1338
dermatitis herpetiformis. Br J Dermatol 1969; 81: 692-96. 22. Seah PP, Fry L, Hoffbrand AV, Holborow EJ. Tissue antibodies in dermatitis herpetiformis and adult coeliac disease. Lancet 1971; i: 834-36. 23. Eterman KP, Feltkamp TEW. Antibodies to gluten and reticulin in gastrointestinal diseases. Clin Exp Immunol 1978;; 31: 92-99. 24. Kárpáti S, Stolz W, Meurer M, Krieg T, Braun-Falco O. Extracellular binding sites of IgA anti-jejunal antibodies on normal small bowel detected by indirect immunoelectron microscopy. J Invest Dermatol (in 25.
press). Takahashi-Iwagana H, Fujita T. Lamina propria of intestinal mucosa as a typical reticular tissue. A scanning electron microscopic study of the rat
Protection
jejunum. Cell Tissue Res 1985; 242: 57-66. 26. Martini A, Lorini R, Zanaboni D, Ravelli A, Burgio R. Frequency of autoantibodies in normall children. Am J Dis Child 1989; 143: 493-96. 27. Unsworth DJ, Walker-Smith JA, McCarthy D, Holborow EJ. Studies on the significance of the R1 anti-reticulin antibody associated with gluten sensitivity. Int Arch Allergy Appl Immunol 1985; 76: 47-51. 28. Brandtzaeg P, Valnes K, Scott H, Rognum TO, Bjerke K, Baklien K. The human secretory immune system in health and disease. Scand J Gastroenterol 1985; 20 (suppl 114): 17-38. 29. Lancaster-Smith M, Joyce S, Kumar P. Immunoglobulins in the jejunal mucosa in adult coeliac disease and dermatitis herpetiformis after the reintroduction of dietary gluten. Gut 1977; 18: 887-91.
against allergen-induced asthma by salmeterol
The effects of the long-acting &bgr;2-agonist salmeterol on early and late phase airways events provoked by inhaled allergen were assessed in a group of atopic asthmatic patients. In a placebocontrolled study, salmeterol 50 µg inhaled before allergen challenge ablated both the early and late phase of allergen-induced bronchoconstriction over a 34 h time period. Salmeterol also completely inhibited the allergen-induced rise in non-specific bronchial responsiveness over the same time period. These effects were shown to be unrelated to prolonged bronchodilatation or functional antagonism. These data suggest novel actions for topically active long-acting &bgr;2-agonists in asthma that extend beyond their protective action on airways smooth muscle.
Introduction
_
Asthma is one of the commonest clinical expressions of atopy. During early life exposure of the airways to common environmental allergens results in specific sensitisation.1 Subsequent repeated exposure to the same allergens results in mucosal inflammation caused by mediator release from mast cells and eosinophils .2 These events can be modelled by allergen provocation: the early asthmatic response peaks at 15 min and recovers by 60-90 min and the late phase of airways obstruction starts within 2 h and lasts for 12 h or more.3Because these events are paralleled by a progressive rise in non-specific responsiveness of the airways, a characteristic feature of asthma, they have been used to evaluate the mechanisms of anti-asthma drugs.4 The early asthmatic response follows the release of bronchospastic mediators such as histamine, prostaglandin Dz, and leukotriene C4 from IgE-triggered mast cells, whereas the late phase responses involve the recruitment and activation of eosinophils with release of leukotriene C4, plateletactivating factor, reactive species of oxygen, and tissuedamaging basic proteins.5 &bgr;z-adrenoceptor agonists such as salbutamol and terbutaline are highly effective in the treatment of asthma, especially when given by inhalation. In addition to their direct bronchodilator effect,6 these drugs are potent inhibitors of mast cell mediator secretionand both
activities probably contribute to their effect in abrogating the early asthmatic response to allergen challenge 8 By contrast, inhaled (32-agonists are reported to be ineffective against the late asthmatic response after allergen challenge or the accompanying rise in non-specific bronchial responsiveness.9 Since the latter events are a consequence of airway inflammation involving leucocyte and especially eosinophil influx, it has been proposed that this class of drug treats only the symptoms of asthma without affecting the
underlying inflammatory processes.1o Salmeterol is a new topically active long-acting (32 agonist. The component of the drug that interacts with &bgr;2-receptors is identical to salbutamol, and its long duration of action is accounted for by a long lipophilic side chain which interacts with a binding domain in the vicinity of the &bgr;2-receptor (the exosite).11 In vitro and in vivo salmeterol inhibits the constriction of animal airway smooth muscle for up to 7 h12 and it inhibits the release of the bronchospastic mediators from IgE-triggered human lung mast cells for up to 12 h. 13 In a single inhaled dose of 50 g, it produces bronchodilatation for at least 12 h,14,15 We report here the effects of inhaled salmeterol on the early and late asthmatic responses and the rise in bronchial responsiveness provoked by inhaled allergen in a group of atopic asthmatic subjects. In an attempt to clarify its mode of action in allergen-induced asthma we also determined the duration of its effects of bronchodilatation and protection against histamine-induced bronchoconstriction.
Patients and methods Recordings of forced expiratory volume in 1 s (FEV1) were made by means of a dry wedge bellows spirometer (Vitalograph Ltd, Buckingham, UK). Nebulised histamine acid phosphate (Sigma, Poole, Dorset, UK) and 0-9% sodium chloride (saline) were administered by way of a valve box and mouthpiece with the patient taking five full inspirations over 30 s from functional residual capacity to total lung capacity. The solutions were aerosolised by
ADDRESSES: Medicine I, Southampton General Hospital (O. P. Twentyman, MRCP, J. P. Finnerty, MRCP, Prof S. T. Holgate, FRCP), and Medical Division, Glaxo Group Research, Greenford, Middlesex, UK (A Harris, BSc, J. Palmer, MRCP). Correspondence to Dr O. P. Twentyman, Papworth Hospital, Papworth Everard, Cambridge
CB3 8RE, UK.
1339
CHARACTERISTICS OF STUDY SUBJECTS
S=salbutamol, B=beclomethasone diproprionate- both by metered-dose inhaler.
of an ’Inspiron mini-neb’ jet nebuliser (Bard International Ltd, Sunderland, UK) driven by compressed air at a flow rate of 8 means
litres/min to achieve an output of 0-35 ml/min and a mass median particle diameter of 5-3 pm. After the baseline recording of FEV l’ nebulised saline was given and FEV, recorded 3 min later. Doubling incremental concentrations of histamine (0-015-16 mg/ml saline [0049-521 pmol/ml]) were then given every 5 min and FEV recorded 3 min afterwards until the FEV had fallen to than 20% below the post-saline value. For each subject the allergen extract (group B-2 grass
more
pollen or Dermatophagoides pteronyssinus: Bencard, Brentford, Middlesex, UK) that produced the largest skin weal was used for allergen inhalation challenge. Dose ranging with inhaled allergen was done to identify subjects with late asthmatic responses and to determine the dose to be given in the main study. Incremental two to ten fold concentrations of aerosolised allergen in saline were inhaled in five breaths over 30 s through the nebuliser from functional residual capacity to total lung capacity by a method modified from that of Chai et al.16 Each allergen concentration was inhaled with 10 min intervals, and FEV was measured after 5 and 10 min until it had fallen to more than 20% below the post-saline value. Further measurements of FEV1 were made regularly up to 7-5 h. Only subjects who experienced a fall in FEV, of more than 14% from baseline 3-5-7-5 h after challenge (late asthmatic response) took part in the allergen challenge study. The cumulative concentration of allergen producing a more than 20% fall in FEV in the early asthmatic response (PC,, allergen) identified by dose ranging for each subject was used for the single-dose allergen challenges. Two studies were done; they were approved by the Southampton Hospitals and University joint ethical committee and written informed consent was obtained from each subject. Eight atopic asthmatic subjects (subjects 1-8; table) aged 21-31 (median 21-5) years took part in the first study to measure the duration of bronchodilatation and protection against histamineinduced bronchoconstriction. On entry their mean (SEM) FEV1 was 3-59 (0-25) litres (87-0 [4’3%] predicted) and their geometric mean PC, histamine 0-30 (range 0-037-2-2) mg/ml. Inhaled salbutamol was discontinued 8 h and inhaled corticosteroids at least 48 h before each study period. The subjects attended the laboratory for two randomised study periods separated by at least 12 days, each period lasting 3 days. On day 1 they attended at 1800 h for two measurements of PC20 histamine with FEV allowed to recover
spontaneously over at least 1 h between tests. The next morning at 0900 h, PCZ° histamine was measured again. The baseline FEV for the study period was then recorded after the FEV had been allowed to recover spontaneously over at least 1 h. Next, FEV was recorded 3 min after saline inhalation, and then either salmeterol 50 gg (two puffs) or placebo was given by metered-dose inhaler in a double-blind and randomised manner. FEV1 was recorded at 10 min and then a sham challenge with nebulised saline was given to each subject by way of the nebuliser (five full inspirations over 30 s from functional residual capacity to total lung capacity). FEV! was recorded every 10 min for 1 h and thereafter every 30 min until 95h after the saline challenge. Measurements of PC histamine were made 1 -5 h, 3-5 h, 5-5 h, 7-5 h, and 9-5 h after the challenge and FEV1 was allowed to recover spontaneously between each test. After the final histamine challenge, bronchoconstriction was reversed with inhaled salbutamol (2700 ng). On the third day (32 h and 34 h after
the saline challenge) the subjects reattended for two further histamine bronchoprovocation tests. Eight atopic asthmatic subjects (1-6, 9, 10; table) aged 21-31 (median 22) years took part in the second study to assess the effect of salmeterol against allergen-provoked airway responses. On entry their mean FEV1 was 3-67 (0-27) litres (88-6 [5-8]% predicted) and their geometric mean PC20 histamine 0-36 (range 0-037-2-2) mg/ml. The protocol was identical to that of study 1 except that instead of the saline sham challenge 10 min after salmeterol or placebo, the subjects inhaled the previously determined PCzo allergen. For all analyses a probability value of less than 0 05 was accepted as significant. The two studies were analysed in the same way. The PC20 histamine was determined by linear interpolation from the histamine dose response curve plotted as change in FEV, from post-saline baseline against the concentration of histamine plotted on a logarithmic scale. PC20 histamine values were analysed after logarithmic transformation. The 0900 h Pq, and the subsequent pre-challenge baseline FEV measurements on day 2 of each study period were used to standardise the data. Change in FEV, was expressed as a percentage from baseline, and the change in histamine responsiveness (&Dgr;PC20) in doubling dilutions of histamine from baseline (&Dgr;PC20) = log2 [PC20 baseline]-log2 [PC20 time x]). The studies were designed with two measurements of FEV and PC20 on days 1 and 3 of each treatment period. Comparisons between the measurements on day 1 and day 3 were made by two-way analysis of variance (ANOVA) to determine whether the second measurement was affected by the first on any day. Then ANOVA was used to make comparisons between treatments on day 1 and day 3, and within each study period between days 1 and 3, with both the measurements made on these days.17 Comparisons between treatments on day 2 of each study period were made at baseline, 20 min, and 7-5 h for FEV and at baseline,1 -5 h, and 7-5 h for PCo histamine by Student’s paired t test. Within each treatment period comparisons were made between baseline and the FEV1 values after salmeterol or placebo at 20 min and 7-5 h, and between baseline and the PC20 histamine values at 1-5 h and 7-5 h by Student’s paired t teSt.17
Results Ten
atopic asthmatic subjects took part in these studies (table). The 9-5h measurements were omitted in one subject in study 1 and in two subjects in study 2, so statistical comparisons were made at 7-5 h on day 2. There were no significant differences between the first and second measurements of FEVI and PC20 histamine on day 1 and day 3 in either study. No significant differences between treatments in baseline FEV or baseline PC20 histamine were identified in either study. Study 1 (saline challenge) There were no significant differences between treatments in either PC20 histamine or FEV1 on day 3 (figure). Within each treatment period there were no significant differences between day 1 and day 3 in either PC20 histamine or FEV1. Comparisons within study periods on day 2 showed that after placebo the mean (SEM) FEV rose 0-65 (1-2)% before saline challenge, 3-1 (1-5)% (not significant) at 20 min, and 1-4 (1’4)% (not significant) at 7-5h after saline challenge. Salmeterol produced a 4-8 (1-6)% increase in FEV1 before saline challenge and a 7-4 (2- 1)% (p < 0-006) increase at 20 min after saline challenge. This increase was maintained beyond 75h, at which time it measured 73 (2-7)% (p < 0-023) (figure). The differences in FEV1 between salmeterol and placebo treatment periods were not significant at 20 min or 75 h. During the placebo period on day 2 there was no significant change in PC20 histamine (figure). Inhaled salmeterol given before saline challenge
1340
protected the airways against histamine, leading to rises in PC20 of 4-0 (0-5) doubling dilutions (p < 0-001) at 1.5 h and at 7-5 h. The 3-2 (0-6) doubling dilutions (p
dermatitis herpetiformis. Br J Dermatol 1969; 81: 692-96. 22. Seah PP, Fry L, Hoffbrand AV, Holborow EJ. Tissue antibodies in dermatitis herpetiformis and adult coeliac disease. Lancet 1971; i: 834-36. 23. Eterman KP, Feltkamp TEW. Antibodies to gluten and reticulin in gastrointestinal diseases. Clin Exp Immunol 1978;; 31: 92-99. 24. Kárpáti S, Stolz W, Meurer M, Krieg T, Braun-Falco O. Extracellular binding sites of IgA anti-jejunal antibodies on normal small bowel detected by indirect immunoelectron microscopy. J Invest Dermatol (in 25.
press). Takahashi-Iwagana H, Fujita T. Lamina propria of intestinal mucosa as a typical reticular tissue. A scanning electron microscopic study of the rat
Protection
jejunum. Cell Tissue Res 1985; 242: 57-66. 26. Martini A, Lorini R, Zanaboni D, Ravelli A, Burgio R. Frequency of autoantibodies in normall children. Am J Dis Child 1989; 143: 493-96. 27. Unsworth DJ, Walker-Smith JA, McCarthy D, Holborow EJ. Studies on the significance of the R1 anti-reticulin antibody associated with gluten sensitivity. Int Arch Allergy Appl Immunol 1985; 76: 47-51. 28. Brandtzaeg P, Valnes K, Scott H, Rognum TO, Bjerke K, Baklien K. The human secretory immune system in health and disease. Scand J Gastroenterol 1985; 20 (suppl 114): 17-38. 29. Lancaster-Smith M, Joyce S, Kumar P. Immunoglobulins in the jejunal mucosa in adult coeliac disease and dermatitis herpetiformis after the reintroduction of dietary gluten. Gut 1977; 18: 887-91.
against allergen-induced asthma by salmeterol
The effects of the long-acting &bgr;2-agonist salmeterol on early and late phase airways events provoked by inhaled allergen were assessed in a group of atopic asthmatic patients. In a placebocontrolled study, salmeterol 50 µg inhaled before allergen challenge ablated both the early and late phase of allergen-induced bronchoconstriction over a 34 h time period. Salmeterol also completely inhibited the allergen-induced rise in non-specific bronchial responsiveness over the same time period. These effects were shown to be unrelated to prolonged bronchodilatation or functional antagonism. These data suggest novel actions for topically active long-acting &bgr;2-agonists in asthma that extend beyond their protective action on airways smooth muscle.
Introduction
_
Asthma is one of the commonest clinical expressions of atopy. During early life exposure of the airways to common environmental allergens results in specific sensitisation.1 Subsequent repeated exposure to the same allergens results in mucosal inflammation caused by mediator release from mast cells and eosinophils .2 These events can be modelled by allergen provocation: the early asthmatic response peaks at 15 min and recovers by 60-90 min and the late phase of airways obstruction starts within 2 h and lasts for 12 h or more.3Because these events are paralleled by a progressive rise in non-specific responsiveness of the airways, a characteristic feature of asthma, they have been used to evaluate the mechanisms of anti-asthma drugs.4 The early asthmatic response follows the release of bronchospastic mediators such as histamine, prostaglandin Dz, and leukotriene C4 from IgE-triggered mast cells, whereas the late phase responses involve the recruitment and activation of eosinophils with release of leukotriene C4, plateletactivating factor, reactive species of oxygen, and tissuedamaging basic proteins.5 &bgr;z-adrenoceptor agonists such as salbutamol and terbutaline are highly effective in the treatment of asthma, especially when given by inhalation. In addition to their direct bronchodilator effect,6 these drugs are potent inhibitors of mast cell mediator secretionand both
activities probably contribute to their effect in abrogating the early asthmatic response to allergen challenge 8 By contrast, inhaled (32-agonists are reported to be ineffective against the late asthmatic response after allergen challenge or the accompanying rise in non-specific bronchial responsiveness.9 Since the latter events are a consequence of airway inflammation involving leucocyte and especially eosinophil influx, it has been proposed that this class of drug treats only the symptoms of asthma without affecting the
underlying inflammatory processes.1o Salmeterol is a new topically active long-acting (32 agonist. The component of the drug that interacts with &bgr;2-receptors is identical to salbutamol, and its long duration of action is accounted for by a long lipophilic side chain which interacts with a binding domain in the vicinity of the &bgr;2-receptor (the exosite).11 In vitro and in vivo salmeterol inhibits the constriction of animal airway smooth muscle for up to 7 h12 and it inhibits the release of the bronchospastic mediators from IgE-triggered human lung mast cells for up to 12 h. 13 In a single inhaled dose of 50 g, it produces bronchodilatation for at least 12 h,14,15 We report here the effects of inhaled salmeterol on the early and late asthmatic responses and the rise in bronchial responsiveness provoked by inhaled allergen in a group of atopic asthmatic subjects. In an attempt to clarify its mode of action in allergen-induced asthma we also determined the duration of its effects of bronchodilatation and protection against histamine-induced bronchoconstriction.
Patients and methods Recordings of forced expiratory volume in 1 s (FEV1) were made by means of a dry wedge bellows spirometer (Vitalograph Ltd, Buckingham, UK). Nebulised histamine acid phosphate (Sigma, Poole, Dorset, UK) and 0-9% sodium chloride (saline) were administered by way of a valve box and mouthpiece with the patient taking five full inspirations over 30 s from functional residual capacity to total lung capacity. The solutions were aerosolised by
ADDRESSES: Medicine I, Southampton General Hospital (O. P. Twentyman, MRCP, J. P. Finnerty, MRCP, Prof S. T. Holgate, FRCP), and Medical Division, Glaxo Group Research, Greenford, Middlesex, UK (A Harris, BSc, J. Palmer, MRCP). Correspondence to Dr O. P. Twentyman, Papworth Hospital, Papworth Everard, Cambridge
CB3 8RE, UK.
1339
CHARACTERISTICS OF STUDY SUBJECTS
S=salbutamol, B=beclomethasone diproprionate- both by metered-dose inhaler.
of an ’Inspiron mini-neb’ jet nebuliser (Bard International Ltd, Sunderland, UK) driven by compressed air at a flow rate of 8 means
litres/min to achieve an output of 0-35 ml/min and a mass median particle diameter of 5-3 pm. After the baseline recording of FEV l’ nebulised saline was given and FEV, recorded 3 min later. Doubling incremental concentrations of histamine (0-015-16 mg/ml saline [0049-521 pmol/ml]) were then given every 5 min and FEV recorded 3 min afterwards until the FEV had fallen to than 20% below the post-saline value. For each subject the allergen extract (group B-2 grass
more
pollen or Dermatophagoides pteronyssinus: Bencard, Brentford, Middlesex, UK) that produced the largest skin weal was used for allergen inhalation challenge. Dose ranging with inhaled allergen was done to identify subjects with late asthmatic responses and to determine the dose to be given in the main study. Incremental two to ten fold concentrations of aerosolised allergen in saline were inhaled in five breaths over 30 s through the nebuliser from functional residual capacity to total lung capacity by a method modified from that of Chai et al.16 Each allergen concentration was inhaled with 10 min intervals, and FEV was measured after 5 and 10 min until it had fallen to more than 20% below the post-saline value. Further measurements of FEV1 were made regularly up to 7-5 h. Only subjects who experienced a fall in FEV, of more than 14% from baseline 3-5-7-5 h after challenge (late asthmatic response) took part in the allergen challenge study. The cumulative concentration of allergen producing a more than 20% fall in FEV in the early asthmatic response (PC,, allergen) identified by dose ranging for each subject was used for the single-dose allergen challenges. Two studies were done; they were approved by the Southampton Hospitals and University joint ethical committee and written informed consent was obtained from each subject. Eight atopic asthmatic subjects (subjects 1-8; table) aged 21-31 (median 21-5) years took part in the first study to measure the duration of bronchodilatation and protection against histamineinduced bronchoconstriction. On entry their mean (SEM) FEV1 was 3-59 (0-25) litres (87-0 [4’3%] predicted) and their geometric mean PC, histamine 0-30 (range 0-037-2-2) mg/ml. Inhaled salbutamol was discontinued 8 h and inhaled corticosteroids at least 48 h before each study period. The subjects attended the laboratory for two randomised study periods separated by at least 12 days, each period lasting 3 days. On day 1 they attended at 1800 h for two measurements of PC20 histamine with FEV allowed to recover
spontaneously over at least 1 h between tests. The next morning at 0900 h, PCZ° histamine was measured again. The baseline FEV for the study period was then recorded after the FEV had been allowed to recover spontaneously over at least 1 h. Next, FEV was recorded 3 min after saline inhalation, and then either salmeterol 50 gg (two puffs) or placebo was given by metered-dose inhaler in a double-blind and randomised manner. FEV1 was recorded at 10 min and then a sham challenge with nebulised saline was given to each subject by way of the nebuliser (five full inspirations over 30 s from functional residual capacity to total lung capacity). FEV! was recorded every 10 min for 1 h and thereafter every 30 min until 95h after the saline challenge. Measurements of PC histamine were made 1 -5 h, 3-5 h, 5-5 h, 7-5 h, and 9-5 h after the challenge and FEV1 was allowed to recover spontaneously between each test. After the final histamine challenge, bronchoconstriction was reversed with inhaled salbutamol (2700 ng). On the third day (32 h and 34 h after
the saline challenge) the subjects reattended for two further histamine bronchoprovocation tests. Eight atopic asthmatic subjects (1-6, 9, 10; table) aged 21-31 (median 22) years took part in the second study to assess the effect of salmeterol against allergen-provoked airway responses. On entry their mean FEV1 was 3-67 (0-27) litres (88-6 [5-8]% predicted) and their geometric mean PC20 histamine 0-36 (range 0-037-2-2) mg/ml. The protocol was identical to that of study 1 except that instead of the saline sham challenge 10 min after salmeterol or placebo, the subjects inhaled the previously determined PCzo allergen. For all analyses a probability value of less than 0 05 was accepted as significant. The two studies were analysed in the same way. The PC20 histamine was determined by linear interpolation from the histamine dose response curve plotted as change in FEV, from post-saline baseline against the concentration of histamine plotted on a logarithmic scale. PC20 histamine values were analysed after logarithmic transformation. The 0900 h Pq, and the subsequent pre-challenge baseline FEV measurements on day 2 of each study period were used to standardise the data. Change in FEV, was expressed as a percentage from baseline, and the change in histamine responsiveness (&Dgr;PC20) in doubling dilutions of histamine from baseline (&Dgr;PC20) = log2 [PC20 baseline]-log2 [PC20 time x]). The studies were designed with two measurements of FEV and PC20 on days 1 and 3 of each treatment period. Comparisons between the measurements on day 1 and day 3 were made by two-way analysis of variance (ANOVA) to determine whether the second measurement was affected by the first on any day. Then ANOVA was used to make comparisons between treatments on day 1 and day 3, and within each study period between days 1 and 3, with both the measurements made on these days.17 Comparisons between treatments on day 2 of each study period were made at baseline, 20 min, and 7-5 h for FEV and at baseline,1 -5 h, and 7-5 h for PCo histamine by Student’s paired t test. Within each treatment period comparisons were made between baseline and the FEV1 values after salmeterol or placebo at 20 min and 7-5 h, and between baseline and the PC20 histamine values at 1-5 h and 7-5 h by Student’s paired t teSt.17
Results Ten
atopic asthmatic subjects took part in these studies (table). The 9-5h measurements were omitted in one subject in study 1 and in two subjects in study 2, so statistical comparisons were made at 7-5 h on day 2. There were no significant differences between the first and second measurements of FEVI and PC20 histamine on day 1 and day 3 in either study. No significant differences between treatments in baseline FEV or baseline PC20 histamine were identified in either study. Study 1 (saline challenge) There were no significant differences between treatments in either PC20 histamine or FEV1 on day 3 (figure). Within each treatment period there were no significant differences between day 1 and day 3 in either PC20 histamine or FEV1. Comparisons within study periods on day 2 showed that after placebo the mean (SEM) FEV rose 0-65 (1-2)% before saline challenge, 3-1 (1-5)% (not significant) at 20 min, and 1-4 (1’4)% (not significant) at 7-5h after saline challenge. Salmeterol produced a 4-8 (1-6)% increase in FEV1 before saline challenge and a 7-4 (2- 1)% (p < 0-006) increase at 20 min after saline challenge. This increase was maintained beyond 75h, at which time it measured 73 (2-7)% (p < 0-023) (figure). The differences in FEV1 between salmeterol and placebo treatment periods were not significant at 20 min or 75 h. During the placebo period on day 2 there was no significant change in PC20 histamine (figure). Inhaled salmeterol given before saline challenge
1340
protected the airways against histamine, leading to rises in PC20 of 4-0 (0-5) doubling dilutions (p < 0-001) at 1.5 h and at 7-5 h. The 3-2 (0-6) doubling dilutions (p
