The effect of ipratropium and fenoterol on methacholine-histamine-induced bronchoconstriction

Methacholine challenge testing: comparative pharmacology

Standardization of the methacholine inhalation challenge, the most common direct bronchoprovocation test, is important. One aspect of standardization is the appropriate washout period for pharmacologic agents which affect the response. This review summarizes the available data on pharmacologic inhibition of the methacholine response. Specific (anti-muscarinic) agents demonstrate marked bronchoprotection (up to 7 days for the long-acting drugs) which lasts longer than the duration of bronchodilation. The functional antagonist (beta 2 agonist class of medications) shows marked, but less, bronchoprotection which is relatively short lived and is similar to the duration of bronchodilator efficacy. Tolerance develops quickly, especially to the long-acting agents. Single doses of controller medications, such as inhaled corticosteroids (ICS) and leukotriene receptor antagonists, have no effect on the methacholine test, while regular use, at least for ICS, has a modest protective effect whose duration is uncertain and likely variable. Theophylline has a small effect and H1 blockers (all generations) have a negligible effect.

[Occurrence of delayed symptoms after a challenge test with methacholine]

There are few prospective studies available on the development of delayed symptoms following challenge tests with methacholine (MCT) at the currently recommended doses. The objective of this study was to describe the nature and frequency of respiratory symptoms suggestive of bronchospasm developing within 24hours after a MCT. The study was offered to adult patients who underwent MCT seen consecutively between June and October 2015. Following the test, a questionnaire adapted from the GINA asthma control questionnaire bearing on diurnal and nocturnal symptoms (cough, dyspnoea, wheeze and tightness), was delivered to the patient and the replies collected by telephone 24hours later. Of the 101 patients included (initial FEV1 2.82±0.79L), 46 (46 %) were MCT+ and 55 (54 %) MCT-. Among the MCT-, 4 (7 %) presented with immediate symptoms (S+) and 4 (7 %) with delayed symptoms. Among the MCT+ patients, 36 (78 %) presented with immediate symptoms (P<0.001 compared with the MCT- patients), and 39 (85 %) with delayed symptoms (P<0.001 compared with the MCT- patients). Delayed symptoms developed with a mean of 5h30 after the provocation test. Immediate and delayed symptoms were more frequent in subjects having significant non-specific bronchial hyper-reactivity. Informing patients of the risk of developing delayed symptoms seems useful and allows optimization of their management after a MCT.

Anticholinergic therapy for chronic asthma in children over two years of age

BACKGROUND

In the intrinsic system of controlling airway calibre, the cholinergic (muscarinic) sympathetic nervous system has an important role. Anticholinergic, anti muscarinic bronchodilators such as ipratropium bromide are frequently used in the management of childhood airway disease. In asthma, ipratropium is a less potent bronchodilator than beta-2 adrenergic agents but it is known to be a useful adjunct to other therapies, particularly in status asthmaticus. What remains unclear is the role of anticholinergic drugs in the maintenance treatment of chronic asthma.

OBJECTIVES

To determine the effectiveness of anticholinergic drugs in chronic asthma in children over the age of 2 years.

SEARCH STRATEGY

The Cochrane Airways Group trials register and reference lists of articles were searched in January 2002.

SELECTION CRITERIA

Randomised controlled trials in which anticholinergic drugs were given for chronic asthma in children over 2 years of age were included. Studies including comparison of: anticholinergics with placebo, and anticholinergics with any other drug were included.

DATA COLLECTION AND ANALYSIS

Eligibility for inclusion and quality of trials were assessed independently by two reviewers.

MAIN RESULTS

Eight studies met the inclusion criteria.Three papers compared the effects of anticholinergic drugs with placebo, and a meta-analysis of these results demonstrated no statistically significant benefit of the use of anticholinergic drugs over placebo in any of the outcome measures used. The results of one of these trials could not be included in the meta-analysis but the authors did report significantly lower symptom scores with inhaled anticholinergics compared with placebo. However, there was no significant difference between ipratropium bromide and placebo in the percentage of symptom-free nights or days. Two trials studied the effects of anticholinergics on bronchial hyper responsiveness to histamine, by measuring the provocation dose of histamine needed to cause a fall of 20 % in FEV1 (PD 20). One study (comparing anticholinergics with placebo) reported a statistically significant increase in PD 20 but this was not found in another study (comparing anticholinergics with a beta-2 agonist). Both trials also examined the effect of anticholinergic drugs on diurnal variation in peak expiratory flow rate (PEFR) and reported no significant effect. Two studies compared the addition of an anticholinergic drug to a beta-2 agonist with the beta-2 agonist alone. Both trials failed to show any significant benefit from the long term use of combined anticholinergics with beta-2 agonists compared with beta-2 agonists alone. One trial compared the effects of oral and inhaled anticholinergic drugs with placebo. No statistically significant differences were found in any of the outcome measures except for a higher FEV1 / VC ratio and RV / TLC ratio with oral anticholinergic therapy when compared with placebo.

REVIEWER'S CONCLUSIONS

The present review summarises the best evidence available to date. Although there were some small beneficial findings in favour of anticholinergic therapy, there is insufficient data to support the use of anticholinergic drugs in the maintenance treatment of chronic asthma in children.

Virus associated immune and pharmacologic mechanisms in disorders of respiratory and cutaneous atopy

Anaphylaxis represents non-atopic immediate hypersensitivity, whereas manifestations of atopic immediate hypersensitivity include bronchial asthma, hay fever, allergic rhinitis, chronic urticaria, and atopic dermatitis. In spite similar antigen exposure, only a minority of the population shown some form of atopic disease. Atopic disease with its spontaneous pattern of familial occurrence cannot be induced at will.

The exact pathogenesis of atopy is yet to be elucidated. Two theories prevail: 1) atopy is a primary disorder of the immune system with sequelae in the various effector tissues; and 2) a concept of atopy as a primary autonomic imbalance, essentially beta adrenergic in character, with sequelae in effector cells, including those engaged in the production of antibodies. The autonomic imbalance is perceived as caused not by some disorder of the autonomic nervous system itself but by a defector functioning of its effector cells. These two concepts are not mutually exclusive. The IgE antibody, which mediates allergic reactions, is essentially identical with atopic reagin in various animal species.

The beta adrenergic theory regards atopic disorders (i.e., perennial and seasonal allergic rhinitis, bronchial asthma, and atopic dermatitis) not as immunologic diseases but as unique patterns of altered reactivities to a broad spectrum of immunologic, psychic, infectious, chemical and physical stimuli. The antigen-antibody interaction is given the same role as that of a broad category of nonspecific stimuli that function only to trigger the same defective homeostatic mechanism in the various effector cells involved in immediate hypersensitivities. Current evidence favors the possibility that there are inherited and/or acquired multiple abnormalities in the receptor—adenylate cyclase—cyclic AMP system of all effector cells that are critical in the organization of immune reactivities.

Atopic abnormality may be 1) acquired by functional receptor regulatory shifts caused by hormonal changes, infection (viral, bacterial, etc), allergic tissue injury or other event; 2) genetically determined; or 3) caused by autoimmune disease. One, two or all three of these effector mechanisms may be operative in a particular disease.

There is an important relationship between asthma and viral respiratory infection. A history of childhood viral respiratory illness is a risk factor for the development of chronic obstructive airway syndromes in later life. Asthmatic attacks occurred only when the infection produced fever, malaise, cough or coryza. The dominant role of fever in these episodes immediately suggests the profound involvement of adrenergic effector mechanisms. The presence of autoantibodies to beta-adrenoceptors in patients correlated well with a reduced beta—and an increased alpha-adrenergic responsiveness. Virus infections can elicit autoantibody formation.

In patients with atopic dermatitis an increased susceptibility and abnormal host response to viral infections in general. Defective cytotoxic T cells, abnormally functioning macrophages and natural killer cells, a reduced production of IFNα in children, and of IFNγ in atopic patients with food allergy has recently been demonstrated. Lymphocytic cyclic AMP-phosphodiesterase, that destroys cyclic AMP, is increased in atopic dermatitis and in allergic respiratory disease of adults, and this increased activity correlated closely with histamine release from basophils. Peripheral blood leukocytes and lymphocytes in atopic dermatitis have frequently demonstrated impaired beta adrenergic reactivity.

Allergic tissue injury may be initiated by antigen-specific IgE antibodies that combine with Fcε receptors on various cell types and trigger mediator release upon encounter with the antigen. Various noxious agents that are capable of triggering asthma are capable of releasing inflammatory mediators from the same target cells. Accounting only for those pharmacologic mediators where the cell-type has been identified, the spectrum of mediator-storing, synthesizing, or transporting cells includes neutrophil leucocytes, basophilic leucocytes eosinophilic leucocytes; mast cells, “chromaffin-positive” mast cells, enterochromaffin cells, chromaffin cells; platelets, neurosecretory cells and nerve cells that potentially produce all amine-mediators as well as prostaglandins and kinins.

Lung deposition and protective effect of terbutaline delivered from pressurized metered-dose inhalers and the Turbuhaler in asthmatic individuals

We investigated the relationship between pulmonary deposition of terbutaline and bronchoprotection against methacholine and histamine with the Turbuhaler (AstraZeneca, Lund, Sweden) and a pressurized metered dose inhaler (pMDI) in 13 asthmatic patients. The study was done with a randomized, double blind, double dummy, and crossover design. On different days, the provocative concentration of histamine causing a 20% decrease in FEV(1) (PC(20) histamine) and PC(20) methacholine were determined before and at 1.5, 3, and 6 h after inhalation of 0.25 or 0.5 mg of terbutaline sulfate. The Turbuhaler delivered significantly more drug than did the pMDI (% of the nominal metered dose and 95% confidence interval): 20.8% (16.4 to 26.6%) and 16.9% (13.2 to 21.7%) versus 4.8% (3.8 to 6.1%) and 7.4% (5.8 to 9.5%), respectively. Average protection against histamine over 6 h was 0.66 (95% CI: 0.45 to 0.87) doubling concentrations (DC) after inhalation of 0.25 mg and 1.08 (95% CI: 0.87 to 1.29) DC after 0.5 mg terbutaline via pMDI, and 1.07 (95% CI: 0.87 to 1.29) DC after 0.25 mg and 1.24 (95% CI: 1.03 to 1.45) DC after 0.50 mg via Turbuhaler. Protection against methacholine was also dose- and device-dependent. The dose needed to obtain the same pulmonary deposition with the pMDI was 3.14 times greater than with the Turbuhaler, and that needed for the same protective effect was 2.1 and 3.2 times greater for histamine and methacholine, respectively. We conclude that pulmonary deposition of terbutaline was predictive of the clinical response.

Effects of a beta2-agonist on airway hyperreactivity in subjects with cervical spinal cord injury

STUDY OBJECTIVE

Aerosolized ipratropium bromide or orally administered baclofen or oxybutynin chloride (Ditropan) block methacholine-associated airway hyperreactivity in subjects with chronic cervical spinal cord injury (SCI), whereas these agents do not inhibit airway hyperreactivity associated with the inhalation of histamine. The present study was performed to determine whether pretreatment with a beta2-agonist attenuates airway hyperresponsiveness in these subjects.

PARTICIPANTS

Subjects with chronic cervical SCI previously demonstrating airway hyperreactivity were challenged with methacholine (n = 9) or histamine (n = 16) alone and, on a separate day, 25 min following inhalation of nebulized metaproterenol sulfate.

RESULTS

Inhalation of the beta2-agonist was associated with an increase in provocative concentration causing a 20% decrease in FEV1 (PC20) values (geometric mean) from 1.01+/-2.76 to 20.54+/-6.24 mg/mL for methacholine and from 2.29+/-2.26 to 19.82+/-5.93 mg/mL for histamine. No correlation was found between specific PC20 values for individual subjects and percentage improvement in FEV1 (liter) following inhalation of metaproterenol sulfate and between PC20 values and baseline FEV1 percent.

CONCLUSION

These data, combined with findings that patients with chronic high cervical SCI experience increased breathlessness following exposure to exogenous agents, suggest that long-term prophylactic beta2-agonist therapy may reduce respiratory symptoms associated with airway hyperreactivity in these patients.

Protective effects of different doses of inhaled fenoterol on methacholine-induced bronchoconstriction in asthmatic children

OBJECTIVE

To evaluate the protective effect of different doses of inhaled fenoterol (F) on bronchoconstriction induced by methacholine (M).

DESIGN

Randomized double-blind study.

SETTING

Referrence center.

PARTICIPANTS

9 children (aged from 7 to 15 years old), with mild or moderate asthma and allergic to D. pteronyssinus.

INTERVENTION

On the first day, the M concentration necessary to induce a 20% fall in the forced expiratory volume in the first second (FEV1; PC20FEV1) was determined using closed circuit inhalation (De Vilbiss 646). On subsequent days, the children inhaled a dose of F (25 or 50 or 100 or 200 micrograms) through the same circuit and, after 15 minutes the FEV1 was measured, becoming the basal value. Bronchoprovocation was then initiated using the concentration prior to the PC20FEV1 of the first day and continuing until there was a 20% fall in the FEV1. This concentration was the "new" PC20FEV1.

RESULTS

F in a dose of 25 micrograms protected 2 of the 9 children, in a dose of 50 mg protected 4 of the 9 and in doses of 100 and 200 micrograms protected all children. We did not observe any relationship between the magnitude of the bronchodilation and bronchoprotection induced by the inhalation of F.

CONCLUSIONS

Our results suggest that a dose of 100 micrograms of F is capable of inducing bronchoprotection in children with mild/moderate asthma.

The effects of ipratropium bromide on histamine-induced bronchoconstriction in subjects with cervical spinal cord injury

Previously, we reported that a majority of subjects with chronic cervical spinal cord injury (SCI) demonstrated airway hyperreactivity in response to inhaled methacholine. To further investigate mechanisms of airway hyperreactivity, 15 male subjects with cervical SCI were challenged with aerosolized histamine, and on a separate day responders were rechallenged 30 min after the inhalation of 72 micrograms of ipratropium bromide. Twelve of 15 subjects demonstrated airway hyperresponsiveness to histamine (geometric mean PC20 of 1.27 mg/ml), which was not blocked by pretreatment with ipratropium bromide (geometric mean PC20 1.50 mg/ml). Baseline forced vital capacity and forced expiratory volume in 1 sec were not significantly different between responders and nonresponders (2.8 +/- 0.6 vs. 3.0 +/- 0.4 L and 2.3 +/- 0.6 vs. 2.4 +/- 0.2 L, respectively). Findings that subjects with cervical SCI are hyperresponsive to methacholine and histamine, chemical agents with direct action through distinct receptor systems, suggest that bronchial hyperreactivity in these subjects represents a nonspecific process similar to that observed in patients with asthma.

A method for measuring the effects of anticholinergics on histamine-induced bronchoconstriction in normal subjects. Oxitropium bromide provides dose-dependent protection

To study whether it would be possible to assess anticholinergic drugs in normal subjects with histamine-(HIST) induced bronchoconstriction, three doses of oxitropium bromide (100, 200 and 400 micrograms) was inhaled in random order by twelve normal volunteers in a single-blind, placebo-controlled study. Dose response slope [DRS = maximal percentual fall in pulmonary function/maximal noncumulative histamine dose (mumol)] was used as an index of bronchial reactivity, and was calculated for FEV1 (DRSFEV1) and area under the flow-volume curve (DRSAEFV). The bronchial reactivity and its reproducibility was first tested with a standard provocation method. An abbreviated, single-dose, method was used in the measurement of the effects of oxitropium. The reproducibility of HIST-provocations were good with intraclass correlations of 0.97 and 0.99 for logDRSFEV1 and logDRSAEFV, respectively. However, DRSAEFV seemed to be better in this respect as DRSFEV1. Also, the single-dose method gave results that were comparable to the standard one. The largest dose of oxitropium diminished the median DRS from 2.6 to 0.01 and from 5.2 to -0.2 for FEV1 and AEFV, respectively. All oxitropium doses differed significantly from placebo (P < 0.01) and from each other (P < 0.05) with DRSAEFV-values, but when DRSFEV1 was used, a significant difference was detected only between placebo and active treatment (P < 0.01). In conclusion, since the vagal mechanisms seem to be the predominant system mediating HIST-induced bronchoconstriction in normal subjects, it is possible with DRSAEFV to evaluate the efficacy of anticholinergics against HIST-induced bronchoconstriction in these subjects.

Effects of beta 2-receptor agonists on airway responsiveness

Airway hyper-responsiveness is one of the characteristics of asthma. It may be distinguished by airway hyper-sensitivity and an increase of the maximal response plateau. Short-acting beta 2-agonists have an acute protective effect on airway sensitivity, which is shorter in duration than the bronchodilating effect, without affecting the maximal response plateau. Long-term treatment has no beneficial effect on airway responsiveness. A diminishment of the protection against metacholine- and histamine-induced airway obstruction and a rebound increase of this after cessation of continuous treatment have been reported. Single doses of long-acting beta 2-agonists give a prolonged protection against methacholine- and histamine-induced airway sensitivity of at least 12 hours. A small decrease in the maximal response plateau has been noted. Currently, there is little data on long-term treatment. One study has described the development of tolerance to the protecting effect on methacholine-induced airway sensitivity after 2 months treatment. However, a protection by 1.0 doubling dose remained and the bronchodilating effect was not influenced. So far, no rebound increase in airway sensitivity has been reported after cessation of continuous treatment.

Effects of corticosteroids on bronchodilator action in chronic obstructive lung disease

BACKGROUND

Short term treatment with corticosteroids does not usually reduce airflow limitation and airway responsiveness in patients with chronic obstructive lung disease. We investigated whether corticosteroids modulate the effects of inhaled salbutamol and ipratropium bromide.

METHODS

Ten non-allergic subjects with stable disease were investigated; eight completed the randomised, double blind, three period cross over study. Treatment regimens consisted of 1.6 mg inhaled budesonide a day for three weeks, 40 mg oral prednisone a day for eight days, and placebo. After each period cumulative doubling doses of salbutamol, ipratropium, a combination of salbutamol and ipratropium, and placebo were administered on separate days until a plateau in FEV1 was reached. A histamine challenge was then performed.

RESULTS

At the end of placebo treatment mean FEV1 was 55.5% predicted after inhaled placebo, 67.9% predicted after salbutamol and 64.0% predicted after ipratropium. Compared with the results after the placebo period the FEV1 with salbutamol increased by 0.7% predicted after treatment with budesonide and by 0.7% predicted after treatment with prednisone; the FEV1 with ipratropium increased by 0.7% predicted after budesonide and by 4.8% predicted after prednisone; none of these changes was significant. After placebo treatment the geometric mean PC20 was 0.55 mg/ml after placebo, 1.71 mg/ml after salbutamol and 0.97 mg/ml after ipratropium. Compared with the placebo period the PC20 with salbutamol was increased by 0.86 doubling concentrations after treatment with budesonide, and by 0.67 doubling concentrations after prednisone; the PC20 with ipratropium increased by 0.03 and 0.34 doubling concentrations after budesonide and after prednisone respectively compared with placebo; none of these changes was significant.

CONCLUSIONS

In non-allergic subjects with chronic obstructive lung disease short term treatment with high doses of inhaled or oral corticosteroids does not modify the bronchodilator response to salbutamol or ipratropium or the protection provided by either drug against histamine. Salbutamol produces greater protection from histamine induced bronchoconstriction than ipratropium.

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

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

The protective effect of a beta 2 agonist against excessive airway narrowing in response to bronchoconstrictor stimuli in asthma and chronic obstructive lung disease

Beta 2 agonists reduce airway hypersensitivity to bronchoconstrictor stimuli acutely in patients with asthma and chronic obstructive lung disease. To determine whether these drugs also protect against excessive airway narrowing, the effect of inhaled salbutamol on the position and shape of the dose-response curves for histamine or methacholine was investigated in 12 patients with asthma and 11 with chronic obstructive lung disease. After pretreatment with salbutamol (200 or 400 micrograms) or placebo in a double blind manner dose-response curves for inhaled histamine and methacholine were obtained by a standard method on six days in random order. Airway sensitivity was defined as the concentration of histamine or methacholine causing a 20% fall in FEV1 (PC20). A maximal response plateau on the log dose-response curve was considered to be present if two or more data points for FEV1 fell within a 5% response range. In the absence of a plateau, the test was continued until a predetermined level of severe bronchoconstriction was reached. Salbutamol caused an acute increase in FEV1 (mean increase 11.5% predicted in asthma, 7.2% in chronic obstructive lung disease), and increase in PC20 (mean 15 fold in asthma, fivefold in chronic obstructive lung disease), and an increase in the slope of the dose-response curves in both groups. In subjects in whom a plateau of FEV1 response could be measured salbutamol did not change the level of the plateau. In subjects without a plateau salbutamol did not lead to the development of a plateau, despite achieving a median FEV1 of 44% predicted in asthma and 39% in chronic obstructive lung disease. These results show that, although beta 2 agonists acutely reduce the airway response to a given strength of bronchoconstrictor stimulus, they do not protect against excessive airflow obstruction if there is exposure to relatively strong stimuli. This, together with the steepening of the dose-response curve, could be a disadvantage of beta 2 agonists in the treatment of moderate and severe asthma or chronic obstructive lung disease.

Measuring the bronchial effect of bronchodilating drugs in healthy subjects after methacholine provocation. Salbutamol as a model drug

To study whether it would be possible to assess bronchodilating drugs in healthy subjects with methacholine - induced bronchoconstriction, salbutamol 100, 200 and 300 micrograms was inhaled in random order by 12 healthy volunteers in a double-blind, placebo-controlled study. Dose response "slope" (DRS = maximum percentage fall in pulmonary function/maximal noncumulative methacholine dose (mumols] was used as an index of bronchial reactivity, and was calculated for forced expiratory flow volume in 1 s (DRSFEV1) and area under the flow-volume curve (DRSAEFV). Bronchial reactivity and its reproducibility were first tested by a standard methacholine provocation method. An abbreviated, single-dose method was used to measure the effect of salbutamol. The reproducibility of methacholine provocation was good, and the single-dose and standard methods gave comparable results. The DRS-values of all the doses of salbutamol differed significantly from placebo and from each other. AEFV did not show any advantage over the FEV1 in this context. A significant negative association between the dose of salbutamol (microgram/kg) and airway reactivity was observed. In conclusion, use of the DRS showed it possible to evaluate the protective efficacy of beta 2-adrenergic agonists against induced bronchoconstriction in healthy subjects.

Reproducibility of methacholine induced bronchoconstriction in healthy subjects: the use of area under the expiratory flow-volume curve to express results

The usefulness of the pulmonary function variable, area under the expiratory flow-volume curve (AEFV), in methacholine provocation (MP) studies in normal subjects was evaluated. The baseline coefficients of variation (CV), maximal fall from post-saline values (MAX) and dose-response slope [DRS = maximal percentage fall in pulmonary function/maximal noncumulative methacholine dose (mumol)] were calculated for AEFV, and were compared to those of forced expiratory volume in one second (FEV1), maximum expiratory flow at 50% (MEF50%) and at 25% (MEF25%). Also the repeatability after 2 and 8 weeks was assessed. The rank order of CVs was FEV1 less than AEFV less than MEF50% approximately MEF25% all differences, except MEF50% vs. MEF25%, being significant (P less than 0.05). The order of sensitivities (estimated with MAX and DRS) was FEV1 less than AEFV less than MEF50% less than MEF25%. Again, all differences were significant (AEFV vs. MEF50% P less than 0.01, others P less than 0.001). After two weeks the correlation coefficients for MAX- and DRS-values of AEFV were 0.84 and 0.94 (P less than 0.001), respectively. After an eight week period the correlations were still high, 0.86 and 0.92 (P less than 0.001), respectively, but the actual MAX- and DRS-values tended to be smaller than eight weeks before. The repeatability of MAX of AEFV was not quite as high as that of FEV1. On the other hand, the correlations of DRS-value derived from AEFV were markedly better than those derived from FEV1. In conclusion, MP in normal subjects is well repeatable at least within two weeks, but after an eight week period disturbing factors may intervene reducing repeatability. AEFV can be considered at least as good a pulmonary function variable as FEV1 in demonstrating bronchoconstriction during MPs in normal subjects, and it might even be a better variable to obtain DRS-values than other variables tested.

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

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

Effect of yoga breathing exercises (pranayama) on airway reactivity in subjects with asthma

The effects of two pranayama yoga breathing exercises on airway reactivity, airway calibre, symptom scores, and medication use in patients with mild asthma were assessed in a randomised, double-blind, placebo-controlled, crossover trial. After baseline assessment over 1 week, 18 patients with mild asthma practised slow deep breathing for 15 min twice a day for two consecutive 2-week periods. During the active period, subjects were asked to breathe through a Pink City lung (PCL) exerciser--a device which imposes slowing of breathing and a 1:2 inspiration:expiration duration ratio equivalent to pranayama breathing methods; during the control period, subjects breathed through a matched placebo device. Mean forced expiratory volume in 1 s (FEV1), peak expiratory flow rate, symptom score, and inhaler use over the last 3 days of each treatment period were assessed in comparison with the baseline assessment period; all improved more with the PCL exerciser than with the placebo device, but the differences were not significant. There was a statistically significant increase in the dose of histamine needed to provoke a 20% reduction in FEV1 (PD20) during pranayama breathing but not with the placebo device. The usefulness of controlled ventilation exercises in the control of asthma should be further investigated.

Comparative protective effect of the inhaled beta 2-agonist salbutamol (albuterol) on bronchoconstriction provoked by histamine, methacholine, and adenosine 5'-monophosphate in asthma

We have investigated the ability of salbutamol to protect against bronchoconstriction induced by methacholine, histamine, and adenosine 5'-monophosphate (AMP) in nine subjects with asthma. In a double-blind, placebo-controlled study, salbutamol, 2.5 mg administered by nebulization, increased the geometric mean provocation concentrations of methacholine, histamine, and AMP required to produce a 20% decrease in FEV1 from 0.3 to 2.2, 0.4 to 3.8, and 4.0 to 106.7 mg/ml after placebo and active treatment, respectively (p less than 0.01). Thus, this dose of beta 2-adrenoceptor agonist displaced the concentration-response curves for methacholine, histamine, and AMP to the right in a parallel fashion by 8.8 (0.6 to 29.3)-, 10.3 (1.4 to 33)-, and 26.6 (1.5 to 76.6)-fold, respectively, the difference between the results for AMP and those for histamine and methacholine being statistically significant (p less than 0.01). For six of the nine subjects studied, salbutamol displaced the concentration-response curve for AMP to the right by greater than 50-fold. There was no correlation between bronchodilatation and protection against bronchoconstriction induced by any of the agonists. We conclude that salbutamol protects against bronchoconstriction provoked by methacholine and histamine by functional antagonism, whereas with AMP, an additional activity is demonstrable, possibly involving inhibition of mast cell-mediator release.

Airways responses to ipratropium bromide do not vary with time in asthmatic subjects. Studies of interindividual and intraindividual variation of bronchodilatation and protection against histamine-induced bronchoconstriction

Bronchial histamine provocation tests were performed in nine patients with nonallergic asthma on four consecutive days 45 minutes after inhalation of placebo or ipratropium bromide in a dose-response manner (40 micrograms, 200 micrograms, and 800 micrograms). The drugs were administered double-blind, one dose on each day. This procedure was repeated identically after three to nine months to investigate whether the bronchial responses to ipratropium bromide are constant or change with time. Ipratropium bromide induced a significantly better bronchodilation and protection against histamine-induced bronchoconstriction than placebo with no differences between the three doses. No correlation between bronchodilatation and protection was found. In six asthmatic patients ("responders") ipratropium bromide induced a significant protective effect against histamine-induced bronchoconstriction but no dose-response relationship was found. In three patients none or a very poor protective effect was found at all dose levels ("nonresponders"). The protective effect of ipratropium bromide against histamine-induced bronchoconstriction did not differ between the first and second occasion. Thus, the bronchoprotection differed between different asthmatic subjects but did not vary with time (three to nine months) within the same subject. This finding seems to be of clinical importance since it implicates that the effect of anticholinergic agents on the airways is predictable.

The effect of nifedipine on bronchial reactivity to inhaled histamine and methacholine: a comparative study in normal and asthmatic subjects

The effect of pretreatment with nifedipine 20 mg sublingually on the bronchoconstrictor response to inhaled histamine and methacholine in asthmatic and normal subjects has been studied. For each agonist the provocation concentration required to produce a 15% fall in FEV1 (PC15) and a 35% fall in specific conductance (PC35) was determined. In the group of asthmatic subjects the responses to histamine were significantly attenuated by histamine, PC15 increasing from 0.29 mg/ml to 0.68 mg/ml (P less than 0.001) and PC35 increasing from 0.25 mg/ml to 0.58 mg/ml (P less than 0.001). Responses to methacholine showed less modification by nifedipine. PC15 increased from 0.23 mg/ml to 0.32 mg/ml (P less than 0.05). Changes in PC35 were not significant. In the group of normal subjects no attenuation of the response to methacholine was produced by nifedipine but significant increases of PC15 (P less than 0.002) and PC35 (P less than 0.005) were produced by the agent. The results are consistent with nifedipine exerting an effect principally on mediators dependent on external calcium sources for stimulus-contraction coupling in the airways. The magnitude of change in the histamine response of the two groups was similar, suggesting calcium dependent mechanisms are not involved in asthmatic hyper-responsiveness.

Corticosteroids and cromolyn sodium as modulators of airway inflammation

Heightened airway reactivity is a cardinal feature of asthma and correlates with many clinical features of the illness, such as the acute response to bronchodilator drugs, the magnitude of diurnal fluctuations in lung function, and the amount of therapy required to control symptoms. Data have accumulated indicating that a reduction in airway reactivity can decrease asthma morbidity, and many advocate treating asthmatic patients prophylactically to prevent acute exacerbations from developing, rather than responding to them after they have occurred. This approach is particularly effective if it is used when the airways are being exposed to stimuli to which they are sensitive. A number of drugs have been purported to reduce airway reactivity, but the most convincing evidence supports the effects of cromolyn and inhaled and oral steroids. Although each type of drug has its own advantages and disadvantages and different modes of action, the common denominator is believed to be a reduction in the state of airway inflammation.

Dose related effects of salbutamol and ipratropium bromide on airway calibre and reactivity in subjects with asthma

The relationship between change in airway calibre and change in airway reactivity after administration of bronchodilator drugs has been investigated by comparing the effect of increasing doses of inhaled salbutamol and ipratropium bromide on the forced expiratory volume in one second (FEV1), specific airways conductance (sGaw), and the dose of histamine causing a 20% fall in FEV1 (PD20) in six subjects with mild asthma. On each of 10 occasions measurements were made of baseline FEV1, sGaw, and PD20 after 15 minutes' rest, and followed one hour later, when the FEV1 had returned to baseline, by a single nebulised dose of salbutamol (placebo, 5, 30, 200 and 1000 micrograms) or ipratropium (placebo, 5, 30, 200 and 1000 micrograms) given in random order. Measurements of FEV1, sGaw, and PD20 were repeated 15 minutes after salbutamol and 40 minutes after ipratropium. Salbutamol and ipratropium caused a similar dose related increase in FEV1 and sGaw, with a mean increase after the highest doses of 0.76 and 0.69 litres for FEV1 and 1.15 and 0.96 s-1 kPa-1 for sGaw. Salbutamol also caused a dose related increase in PD20 to a maximum of 2.87 (95% confidence interval 2.18-3.55) doubling doses of histamine after the 1000 micrograms dose, but ipratropium bromide caused no significant change in PD20 (maximum increase 0.24 doubling doses, 95% confidence interval -0.73 to 1.22). Thus bronchodilatation after salbutamol was associated with a significantly greater change in airway reactivity than a similar amount of bronchodilatation after ipratropium bromide. This study shows that the relation between change in airway reactivity and bronchodilatation is different for two drugs with different mechanisms of action, suggesting that change in airway calibre is not a major determinant of change in airway reactivity with bronchodilator drugs.

Long term study of the effect of sodium cromoglycate on non-specific bronchial hyperresponsiveness

A double blind, crossover study was undertaken to determine whether non-specific hyperresponsiveness in subjects with asthma was reduced by long term treatment with sodium cromoglycate and, if so, whether this was related to change in lung function. Forty four adult asthmatic subjects (41 atopic, three non-atopic) entered the one year study at intervals staggered over six months. After a baseline period to ensure that asthma control was stable subjects entered the treatment period, during which they inhaled sodium cromoglycate 20 mg four times daily or matching placebo four times daily for 16 weeks each, in random order. Response was assessed at four weekly intervals by measurement of lung function and histamine inhalation tests, from which the provocative concentration of histamine causing a 20% fall in FEV1 (PC20H) was calculated. The assessment included daily symptom score, morning and evening Airflow-meter readings and treatment; mean values for each treatment period and also for the final four weeks of each period were compared. There were no significant differences between placebo and sodium cromoglycate treatment for PC20H, FEV1, morning or evening flow meter readings, bronchodilator usage, or symptom scores for the group as a whole, for the 16 week period or for the final four weeks of each period. Thirteen subjects showed better morning and evening flow meter readings while taking sodium cromoglycate than while taking placebo and eight better readings with placebo than with sodium cromoglycate (p less than 0.05). Improvement in lung function did not correlate with baseline lung function or baseline PC20H, or with features of atopy. These results suggest that long term sodium cromoglycate treatment does not alter non-specific bronchial responsiveness in adult asthmatic subjects.

Combined bronchodilator protection against histamine-induced bronchoconstriction in man

Sixteen stable asthmatics had the protective effects of inhaled fenoterol (200 micrograms) and inhaled ipratropium bromide (60 micrograms) against standardized histamine inhalation tests at 1 h examined in a randomized double blind fashion. There was no significant difference in the baseline forced expired volume in 1 s (FEV1) for the two study days (P greater than 0.05). There was an increase in FEV1 at 1 h on the fenoterol and ipratropium day compared with the fenoterol day (0.26 versus 0.17 l; P less than 0.05). The geometric mean provocative concentration of histamine to cause a 20% fall in FEV1 (PC20) was 6.31 mg/ml after fenoterol and 8.51 mg/ml after fenoterol and ipratropium (P = 0.038). There was no significant relationship between bronchodilator effect of the bronchodilators and the increase in PC20 from pre-study values, r = 0.307 (P = 0.25) for fenoterol alone and r = 0.195 (P = 0.47) for fenoterol and ipratropium. The relationship between pre-study histamine responsiveness and the increase in PC20 caused by the bronchodilators just failed to reach statistical significance, r = -0.441 (P = 0.09) for fenoterol alone and r = -0.47 (P = 0.06) for fenoterol and ipratropium. The study has shown a greater right shift of histamine responsiveness for combined inhaled fenoterol and ipratropium compared with inhaled fenoterol alone in this group of asthmatics.

Review of ipratropium bromide in induced bronchospasm in patients with asthma

This article reviews published reports on the efficacy of ipratropium bromide in preventing stimulus-induced bronchospasm in patients with asthma. The efficacy of ipratropium was assessed by its influence on airway constrictor responses to various bronchoprovocation stimuli; effects of medication on resting (pre-challenge) pulmonary functions were considered separately. The results indicate that administration of a single dose of ipratropium 30 to 90 minutes before challenge offers some protection against induced bronchospasm. However, in most instances, including challenge with histamine, allergen, or exercise, the protection is variable and incomplete; as expected, the anticholinergic drug provides better protection when the stimulus is methacholine. Most bronchoprovocation stimuli evoke mixed-airway responses with constriction of peripheral as well as central airways. The effects of ipratropium are exerted predominately on central airways. Other therapeutic agents, such as the beta agonists, with more influence on small, peripheral airways, offer greater protection than ipratropium on stimulus-induced bronchospasm.

Ipratropium bromide in asthma. A review of the literature

In comparative studies of asthma, ipratropium bromide has been shown to have a slower onset of bronchodilator action but a longer duration of effect than beta agonists. An additive effect of ipratropium and beta agonists has been demonstrated, in addition to prolongation of the bronchodilator response. Most studies do not show a definite difference in responsiveness of atopic versus nonatopic asthmatic patients; there are, however, reports indicating a greater responsiveness to anticholinergic agents than to beta agonists in patients with chronic bronchitis and emphysema. Ipratropium has been shown not to affect mucociliary clearance, sputum volume, or viscosity. It effectively inhibits the bronchial response to methacholine and, to a lesser degree, to histamine, serotonin, bradykinin, and antigen. Protection against exercise-induced asthma with this drug has been variable, but ipratropium has been found particularly useful in psychogenic asthma. Its role in occupational asthma remains to be determined.

Specific antagonism of adenosine-induced bronchoconstriction in asthma by oral theophylline

The airway response to increasing concentrations of inhaled-adenosine and histamine after oral theophylline or matched placebo was studied in nine asthmatic subjects. Changes in airway calibre were followed as sGaw and FEV1 and concentration-response curves constructed. Inhaled adenosine caused concentration-related bronchoconstriction and was four-five times less potent than inhaled histamine. Theophylline, which achieved a mean plasma level of 15.9 and 16.6 micrograms/ml on the histamine and adenosine study days respectively, caused significant increases in FEV1 (17%) and sGaw (41-53%) whereas placebo had no effect. Theophylline also protected the airways against histamine-and adenosine-induced bronchoconstriction. However theophylline had a greater protective effect against adenosine (concentration-ratio 17.4 for FEV1 and 12.8 for sGaw) than against histamine (concentration ratio 5.6 for FEV1 and 5.4 for sGaw (P less than 0.05]. At therapeutic concentrations theophylline is a specific antagonist of the airway effects of adenosine in addition to being a bronchodilator and a functional antagonist.

Protective effect by UCB JO28 against histamine and methacholine induced bronchial hyperreactivity

UCB JO28 [( 2-[2-[4-(diphenylmethylene)-1-piperidinyl] ethoxy] ethoxy] acetic acid, hydrochloride) is derived from diphenylmethylene piperidine. Animal experiments have shown that it has spasmolytic properties for smooth muscle, particularly in the bronchi, as well as anti-Hl, anticholinergic and anti-serotonin activities. The degree of protection by JO28 against histamine and methacholine-induced bronchospasm has been investigated in 20 asthmatic patients with serious airways hyper-reactivity. Protection against histamine-induced bronchospasm was almost complete in 11 out of 12 patients, whereas protection against methacholine-induced bronchospasm, although clearly present in seven of eight patients, was less marked.

Protective effect of oral oxyphenonium bromide, terbutaline and theophylline against the bronchial obstructive effects of inhaled histamine, acetylcholine and propranolol

The protective effects of oxyphenonium bromide, terbutaline and theophylline were compared in 8 asthmatic patients by determination of the degree of non-specific airway reactivity after 1 week of oral treatment according to a fixed dose scheme in a double-blind random order: oxyphenonium bromide 3 X 10 mg; terbutaline 3 X 5 mg; theophylline 2 X 300 mg and placebo. Controlled, standardized inhalation provocation tests were carried out with histamine, acetylcholine and propranolol. The study was monitored by measuring blood concentrations of the 3 drugs, and their effect on the plasma cAMP concentration was also determined. Significant protection by oxyphenonium bromide against the bronchial obstructive effects of acetylcholine and propranolol was observed, but not against the effect of inhaled histamine. The other two drugs provided no significant protection against the inhaled agents. The absence of any protective effect of terbutaline and theophylline might have resulted from too low a blood concentration. The observed differences in protection could not be explained by changes in pulmonary function. The study suggests dissociation between the bronchodilating effect of a drug and its protective effect against inhaled substances.

Variable inhibition of histamine-induced bronchoconstriction by atropine in subjects with asthma

To determine whether treatment with atropine causes dose-dependent inhibition of histamine-induced bronchoconstriction, we constructed dose-response curves to inhaled histamine after inhalation of placebo and 0.26 and 2.08 mg of atropine in eight subjects with mild asthma. Both doses of atropine significantly inhibited histamine-induced bronchoconstriction, and 2.08 mg caused significantly greater inhibition than 0.26 mg. Baseline specific airway resistance was significantly reduced by both doses of atropine but was no different after 2.08 mg than after 0.26 mg. There were considerable differences in the efficacy of atropine among individuals. We conclude that atropine causes dose-dependent inhibition of histamine-induced bronchoconstriction and that this effect is not merely a function of the atropine-induced in baseline airway caliber. The large magnitude of the atropine effect in some subjects and the small magnitude of the effect in others suggest that there is variability in the degree of involvement of muscarinic mechanisms in the exaggerated bronchomotor response to histamine in asthmatic subjects.

Effect of aerosol fenoterol on the severity of bronchial hyperreactivity in patients with asthma

Beta adrenergic agents given by aerosol decrease the responsiveness of the airways to histamine and methacholine in subjects with asthma, causing a shift of the dose response curve to the right. To find out whether the shift is related to the dose of beta adrenergic agent given and to determine the duration of the reduced responsiveness, eight subjects with asthma were given histamine inhalation tests after inhaled saline and after increasing doses of inhaled fenoterol on different days. The histamine inhalation tests were repeated at hourly intervals for five hours after a selected dose of fenoterol. Fenoterol caused a dose related shift to the right of the histamine dose response curve in each subject and in some the dose response relationship reached the "non-symptomatic range." The shift in the dose response curve was short lived and had returned towards the control position within three hours in all subjects. There was no change in shape of the curves at the time of maximal shift. The results show that inhaled fenoterol greatly reduces the airway responsiveness to histamine, but up to 400 micrograms of fenoterol every four to five hours may be needed to keep the responsiveness of the airways in the non-symptomatic range.

Unimodal distribution of bronchial responsiveness to inhaled histamine in a random human population

The population distribution of bronchial responsiveness to inhaled histamine was examined in 300 randomly selected caucasian college students (aged 20 to 29 years). Bronchial responsiveness was measured as the histamine threshold, defined as the concentration producing an FEV1 fall greater than 2 SD below the mean of five prehistamine FEV1 measurements. The cumulative prevalence of asthma was 9.3 percent, including 2.7 percent with current asthma, 3.3 percent with asthma following allergen exposure only, and 3.3 percent with remote asthma. Allergic rhinitis was present in 10.7 percent; nonallergic rhinitis in 16.3 percent; 63.7 percent had neither asthma nor rhinitis. Histamine threshold ranged from unmeasurable (greater than 8 mg/ml) in 36 percent to 0.125 mg/ml in 0.3 percent. The distribution of histamine threshold values in the responsive range was unimodal, the asthmatic subjects representing a subgroup within the hyperresponsive distribution tail rather than a separate distribution peak. Examination of the FEV1 response to 8 mg/ml showed a range between 2.8 SD increase and 100 SD reduction; the population distribution of this variable was unimodal and log normal. We concluded that there is a continuous unimodal log normal distribution of bronchial responsiveness to inhaled histamine in a random human population. Rather than representing a separate (bimodal) peak or a sharp cutoff (of a unimodal tail), the asthmatic subjects show substantial overlap with the remainder of the population.

Standardization of inhalation provocation tests. Dose vs concentration of histamine

The importance of histamine dose vs histamine concentration in determining the response to inhaled histamine was evaluated by comparing the effect of 30 sec and two min inhalation times on duplicate histamine inhalation tests in 15 asthmatic patients. The histamine provocation concentration required to produce a 20 percent FEV1 fall after 30 sec inhalations (30 sec PC20) was on average 3.6-fold greater than the two min PC20. Individually, ten of the 15 fell within the range of dose reproducibility (+/- one doubling dose), while five subjects fell outside this range, three with 30 sec PC20 less than twice two min PC20 and two with 30 sec PC20 greater than 8 X two min PC20. Seven subjects had duplicate measurements of both 30 sec PC20 and two min PC20; the two min PC20 was more reproducible than the 30 sec PC20 in all seven. The better reproducibility of the two min PC20 is likely due to a more reproducible inspiratory time over the two-minute breathing period. These findings have relevance in standardization of inhalation challenge tests, and in comparing results of such tests done by different techniques.