Long-term effects of a long-acting beta 2-adrenoceptor agonist, salmeterol, on airway hyperresponsiveness in patients with mild asthma

BACKGROUND

Asthma is characterized by hyperresponsiveness of the airways to bronchoconstrictive stimuli. Long-acting beta 2-adrenoceptor agonists have been introduced as a new therapeutic approach, but there is growing concern about whether control of asthma may deteriorate with the regular use of these agents. We investigated the long-term effects of the beta 2 agonist salmeterol on bronchodilation and on airway hyperresponsiveness to the bronchoconstrictive agent methacholine in mild asthma.

METHODS

In a parallel, double-blind study, 24 patients with mild asthma were randomly assigned to treatment with either inhaled salmeterol (50 micrograms, twice daily) (n = 12) or placebo (n = 12) during an eight-week trial. Methacholine challenge was performed before, during, and after the treatment period. Methacholine responsiveness was measured as the provocative concentration (PC20) that caused a 20 percent decrease in the forced expiratory volume in one second (FEV1).

RESULTS

There was a significant increase in FEV1 one hour after the inhalation of salmeterol (P = 0.006), which did not differ significantly on days 0, 28, and 56 of the treatment period (increase, 9.8, 9.4, and 8.8 percent of predicted FEV1, respectively; P = 0.91). On the first treatment day, salmeterol afforded significant protection against methacholine-induced bronchoconstriction, as shown by a 10-fold increase in the PC20 as compared with the value at entry (P less than 0.001). After four and eight weeks of treatment, however, the salmeterol-induced change in the PC20 was significantly attenuated (P less than 0.001) to only a twofold increase. Two and four days after treatment ended, the PC20 was not significantly different from the value before treatment (P = 0.15).

CONCLUSIONS

Regular treatment of patients with mild asthma with salmeterol leads to tolerance to its protective effects against a bronchoconstrictor stimulus, in this case inhaled methacholine, despite well-maintained bronchodilation. This finding raises concern about the effectiveness of prolonged therapy with long-acting beta 2-adrenoceptor agonists in asthma.

The effect of an inhaled neutral endopeptidase inhibitor, thiorphan, on airway responses to neurokinin A in normal humans in vivo

Neuropeptides such as neurokinin A (NKA) have been proposed as important mediators of bronchoconstriction and airway hyperresponsiveness in asthma. Inhaled NKA causes bronchoconstriction in patients with asthma, but not in normal subjects. This is possibly due to the activity of an endogenous neuropeptide-degrading enzyme: neutral endopeptidase (NEP). We investigated whether a NEP-inhibitor, thiorphan, reveals bronchoconstriction to NKA or NKA-induced changes in airway responsiveness to methacholine in normal humans in vivo. Eight normal male subjects participated in a double-blind crossover study, using thiorphan as pretreatment to NKA challenge. Dose-response curves to inhaled NKA (8 to 1,000 micrograms/ml, 0.5 ml/dose) were recorded on 2 randomized days 1 wk apart, and methacholine tests were performed 48 h before and 24 h after the NKA challenge. Ten minutes prior to NKA challenge the subjects inhaled either thiorphan (2.5 mg/ml, 0.5 ml) or placebo. To detect a possible nonspecific effect of thiorphan, we investigated the effect of the same pretreatment with thiorphan or placebo on the dose-response curve to methacholine in a separate set of experiments. The response was measured by the flow from standardized partial expiratory flow-volume curves (V40p), expressed in percent fall from baseline. NKA log dose-response curves were analyzed using the area under the curve (AUC) and the response to the highest dose of 1,000 micrograms/ml (V40p,1000). The methacholine dose-response curves were characterized by their position (PC40V40p) and the maximal-response plateau (MV40p). Baseline V40p was not affected by either pretreatment (p greater than 0.15).(ABSTRACT TRUNCATED AT 250 WORDS)

The long-term effect of nedocromil sodium on the maximal degree of airway narrowing to methacholine in atopic asthmatic subjects

Airway hyperresponsiveness in asthma is characterized by increased airway sensitivity and by excessive maximal airway narrowing. Long-term inhalation therapy with nedocromil sodium has been shown to reduce increased airway sensitivity in asthma. However, it is unknown whether it also attenuates excessive airway narrowing. We studied the long-term effects of nedocromil on the maximal degree of airway narrowing to methacholine. Twenty-seven atopic asthmatic adults (21-39 years), with a measurable maximal-response plateau on the dose-response curve (20-55% fall in FEV1), were randomly allocated into two parallel treatment groups. They received either inhaled nedocromil 4 mg q.i.d. or placebo, for 8 weeks following a 2 week baseline period. Every 2 weeks, complete dose-response curves to inhaled methacholine were obtained. The response was measured by FEV1 and by volume history standardized partial expiratory flow-volume curves (V40p). A maximal-response plateau was considered if three or more of the highest data points fell within a 5% response range, the maximal response being the average value on the plateau (MFEV1, MV40p). Airway sensitivity was defined as the provocative concentration of methacholine causing a 20% fall in FEV1 (PC20FEV1) or 40% fall in V40p (PC40 V40p). Twenty-four subjects completed the study. Baseline FEV1 or V40p did not change during either treatment (P greater than 0.07). There were no significant changes in MFEV1 or MV40p during treatment with nedocromil (P greater than 0.07). Neither were these changes significantly different between the two groups (P greater than 0.25).(ABSTRACT TRUNCATED AT 250 WORDS)

Auranofin in the treatment of steroid dependent asthma: a double blind study

BACKGROUND

Long term administration of oral corticosteroids in patients with asthma may be associated with serious side effects. Non-steroidal anti-inflammatory drugs, including gold salts, have been shown to reduce the need for systemic corticosteroid treatment in uncontrolled studies. The effect of oral gold (auranofin) on asthma symptoms, lung function, and the need for oral prednisone treatment was investigated.

METHODS

A 26 week randomised, double blind, placebo controlled, parallel group trial of auranofin was performed in 32 patients with moderately severe chronic asthma who required an oral corticosteroid dose of at least 5 mg prednisone a day (or equivalent) or 2.5 mg/day prednisone plus more than 800 micrograms/day inhaled corticosteroids. Auranofin was given orally in a dose of 3 mg twice daily. Asthma symptoms, lung function, and adverse effects were assessed at regular intervals. After 12 weeks of treatment prednisone dosage was tapered down by 2.5 mg every two weeks if the patient was clinically stable. Asthma exacerbations were treated with short courses of high doses of oral steroids.

RESULTS

Twenty eight of the 32 patients, 13 in the placebo group and 15 in the auranofin group, completed the study. The total corticosteroid reduction achieved after 26 weeks of treatment was significantly greater (4 mg) in the auranofin group than in the placebo group (0.3 mg). The number of exacerbations requiring an increase of steroids was greater in the placebo group (2.1) than in the active group (0.9). A significant increase in FEV1 of 6.4% predicted occurred in the auranofin group during the study and there was a reduction of asthma symptoms such as wheezing and cough. There was no difference between the groups in peak flow measurements or in the number of asthma attacks. The incidence of side effects of auranofin was low, but exacerbations of constitutional eczema were noticeable.

CONCLUSION

Auranofin provides an effective adjunct to treatment for steroid dependent asthma, leading to a reduction of oral steroid dose.

Quantification of theophylline-induced eosinopenia and hypokalaemia in healthy volunteers

The relationship between theophylline pharmacokinetics and its eosinopenic and hypokalaemic effects were studied in 6 healthy volunteers after an oral dose of theophylline 250 mg. The mean peak theophylline concentration (Cmax) of 8.33 +/- 2.16 mg/L occurred 1.02 +/- 0.26 h after ingestion. The delay between the Cmax and the subsequent eosinopenic or hypokalaemic nadirs was 4.52 +/- 1.73 and 3.65 +/- 1.32 h, respectively. The time courses of theophylline and its effects were linked by a sigmoid Emax effect model. The maximal eosinopenic and hypokalaemic effects (Emax) of the drug were 83 +/- 25.8% and 16 +/- 9.7% of the possible, respectively. The theophylline concentrations causing 50% of the Emax (EC50) were 5.06 +/- 1.84 and 5.04 +/- 2.09 mg/L, respectively. The data obtained with our methodology indicate that, in humans, theophylline induced eosinopenia could be mediated through a receptor and/or postreceptor mechanism unrelated to the mechanism of theophylline induced bronchodilation. We conclude that therapeutic theophylline plasma concentrations have a profound effect on the redistribution of blood eosinophils.

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.

The effect of inhaled corticosteroids on the maximal degree of airway narrowing to methacholine in asthmatic subjects

Airway hyperresponsiveness in asthma is characterized by an increase in sensitivity and in maximal response to airway-narrowing stimuli. Long-term therapy with inhaled corticosteroids is known to reduce airway hypersensitivity in asthmatic patients. To investigate whether these drugs also reduce the maximal degree of airway narrowing we studied the effects of inhaled budesonide on the maximal response plateau of the dose-response curve to inhaled methacholine in mildly asthmatic patients in whom a raised plateau could be measured. Sixteen atopic patients with mild asthma were placed randomly into two parallel treatment groups to receive double-blindly either budesonide (400 micrograms twice daily) or placebo, inhaled via a Turbuhaler, for 4 wk. Before treatment, after 2 and 4 wk of treatment, and after 2 and 4 wk of wash-out, complete dose-response curves to methacholine were obtained using a standardized 2-min tidal breathing method. The response was measured by FEV1, expressed in % fall from baseline. A plateau on the log dose-response curve was considered if three or more data points fell within a 5% response range. The maximal response was obtained by averaging the values on the plateau (MFEV1), and the sensitivity was calculated from the provocative concentration of methacholine, causing a 20% fall in FEV1 (PC20). After 4 wk of budesonide treatment, mean MFEV1 decreased from 41.6 to 33.7% fall (p = 0.0004). The changes in MFEV1 were significantly different between placebo and budesonide (p = 0.03). The geometric mean PC20 increased from 3.4 to 6.3 mg/ml (p = 0.02), but the changes in PC20 were not different between the two groups (p = 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of an inhaled leukotriene antagonist, L-648,051, on early and late asthmatic reactions and subsequent increase in airway responsiveness in man

We have investigated the protective effects of the inhaled cysteinyl leukotriene antagonist, L-648,051, on allergen-induced early asthmatic response (EAR) and late asthmatic response (LAR) and the subsequent changes in bronchial responsiveness to methacholine. Ten atopic men with asthma participated in a double-blind, crossover, placebo-controlled trial. All subjects had documented EAR and LAR to house dust-mite extract. Responsiveness to methacholine was measured the day before and the day after a standardized allergen-challenge test. L-648,051 was inhaled in two doses of 12 mg 20 minutes before and 3 hours after the allergen challenge. The response was obtained from FEV1 and flows from maximal (V40m) and partial (V40p) expiratory flow-volume curves. All subjects had an EAR and LAR during placebo therapy, but only a minority demonstrated an increase in methacholine responsiveness of more than one doubling dose. The ratio of V40m to V40p during methacholine challenge was higher than during both EAR and LAR (p less than 0.05). There was no difference between drug- and placebo-therapy periods in baseline function, EAR, LAR, ratio of V40m to V40p, and the allergen-induced hyperresponsiveness (p greater than 0.1). These results indicate that an effective aerosolized leukotriene antagonist in man does not protect against allergen-induced airflow obstruction, despite the evidence of an inflammatory response to allergen challenge. This suggests that either the potency or duration of activity of L-648,051 is limited or that leukotrienes C4 and D4 do not play a causative role in human allergic asthma.

The long-term effects of nedocromil sodium and beclomethasone dipropionate on bronchial responsiveness to methacholine in nonatopic asthmatic subjects

We investigated the effects of long-term treatment with two anti-inflammatory drugs, nedocromil sodium and beclomethasone dipropionate, on airway hyperresponsiveness to methacholine (PC20), on baseline FEV1 and on the bronchodilating effect of a deep breath in 25 nonsteroid-dependent nonatopic asthmatic adults. In all subjects the prestudy PC20 was less than 8 mg/ml, the postbronchodilator FEV1 was greater than 75% predicted, and skin prick tests and RAST to 13 common allergens were negative. After 2 months run-in, the subjects were randomly allocated into 3 parallel treatment groups to inhale double-blind either 4 mg nedocromil (n = 9) or 100 micrograms beclomethasone (n = 8) or placebo (n = 8) 4 times daily for 4 months. PC20 was measured using the 2-min tidal breathing method. The effect of a deep breath was measured during methacholine-induced bronchoconstriction by standardized maximal and partial expiratory flow-volume curves and was expressed as a flow ratio (M/P ratio). Pretreatment values of FEV1, PC20, and M/P ratio were not different between the 3 groups. PC20 did not change in the placebo group, but increased significantly by a factor of 3 after 8 wk of treatment with beclomethasone or nedocromil (p less than 0.001). FEV1 did not change after treatment with placebo or nedocromil (p greater than 0.2), but increased (mean change 0.2 L, SD 0.2) after 4 wk of treatment with beclomethasone (p less than 0.05). Geometric mean M/P ratio increased from 1.98 to 2.66 after 4 wk of beclomethasone (p less than 0.01), but not after nedocromil or placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchial hyperresponsiveness: the need for a distinction between hypersensitivity and excessive airway narrowing

Bronchial hyperresponsiveness is currently defined as an increase in sensitivity to a wide variety of airway narrowing stimuli. Most patients with asthma and chronic obstructive pulmonary disease (COPD) exhibit such an enhanced sensitivity. In asthma, in particular, this hypersensitivity is accompanied by excessive degrees of airway narrowing. This raises the question as to whether measures of sensitivity, e.g. the provocative concentration or dose producing 20% fall in FEV1 (PC20 or PD20), comprise all the relevant information in bronchial hyperresponsiveness. In adjunct to model studies, there is experimental evidence in man that the potential mechanisms of bronchial hyperresponsiveness can be divided into those causing hypersensitivity and those responsible for the increase in the maximal attainable degree of airway narrowing. The recognition and distinction of these components of hyperresponsiveness have clinical implications in the diagnosis and therapy of asthma and COPD. Bronchial hyperresponsiveness is a composite functional disorder, which requires treatment of each of its components.

Bronchial hyperresponsiveness: the need for a distinction between hypersensitivity and excessive airway narrowing

Bronchial hyperresponsiveness is currently defined as an increase in sensitivity to a wide variety of airway narrowing stimuli. Most patients with asthma and chronic obstructive pulmonary disease (COPD) exhibit such an enhanced sensitivity. In asthma, in particular, this hypersensitivity is accompanied by excessive degrees of airway narrowing. This raises the question as to whether measures of sensitivity, e.g. the provocative concentration or dose producing 20% fall in FEV1 (PC20 or PD20), comprise all the relevant information in bronchial hyperresponsiveness. In adjunct to model studies, there is experimental evidence in man that the potential mechanisms of bronchial hyperresponsiveness can be divided into those causing hypersensitivity and those responsible for the increase in the maximal attainable degree of airway narrowing. The recognition and distinction of these components of hyperresponsiveness have clinical implications in the diagnosis and therapy of asthma and COPD. Bronchial hyperresponsiveness is a composite functional disorder, which requires treatment of each of its components.

The effect of inhaled budesonide on the maximal degree of airway narrowing to leukotriene D4 and methacholine in normal subjects in vivo

In normal humans in vivo, maximal airway narrowing to LTD4 is more severe than to methacholine. Moreover, LTD4 heightens the maximal response to methacholine for several days. To investigate whether or not this is due to inflammatory changes in the airway wall, we studied the effects of the corticosteroid budesonide on the dose-response curves to inhaled LTD4 and to methacholine. In a two-period, double-blind, placebo-controlled design, budesonide (400 micrograms twice a day) or placebo was inhaled by eight normal subjects on six consecutive days, with a 3-wk washout. Complete dose-response curves to LTD4 (0.36 to 43 nmol) were performed on Day 5, and to methacholine (1.28 to 655 mumol) on Days 4 and 6 of each period using a validated method. The response was measured by FEV1 and standardized partial expiratory flow-volume curves (V40p), and was expressed as the percent fall from baseline. A maximal response plateau was considered if more than two doses fell within a 5% response range. All subjects reached plateaus to methacholine and to LTD4. Budesonide reduced the maximal response to LTD4 (mean difference with placebo, 7.9% fall for FEV1, and 8.4% fall for V40p; p less than 0.05). During placebo the maximal response to methacholine 24 h after LTD4 was higher than 24 h before (mean change, 2.7% fall in FEV1 and 5.5% fall in V40p; p less than 0.05), but not during budesonide (mean change, -2.5% fall in FEV1 and -0.1% fall in V40p; p greater than 0.2), the changes being significantly different between the two periods (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The combined effects of histamine and methacholine on the maximal degree of airway narrowing in normal humans in vivo

In normal subjects in vivo the dose-response curve to inhaled nonsensitizing stimuli reaches a plateau at mild degrees of airway narrowing. We investigated whether the limitation of the response is due to non-optimal smooth muscle activation, by administering high doses of histamine and methacholine together. In fifteen normal subjects a complete dose-response curve to methacholine was recorded by a tidal breathing method on three randomized days. On a separate day a complete histamine inhalation test was carried out. Each methacholine test was directly followed by double blind inhalation of the highest dose of either histamine or methacholine, or a dose of saline. The response was measured by flows from partial flow-volume curves (V 40p), and was expressed in % fall from baseline. Twelve subjects reached a maximal response plateau to methacholine which was reproducible. The addition of saline or extra methacholine did not change the response from its methacholine plateau value. Histamine caused a small increase in the response on top of the methacholine plateau (+ 9.0% fall; p less than 0.001). However, the response to the combined histamine and methacholine was not significantly larger than the maximal response to histamine alone. We conclude that there is no interaction between histamine and methacholine on the maximal degree of airway narrowing. This suggests that the plateau of the dose-response curve in normal subjects in vivo is due to other factors than limited smooth muscle activation.

The combined effects of histamine and methacholine on the maximal degree of airway narrowing in normal humans in vivo

In normal subjects in vivo the dose-response curve to inhaled nonsensitizing stimuli reaches a plateau at mild degrees of airway narrowing. We investigated whether the limitation of the response is due to non-optimal smooth muscle activation, by administering high doses of histamine and methacholine together. In fifteen normal subjects a complete dose-response curve to methacholine was recorded by a tidal breathing method on three randomized days. On a separate day a complete histamine inhalation test was carried out. Each methacholine test was directly followed by double blind inhalation of the highest dose of either histamine or methacholine, or a dose of saline. The response was measured by flows from partial flow-volume curves (V 40p), and was expressed in % fall from baseline. Twelve subjects reached a maximal response plateau to methacholine which was reproducible. The addition of saline or extra methacholine did not change the response from its methacholine plateau value. Histamine caused a small increase in the response on top of the methacholine plateau (+ 9.0% fall; p less than 0.001). However, the response to the combined histamine and methacholine was not significantly larger than the maximal response to histamine alone. We conclude that there is no interaction between histamine and methacholine on the maximal degree of airway narrowing. This suggests that the plateau of the dose-response curve in normal subjects in vivo is due to other factors than limited smooth muscle activation.

The excretion of leukotriene E4 into urine following inhalation of leukotriene D4 by human individuals

Healthy volunteers underwent bronchial challenge with increasing doses of nebulized leukotriene D4 (0.007 - 200 nmol) at 15 min intervals. Total amounts of 200 nmol (females) and 400 nmol (males) were inhaled, corresponding to approximately 100 nmol and 200 nmol deposited in the lung, respectively. Of the latter amounts 3 +/- 1% (mean +/- S.E.M., n = 5) was found to be excreted as leukotriene E4 into the urine within 12 h. No further excretion after this period was observed. Approximately 50% of the total urinary leukotriene E4 was excreted during the first 2 h. These results suggest that a possible formation of sulfidopeptide leukotrienes in the lung in vivo can be monitored by measuring leukotriene E4 excretion into the urine.

Maximal airway narrowing to inhaled leukotriene D4 in normal subjects. Comparison and interaction with methacholine

We investigated whether or not leukotriene D4 can influence the maximal degree of airway narrowing in normal humans by comparing the maximal responses to inhaled methacholine and LTD4, and evaluating the interaction between both agonists. In 8 normal subjects, methacholine challenges were performed 24 h before and 24 and 72 h after a LTD4 challenge. Doubling doses of methacholine (1.3 to 655 mumol) or LTD4 (0.007 to 192 nmol) were inhaled by using a recently validated method. The highest dose of LTD4 was followed by the maximal dose of methacholine. The response was measured by FEV1 and volume history standardized partial expiratory flow-volume curves (V40p), and was expressed as percent fall from baseline. All subjects reached a maximal response plateau to both agonists. The maximal response plateau to LTD4 was systematically higher than to methacholine on the preceding day (mean difference, 13.4 and 12.7% fall for FEV1 and V40p, respectively) (p less than 0.01). Addition of methacholine on top of the LTD4 plateau caused a further increase in the response (mean, 6.6 and 4.8% fall, respectively) (p less than 0.005). The maximal responses to methacholine at 24 and 72 h after the LTD4 challenge were higher than at 24 h before (mean difference at 24 h, 4.0 and 8.5% fall for FEV1 and V40p, respectively, and at 72 h 5.7 and 9.3% fall) (p less than 0.05). However, the provocative dose of methacholine causing a 10% fall in FEV1 (PD10) or a 40% fall in V40p (PD40) was not altered by the previous LTD4 challenge test.(ABSTRACT TRUNCATED AT 250 WORDS)