality, excluding oxygen supplementation. Bronchodilators have been a mainstay of COPD treatment through their ability to work by both smooth- and non-smooth-muscle mechanisms. Long-acting beta(2)-agonists (i.e., formoterol, salmeterol) dosed twice daily provide more convenient dosing than 4-times-daily regimens of traditional short-acting bronchodilators. Both formoterol and salmeterol have acceptable adverse event profiles when used at recommended doses. There have been no direct clinical outcome studies comparing formoterol and salmeterol, but both have shown some benefits over ipratropium and theophylline in improving the symptoms, spirometric indices, exacerbations, and quality of life of patients with COPD.

CONCLUSIONS

Based on current evidence, long-acting beta(2)-agonists are acceptable first-line agents for patients with COPD.

Formoterol 12 microg BID administered via single-dose dry powder inhaler in adults with asthma suboptimally controlled with salmeterol or on-demand salbutamol: a multicenter, randomized, open-label, parallel-group study

BACKGROUND

Although salmeterol and formoterol are both long-acting beta(2) adrenergic receptor agonist bronchodilators, there are distinct differences between them that could translate into differences in clinical response in some patients.

OBJECTIVE

The goal of this study was to examine the efficacy of formoterol in patients with moderate to severe persistent asthma that was suboptimally controlled with an inhaled corticosteroid (ICS) combined with on-demand salbutamol (albuterol in the United States) with or without salmeterol.

METHODS

This multicenter, 4-week, randomized, open-label, parallel-group study included adult patients (age >/=18 years) with suboptimally controlled asthma (mean salbutamol use, >/=2 puffs/d via pressurized metered-dose inhaler [100 microg/puff]). Patients were randomized in a 2:1 ratio to receive formoterol 12 microg BID via single-dose dry powder inhaler plus on-demand salbutamol or to continue their existing treatment with either on-demand salbutamol alone or salmeterol 50 microg BID via multidose dry powder inhaler plus on-demand salbutamol. ICS regimens were unchanged during the trial. The primary efficacy variable was evening predose peak expiratory flow (PEF). Secondary variables included further measures of asthma symptom control.

RESULTS

A total of 6239 adult patients entered the study; data from 6155 patients were available for analysis. Patients who were switched from salmeterol to formoterol reported a significant increase in mean (SD) evening predose PEF compared with patients who continued their existing treatment (402.9 [112.1] vs 385.5 [107.5] Umin, respectively; P < 0.001). Similarly, patients who were switched from on-demand salbutamol alone to formoterol plus on-demand salbutamol reported a significant increase in mean evening predose PEF compared with those who continued treatment with on-demand salbutamol alone (409.3 [105.6] vs 385.0 [105.3] L/min, respectively; P < 0.001). The results for the secondary efficacy measures mirrored the significant improvements seen in patients switched to formoterol compared with those who continued to receive on-demand salbutamol alone or salmeterol plus on-demand salbutamol.

CONCLUSION

In this study, formoterol significantly improved lung function and control of asthma symptoms and decreased use of rescue medication in patients whose asthma had been suboptimally controlled with an ICS in combination with on-demand salbutamol with or without salmeterol.

The long and short of beta2-agonists

For patients whose asthma is not adequately controlled with inhaled corticosteroid (ICS) therapy alone, increasing the dose of ICS or the addition of a long-acting beta(2)-agonist is recommended. Greater improvements in lung function are achieved with the addition of a long-acting beta(2)-agonist to ICS therapy, rather than doubling the dose of ICS. Formoterol and salmeterol have a similarly long duration of effect (up to 12 h). However, as a result of their different chemical structures, there are marked pharmacological differences in the mechanism of action which affect their speeds of onset. These differences amount to a more rapid onset of effect for formoterol compared with salmeterol. Long-acting beta(2)-agonists appear to be well tolerated at elevated doses. These two features (tolerability at high doses and rapid onset of effect) support the use of formoterol as a reliever medication in addition to use in maintenance therapy. The long-acting beta(2)-agonists can be considered as beneficial additions to ICS therapy for the management of moderate-to-severe asthma.

Formoterol delivered by Turbuhaler: in pediatric asthma

Formoterol is an inhaled long-acting beta(2)-adrenoceptor agonist, with a rapid onset of action and a bronchodilator effect that lasts for at least 12 hours. As add-on therapy to anti-inflammatory medication (e.g. corticosteroids), formoterol 4.5 and 9 microg twice daily delivered by Turbuhaler for 3 months significantly improved lung function (change from baseline in forced expiratory volume in 1 second and/or peak expiratory flow) compared with placebo in randomised, double-blind trials in pediatric patients (aged 6-17 years). In addition, formoterol 9 microg twice daily for 12 weeks reduced the use of rescue medication compared with salmeterol 50 microg twice daily in a nonblind trial in pediatric patients (aged 7-16 years). Single-dose formoterol 4.5 or 9 microg delivered by Turbuhaler provided significant prophylaxis against exercise-induced bronchoconstriction compared with placebo, and demonstrated a longer duration of effect than terbutaline, in a randomized, double-blind, crossover trial in pediatric patients (aged 8-17 years). Formoterol delivered by Turbuhaler was well tolerated in pediatric patients, with respiratory infection being the most commonly reported adverse event.

Altering airway surface liquid volume: inhalation therapy with amiloride and hyperosmotic agents

The thin layer of liquid lining the entire respiratory tract is the first line of defense against the continuous insult of inhaled bacteria and noxious chemicals. Many chronic obstructive diseases of the airway may reflect decreased airway surface liquid, which results from imbalances in ion transport and mucus production. Reduction in the thickness of airway surface liquid leads to reduced mucociliary clearance rates, causing mucus accumulation and infection in the airway. In this chapter, two inhalation therapies to replenish airway surface liquid and enhance mucociliary clearance are discussed: (1) aerosolized hyperosmotic agents; and (2) aerosolized sodium channel blockers. The advantages and disadvantages of each therapy are discussed, as well as future directions for improving airway surface liquid volume by inhalation pharmacotherapy.

Single-dose comparison of formoterol (Oxis) Turbuhaler 6 microg and formoterol Aerolizer 12 microg in moderate to severe asthma: a randomised, crossover study

Formoterol inhaled via Turbuhaler (Oxis) or Aerolizer (Foradil) produces fast and long-lasting bronchodilation in asthmatic patients. While formoterol Turbuhaler provides sustained efficacy for > or =12h at a metered dose of 6 microg (delivered dose 4.5 microg), the recommended metered dose for formoterol Aerolizer is 12 microg (delivered dose unknown). This difference may be attributable to improved lung deposition with the Turbuhaler. This open, randomised, crossover study compared the effects of a single metered dose of formoterol Turbuhaler 6 microg and formoterol Aerolizer 12 microg in 16 patients with stable moderate-to-severe asthma. Pulmonary function, assessed by measuring specific airway conductance (sGaw), was determined at intervals of < or =8h post-inhalation of each drug on separate study days. Both inhalers increased sGaw at all time points. There were no significant differences between the two formulations in onset of activity, maximum effect, duration of effect or area under the response curve. Furthermore, both treatments were well tolerated with no differences in adverse events, blood pressure or heart rate; thus the formoterol Turbuhaler may, therefore, have an improved therapeutic index. This pilot study indicates that the same clinical effect can be achieved with half the metered dose (6 microg) of formoterol Turbuhaler compared with formoterol Aerolizer (12 microg).

Beta-agonists

Beta-Agonists are a mainstay of asthma treatment. Short-acting beta-agonists are the most effective bronchodilators for rescue or quick relief of symptoms. Long-acting beta-agonists have a key role in long-term control when added to inhaled corticosteroid therapy, and are especially useful in the control of nocturnal asthma. Both types of beta-agonists may be used in the prophylaxis of exercise-induced asthma with long-acting beta-agonists providing more prolonged protection. beta-Agonists have minimal side effects and are safe when used appropriately.

Formoterol therapy for chronic obstructive pulmonary disease: a review of the literature

Numerous clinical trials have investigated the use of formoterol, a long-acting beta2-agonist, for the treatment of chronic obstructive pulmonary disease (COPD). Formoterol provides bronchodilation as rapidly as albuterol, yet its efficacy and duration of action are similar to those of salmeterol. It demonstrates better spirometric efficacy than either ipratropium or theophylline alone, and its efficacy improves when administered in combination with ipratropium. Formoterol improves patients' quality of life and has a good safety profile. It is better tolerated than theophylline and has a similar tolerability to albuterol, salmeterol, and ipratropium. In short, formoterol is a bronchodilator with rapid onset of action and prolonged duration of action with a favorable efficacy, safety, and tolerability profile when used in patients with COPD. It provides a valid therapeutic option in the pharmacologic treatment of this disease.

Formoterol Turbuhaler 4.5 microg (delivered dose) has a rapid onset and 12-h duration of bronchodilation

Clinical trials show that formoterol (Oxis) Turbuhaler 4.5 microg delivered dose (6 microg metered dose) has a rapid onset of bronchodilation similar to that of salbutamol and a 12-h duration of action. Maximum increase in FEV(1) and duration of bronchodilation are dose-dependent, the 4.5 microg dose being the lowest dose tested giving both effects. Clinical studies investigating onset of bronchodilation show a significant increase in specific airway conductance occurring within 1 min after inhalation of formoterol Turbuhaler 4.5 microg. When measured from 3-20 min after inhalation, formoterol Turbuhaler 4.5 microg showed similar increases in FEV(1) to salbutamol administered via pMDI. No difference in onset of bronchodilation was observed between the formoterol Turbuhaler 4.5 and 9 microg doses.Single-dose studies and studies of 1-12 weeks' duration show that formoterol Turbuhaler 4.5 microg produces a significant and clinically important mean bronchodilating effect for > or =12 h after inhalation. In the cited studies no significant differences in duration of bronchodilation were observed between the formoterol Turbuhaler 4.5 and 9 microg doses.

CONCLUSION

clinical data show that formoterol Turbuhaler 4.5 microg is an effective dose in patients with asthma, with a rapid onset of bronchodilation and a duration of at least 12 h.