Effects of N-aralkyl substitution of beta-agonists on alpha- and beta-adrenoceptor subtypes: pharmacological studies and binding assays

Million-year-old DNA sheds light on the genomic history of mammoths

Temporal genomic data hold great potential for studying evolutionary processes, including speciation. However, sampling across speciation events would in many cases require genomic time series that stretch well into the Early Pleistocene (>1 million years). Although theoretical models suggest that DNA should survive on this timescale¹, the oldest genomic data recovered so far is from a 560-780 ka old horse specimen². Here we report the recovery of genome-wide data from three Early and Middle Pleistocene mammoth specimens, two of which are more than one million years old. We find that two distinct mammoth lineages were present in eastern Siberia during the Early Pleistocene. One of these gave rise to the woolly mammoth, whereas the other represents a previously unrecognised lineage that was ancestral to the first mammoths to colonise North America. Our analyses reveal that the North American Columbian mammoth traces its ancestry to a Middle Pleistocene hybridisation between these two lineages, with roughly equal admixture proportions. Finally, we show that the majority of protein-coding changes associated with cold adaptation in woolly mammoths were present already a million years ago. These findings highlight the potential of deep time palaeogenomics to expand our understanding of speciation and long-term adaptive evolution.

The adrenergic receptor subtypes present in frog (Rana esculenta) skin

Frog skin transports ions and water under hormonal control. In spite of the fundamental role played by adrenergic stimulation in maintaining the water balance of the organism, the receptor subtype(s) present in the skin have not been identified yet. We measured the increase in short-circuit current (ISC, an estimate of ion transport) induced by cirazoline, clonidine, xamoterol, formoterol, or BRL 37344, in order to verify the presence of alpha1, alpha2, beta1, beta2, or beta3 receptor subtypes, respectively. Only after treatment with formoterol, BRL 37344 and, to a lesser extent, cirazoline was measured a significant increase in ISC (57%, 33.2%, and 4.7%, respectively). The formoterol and BRL 37344 concentrations producing half-maximal effect (EC50) were 1.12 and 70.1 nM, respectively. Moreover, the formoterol effect was inhibited by treatment with ICI 118551 (antagonist of beta2 receptors) while SR 59230A (antagonist of beta3 receptors) had no effect; opposite findings were obtained when the BRL 37344 stimulation was investigated. Finally, by measuring the transepithelial fluxes of 22Na+ and 36Cl-, we demonstrated that Na+ absorption is increased by activation of beta2 and beta3 and is cAMP-sensitive, whereas the Cl- secretion is only increased by activation of beta2 receptors and is cAMP- and calmodulin-sensitive.

The use of inhaled formoterol in the treatment of asthma

OBJECTIVE

To discuss the clinical efficacy and safety of formoterol when used to relieve symptoms of asthma and prevent exercise-induced bronchoconstriction (EIB).

DATA SOURCES

A PubMed search was performed for articles published between 1997 and 2005 with the keywords formoterol, asthma, and long-acting beta2-adrenergic agonist, with cross-referencing to identify peer-reviewed journal articles.

STUDY SELECTION

Published articles on the clinical use of formoterol for asthma or EIB were included as well as articles detailing the pharmacologic properties of the drug. To present a thorough review of the literature, published studies based on patient number, study design, or other measures of study quality were not excluded.

RESULTS

Formoterol is the only long-acting beta2-adrenergic agonist that combines a rapid onset of action (within 3 minutes) with a long duration of effect (approximately 12 hours). Clinically, as recommended by asthma treatment guidelines, formoterol in conjunction with inhaled corticosteroids (ICSs) is a preferred treatment for moderate to severe persistent asthma. Significant clinical data support the use of formoterol in combination with ICSs for the treatment of asthma, with studies demonstrating improved pulmonary function and symptom scores and decreased need for maintenance ICSs and short-acting beta2-adrenergic agonists (SABAs) as relief medication. Recent studies also demonstrate that use of formoterol as needed as relief medication is associated with a prolonged time to exacerbation, improved pulmonary function, and decreased asthma symptoms. When used as monotherapy, formoterol provides protection against EIB. Clinical data also demonstrate that formoterol is safe and well tolerated even in high doses, with an adverse event profile similar to that of SABAs.

CONCLUSION

Overall, formoterol is safe and effective as adjunct controller therapy for moderate and severe persistent asthma and as monotherapy for EIB.

β-ADRENOCEPTOR-MEDIATED INHIBITION OF MEDIATOR RELEASE FROM HUMAN PERIPHERAL BLOOD-DERIVED MAST CELLS

1. Mast cells cultured from human peripheral blood have been used as a cell model for functional studies of human mast cells, particularly human lung mast cells. However, the beta-adrenoceptor subtype expressed by these cultured cells has not been identified. The aim of the present study was to characterize pharmacologically the beta-adrenoceptors involved in the suppression of IgE-mediated release of mediators, including histamine, prostaglandin (PG) D2 and leukotriene (LT) C4 from cultured mast cells. 2. Mast cells were cultured from mast cell progenitors isolated from peripheral blood in the presence of 200 ng/mL stem cell factor and 50 ng/mL interleukin-6. Mast cells were sensitized with human myeloma IgE, treated with beta-adrenoceptor agonists or antagonist and then challenged with anti-human IgE. The release of histamine, PGD2 and LTC4 from mast cells was determined. 3. Both isoprenaline and salbutamol inhibited anti-IgE-induced release of histamine, PGD2 and LTC4 from cultured mast cells in a dose-dependent manner. Isoprenaline was a more potent inhibitor than salbutamol. The pD2 values for the inhibition of the release of histamine, PGD2 and LTC4 were 7.37 +/- 0.12, 8.38 +/- 0.23, 8.85 +/- 0.23, respectively, for isoprenaline and 6.96 +/- 0.12, 7.65 +/- 0.36, 7.91 +/- 0.64, respectively, for salbutamol. The selective beta3-adrenoceptor agonist BRL-37344 failed to affect anti-IgE-induced histamine release from cultured mast cells. 4. The selective beta2-adrenoceptor antagonist ICI 118 551 (108 mol/L) strongly reversed the concentration-dependent suppression of histamine release by isoprenaline and salbutamol; however, the selective beta1-adrenoceptor antagonist atenolol (106 mol/L) did not have any effect. 5. These results indicate that both isoprenaline and salbutamol act at beta2-adrenoceptors to suppress IgE-mediated mediator release from cultured human mast cells.

Long-acting beta2-agonists: comparative pharmacology and clinical outcomes

Salmeterol and formoterol are both long-acting beta(2)-adrenoceptor agonists (beta(2)-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting beta(2)-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting beta(2)-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting beta(2)-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting beta(2)-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting beta(2)-agonists. Monotherapy with long-acting beta(2)-agonists is not recommended.

Trachea relaxing effects and beta2-selectivity of SPFF, a newly developed bronchodilating agent, in guinea pigs and rabbits

In this paper we evaluated the bronchodilator effects of SPFF [2-(4-amino-3-chloro-5-trifluomethyl-phenyl)-2-tert-butylamino-ethanol chloride], a newly synthesized beta(2) adrenergic agonist in guinea pigs and rabbits, in comparison with other beta(2) adrenergic agonists, isoprenaline or salbutamol. We studied in vitro the bronchodilator effects of SPFF and isoprenaline on isolated guinea pig trachea strips with or without the precontraction of bronchocontractors (acetylcholine and histamie). The positive chronotropic effects of SPFF and isoprenaline on isolated guinea pig left atria were also tested in vitro. Potency values (pD(2), pA(2) or ED(50)) were determined from the cumulative concentration-response curves. The results showed that SPFF and isoprenaline dose-dependently relaxed the isolated guinea pig trachea strips and the pD(2) values of both drugs were 7.66+/-0.68 and 8.79+/-0.19, respectively. Moreover, we confirmed that the bronchodilator effect of SPFF was due to the activation of beta(2) adrenoceptor because this effect was easily antagonized by ICI-118551 (pA(2) 8.90+/-0.01), a specific beta(2) adrenoceptor antagonist. SPFF also dose-dependently relaxed the isolated guinea pig trachea strip precontraction with acetylcholine or histamine with ED(50) values of 10.2+/-0.7 microM and 550+/-38.2 nM, respectively. Furthermore, the positive chronotropic effect of SPFF on isolated guinea pig left atria (pD(2) 5.41+/-0.38) was much weaker than that of isoprenaline (pD(2) 8.75+/-0.24), which implied that SPFF was more selective to airway beta(2) adrenoceptor than isoprenaline; the beta(1)/beta(2) selectivity assay also showed that SPFF was about 162 times more selective to beta(2) adrenoceptor than isoprenaline. A radioligand binding experiment using guinea pig lung and cardiac ventricle as beta(2) and beta(1) adrenoceptor sources, respectively, also demonstrated that SPFF possesses high affinity (27.3 nM) and selectivity (4.6 fold) to beta(2) adrenoceptors. The protective effects of SPFF and salbutamol on bronchospasm induced by bronchoconstrictor aerosol in guinea pigs in vivo were investigated, and the Konzett and Rössler experiment in rabbits in vivo was also carried out. SPFF significantly prolonged the latency time of histamine and acetylcholine induced asphyxiation collapse in guinea pigs: the ED(50) value of SPFF i.g. was 0.32+/-0.05 mg.kg(-1) in this experiment. Meanwhile, the ED(50) values of salbutamol was 2.37+/-0.22, which meant that the bronchorelaxation effect of salbutamol was about 6 times less potent than that of SPFF. The Konzett and Rössler experiment performed in anesthetized rabbit showed that intraduodenal administration of SPFF exerted action of longer duration than salbutamol. From the results above we suggested that SPFF was a potent, long-acting bronchodilator with relatively higher beta(2) adrenoceptor selectivity.

The effects of regular inhaled formoterol and budesonide on preformed Th-2 cytokines in mild asthmatics

In a recent placebo-controlled study in mild atopic asthmatics, we observed a significant decrease in eosinophils in the bronchial submucosa, after 2 months oftreatment with inhaled formoterol and budesonide. Biopsy material from each treatment group; formoterol (24 microg bid), budesonide (400 microg b. i. d.) and placebo has been further assessed to investigatethe role of Th-2 cytokines by immunohistochemistry using Mabs to eosinophils as an index of inflammation, IL-4 and IL-5. Treatment with formoterol significantly reduced the number of eosinophils (EG2+) in the submucosa and epithelium, but this was not paralleled by changes in cytokine immunoreactivity In contrast, treatment with budesonide significantly reduced both the number of eosinophils (EG2+) and immunoreactivity for IL-4 and IL-5 in the submucosa. Thus, while budesonide has effects on cytokines involved in eosinophil recruitmentthis explanation does not apply tothe eosinopaenia observed with the long-acting beta2 adrenoreceptor agonist formoterol.

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

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

Tocolytic effects of a long-acting beta2-adrenoceptor agonist, formoterol, in rats

We have assessed the tocolytic activity of formoterol, a novel long-acting and potent beta2-adrenoceptor agonist, through its production of cyclic adenosine monophosphate, in comparison with ritodrine, a beta2-adrenoceptor agonist used clinically to counter premature delivery. Formoterol and ritodrine inhibited the amplitude and frequency of rat uterine contraction, with IC50 values of 3.8 x 10(-10) and 4.7 x 10(-7) M, respectively. Intravenous administration of formoterol or ritodrine caused inhibition of uterine motility and increased heart rate in a dose-dependent manner. Inhibition of uterine motility by oral administration of formoterol (0.3 and 1 mg kg(-1)) continued for at least 60 min, whereas that with ritodrine (100 mg kg(-1)) persisted for 15 min with rapid recovery thereafter in pregnant rats. The beta-adrenoceptor binding of [125I]iodopindolol to the myometrium of pregnant rats was competitive with formoterol and ritodrine, with Ki values of 0.04 and 6.10 nM, respectively. Formoterol (10(-6)-10(-4) M) and ritodrine (10(-6)-10(-4) M) increased the level of cyclic adenosine monophosphate in lymphocytes in a dose-dependent manner. The results suggested that formoterol caused relaxation of uterine motility through production of cyclic adenosine monophosphate. Thus, formoterol may be useful as a treatment to counter premature delivery.

Systemic effects of formoterol and salmeterol: a dose-response comparison in healthy subjects

BACKGROUND

The main adverse effects of inhaled long acting beta(2) agonists relate to their systemic activity. The systemic effects seen over eight hours after inhalation of three doses of salmeterol and formoterol were therefore compared in normal subjects.

METHODS

A double blind, randomised, crossover study was carried out in 16 healthy subjects who inhaled formoterol 24, 48 and 96 microg (via Turbuhaler((R))), salmeterol 100, 200 and 400 microg (via Diskhaler((R))), or placebo on separate days. Heart rate, systolic and diastolic blood pressure, and plasma potassium and glucose concentrations were measured for eight hours following each drug and mean values were used to plot the time course of change after each dose. Mean maximum (or minimum) absolute values were used to construct dose-response curves to calculate the relative dose potency of the two drugs. Lunch was taken after the four hour readings and, since this caused additional changes to the main outcome measures, data from the first four hours are also presented in a post hoc analysis.

RESULTS

Both salmeterol and formoterol caused an early dose dependent increase in heart rate and glucose concentrations and a fall in diastolic blood pressure and plasma potassium concentration; formoterol also caused an early increase in systolic blood pressure. The cardiovascular effects occurred more rapidly than the metabolic effects and the response to formoterol was faster than that of salmeterol, apart from the glycaemic response. The effects of salmeterol were slightly more prolonged than those of formoterol, although some dose related effects were apparent at eight hours with both drugs. The relative dose potency for formoterol compared with salmeterol at four and eight hours for the different end points excluding systolic blood pressure ranged from 1.6 to 7.0 after adjusting for baseline values. Relative dose potencies (95% CI) for maximum heart rate and plasma potassium concentrations were 4.1 (3.0 to 5.6) and 5.8 (4.1 to 8.6) over four hours and 2.4 (1.2 to 3.8) and 3.0 (1.2 to 5.7) over eight hours.

CONCLUSIONS

Formoterol and salmeterol cause dose related changes in heart rate, diastolic blood pressure, and plasma glucose and potassium concentrations. Formoterol has a more rapid onset for most end points whereas salmeterol has slightly more prolonged activity. Both drugs have a relatively modest therapeutic window. The relative dose potencies of the two drugs for the main end points were similar to the fourfold difference in recommended doses. Some differences in the pharmacological profile of the two drugs emerged and are as yet unexplained.

A 3-month comparison of formoterol with terbutaline via turbuhaler. A placebo-controlled study

BACKGROUND AND AIM

Oxis Turbuhaler is a new dry powder formulation of long-acting beta2-agonist formoterol. This study compared the efficacy and safety of regular use of the long-acting beta2-agonist formoterol and the short-acting terbutaline for 3 months in patients with asthma.

METHOD

After 1-week run-in, 343 patients received either formoterol 12 microg bid (F) (delivered dose of 9 microg), terbutaline 500 microg qid (T) or placebo qid, in a parallel-group, double-blind, randomized manner. They had a mean of 61% of predicted forced expiratory volume in 1 second (FEV1) and a mean reversibility of 26%. Eighty-nine percent used inhaled corticosteroids.

RESULTS

During run-in mean morning peak expiratory flow (PEF L/min) for F was 366 and 348 for T, and 344 for placebo (P). The F group improved morning PEF significantly compared with P (P = .0022) and T (P = .0001). Changes from run-in were + 18, -1.5, and +5 L/min after F, T, and P, respectively. The F group was statistically significantly better than P and T in increasing evening PEF and in reducing night-time asthma. The F and T statistically significantly reduced the use of rescue medication compared with P. The bronchodilating response to the study drug and to an additional 1.25 mg terbutaline was of the same magnitude before and throughout the study. No statistically significant treatment-by-time interaction was observed (P > .20). There were no adverse effects of clinical relevance.

CONCLUSION

Formoterol Turbuhaler, 12 microg bid, was more effective than terbutaline Turbuhaler, 0.5 mg qid, and placebo. Regular use of formoterol or terbutaline did not significantly influence the response to additional inhalation of terbutaline.

Beta-adrenoceptor regulation and functional responses in the guinea-pig following chronic administration of the long-acting beta 2-adrenoceptor agonist formoterol

Formoterol is a long acting beta 2-adrenoceptor agonist designed for the alleviation of the symptoms of asthma. This study examined the effects of 14 day administration of formoterol (200 micrograms/kg/day i.p.) on beta 1- and beta 2-adrenoceptors in guinea-pig cardiac and lung tissue. Quantitative autoradiography was used to measure changes in receptor density and organ bath studies determined alterations in functional response. Formoterol treatment produced marked reductions of between 43% and 77% in beta 2-adrenoceptor density in all regions of the heart (atrioventricular node, bundle of His, right and left bundle branches, interventricular and interatrial septa, right and left atria, ventricles and apex) and lung (bronchial and vascular smooth muscle and parenchyma) (P < 0.01, n = 6). beta 1-Adrenoceptor density remained unchanged in all cardiac and lung regions. In functional studies (-)-isoprenaline was 4 fold less potent at causing relaxation of carbachol (1 microM) precontracted tracheal smooth muscle (pD2: control 8.49 +/- 0.03, formoterol 7.91 +/- 0.10, P < 0.001, n = 4), but formoterol treatment did not change the ability of (-)-isoprenaline to elicit a maximum response. The pKB values for ICI 118,551, 7.33 +/- 0.08 in the control and 7.20 +/- 0.01 in formoterol treated animals, were between those expected for beta 1- and beta 2-adrenoceptors suggesting involvement of both subtypes in the response. In spontaneously beating right atria and electrically paced left atria, tissues in which responses are largely mediated by beta 1-adrenoceptors, there was no significant change in responses to (-)-isoprenaline (right atria pD2: control 8.45 +/- 0.02; formoterol 8.42 +/- 0.11; P = 0.77, n = 4) (left atria pD2: control 8.25 +/- 0.03; formoterol 8.47 +/- 0.08; P = 0.09, n = 4). In the presence of CGP 20712A (100 nM) the pKB values did not change with formoterol treatment (left atria: control 9.59 +/- 0.12, formoterol 9.66 +/- 0.12; P = 0.70, n = 4) (right atria: control 8.93 +/- 0.11, formoterol 9.11 +/- 0.07; P = 0.25, n = 4). The doses and route of administration of formoterol used in this study differs from those used clinically. However, this study demonstrates that chronic formoterol administration produces selective down-regulation of beta 2-adrenoceptors in the lung and heart. The changes in the lung are accompanied by a shift to the right in the concentration-response curve to beta-agonist stimulation with no change in the maximum response.

Studies on serotonin (5-HT)3-receptor antagonist effects of enantiomers of 4,5,6,7-tetrahydro-1H-benzimidazole derivatives

We assessed the 5-HT3-receptor antagonist effects of 4,5,6,7-1H-benzimidazole compounds which are derivatives of YM060, a potent and selective 5-HT3-receptor antagonist, in isolated guinea pig colon. YM114 (KAE-393), YM-26103-2, YM-26308-2 (3 x 10(-9) to 3 x 10(-8) M) produced concentration-dependent shifts to the right of the dose-response curves for both 5-HT and 2-methyl-5-HT (2-Me-5-HT). YM114 (pA2 = 9.08 against 5-HT, pA2 = 8.88 against 2-Me-5-HT), YM-26103-2 (pA2 = 8.27 against 5-HT, pA2 = 8.19 against 2-Me-5-HT), and YM-26308-2 (pA2 = 8.58 against 5-HT, pA2 = 8.4 against 2-Me-5-HT) showed similar pA2 values irrespective of the agonist used, suggesting that they have 5-HT3-receptor blocking activity irrespective of the N-position at the aromatic ring. Since these compounds have an asymmetric center, their enantiomers exist. The S-isomers were one to three orders of magnitude less potent than the respective R-isomer compounds, indicating that the stereochemical configuration of 4,5,6,7-tetrahydro-1H-benzimidazoles is an important determinant of their affinity for 5-HT3 receptors. These results suggest that the highly potent 5-HT3 receptor antagonism and high selectivity for 5-HT3 receptors of 4,5,6,7-tetrahydro-1H-benzimidazole derivatives are conserved irrespective of the position of the nitrogen atom in the aromatic ring and that 5-HT3 receptors favor the R-isometric conformation of these compounds.

Effects of glucocorticoids and beta-adrenoceptor agonists on the proliferation of airway smooth muscle

An increase in airway smooth muscle is a characteristic feature of asthma. Because beta-adrenoceptor agonists and corticosteroids are commonly used in the treatment of asthma we have studied the effects of these medicines on the growth of airway smooth muscle. These agents were incubated with bovine airway smooth muscle cells for 40 h for measurement of thymidine incorporation and 64 h for measurement of cell counts. Salbutamol inhibited thymidine incorporation (IC50 = 60 nM) and led to a reduction in cell number (IC50 = 10 nM). At 10 microM there was a 14.6 +/- 2.6% reduction in cell number. Salmeterol also inhibited the growth of the airway smooth muscle cells but the effect did not plateau at 10 microM. At this concentration there was an 89.5 +/- 3.6% reduction in thymidine incorporation and a 44.1 +/- 5.2% reduction in cell number. Cortisol and beclomethasone dipropionate were more potent than salbutamol in inhibiting thymidine incorporation with IC50 values of 5 nM and 0.2 nM respectively. Cortisol 100 nM led to a 16.6 +/- 6.5% reduction and beclomethasone dipropionate 3 nM led to a 17.8 +/- 5.8% reduction in cell number. If similar effects occur in man and in vivo, these medicines could act directly on airway smooth muscle to inhibit the development of hyperplasia.

Time course and duration of bronchodilatation with formoterol dry powder in patients with stable asthma

BACKGROUND

Formoterol, a new beta 2 agonist, is long and fast acting when given as an aerosol. The aim was to determine the onset and duration of bronchodilatation with formoterol as a dry powder compared with salbutamol dry powder and with placebo.

METHODS

Fifteen patients with stable asthma with a reversibility of 15% or more participated in a double blind, within patient study. On five different days the patients received formoterol 6 micrograms, 12 micrograms, or 24 micrograms, salbutamol 400 micrograms, or placebo in random order. Forced expiratory volume in one second (FEV1) was measured 10 minutes before, 30 minutes after, and then every hour for up to 12 hours after treatment. Specific airway resistance (sRaw) and specific airway conductance (sGaw) were measured immediately before and one, three, five, 10, 15, and 30 minutes after treatment.

RESULTS

Formoterol 12 micrograms and 24 micrograms caused bronchodilatation as rapidly as salbutamol 400 micrograms. Peak values were not significantly different in the active treatments. The duration of action, calculated as median time with 20% or more of the maximum achieved increase in FEV1, was sustained for 9 hours and 16 minutes with salbutamol 400 micrograms, for 9 hours and 45 minutes with formoterol 6 micrograms, for 11 hours and 22 minutes with formoterol 12 micrograms, and for 11 hours and 42 minutes with formoterol 24 micrograms.

CONCLUSIONS

Formoterol as a dry powder at doses of 12 micrograms and 24 micrograms produces a rapid onset of action and has a bronchodilator effect comparable with salbutamol 400 micrograms as a dry powder. The bronchodilatation was sustained for 11-12 hours. Formoterol 6 micrograms caused similar bronchodilatation but more slowly and for a shorter time.

Salmeterol, formoterol, and salbutamol in the isolated guinea pig trachea: differences in maximum relaxant effect and potency but not in functional antagonism

BACKGROUND

Formoterol and salmeterol are new long acting beta 2 adrenoceptor agonists. The maximum relaxant effect, potency and functional antagonism against carbachol induced contraction for salmeterol, formoterol and salbutamol have been compared in the guinea pig isolated trachea. In addition, the possibility of inducing a non-beta adrenoceptor mediated relaxation by salmeterol was studied.

METHODS

Concentration response experiments were conducted with isolated tracheal preparations (n = 4-6 in all experiments), precontracted by carbachol to cause either 40% (60 nmol/l), 80% (0.3 mumol/l) or 100% (3 mumol/l, supramaximal) of the maximum contraction. Each beta agonist was added cumulatively at each level of precontraction. Additional cumulative concentration response experiments were conducted for salmeterol alone at the highest level of precontraction, with and without beta blockade by sotalol (1 mmol/l). With the drug concentrations which produced the maximum response and the highest level of precontraction, the relaxation of formoterol (10 nmol/l) and salmeterol (1 mumol/l) was also compared non-cumulatively. Finally, with the corresponding drug concentrations and precontraction, the relaxant effect was compared for formoterol (10 nmol/l) in salmeterol relaxed airways with that of salmeterol (1 mumol/l) in formoterol relaxed airways.

RESULTS

The increase in carbachol concentration from 60 nmol/l to 3 mumol/l induced a rightward shift in the mean (SE) concentration (log steps) causing 50% maximum relaxation for salmeterol (0.73 (0.17)), formoterol (0.85 (0.18)), and salbutamol (1.13 (0.11)). Significant differences in the maximum relaxant effect were shown at the highest level of precontraction only, with a remaining active tension of percentage precontraction of 27% (4%) for 1 mumol/l salbutamol and 35% (3%) for 10 nmol/l formoterol compared with 50% (2%) for 1 mumol/l salmeterol. The rank order of potency was: formoterol > salbutamol approximately salmeterol at all levels of precontraction (-log EC50: 9.32 (0.05) for formoterol, 7.82 (0.08) for salbutamol, and 7.50 (0.13) for salmeterol at 80% maximum precontraction). Beta blockade by sotalol (1 mmol/l) significantly inhibited the relaxation induced by salmeterol (1 mumol/l) (remaining active tension: 104% (1%) v 71% (11%) of precontraction) but not the relaxation induced by salmeterol (10 mumol/l) (remaining active tension: 75% (5%) v 71% (12%) of precontraction). In the non-cumulative experiments, formoterol displayed more relaxant effect than salmeterol (remaining active tension: 51% (6%) v 65% (6%) of precontraction). Finally, formoterol significantly relaxed salmeterol relaxed airways (relaxant effect: 22% (8%) of precontraction) whereas there was no significant response to salmeterol in formoterol relaxed airways (relaxant effect: 5% (12%) of precontraction).

CONCLUSIONS

In the guinea pig isolated trachea, formoterol and salbutamol produce more relaxant effect than salmeterol, suggesting that salmeterol is a partial beta 2 agonist. Very high concentrations of salmeterol may induce non-beta adrenoceptor mediated relaxation. Formoterol is more potent than both salbutamol and salmeterol. There is no pronounced difference in the magnitude of antagonism against carbachol induced contractions between salmeterol, formoterol, and salbutamol.

Long acting inhaled beta-adrenoceptor agonists the comparative pharmacology of formoterol and salmeterol

Formoterol and salmeterol are chemically distinct, highly selective beta-2-adrenoceptor agonists developed to provide sustained (12h+) relief of airway obstruction in diseases such as asthma. Despite their similar long duration of action, these drugs differ. Formoterol has a faster onset of action in both experimental and clinical tests than that of salmeterol. Salmeterol, but not formoterol, behaves as a beta-adrenoceptor antagonist in some experimental models due to its considerably weaker efficacy at the beta 2-adrenoceptor in vitro although their are no established clinical consequences of this antagonism. Both formoterol and salmeterol display a peculiar "reassertion" behaviour in isolated airway smooth muscle subjected to beta-adrenoceptor antagonism and then washed with antagonist-free buffer. Both formoterol and salmeterol are highly efficient inhibitors of a number of indices of acute inflammatory processes in cells and tissues of human or animal origin. However, neither of these drugs has a proven clinical anti-inflammatory effect in chronic asthma in humans. Surprisingly, recent biophysical studies of formoterol and salmeterol have provided strong evidence that their individual patterns of onset speed, duration of action and "reassertion" are due to a common drug-lipid membrane interaction rather than drug-adrenoceptor interactions. A membrane-drug diffusion microkinetic model is presented to describe these phenomena.

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

Formoterol is an innovative, highly potent, beta 2-adrenoceptor-selective agonist combining the clinical advantages of rapid onset of action with a duration of action in excess of 12 h. In vitro, formoterol is a potent airway smooth muscle relaxant with high efficacy, and very high affinity and selectivity for the beta 2-adrenoceptor. Formoterol appears to be retained in airway smooth muscle for extended periods since its relaxant effect on human airway smooth muscle is resistant to repeated washing and formoterol displays 'reassertion' of relaxation after washout of a beta-adrenoceptor antagonist. A model based on the diffusion microkinetics of formoterol into the plasmalemma lipid bilayer is proposed as a basis for these properties. In addition to the release of pro-inflammatory mediators from cells such as the mast cell, several other disease processes probably occur in asthma. Leukocytes, notably eosinophils, adhere to the vascular endothelium and emigrate into airway tissues, which may be damaged by these cells if they are activated to release mediators or their granular contents. Plasma and its component proteins are extravasated from the bronchial microcirculation. Formoterol has been demonstrated to potently inhibit these cells and processes in experimental test systems. Continuing clinical research involving histological examination of tissue reactions may allow a more complete determination of the effects of formoterol on inflammatory processes in humans and the clinical relevance of any such effects.

Clinical pharmacology of long-acting beta-receptor agonists

The longer-acting beta-receptor agonists salmeterol and formoterol are effective bronchodilators for at least 12 hours and this should be clinically useful, particularly for nocturnal asthma. Formoterol has a more rapid onset than salmeterol. There are limited dose response data on the two drugs in man but the evidence so far suggests that both drugs have roughly similar beta 2-selectivity to salbutamol and that both are about ten times as potent as salbutamol. Salmeterol may therefore have been marketed at a relatively high dose compared to salbutamol. There is no good clinical evidence to suggest that the drugs have effects other than would be expected from a beta 2-agonist with a prolonged duration of action. Medium-term studies have shown that benefit was maintained in comparison to salbutamol and, in one instance, with salmeterol when compared to placebo. Studies to date have not found any reduction in the bronchodilator response to salbutamol following regular treatment with salmeterol or formoterol, though one study has found reduced protection by salmeterol against methacholine challenge after one and two months' treatment. Longer-term safety has not been assessed.

Long duration and high potency of antiexudative effects of formoterol in guinea-pig tracheobronchial airways

Inflammatory stimulus-induced luminal exudation of plasma proteins is potentially pathogenic in asthma. This study of plasma exudation into tracheobronchial airways examines antiexudative effects (potency and duration of action) of two beta 2-agonists in anesthetized guinea pigs. The exudative response to airway provocations with bradykinin 1.25 x 10(-4) M (5 nmol) was determined in different groups of animals 10, 300, 450, and 600 min, respectively, after the mucosa had been treated topically with salbutamol 10(-6) to 10(-4) M (0.1 to 10 nmol), formoterol 10(-9) to 10(-7) M (0.1 to 10 pmol), or saline (control). Exuded plasma in tracheal lavage liquids was calculated from their contents of the plasma tracer, 125I-albumin, given intravenously 10 min before provocation with bradykinin. Salbutamol (1 and 10 nmol) and formoterol (1 and 10 pmol) promptly inhibited the mucosal exudation (p less than 0.001). Propranolol, 0.1 nmol, reduced (p less than 0.01) the antiexudative effects of both drugs. Only formoterol (1 and 10 pmol) maintained its effect at 300 min, abating gradually at 450 and 600 min. In a group of sensitized guinea pigs, formoterol (1 and 10 pmol) was demonstrated to inhibit also allergen-induced luminal exudation of plasma (p less than 0.001). It is suggested that an antiexudative action may contribute to the long duration of formoterol's antiasthma effect.

Formoterol. A review of its pharmacological properties and therapeutic potential in reversible obstructive airways disease

Formoterol, a long-acting beta 2-selective adrenoceptor agonist, produces dose-proportional bronchodilation in patients with obstructive airways disease with a reversible component. A significant effect occurs within minutes of inhalation of a therapeutic formoterol dose and persists for approximately 12 hours. Oral formoterol has a slower onset of action than the inhaled formulations, but also produces prolonged bronchodilatory effects. Inhaled formoterol has shown a therapeutic efficacy equivalent to or better than comparable dosages of the conventional beta 2-agonists salbutamol, fenoterol and terbutaline in short and long term trials, in both adults and children with asthma. Its prolonged duration of action permits a twice-daily dosage regimen and results in improved control of nocturnal symptoms by reducing the 'morning dip'. Formoterol also compares well with oral slow release theophylline. In addition, significantly more patients with chronic obstructive airways disease (COAD) had an improvement in symptoms when treated with formoterol compared with salbutamol or fenoterol. Noncomparative studies indicate formoterol also provides effective prophylaxis of exercise-induced asthma. Development of tachyphylaxis has not been observed. Formoterol is generally well tolerated. Adverse effects observed represent predictable extensions of its pharmacology. Tremor and palpitations are most frequently reported. The incidence of adverse events is dose-proportional and therefore related to the route of administration, being more frequent following oral than inhalation therapy. The long-acting beta 2-agonists, including formoterol, represent a significant advance over current maintenance or prophylactic bronchodilator therapy with intermediate-acting beta 2-agonists such as salbutamol, fenoterol and terbutaline, predominantly because of the twice daily administration regimen. However, comparisons with other long-acting beta 2-agonists, such as salmeterol, evaluation of its role in improving symptom control in patients failing to respond to prophylactic therapy, and clarification of the optimal role of beta 2-agonists in asthma maintenance therapy are required to fully determine the value of formoterol in the management of obstructive airways disease.

Formoterol, a new long acting beta 2 agonist for inhalation twice daily, compared with salbutamol in the treatment of asthma

Sixteen patients with stable chronic asthma participated in a double blind crossover study comparing the new inhaled long acting beta 2 agonist formoterol with salbutamol. Inhaled (n = 15) and oral steroid (n = 1) treatment were maintained at the same daily dose throughout the study. For four weeks the patients received either formoterol 24 micrograms twice daily or salbutamol 400 micrograms twice daily, plus additional puffs (with the same drug) when needed. Asthma symptoms, additional puffs of beta 2 agonist, peak expiratory flow (PEF), and side effects were recorded daily. During treatment with formoterol the patients used fewer additional puffs of beta 2 agonist, had better symptom scores, less disturbed sleep, more days without additional aerosol, and higher PEF both morning and evening than during salbutamol treatment. Thus formoterol 24 micrograms twice daily gave long lasting bronchodilatation and asthma symptoms were well controlled with regular twice daily administration.

Formoterol fumarate, a new beta 2-adrenoceptor agonist. Acute studies of selectivity and duration of effect after inhaled and oral administration

Four double-blind, double-dummy, randomized, crossover studies were performed in nine asthmatic patients to evaluate beta 2-adrenoceptor selectivity and the duration of effect of formoterol. One study with cumulatively increasing doses of formoterol and salbutamol showed that with the inhaled route, formoterol was 5-15 times more potent than salbutamol with respect to bronchodilation. In a second study, 6 micrograms formoterol and 0.1 mg salbutamol were given for comparison of effect duration. Five hours after salbutamol inhalation the FEV1 values were back to basal. Eight hours after formoterol inhalation about 75% of the maximum bronchodilation remained and the FEV1 was significantly higher than after salbutamol inhalation. By oral route, a study with cumulatively increasing doses showed that as a bronchodilator formoterol was about 50 times more potent than salbutamol. The same potency difference was seen for increase of heart rate and decrease of diastolic blood pressure, indicating that the clinical selectivity for beta 2-adrenoceptors is equal for the two drugs. In a fourth study comparable doses by oral route did not show any difference in the duration of bronchodilation. We conclude that inhaled formoterol is 5-15 times more potent than salbutamol. Inhaled formoterol produces longer duration of bronchodilation, with clinically relevant bronchodilation for at least 8 h. The prolonged duration of formoterol was not seen with oral treatment.

Comparison of the chronotropic effect and the cyclic AMP accumulation induced by beta 2-agonists in rat heart cell culture

1 The chronotropic response and the variation in cyclic adenosine 3',5'-monophosphate (cyclic AMP) accumulation induced by isoprenaline and six beta 2-selective agonists (fenoterol, salmefamol, soterenol, zinterol, salbutamol and formoterol) were analyzed on cultured heart cells of the rat. 2 The compounds elicited an enhancement of the frequency, but the time course of the variation of the beating rate was not identical for all of them. A rapid onset was observed for isoprenaline, zinterol and formoterol while it was slower for fenoterol, salmefamol and salbutamol. 3 In contrast with isoprenaline, the beta 2-selective agonists gave concentration-beating frequency curves which were not sigmoidal. Their effects extended up to a concentration of 5 to 6 orders of magnitude. Nevertheless, the concentration at which the maximal effect occurred and the intrinsic activities of the various compounds agrees better with the responses observed on guinea-pig atria than with those on trachea. 4 All the beta 2-selective agonists increased the accumulation of cyclic AMP in rat heart cells with a maximal effect at 10(-5)M or less. The effects of beta 2-agonists on cyclic AMP production showed some analogies with those on beating frequency of the heart cells. The increase in cyclic AMP accumulation induced by beta 2-agonists also corresponded to their chronotropic effects on guinea-pig atria. Thus, the correlation coefficient between the inverse of the log of the concentration producing the half maximal cyclic AMP accumulation in cultured heart cells and the pD2 values on guinea-pig atria was 0.93. 5 It is concluded that, in contrast to what was observed in other models, the beta 2-selective agonists induce an increase in the production of cyclic AMP in rat heart cells. Furthermore, the effects of the beta 2-agonists on cyclic AMP accumulation and on beating rate in the heart cells may correspond with their beta 1-adrenoceptor potencies.