Beta2-adrenoceptor agonists for dysmenorrhoea

BACKGROUND

Dysmenorrhoea is a common gynaecological complaint that can affect as many as 50% of premenopausal women, 10% of whom suffer severely enough to be rendered incapacitated for one to three days during each menstrual cycle. Primary dysmenorrhoea is where women suffer from menstrual pain but lack any pathology in their pelvic anatomy. Beta2-adrenoceptor agonists have been used in the treatment of women with primary dysmenorrhoea but their effects are unclear.

OBJECTIVES

To determine the effectiveness and safety of beta2-adrenoceptor agonists in the treatment of primary dysmenorrhoea.

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register; CENTRAL (The Cochrane Library 2011, Issue 8); MEDLINE; EMBASE; PsycINFO and the EBM Reviews databases. The last search was on 22 August 2011.

SELECTION CRITERIA

Randomised controlled trials comparing beta2-adrenoceptor agonists with placebo or no treatment, each other or any other conventional treatment in women of reproductive age with primary dysmenorrhoea.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted the data.

MAIN RESULTS

Five trials involving 187 women with an age range of 15 to 40 years were included. Oral isoxsuprine was compared with placebo in two trials; terbutaline oral spray, ritodrine chloride and oral hydroxyphenyl-orciprenalin were compared with placebo in a further three trials. Clinical diversity in the studies in terms of the interventions being evaluated, assessments at different time points and the use of different assessment tools mitigated against pooling of outcome data across studies in order to provide a summary estimate of effect for any of the comparisons. Only one study, with unclear risk of bias, reported pain relief with a combination of isoxsuprine, acetaminophen and caffeine. None of the other studies reported any significant clinical difference in effectiveness between the intervention and placebo. Adverse effects were reported with all of these medications in up to a quarter of the total number of participants. They included nausea, vomiting, dizziness, quivering, tremor and palpitations.

AUTHORS' CONCLUSIONS

The evidence presented in this review was based on a few relatively small-sized studies that were categorised to have unclear to high risk of bias, which does not allow confident decision-making at present about the use of beta2-adrenoceptor agonists for dysmenorrhoea. The benefits as reported in one study should be balanced against the wide array of unacceptable side effects documented with this class of medication. We have emphasised the lack of precision and limitations in the reported data where appropriate.

Mononuclear cell membranes: stabilization by reproterol and cromoglycate, destabilization by fenoterol and salbutamol

Electron paramagnetic resonance (EPR) spectroscopy with spin labels 5- and 16-doxyl-stearic acid (DSA) was used to differentiate between actions of beta-agonists on human mononuclear cell membrane. Reproterol (CAS 13055-82-8), salbutamol (CAS 51022-70-9) and fenoterol (CAS 1944-12-3) compared to cromoglycate (CAS 15826-37-6) were used at concentrations of 10-100 nmol/l per 10(7) cells. With reproterol, order and polarity was not much changed, whereas salbutamol and fenoterol significantly destabilized the membrane to similar extent. Cromoglycate acted in a stabilizing fashion. With trypan blue exclusion, reproterol and cromoglycate showed stable values, whereas salbutamol and fenoterol augmented permeability. Thus, by conventional lipid spin labeling the discrimination between salbutamol and fenoterol could not be carried out. In contrast, previous lipid peroxidation studies in a model system had revealed a decrease by reproterol, no change by salbutamol and an increase by fenoterol. Also, using fenoterol, protein spin label 4-maleimido-TEMPO (2, 2, 6, 6-tetramethyl-1-piperidinyloxy) showed an increase of membrane rigidity of mononuclear cells. Moreover, mast cells of different origin were previously found tween beta-agonists. Reproterol in all tests behaved in a therapeutically profitable way. In conclusion, in addition to lipid spin labeling other methods and materials should be considered, to finally arrive at a more realistic differentiation between, for instance, salbutamol and fenoterol. The term "membrane (de) stabilization" should not generally be used without careful consideration of the type of cell/membrane in question.

Effect of reproterol either alone or combined with disodium cromoglycate on airway responsiveness to methacholine

Regular use of inhaled beta2-agonists might lead to tolerance as reflected in a loss of bronchoprotection. In vitro-data suggest that this might be prevented by disodium cromoglycate (DSCG). Therefore, we studied the effect of the beta2-agonist reproterol in combination with DSCG. In a cross-over design, 19 subjects with airway hyperresponsiveness inhaled either placebo, 1mg reproterol, 2 mg DSCG, or 1mg reproterol plus 2 mg DSCG 4x daily over 2 weeks. Treatment periods were separated by > or = 7 days. Before and at the end of periods, lung function and methacholine responsiveness were determined in the morning, and 6h later the bronchodilator effect and the protection against methacholine-induced bronchoconstriction. Reproterol or DSCG or their combination did not exert detrimental effects on lung function, airway responsiveness, or bronchodilator capacity. However, bronchoprotection was significantly reduced (p < 0.05) after treatment with placebo, reproterol or reproterol plus DSCG, the respective changes being 0.59, 0.96 and 1.37 doubling concentrations. All changes were small as compared to intraindividual variability. In this model all treatments except with DSCG caused a significant but small loss of protection against methacholine-induced bronchoconstriction. Thus, tolerance was not prevented by 2 weeks of additional treatment with DSCG, in contrast to in vitro findings.

Inhibition by reproterol of cAMP PDE in intact mastocytoma P-815 cells

In vitro studies in rat mastocytes and human monocytes suggested that reproterol (a selective beta(2)-adrenoceptor agonist with a theophylline moiety) exerts anti-inflammatory actions through inhibition of cyclic AMP (cAMP) PDE activity. Thus, reproterol was tested for its ability to inhibit cAMP PDE in cultured mouse mastocytoma P-815 cells. cAMP PDE activity was measured in intact cells by spectrofluorometry using the fluorescent substrate 2'-O-anthraniloyl cAMP. Reproterol was more potent than theophylline to inhibit cAMP PDE (pIC(50)=4.28+/-0.25 vs. 3.16+/-0.05). This contrasted with disrupted cells, where the PDE inhibitory potency of reproterol was low (pIC(50)=2.85+/-0.03) and similar to that of theophylline (pIC(50)=2.66+/-0.19). No cAMP PDE inhibition was found with other beta(2)-agonists tested (fenoterol, salbutamol, salmeterol and formoterol). Finally, the selective PDE inhibitors calmidazolium (100 nM), milrinone (5 microM) and rolipram (50 microM) inhibited cAMP PDE activity by approximately 20, 30 and 25% respectively. In conclusion, reproterol potently and non-specifically inhibited intracellular cAMP phosphodiesterases in intact mastocytoma cells. This can explain the previously reported beta(2)-adrenoceptor-independent anti-inflammatory actions of reproterol in vitro. Further studies are required to define the anti-inflammatory potential of reproterol in asthma.

Different mechanisms of action of beta2-adrenergic receptor agonists: a comparison of reproterol, fenoterol and salbutamol on monocyte cyclic-AMP and leukotriene B4 production in vitro

BACKGROUND

Beta2-adrenergic receptor agonists have several effects on airway function, most of which are mediated in a variety of cell types resulting in increased c-AMP-production and inhibition of inflammatory mediator production. However, their stimulating effects on cAMP-production became known to be inversed by increasing phosphodiesterase (PDE) activity and degradation of cAMP. Therefore, in this study we have evaluated the efficacy of reproterol, a dual acting beta2-adrenoceptor agonist and PDE-inhibitor, as compared to salbutamol and fenoterol with respect to production of cAMP and LTB4 in cultured monocytes.

METHODS

Isolated human monocytes (10(5)/ml) were incubated (n = 9) in suspension with beta2-adrenoceptor agonists (10(-10) -10(-4) M) for 30 minutes with and without IBMX. Then, cAMP production was determined following treatment with Triton-X100. Production of LTB4 was measured following incubation of beta2-adrenoceptor agonists for 4 hrs in the presence of LPS (10 mg/ml). cAMP and LTB subset 4 were measured in culture supernatants by enzyme immunoassay.

RESULTS

At 10(-5) M, production of cAMP was significantly stimulated by reproterol > fenoterol > salbutamol in a dose-dependent manner to an extent of *128%, *65%, 13% (*p<0.04) respectively. In contrast, LTB4-production was inhibited significantly to a similar degree by salbutamol and reproterol in a dose-dependent manner by 59% and 49% (10(-5) M, p<0.03), respectively, with decreasing inhibition (15%) after fenoterol. Following co-incubation with IBMX, cAMP production only increased significantly (p<0.002) after fenoterol (+110%) compared to salbutamol (+29%) and reproterol (+50%) (ANOVA, p<0.001).

CONCLUSION

These data suggest effects of the theophylline constituent of reproterol to inhibit adenylyl cyclase induced phosphodiesterase activity. The advantageous synergistic effects of reproterol on cAMP-production need to be further explored in trials.

Conductimetric determination of reproterol HCl and pipazethate HCl and salbutamol sulphate in their pharmaceutical formulations

A simple and sensitive conductimetric method for the determination of salbutamol sulphate and reproterol and pipazethate hydrochlorides is presented based on their ion associates with phosphotungstic and phosphomolybdic acids. The effect of solvent, molar ratio, reagent concentration and temperature were studied, and the solubility products of the formed ion associates were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.82-100.54, 99.75-100.12 and 99.95-100.40%, and coefficient of variation 0.28-0.52, 0.16-0.36 and 0.19-0.33 for salbutamol sulphate, reproterol HCl and pipazathate HCl, respectively.

Screening of beta-2 agonists and confirmation of fenoterol, orciprenaline, reproterol and terbutaline with gas chromatography-mass spectrometry as tetrahydroisoquinoline derivatives

A new method for a comprehensive screening and confirmation of beta-2 agonists in human urine is presented based on gas chromatography-low-resolution mass spectrometry (GC-MS) using electron impact ionisation (EI). After hydrolysis of the conjugates with beta-glucuronidase/arylsulfatase a derivatisation step with formaldehyde converts fenoterol, orciprenaline, reproterol and terbutaline to one derivative, a tetrahydroisoquinoline, while the other beta-2 agonists remain unchanged. Liquid-liquid extraction and trimethylsilylation follow. The tetrahydroisoquinoline derivatives show good gas chromatographic and mass spectrometric behaviour. The detection limit of these four beta-2 agonists in the screening using low-resolution mass spectrometry is 10 ng/ml of urine. The other beta-2 agonists are detected as parent compounds with the same recovery after sample preparation with and without formaldehyde. The EI mass spectra of the tetrahydroisoquinoline derivatives are presented.

beta-agonistic bronchodilators: comparison of dose/response in working rat hearts

STUDY OBJECTIVES

Different beta-agonists are compared with regard to their cardiodepressive side effects.

DESIGN

The metaphenolic bronchodilators reproterol, salbutamol, fenoterol, and terbutaline were introduced at a dosage of 0.0005 micromol to a maximum of 10 micromol per gram of heart tissue into the isolated working rat heart under hypoxic conditions, and the response was observed during subsequent reoxygenation. As an index of external heart work, aortic flow was measured. Heart rate, coronary flow, and developed pressure were recorded. At the end of heart perfusion, mitochondria were isolated and analyzed for adenosine triphosphatase activity, adenosine triphosphate (ATP) synthesis, and membrane fluidity. Moreover, intact mitochondria and lipid peroxidation were investigated using a model system.

MEASUREMENTS AND RESULTS

Compared to controls, reproterol gave the most favorable results, with an increase of 25 to 30% of aortic flow during reoxygenation at a concentration of 10 micromol/g heart tissue. In contrast, both fenoterol and salbutamol at a concentration of 1 micromol/g heart tissue decreased aortic flow during reoxygenation, whereas terbutaline had a negative influence on aortic flow at 0.01 to 0.1 micromol/g heart tissue. Mitochondria of these hearts were isolated at the end of the experiment. Mitochondrial ATP synthesis was increased above controls at nearly all concentrations of reproterol. ATP synthesis was decreased at 1 micromol and 10 micromol fenoterol. As little as 0.0005 micromol terbutaline decreased ATP synthesis by 50%. In intact mitochondria, adenosine diphosphate (ADP) to oxygen ratios were found to be increased with terbutaline and fenoterol, indicating ADP consumption by myokinase activation. Lipid peroxidation was increased in a model system between concentrations of 0.002 micromol/mg and 0.04 micromol/mg phosphatidylcholine by fenoterol and terbutaline, whereas a decrease was noted with reproterol. Membrane fluidity was found increased after addition of reproterol, which supports the evidence of efficient ATP synthesis by this compound.

CONCLUSIONS

Cardiodepressive side effects and greater toxicity of fenoterol and terbutaline were found under the conditions of our experiment. Salbutamol and, in particular, reproterol appear much better tolerated. In addition to partial beta-adrenergic agonism, reproterol may exert an inhibitory influence on adenosine receptor sites and phosphodiesterase, which could result in membrane stabilization by saving cyclic adenosine monophosphate or ATP.

Reproterol--A monomolecular combination of orciprenaline and theophylline: novel aspects of its mode of action in asthma

BACKGROUND AND OBJECTIVE

Reproterol is a monomolecular combination of orciprenaline and theophylline used as beta-adrenergic agonist to induce bronchodilation in bronchial asthma. Since the mechanism of action of reproterol has not been investigated so far, its potential anti-inflammatory activity in asthma remains still unknown. Therefore, we have studied in vitro whether the theophylline component of the reproterol molecule might enhance the stimulatory effect of the beta-adrenoceptor on cAMP production resulting in suppression of inflammatory mediator production.

METHODS

The effects of reproterol, orciprenaline and theophylline (10(-9)-10(-5) M) on spontaneous cAMP (5 x 10(4) cells/30 min)- and on LPS (10 microg/ml)-stimulated LTB4 production (10(5) cells/4 h) were determined in normal monocytes in vitro.

RESULTS

Production of cAMP (n = 9) was significantly augmented in a dose-dependent manner by orciprenaline (30 +/- 8%) and theophylline (28 +/- 10%), but mostly by reproterol (127 +/- 8%) at 10(-5) M. Despite incubation with propranolol, significant stimulation of cAMP production was notable following reproterol therapy. Production of LTB4 was significantly inhibited by reproterol (-48 +/- 14%) and less by theophylline (-28 +/- 10%), but was stimulated by orciprenaline (+20 +/- 8%) at 10(-5) M.

CONCLUSION

We conclude that reproterol exerts a strong stimulatory effect on monocyte cAMP production and a suppressive effect on LTB4 production possibly due to a synergistic mode of action on adenylate cyclase activity and inhibition of phosphodiesterases. More clinical studies in bronchial asthma will be needed to determine whether these results may translate into clinically relevant effects.

Enhancement by reproterol of the ability of disodium cromoglycate to stabilize rat mastocytes

The beta2-adrenoceptor agonist reproterol and disodium cromoglycate (DSCG) are used in fixed combination for the treatment of asthma, because they act on bronchial smooth muscle and inflammatory cells, respectively. Here, we investigated if reproterol can also act in rat mast cells in vitro to facilitate the inhibitory action of disodium cromoglycate (DSCG) on histamine secretion induced by compound 48/80. Reproterol was as potent as DSCG to inhibit histamine release in rat mast cells (32.8+/-6.0 vs. 36.7+/-6.2% at 1 microM of each compound, n=10 and n=8 respectively). Mast cell stabilization by DSCG (1-100 microM) was strongly and significantly enhanced in the presence of a fixed saturating concentration of reproterol (100 microM). Conversely, the combination of DSCG (1-100 microM) with the beta2-agonist used as reference compound, salbutamol (100 microM) did not inhibit histamine release more than DSCG alone. In combination with a saturating concentration of DSCG (100 microM), reproterol inhibited histamine release more than reproterol alone. The potent adenylate cyclase stimulator forskolin (50 microM) was able to inhibit histamine release to a similar extent as DSCG and significantly (P<0.05) enhanced the inhibition of histamine release by DSCG. Finally, the phosphodiesterase inhibitor theophylline (100 microM) was equipotent to reproterol and DSCG in stabilizing rat mast cells. In conclusion, reproterol enhances the ability of disodium cromoglycate to stabilize rat mast cells. This effect is not shared by salbutamol and can be, at least in part, independent of beta2-adrenoceptor stimulation.

Excretion study of the beta2-agonist reproterol in human urine

An excretion study of the beta2-agonist 7-[3-[(beta-3,5-trihydroxyphenethyl)amino]-propyl]theophylline (reproterol) in human urine, which is reportedly misused by athletes and horses as a doping agent, is presented. The study was performed after an oral administration of 20 mg of reproterol hydrochloride. The collected urine samples were prepared using the standard anabolic steroid extraction procedure and analyzed by gas chromatography coupled with quadrupole mass spectrometry and, also, with high-resolution mass spectrometry (HRMS). The main reproterol metabolite was found, whereas unchanged reproterol was not detected. The structure of the main metabolite was confirmed by an accurate HRMS measurement of diagnostic ions. Finally, an excretion urine profile of the main metabolite is presented. The mass spectrum of another possible unidentified reproterol metabolite is also reported.

Comparative effects of a fixed combination of reproterol hydrochloride and disodium cromoglycate with each agent alone on antigen-induced airway responses in sheep

The purpose of this study was to compare the effectiveness of an eight day treatment with clinically relevant doses of a fixed combination of the beta 2 mimetic reproterol hydrochloride and disodium cromoglycate with each agent given alone against antigen-induced early (EAR) and late airway responses (LAR) as well as post-antigen-induced airway hyperresponsiveness (AHR) in allergic sheep. Animals were treated in a randomized fashion with either the inhaled combination (n = 6), reproterol hydrochloride alone (n = 6), disodium cromoglycate alone (n = 6), or placebo (n = 8). Treatments (two puffs from a metered dose inhaler) were given three times a day for 7 days and once on the 8th day 1 h before airway challenge with Ascaris suum antigen. In the placebo trial, antigen challenge resulted in EAR and LAR as measured by increases in specific lung resistance; these changes were followed 24h later by AHR to inhaled carbachol. With respect to the placebo trial, treatment with reproterol hydrochloride reduced the EAR (P < 0.05) and blocked the LAR (P < 0.05), but had no effect on the post-challenge AHR. Treatment with disodium cromoglycate also reduced the EAR (P < 0.05), blocked the LAR (P < 0.05), and blocked the post-antigen-induced AHR (P < 0.05). Treatment with the fixed combination reduced the EAR (P < 0.05), blocked the LAR (P < 0.05), and blocked the post-antigen-induced AHR (P < 0.05). Comparison of the different agents indicated that the fixed combination gave significantly increased protection against the EAR than either agent alone, gave slightly better (P < 0.05) protection against the late response than cromolyn sodium and gave better protection against post-antigen-induced AHR than reproterol hydrochloride alone. These results suggest that a fixed combination of a beta 2-mimetic and disodium cromoglycate provides some increased protection against antigen-induced airway responses when compared to either agent alone in a controlled laboratory setting.

Superoxide radical scavenging by phenolic bronchodilators under aprotic and aqueous conditions

Asthmatic airway disease is accompanied by the appearance of inflammatory cells which produce reactive oxygen species (ROS). Therefore, the radical scavenging properties of the bronchodilators reproterol, fenoterol, salbutamol and terbutaline toward superoxide anion radicals and hydroperoxyl radicals were investigated in a model system by electron paramagnetic resonance spectroscopy (EPR) and photometric approaches. The substances under study showed activity in superoxide radical scavenging under aprotic and protic conditions as well. The efficiency of the reaction decreased in the order: fenoterol > salbutamol > reproterol > terbutaline > oxyfedrine when DMSO was used as an aprotic solvent. In an aqueous system, the rate constants decreased in the order: fenoterol > reproterol > salbutamol. It is suggested that the antioxidant effect of these beta2-agonists is an additional advantage in treatment of asthmatic lung disease, reducing the negative consequences of airway inflammation.

Tolerability and in vivo performance of a novel freon-free metered dose inhaler for a fixed combinational product of reproterol and disodium cromoglycate

The present study was conducted to describe and compare the in vivo performance (systemic exposure), clinical and laboratory safety of a fixed combinational product of inhaled reproterol (CAS 54063-54-6) plus disodium cromoglycate (DSCG; CAS 15826-37-6) using a novel freon (CFC)-free metered dose inhaler (MDI), which uses 1,1,1,2,3,3,3-heptafluoropropane (HFA-227; CAS 431-89-0) as propellant and polyoxyethylene glyceryl trioleate (Tagat TO; CAS 68958-64-5) as surfactant relative to the conventional freon-driven MDI Allergospasmin in healthy male and female volunteers. Twenty-four young male and female healthy subjects were randomly allocated in gender-balanced fashion to 4 parallel treatment groups with single and repeated dosing of either reproterol + DSCG by HFA- or CFC-MDI (each time N = 8) or placebo by HFA- or CFC-MDI (each time N = 4) using matched placebo devices thus allowing a double-blind (with regard to placebo) approach. Treatments consisted of a single morning dose of 2 actuations followed 4 days later by a 1 week treatment course of 2 actuations four times daily. Subjects were investigated extensively in terms of blood pressure, pulse rate, electrocardiography, spirometry, respiratory rate, body temperature, laboratory safety (haematology, clinical chemistry, urinalysis) and clinical well-being. There were no treatment, compound or device related effects for any of the tolerability and safety end points. The treatments were well tolerated. In particular, there was no irritative cough or any sign of broncho-irritation on application. Adverse events were reported in a total of 9 subjects: 3/8, 4/8, 0/4 and 2/4 subjects treated with reproterol + DSCG by HFA-MDI, reproterol + DSCG by CFC-MDI, placebo by HFA-MDI and placebo by CFC-MDI, respectively. Of these, 6 events in 6 subjects receiving the active treatments were considered probably or definitely related to the test drug administration (i.e. adverse drug reactions): after reproterol + DSCG one subject in each treatment group (HFA-MDI and CFC-MDI) complained of an unpleasant bitter taste immediately after application; one further subject in each group complained of headache. Under treatment with reproterol + DSCG by CFC-MDI one male subject complained of mild transient nausea with onset on day 5. Under treatment with reproterol + DSCG by HFA-MDI one female subject complained of mild dizziness and mildly disturbed (blurred) vision with onset on day 1. All adverse events occurred only transitory and required no treatment. Systemic exposure, evaluated by the plasma concentrations of DSCG at 1 h after application, was slightly higher with the HFA-MDI compared to the CFC-MDI. It is concluded that the safety, tolerability and in vivo performance of the newly developed freon-free MDI is at least as well tolerable as the already marketed freon-driven conventional formulation.

Rapid and automated determination of the beta2-agonist reproterol in human plasma by atmospheric pressure chemical ionisation high-performance liquid chromatography-tandem mass spectrometry

An on-line HPLC assay with tandem mass spectrometric detection for the fast and sensitive determination of reproterol in human plasma was developed, utilising a methylated structural analogue as the internal standard. Automated solid-phase extraction of diluted plasma samples, based on 250 microl plasma aliquots, at pH 6.5, allowed a reliable quantification of reproterol down to 400 pg/ml. Injection of 100 microl of plasma extracts onto a 30 mm x 4.6 mm reversed-phase guard column provided retention times ranging from 20 to 30 s for reproterol and the internal standard. The standard curves were linear from 0.2 to 200 ng/ml using weighted linear regression analysis (1/y2). The inter-assay and intra-assay accuracies were -0.9% and +3.2%, exhibiting a precision (C.V.) of +/- 11% and +/- 9.3%, respectively. Up to 100 unknowns may be analysed each 24 h per analyst.

Evaluation of the effect of different fatty acids on the percutaneous absorption of metaproterenol sulfate

The in vitro permeation rates of metaproterenol sulfate (MPS) across hairless mouse skin and TESTSKIN living skin equivalent were very low unless skin permeation enhancers were included in the vehicle. An optimum balance should be established between the chain length of the fatty acid and its molar ratio to MPS in order to enhance its penetration through the skin. Thus, the best flux values were shown by capric acid: MPS, 3:1 molar ratio, and lauric acid:MPS, 1:1 and 2:1 molar ratio, while myristic acid:MPS, 1:1 molar ratio, was the optimum under the experimental conditions used. The mechanism of the enhancing effect was examined by measuring 1H NMR spectra and the apparent partition coefficient of MPS, lauric acid, and the mixture. The apparent partition coefficient of MPS between n-octanol and water was higher for the mixture with lauric acid than for MPS alone. A 1:1 molar ratio formulation of MPS and lauric acid was selected for the in vivo permeation study. The data indicated that lauric acid increased the diffusivity of MPS in the skin by forming a complex and by affecting its partition coefficient between the skin and the delivery system.

A method for bioassay of potency and effectiveness of inhaled bronchodilators in normal subjects

1. Bioassay of inhaled bronchodilator drugs for potency and effectiveness in normal human subjects is rendered difficult and imprecise because bronchomotor tone is low. When attempting to determine log dose-effect relationships for inhaled, nebulised bronchodilator drugs and measuring increased specific airways conductance (sGaw), the coefficient of variation of each mean response is likely to be so large that an intermediate response is not significantly different from either the maximum or no response. 2. A method is described by which inhaled, nebulised bronchodilator drugs can be bioassayed for potency and effectiveness with high precision. The method involves the use of inhaled, nebulised bronchoconstrictor agents (methacholine or histamine) to provide a highly reproducible, near-constant, background reduction in airway conductance in normal human subjects. The activity of bronchodilators is assessed against this background reduction in airway conductance. 3. Log specific airway conductance (log sGaw) was chosen as the response metameter on grounds of normality of distribution and relative homoscedasticity. A central straight line segment of the bronchoconstrictor drug dose-effect curve extending over a 10-fold dose multiple could be found easily; the upper end of this segment occurred near 67-75% reduction in sGaw and was reproducible. 4. The effect of a dose bronchoconstrictor drug causing 67-75% reduction in sGaw waned linearly with time at first, over the effect segment corresponding to the linear segment of the drug's log dose-effect curve. The rate constant of local elimination of bronchoconstrictor drug from its site of action, in inhaled dose equivalents, was deduced from the ratio of the slopes of the linear segments of the log dose-effect and time-effect curves. 5. The maintenance dose rate to maintain the peak effect (67-75% reduction in sGaw) of the loading dose was calculated. The repeated administration of maintenance doses at regular short intervals, at this calculated dose rate, created a steady state of bronchoconstriction equal in extent to the effect of the loading dose. This steady state bronchoconstriction occurred without undue discomfort for the subject and was reproducible. 6. Against this background bronchoconstriction, inhaled, nebulised salbutamol produced a rapidly developing and slowly waning increase in sGaw. Reproducible log dose-effect curves for the bronchodilator drugs salbutamol and reproterol allowed measurement of their potency and effectiveness; the potency of reproterol relative to salbutamol was 0.082 with 95% confidence limits of 0.0504 and 0.131. 7. Estimation of the subject's pharmacodynamic and pharmacokinetic parameters for inhaled methacholine from just three dosage individualising sessions provides estimates accurate enough to be of practical value.

Cholinergic-adrenergic balance: Part 2. Relationship between drug sensitivity and personality

Sensitivity to the centrally active cholinomimetic physostigmine varies dramatically among healthy individuals. The elucidation of the reasons for this variability could contribute to the understanding of the pathophysiology of affective disorders where a cholinergic supersensitivity has been demonstrated. Therefore, personality characteristics and habitual stress-coping strategies were related to sensitivity to physostigmine in eight healthy male volunteers. Cardiovascular and behavioral responses tended to be positively correlated with irritability and emotional liability. Passive, "helpless" strategies for coping with stress were positively related to these responses. The metabolic and neuroendocrine responses to physostigmine were generally unrelated to personality. In view of putative beta-adrenergic disturbances in depression, the responses to the peripheral beta 2-adrenergic agonist reproterol were studied. Irritability and emotionality tended to be positively correlated with cardiovascular responses to reproterol as well as with reductions of heart rate by the peripheral cholinomimetic neostigmine.

Cholinergic-adrenergic balance: Part 1. Relationship between central and peripheral sensitivities

Eight healthy volunteers were studied under double-blind conditions after acute challenge with the peripheral beta 2-agonist reproterol, either alone or combined with the peripheral indirect cholinomimetic neostigmine. Their responses were also studied after administration of the centrally active indirect cholinomimetic physostigmine. The beta-adrenergic rise in heart rate was cholinergically suppressed. The beta-adrenergic rise of plasma cyclic adenosine monophosphate (cAMP) was not cholinergically modulated, while that of plasma glucose tended to be cholinergically suppressed. Physostigmine induced an anergic-anhedonic syndrome accompanied by physiological, metabolic, and neuroendocrine stress phenomena. The beta-adrenergic and cholinergic sensitivities, respectively, of the various parameters investigated tended to be nonsignificantly intercorrelated. Only a limited portion of the variance was explained by drug effects. Sensitivity to neostigmine was completely unrelated to sensitivity to physostigmine. Thus, cholinergic sensitivity seems not to be decisive for the fine tuning of the highly complex regulatory systems studied and peripheral sensitivity not to be representative for the central one, at least if unselective drugs like neostigmine and physostigmine are used.

[Effectiveness of various inhalation aids in children with bronchial asthma]

The effect on lung function of two puffs of a mixture of 1 mg disodium cromoglycate (DNCG) and 0.5 mg of reproterol hydrochloride (Aarane) administered by metered dose inhaler through 4 different spacer devices (Volumatic, Nebuhaler, InspirEase and Synchron-Aerosol) was tested in 18 asthmatic patients (age 8-15 years). There was no loss or gain in the effectiveness of treatment from the tested aerosol according to the type of inhalation device used.

Double-blind crossover study comparing sodium cromoglycate, reproterol, reproterol plus sodium cromoglycate, and placebo in exercise-induced asthma

Sixteen patients were included in the analysis of this double-blind crossover study comparing the effect of sodium cromoglycate, reproterol, sodium cromoglycate plus reproterol, and placebo in exercise-induced asthma. Both the sodium cromoglycate and the reproterol-containing treatment significantly inhibited exercise-induced asthma. The best protection is effected by the combination of sodium cromoglycate and reproterol. A synergistic effect of both medications could not be confirmed statistically so that their combined effect is simply additive.

Plasma levels, heart rate, and blood pressure after intravenous, oral, and aerosol administration of reproterol in man

Three healthy volunteers received single doses of reproterol (D 1959) by means of intravenous infusion, oral and aerosol application, respectively. Administrations were separated by at least 1 week. Plasma levels were measured by means of high performance liquid chromatography. After infusion, plasma levels showed a steep decline, indicative for a rapid distribution. Even though relatively large amounts of drug were given (up to 540 micrograms), this phenomenon caused reproterol levels to drop to values near or below the limit of reliable quantitation (1 ng ml-1) within 60 to 90 min. After oral administration of one or two tablets (containing 20 mg reproterol HCl per tablet), a very short lag time could be observed, indicating fast absorption. After one tablet, plasma level maxima (of plateau-type) were 5-6 ng ml-1 and 2-3 ng ml-1 in two subjects, respectively. After two tablets, plateau level maxima around 18 ng ml-1 and 9 ng ml-1 were found, respectively. After inhalation of a metered aerosol (two puffs of 500 micrograms each) the drug appeared in plasma within minutes, albeit at very low levels, and usually remained detectable at the sub-nanogram level during the time of the experiment (2 h). Due to the very low levels and to some oscillations in the plasma concentration-time curves, a detailed pharmacokinetic assessment could not be carried out. Effects on heart rate and blood pressure were negligible. Only during the infusion of high doses (540 micrograms) was there an increase in heart rate of about 50 to 120 beats min-1. Other side-effects were also negligible.

[Beta 2 stimulants in the therapy of childhood asthma]

Bronchial obstruction, chronic or acute, is due to different anatomical and functional events, mainly to smooth muscular contraction and oedema and secretions. In the first age of life the secretions and thickness of bronchial wool are the most important factors due to small bronchial caliber and poor muscular component. In the older child the most important cause is determined by the reactive spasm of bronchial smooth muscle.

[Intravenous infusion of reproterol (a beta-2-mimetic agent) in the therapy of severe asthma attacks in childhood]

20 children (age range 0.8-14.7 years) with acute severe asthma were alternately randomized to receive one of two different treatment regimes. 10 children (control-group) received Salbutamol inhalation (75 micrograms/kg in 2 ml Saline every two hours). 10 children (reproterol-group) received reproterol infusion (0.2-2.0 micrograms/kg/min in Saline) and inhaled Saline only. Other therapy regimen were identical in both groups: Theophylline infusion, i.v. Prednisolone, adequate fluids intake and oxygen insufflation. Age, severity and maintenance therapy of asthma, and severity of the acute episode, were not significantly different in both groups. Treatment efficacy, assessed with a simple clinical score, the heart and respiratory rates, the peak expiratory flow (PEF) and the blood gases, was comparable in both groups. Side effects, i.e. tachycardia, blood pressure changes and tremor, were also similar and clinically not relevant in both groups. In two children, who previously needed repeated mechanical ventilation, severe respiratory failure could be successfully controlled only when the reproterol dose was raised 10 folds (2.0 micrograms/kg/min). Reproterol infusion can be recommended in children with acute severe asthma, who do not respond satisfactorily to current therapy regimen, particularly in children who previously experienced numerous intubations.

Comparison of bronchodilator effects of Duovent and Reproterol in patients with chronic reversible airway obstruction

The bronchodilator effect of Duovent (a combination of a beta-2-agonist, fenoterol, and an anticholinergic, ipratropium bromide) was compared with that of Reproterol (a pharmacological hybrid which presents both resorcinol and theophylline portions) in 16 patients suffering from chronic reversible airway obstruction. Each of the 16 patients (14 males and 2 females, mean age 65.8 years) had a baseline FEV1 ranging from 30 to 70% of their predicted values (CECA values) (mean value +/- SE of the group: 1,238 +/- 78 ml), which increased at least 15% after the inhalation of two puffs of 400 micrograms fenoterol (percent increase of the group: 26.5 +/- 2%, mean +/- SE). This single-blind study was carried out on 3 different days, between 8:30 a.m. and 4:30 p.m. After measurement of the baseline functional parameters [FVC (forced vital capacity), FEV1 (1-second forced expiratory volume), and FEF25-75 (forced expiratory flow between 25 and 75% of vital capacity)], each patient was given two puffs of placebo the 2nd day, and either of Duovent (200 micrograms of fenoterol and 80 micrograms of ipratropium bromide) or of Reproterol (1 mg) the 1st or the 3rd day, at random. The measurements of functional parameters were repeated after 30, 120, 240, 360 and 480 min. Blood pressure, heart rate and possible side effects were recorded at the same time. Both Duovent and Reproterol, at all times, produced a statistically significant increase in FEV1 and FEF25-75.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchial and cardiovascular responses to inhaled reproterol in asthmatics: a double-blind placebo controlled dose-response study

Reproterol is a synthetic selective beta-adrenoceptor agonist with a xanthine side chain. The bronchial and cardiovascular responses to inhaled reproterol were studied in 14 asthmatics. The study was placebo controlled and double-blind, comparing doubling doses of reproterol from 500 micrograms-8 mg. The peak improvement in FEV1 showed a non-linear dose-response, with an initial plateau at the 1 mg dose producing a mean increase in FEV1 of 17%, but significant further improvement at the 8 mg dose, producing a mean improvement of 29% in FEV1. The time taken for improvement in airways obstruction to start shortened with increasing doses. The duration of bronchodilation was dose-dependent, with the 8 mg dose showing a significantly longer duration of action than the lower doses. The time to drop below 75% of the maximum achieved bronchodilation was 125 min, and was independent of the dose. There were no significant changes in pulse or blood pressure at any dose. The study shows that reproterol is a well tolerated selective beta 2-adrenoceptor agonist whose duration of action and peak effect can be significantly increased by increasing the dose to 8 mg, without producing more unwanted effects.

Evaluation of reproterol's effectiveness in preventing exercise-induced bronchospasm in children

The authors have evaluated the effectiveness of the protection of a new beta 2-adrenergic compound, reproterol, against broncho-constriction induced by physical exercise in a group of individuals of paediatric age sensitive to broncho-stimulation. This study has been carried out comparing reproterol with salbutamol, using placebo as a control, following a randomized single-blind crossover trial. The provocation test has been performed following the instructions of the Italian Society of Paediatrics. The drugs have been administered in the oral liquid form at the dose of 0.28 mg/kg and 0.1 mg/kg of reproterol and salbutamol, respectively. The two substances have shown a similar preventive effectiveness in controlling exercise-induced asthma up to 2 hours from administration with reproterol having a stronger action at the beginning of the observation.

Isolation and characterization of metaproterenol-3-O-sulfate: a conjugate of metaproterenol in human urine

Metaproterenol (1-(3,5-dihydroxyphenyl)-2-isopropylaminoethanol) is primarily converted in humans to metaproterenol-3-O-sulfate following oral administration. Ion exchange column chromatography with a gradient of ammonium acetate buffer permitted the isolation of the ammonium salt of metaproterenol-3-O-sulfate from human urine. Treatment of aliquots of the column eluate with purified sulfatase and subsequent HPLC/fluorescence analysis confirmed the presence of metaproterenol. Comparison of the column eluate with a metaproterenol standard by 250-MHz proton-NMR revealed a pattern consistent with monosubstitution of the resorcinol ring. Negative and positive ion fast atom bombardment/mass spectrometry showed the metabolite to have a (M-H)- m/z of 290 and a (M + H)+ m/z ion of 292. These three methods support the structural assignment of metaproterenol-3-O-sulfate. Enzymatic hydrolysis of urine specimens from 29 different subjects with purified beta-glucuronidase as well as beta-glucuronidase-sulfatase mixtures yielded no significant increase in metaproterenol beyond purified sulfatase-treated urine, thus ruling out the presence of a glucuronide of metaproterenol. Approximately 40% of an oral 20-mg dose, given as either a tablet or a solution, was recovered in the urine as metaproterenol-3-O-sulfate. Approximately 5% of the dose was recovered in the unconjugated form. The majority of the dose was excreted over the first 12 hr with a biological half-life of 5-6 hr followed by a slower excretion phase with a half-life of 20 hr.

The duration of protection from exercise-induced asthma by inhaled salbutamol, and a comparison with inhaled reproterol

beta-Adrenergic bronchodilators can prevent the development of exercise-induced asthma (EIA). To investigate the duration of this effect, we determined the time at which the protective effect of salbutamol diminished significantly in six subjects. All had stable asthma known to be triggered by exercise. Following a control exercise test, identical tests were repeated weekly at various times (1-6 hours) after inhalation of 200 micrograms of salbutamol. Significant protection (less than 75%) was lost in two subjects at 2 hours, in two at 4 hours and in two at 6 hours. A further exercise test was performed after inhalation of 1 mg of reproterol, at the time when salbutamol no longer afforded significant protection. There was a significantly smaller fall in peak expiratory flow rate after exercise (P less than 0.01) with reproterol than with salbutamol, at the same time after inhalation. There was no relationship between the degree or duration of protection from EIA and the bronchodilator effect of the drugs, the age and sex of the subjects, the length of asthma history or severity of base-line EIA, except perhaps the requirement for regular treatment with a steroid aerosol or sodium cromoglycate.

High-performance liquid chromatographic determination of reproterol in plasma using on-line trace enrichment and amperometric detection with a rotating working electrode

A method is described to determine nanogram quantities of reproterol in plasma. It consists of deproteinization of the plasma samples, on-line trace enrichment, and liquid chromatographic separation of the compounds brought on the analytical column, coupled with amperometric detection. Reliable quantitation can be done down to levels of 1 ng/ml.

In vitro effects of reproterol upon tracheo- bronchial, cardiac and cerebral adenylcyclase

In vitro researches documented that reproterol, as well as salbutamol, is a powerful stimulant of adenyl cyclase activity in the trachea and bronchi but less potent than isoprenaline. The stimulation was antagonized by beta-blockers.

Comparative studies of atropine methonitrate and its combination with reproterol in chronic airway obstruction

The therapeutic value of 80 micrograms atropine methonitrate delivered per metered aerosol and its combination with 450 micrograms reproterol was investigated in a controlled double-blind cross-over trial in 17 patients with chronic bronchitis and airway obstruction. All patients were atropine responders. According to the parameters of FEV1 and SGaw atropine methonitrate induced a statistically definite and clinically relevant bronchodilation for more than 3 h compared with placebo. The combination of 80 micrograms atropine methonitrate and 450 micrograms reproterol, however, proved to be clearly superior compared with the mono-compound atropine methonitrate.

Ocular hypertensive response to beta-adrenoceptor agonists

Acute administration of non-selective and relatively selective beta-adrenoceptor agonists elicit a monophasic fall in IOP. The present study indicates that unilateral application of certain beta-agonists on consecutive days can result in marked ocular hypertension. 1-Epinephrine, reproterol and 1-isoproterenol evoked an elevation of IOP on the second and third day after topical administration of a 2% solution in normal rabbits and in rabbits with surgically transected extraocular muscles. In contrast, the same concentration of d-isoproterenol produced hypotensive responses only when administered once daily for three consecutive days. Since d-isoproterenol did not cause a rise in IOP during chronic administration, the mechanism involved in the hypertensive response appears to be more sensitive to the levorotatory form. Administration of timolol inhibited the ocular hypertensive effect of epinephrine and reproterol. Since timolol lowers IOP by depressing formation of aqueous, it is suggested that the rise in IOP following chronic administration of beta-agonists possibly involves an increase in aqueous humor production.

[Postoperative respiratory therapy: bronchospasmolytic activity and side-effects of some recently introduced beta-sympatheticomimetic agents (author's transl)]

Intensive respiratory therapy is essential for reducing postoperative morbidity and mortality in older persons with pre-existing chronic obstructive pulmonary diseases. A new series of beta-adrenergic agents is being frequently used to effect bronchodilatation. Three substances from this group, viz.: reproterol (Bronchospasmin), terbutalin (Bricanyl) and fenoterol (Berotec) were examined in a randomized study in 90 patients. All three substances produced a significant increase in FEV1 and PEFR of up to 10.6 and 15.7 per cent respectively above the initial values. There were no significant differences between the three groups. Contrary to the results obtained by other investigators PaO2 fell in all groups. In the case of fenoterol this decrease was statistically significant with a mean value of 0.36 kPa. The causes for this fall in arterial oxygen pressure are still unknown. It may possible be due to an increased intrapulmonary right-left shunt as a result of increased cardiac output together with a ventilation-perfusion mismatch despite improved airways resistance. Since drastic falls by as much as 2.53 kPa have been observed during treatment with these agents they constitute a potential risk.

Inhibition of methacholine-induced bronchoconstriction with reproterol, a new beta agonist-xanthine derivative

This study compared the efficacy of single oral doses of a new beta adrenergic agonist-xanthine derivative, reproterol, with placebo by measuring the degree of induced bronchodilation and inhibition of response to methacholine challenge in patients with bronchial asthma. In comparison with placebo, 30 mg reproterol was an effective bronchodilator. Attenuation of the response, but not complete blockage of the methacholine-induced bronchoconstriction, was observed with 30 mg reproterol. Methacholine-induced bronchoconstriction is of use in assessing effect and mechanism of the action of new pharmacologic agents.

Inhibition of antigen-induced bronchoconstriction with reproterol, a new beta agonist-xanthine derivative

The purpose of this study was to compare the efficacy of a new bronchodilator, reproterol with standard bronchodilators terbutaline and theophylline in patients with allergic asthma. Efficacy was determined by measuring the initial bronchodilating effect and the inhibition of antigen-induced bronchoconstriction. In a double-blind, randomized, controlled study with single doses of medication, patients were given reproterol (20 mg and 30 mg), anhydrous theophylline (200 mg), terbutaline (5 mg) and placebo prior to challenge with antigen. Prior to administration of antigen both reproterol and terbutaline had measurable bronchodilating effect when compared to placebo. The bronchodilating effect of theophylline was less than placebo. In comparison to placebo both doses of reproterol and terbutaline significantly attenuated the response to antigen challenge whereas the effect of theophylline was negligible.

Reproterol and the muscle of the trachea and bronchi: in vitro and in vivo comparative studies with various drugs used in the treatment of asthma

In vitro in vivo reproterol showed intense spasmolytic effects upon the trachea and bronchi against various spasm-including agents (histamine, acetylcholine, acetyl-beta-methylcholine, 5-hydroxytryptamine, BaCl2). A comparative study with various drug used in the treatment of asthma (isoprenaline, metaproterenol, salbutamol, clenbuterol, papaverine and atropine) has been conducted.