Sodium cromoglycate nebulized solution has an acute bronchodilative effect in patients with aspirin-intolerant asthma (AIA)]

Sodium cromoglycate (SCG) (Intal) is a well-known anti-allergic agent which protects against allergen- and exercise-induced bronchospasms. The effect has been recognized non-acute, unlike that of bronchodilators. However, we have found that some patients with aspirin-intolerant asthma (AIA) show significant improvement soon after a single inhalation of SCG nebulized solution. In this study, we investigated the acute bronchodilator effect of SCG given by nebulizer in adult asthmatics, especially compairing AIA with non-AIA (aspirin-tolerant asthma) patients. Twenty patients with AIA and 11 with non-AIA participated in the study. After performing spirometry on remission, they inhaled either SCG via a nebulizer or 4 ml of placebo in a randomized double-blind fashion. After inhalation, spirometry was performed every ten minutes for one hour. The placebo used was a saline solution of the same osmolarity as that of the SCG nebulized solution. Placebo inhalation provoked asthmatic attacks in five of the patients with AIA and one with non-AIA, but SCG did not. In the AIA group, twelve out of the twenty patients also had improved nasal symptoms soon after inhalation of SCG. Forced expiratory volume in one second (FEV1) was significantly improved 10 minutes after inhalation of SCG. Fifty minutes after SCG inhalation, the percent degree of FEV1 improvement was approximately 17%. However, FEV1 was significantly decreased by approximately 14% after inhalation of placebo. In the non-AIA group, FEV1 was not increased after inhalation of SCG. V25 was not changed after inhalation of SCG in AIA and non-AIA groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oral cromolyn in food allergy: in vivo and in vitro effects

The results obtained in vivo in a group of 24 patients treated with oral cromolyn and compared to a group of 10 patients treated with placebo are reported. All patients were affected by adverse clinical reactions (urticaria and/or angioedema) related to food ingestion. A significant reduction of signs and symptoms were observed after oral cromolyn therapy only in the patients affected by true food allergy (FA), i.e., IgE mediated reactions. No adverse reactions appeared in the treated patients. Because we found an enhancing effect exerted in vitro by cromolyn (SCG) on T-cell responsiveness in previous studies, in the present investigation we analyzed in more detail in vitro effects of SCG on T lymphocytes [i.e., phytohemagglutinin-induced interleukin-2 (IL-2) production] and IL-2 receptor expression on T cells. No significant effect was induced by SCG on IL-2 production, whereas IL-2 receptor expression on surface of T cells appeared significantly increased (P less than 0.001) by adding SCG in cultures. These clinical and immunological results are analyzed and discussed in relation to a possible in vivo effect(s) of cromolyn in allergic diseases.     

Adenosine-induced bronchoconstriction in asthma: Role of mast cell-mediator release

Adenosine, when it is administered by inhalation to asthmatic subjects, is a potent bronchoconstrictor, although its mechanism of action is not known. Since adenosine has been demonstrated to potentiate IgE-dependent mediator release from mast cells, we have investigated the possible relationship between adenosine-induced bronchoconstriction and release of mast cell mediators in 14 asthmatic subjects. In the first study the effect of the putative mast cell-stabilizing drug cromolyn sodium (SCG) was observed on the dose-related changes in SG_aw and FEV₁ produced by inhaled adenosine and histamine in seven subjects. Inhaled SCG (20 mg) had no effect on the airway responses to histamine. In contrast SCG significantly protected against adenosine-induced bronchoconstriction in four of the seven subjects as reflected by a decrease in the airway response to the highest concentrations of adenosine, from 65 ± 8% to 12 ± 3% (mean ± SEM) for SG_aw and 31 ± 7% to 8 ± 3% for FEV,. Those three subjects whose adenosine response was unaffected by SCG had received regular SCG until 12 hr before the studies. In a separate study on eight subjects, a single inhalation of adenosine, causing a maximum 61 ± 4% fall in SG_aw at 10 min, had no significant effect on circulating levels of histamine, neutrophil chemotactic factor, or cyclic AMP. Together these two studies suggest that bronchoconstriction produced by adenosine is not a consequence of enhanced mast cell-mediator release and that the inhibitory effects of SCG occur by a mechanism other than through mast cell stabilization.     

A comparison of ketotifen with clemastine, ipratropium bromide and sodium cromoglycate in exercise-induced asthma

Exercise-induced asthma (EIA) was provoked by a standardized treadmill running for 8 min in seven atopic adult asthmatics. The tests were performed using a double-dummy technique after placebo, oral ketotifen, inhaled clemastine. ipratropium bromide and sodium cromoglycate (SCG), in a random single blind-fashion on different days. The mean post-exercise percentage fall in forced expiratory volume in 1 sec (FEV₁) was 47 (s.e. 6.95), 39 (s.e. 8.35), 27 (s.e. 7.17), 23 (s.e. 7.69) and 7.0 (s.e. 4.62)% respectively. There was significantly less mean bronchoconstriction with SCG (P < 0.01), ipratropium bromide and clemastine (P < 0.05) but not with ketotifen. Six out of seven individual patients had significant protection of EIA with sodium cromoglycate, four with ipratropium bromide, three with clemastine but only one with ketotifen. Ipratropium bromide and clemastine were bronchodilators at rest, whereas SCG and ketotifen were not. Despite its claims to work as a mast cell stabilizing drug, ketotifen in a single dose does not have an effect similar to sodium cromoglycate in EIA, nor does it compare with inhaled clemastine or ipratropium bromide.     

Sodium cromoglycate in histamine and methacholine reactivity in asthma

The effect of increasing concentrations of inhaled sodium cromoglycate (SCG) (2, 10, 20 and 40 g/l) on histamine and methacholine bronchial reactivity was studied in nine patients with extrinsic bronchial asthma. The responses to histamine and methacholine were expressed in terms of provocative concentrations producing 20% fall in the FEV₁ (PC₂₀)- The PC₂₀ for histamine and methacholine was unaffected by all the concentrations of SCG used in the study. These results suggest that the effect of SCG on the bronchial smooth muscle or on the muscarinic receptors is minimal.     

IgE levels in faecal extracts of patients with food allergy

IgE levels in faecal extracts (Copro-IgE levels) were investigated in food allergy (FA) patients before and after the challenge test administration of food allergens. IgE levels were measured by time-resolved fluoroimmunometric assay. In addition, the effects of administration of oral sodium cromoglycate (SCG) on the Copro-IgE levels were studied. Copro-IgE levels in patients with FA, who were placed on an elimination diet, did not differ from those of healthy children. After a challenge test immediate symptoms of urticaria and wheezing were observed in all FA patients. Copro-IgE levels in each patient increased markedly within 24 h of the challenge test. Moreover, FA patients treated orally with SCG showed neither the increase in Copro-IgE levels nor any remarkable symptoms after the challenge. Our results suggest that the increased Copro-IgE levels may be a specific consequence of the local immune response to food allergen stimulation in the gut mucosa.     

Double-blind comparison of the protective effect of sodium cromoglycate and ketotifen on exercise-induced asthma in adults

In a double-blind double-placebo study 10 asthmatics exercised on a treadmill after treatment for 1 week with placebo, or ketotifen 1 mg twice daily, or SCG 10 mg four times daily. The post-exercise percentage fall in FEV1 after SCG but not after ketotifen was significantly smaller than after placebo. A 1-week treatment with SCG but not ketotifen protected against EIA.     

Aspirin desensitization in the treatment of antiphospholipid syndrome during pregnancy in ASA-sensitive patients

PROBLEM: Antiphospholipid syndrome (APS) is associated with thrombosis and poor pregnancy outcome in the presence of antiphospholipid antibodies (aPL). Patients with aPL have a high risk of foetal loss. However, with low-dose aspirin (acetylsalicylic acid; ASA) in combination with subcutaneous heparin, the chances of full-term delivery increase. Nevertheless, ASA treatment is avoided in pregnant, ASA-sensitive women with APS. METHODS: Rapid oral challenge-desensitization to ASA was performed in four pregnant women with a history of APS and aspirin sensitivity. In three patients, desensitization was performed during pregnancy and before the next pregnancy in the fourth. Desensitization was carried out in the ICU using increasing doses of aspirin (0.1-125 mg) over a 24-hr period. RESULTS: Successful ASA desensitization was achieved in all the patients. No severe side effects occurred during the desensitization test. Only one patient required a small oral dose of antihistamines. CONCLUSIONS: Aspirin desensitization may be a safe alternative even during pregnancy if carefully monitored and permit patients with APS to receive treatment with ASA. This would constitute a new indication in pregnant women with APS and ASA sensitivity.     

Nedocromil sodium is more potent than sodium cromoglycate against AMP-induced bronchoconstriction in atopic asthmatic subjects

Nedocromil sodium is a new chemical entity which shows similar properties to sodium cromoglycate (SCG) and in addition exhibits a preferential activity in stabilizing mucosal mast cells. We have compared the effect of inhalation of nebulized placebo, SCG and nedocromil sodium on the bronchoconstrictor response to inhaled adenosine monophosphate (AMP) in eight atopic asthmatic subjects aged 25 yr (range 21-32 yr). The geometric mean provocation doses of AMP required to produce a 20% decrease in FEV1 (PD20FEV1) and a 40% decrease in Vmax30 (PD40 Vmax30) following placebo were 4.9 (0.3-14.2) and 1.8 (0.1-8.4) mumol respectively. Prior inhalation of both SCG and nedocromil sodium significantly inhibited the bronchoconstrictor response to AMP with PD20FEV1s of 36.6 (4.0-132.7) and 134 (12.4-560), and PD40 Vmax30 values of 20.5 (1.4-110) and 101.6 (5-560) mumol respectively (P less than 0.001). Nedocromil sodium was 3.9 (FEV1) and 8.0 (Vmax30) times more potent than SCG (P less than 0.001). In conclusion, both drugs inhibit the bronchoconstrictor response to inhaled AMP, and nedocromil is at least 4-8 times more potent than SCG.     

Inhibition of allergen-induced asthma by three forms of sodium cromoglycate

The effect of three forms of sodium cromoglycate (SCG), 20 mg, on allergen-induced early asthmatic responses was examined in ten stable asthmatics. Dose response allergen inhalation tests were performed on five occasions at intervals of from 1 to 2 weeks to determine the provocation concentration producing a 20% reduction (PC20 allergen) in FEV₁. Placebo was given before the first and the last tests to determine the reproducibility of responses to allergen over the study period; reduced responsiveness was observed in eight of the ten subjects. Major changes in levels-of specific serum antibodies of the IgE and IgG classes did not serve to explain the changes in bronchial responses although there was a trend which suggested IgG-related desensitization. The observed changes in bronchial responses and antibody levels illustrate the requirement for tests of reproducibility of responses by the use of placebo controls at the beginning and end of a series of allergen inhalation challenges. SCG as (i) a micronized powder with lactose, (ii) micropellets without lactose, or (iii) an aerosol, were inhaled double-blind, in random order, 5 min before the additional three allergen inhalation tests. PC₂₀ allergen was reduced following SCG in seven subjects; the differences were statistically significant for the group. There was no observed difference in efficacy between the different forms of SCG. In this study, the efficacy of SCG could not be related to age, atopic status, the initial level of allergen-specific IgE antibody, baseline FEV₁, level of bronchial responsiveness to inhaled histamine or an effect of SCG on responsiveness to histamine.     

Sodium cromoglycate-induced changes in the dose-response curve of inhaled methacholine in cystic fibrosis

Fifteen patients with cystic fibrosis (CF) (aged 7 to 20 years, mean 12.3 years), all known to respond to a methacholine (MCh) challenge, had two MCh challenges preceded by an inhalation of normal saline on one occasion and sodium cromoglycate (SCG) on another. The variation in baseline FEV1 between the two days of the study was 10% or less in all patients. Four patients (27%) gained significant protection with SCG against this non-allergenic challenge and, in two patients, SCG completely blocked the effects of MCh. These results would support clinical studies of SCG in some patients with CF but not the widespread use of SCG in CF.     

Lack of effect of the 5-lipoxygenase inhibitor zileuton in blocking oral aspirin challenges in aspirin-sensitive asthmatics.

BACKGROUND: Leukotrienes (LTs) have been implicated as major mediators of aspirin-(ASA)-induced respiratory reactions. It was therefore logical to assume that an inhibitor of 5-lipoxygenase (5-LO), such as zileuton, given before and during oral challenges with ASA, might prevent ASA-induced respiratory reactions. Indeed, in prior studies, pretreatment of ASA-sensitive respiratory disease patients with leukotriene modifiers eliminated or attenuated respiratory reactions upon re-challenge with the previously established provoking dose of ASA. However, doses higher than the provoking doses were not administered during these reported studies. OBJECTIVE: We wished to determine whether zileuton pretreatment could prevent ASA-induced respiratory reactions in our six volunteers with aspirin-sensitive respiratory disease when ASA challenge doses were started below the usual provoking dose of 60 mg and then increased until a respiratory reaction occurred. METHOD: Aspirin sensitivity was established previously in all six patients during a prior ASA oral challenge. In this study, pretreatment with zileuton 600 mg qid was initiated 7 days prior to, and continued during oral ASA challenges. Patients underwent single-blind oral ASA challenges with escalating doses of ASA, every 3 hours, according to our standard protocol. RESULTS: All six patients reacted to doses of ASA between 45 and 325 mg. Four patients experienced bronchospasm (FEV1 declined 19% to 53%) while receiving zileuton. All six had naso-ocular reactions. Concentrations of urine LTE4 also increased significantly (mean 334 pg/mg Cr at baseline, increasing to 1024 pg/mg Cr at respiratory reactions). CONCLUSIONS: During ASA challenges, zileuton, in standard doses of 600 mg qid was associated with increased synthesis of LTs in five of six patients and naso-ocular reactions in all six patients, as well as bronchospasm in four patients.     

The dose-duration effect of sodium cromoglycate in exercise-induced asthma

Eight patients with exercise-induced asthma participated in a single blind doseduration study comparing the protective effect of inhaled sodium cromoglycate (SCG) in increasing concentrations from 2 to 40 g/l. Saline was used as a control. Effects were assessed from the mean maximal fall in forced expiratory volume in 1 sec (FEV₁) after running on a treadmill for 8 min at 20, 150 and 270 min after drug administration There was no significant difference between the mean baseline values of FEV₁, before and after inhalation of saline and SCG on 4 days of exercise testing. In addition, the maximal percentage falls in FEV₁ in the three control exercise tests carried out at 20, 150 and 270 min after inhalation of saline were also comparable. The mean percentage fall in FEV₁, (s.e.m.) after saline, SCG 2 g./l, SCG 20 g/l and SCG 40 g/l were 29.3 (4.4). 11.7 (4.5), 8.3 (3.1) and 9.4 (2.3) respectively in the first test at 20 min and 24.5(5.1), 14.9 (4.2), 13.1 (2.5)and 13.7 (2.8) respectively in the second test at 150 after treatment. The inhibitory effect of SCG was statistically significant at all the concentrations used and the protection offered by the three concentrations of SCG was comparable. In the third exercise test at 270 min after treatment, the mean maximum percentage change after saline. SCG 2 g/l, SCG 20 g/l and SCG 40 g/l were 26-1 (4.8), 23.0 (6.1), 16.6 (5 0) and 15.8 (4.7) respectively. A partial protection in exercise-induced fall in FEV₁ was observed with 20 g/l and 40 g/l whereas the effect of SCG at 2 g/l had worn off by this time. This study demonstrates that SCG when given by nebulization is effective in exercise-induced asthma throughout the dose range currently used clinically. However, the protection with the lowest dose does not last beyond 2 hr. It is therefore important to adjust the frequency and timing of drug administration with different methods.     

Double-blind crossover trial with oral sodium cromoglycate in children with atopic dermatitis due to food allergy

Thirty-one children with atopic dermatitis, aged 6 months to 10 years, were selected for this trial. All had historical, clinical, and laboratory evidences that allergy to food was the cause of exacerbations of eczema. Either oral sodium cromoglycate (SCG) or a matching placebo was administered orally for 8 weeks, followed by the alternative treatment for a further 8-week period. During the first 4 weeks of each treatment period, patients remained on an exclusion diet. During the second 4 weeks, the offending food(s) was reintroduced into the diet. The severity of the eczema and the changes in severity as a result of diet or challenge were measured both by the clinician (using body diagrams) and by parents (using a daily diary card). Analysis of the clinician's scoring and the patient's diary card scores demonstrated a statistically significant difference in favour of SCG, especially in the group where the placebo preceded the active treatment. Sodium cromoglycate does seem to reduce the exacerbations of atopic dermatitis caused by food allergens.     

Protective activity of inhaled nonsteroidal antiinflammatory drugs on bronchial responsiveness to ultrasonically nebulized water.

Relatively high doses of oral aspirin are needed to afford a significant protective effect against the bronchial obstructive reaction to ultrasonically nebulized distilled water (UNDW) in asthmatic patients. Sodium salicylate at similar doses and indomethacin at normal dose afford no protection. The present study was undertaken to assess the protective activity of these drugs taken by inhalation. Thirteen asthmatic patients performed two UNDW challenges 20 minutes and 24 hours after inhalation of 900 mg lysine acetylsalicylate (L-ASA) or placebo. The volume of UNDW causing a 20% fall in FEV1 (UNDW PD20) was calculated by linear interpolation on the dose-response curve. UNDW response after placebo was not significantly different from the preliminary test (PD20 4.3 +/- 0.7 and 4.1 +/- 04 ml, respectively, mean +/- SE), whereas after L-ASA, UNDW PD20 increased to 17 +/- 2.7 ml (p < 0.01 vs placebo) and remained significantly increased after 24 hours. In another group of 12 patients under the same experimental conditions, an equivalent dose of inhaled sodium salicylate caused no effect. Finally, in a third group of asthmatic patients pretreatment with inhaled indomethacin at two dose levels (6 patients, 25 mg; 10 patients, 50 mg) resulted in a significant dose-related protective effect. These findings indicate that inhaled indomethacin and especially L-ASA exert against UNDW-induced bronchoconstriction a potent protective effect, which appears to be mediated by inhibition of local prostaglandin synthesis in the airways. This fact could have therapeutic implications.     

Means of increasing sensitivity of an in vitro diagnostic test for aspirin intolerance

BACKGROUND: Pseudo-allergic reactions caused by aspirin (acetyl salicylic acid; ASA) often resemble immediate-type hypersensitivity reactions consisting of urticaria and angioedema or rhinoconjunctivitis, asthma and nasal polyps. In the last few years, a new in vitro assay based on determination of sulfidoleucotrienes from isolated leucocytes (cellular allergen stimulation test - CAST) has been introduced for type I allergies and pseudoallergic reactions. In ASA intolerance, there is only limited experience using this assay with - in some studies - only moderate sensitivity. Furthermore, the necessity to use freshly isolated leucocytes from untreated patients is inconvenient for routine settings. OBJECTIVE: The purpose of our study was to search for possibilities of increasing the sensitivity of the test and to use stored blood samples which would permit shipping, two requirements for the clinical suitability of this test. PATIENTS AND METHODS: Leucotriene release in response to ASA and other non-steroidal anti-inflammatory drugs (NSAIDs) was analysed in 38 ASA-intolerant patients (predominantly airway-related symptoms n = 22; predominantly cutaneous symptoms n = 16) and 50 controls. The diagnosis of ASA intolerance was established by history and placebo-controlled oral challenge tests. RESULTS: Using 24 h-stored leucocytes obtained from 10 ASA-intolerant patients and 10 healthy controls there were no significant differences of leucotriene release by resting, ionomycin-, and anti FcepsilonRIalpha-stimulated leucocytes compared with freshly isolated leucocytes. Analysis of ASA + C5a-mediated leucotriene release by stored blood samples in combination with indomethacin- and diclofenac-mediated leucotriene release in ASA-intolerant patients (n = 38) resulted in an increased sensitivity (from 50 to 72.7% in ASA-intolerant patients with predominantly airway-related symptoms and from 81 to 100% in ASA-intolerant patients with predominantly skin symptoms) compared with assays in which only ASA + C5a-mediated leucotriene release has been determined. Moreover, the specificity of the assay remained high (96.7% when analysing different NSAIDs compared with > 99% when analysing only ASA + C5a-mediated leucotriene release). CONCLUSION: In vitro stimulation with ASA + C5a leucocyte stimulation with other NSAIDs should be performed to achieve a higher sensitivity. This finding can be explained by the clinical observation of a high ratio of cross-reactivities between the mentioned NSAIDs.     

Neutrophil chemotactic factor of anaphylaxis (NCF-A) release in aspirin-induced asthma

Neutrophil chemotactic activity (NCA) following oral challenge with aspirin (ASA) was determined in ASA-intolerant asthmatic subjects, and in ASA-tolerant asthmatic and normal subjects. There was a statistically significant fall in FEV₁ and a rise in NCA (P <0.01) following challenge in the ASA-sensitive subjects compared with that of the ASA-tolerant subjects and normal controls. No significant difference was observed between the latter two groups. The chemotactic factor identified in this study had a molecular weight greater than 150 000 which is consistent with NCF-A (neutrophil chemotactic factor of anaphylaxis). The ASA-induced fall in FEV₁ and rise in NCA was further studied in three of the ASA-intolerant asthmatic subjects, with and without pretreatment with inhaled sodium cromoglycate. In these subjects, the drug inhibited both the oral ASA-induced bronchoconstriction and the increase in neutrophil chemotactic activity. These results suggest that ASA-induced asthma involves mediator release from mast cells, as shown by the increase in NCA following ASA challenge and the protective effect of sodium cromoglycate which is considered to inhibit mast-cell degranulation.     

Hypersensitivity to acetylsalicylic acid (ASA) and tartrazine in patients with asthma

One-hundred and forty asthmatics were tested perorally with acetylsalicylic acid (ASA), and/or with the azo-colour tartrazine; a fall in PEF of more than 20% was accepted as a positive result. About one quarter of the patients displayed a positive reaction to one of the two tested agents. No significant correlation was found between the reactions of these, and the presence of atopy, nasal polyposis, sinusitis, rhinitis, sensitivity to cold air, the age at onset, duration of asthma, or history of sensitivity to alcoholic drinks. The history suggested sensitivity to ingested, possibly coloured, food and drink, in only about one third of the tartrazine-positive cases. The ASA provocation tests were mainly applied to patients with doubtful or negative histories of sensitivity to ASA-containing drugs. The frequency of cross-reactivity between the two tested agents was statistically significant; patients reacting to tartrazine were for the most part, also sensitive to ASA. Tests for sensitivity to analgesics and food additives should be conducted as a routine measure in asthmatics, and sensitive patients should be given information on suitable medication and dietary control.     

A comparison of the effects of sodium cromoglycate and beclomethasone dipropionate on pulmonary function and bronchial hyperreactivity in subjects with asthma

After a run-in period of 2 weeks, receiving a regimen of inhaled beta 2-agonists and/or theophyllines, 38 atopic patients with asthma with perennial symptoms were randomly allocated to receive an 8-week treatment of additional inhalation treatment with either sodium cromoglycate (SCG), 2 mg four times daily, and placebo beclomethasone dipropionate (BDP), or BDP, 200 micrograms twice daily, and placebo SCG. After crossover, each group received the opposite treatment for the final 8 weeks. FEV1, FVC, and provocation concentration of histamine causing a 20% fall in FEV1 (PC20) were determined monthly and peak expiratory flow (PEF) daily throughout the study. A significant increase in FEV1, FVC, and PEF (p less than 0.01) was observed after BDP treatment was started, and likewise, in the second period, an increase in both FEV1 and PEF (p less than 0.05) was observed. The total effect on logarithm-natural (Ln) (PC20), i.e., the mean effects of the two periods, was also significant (p less than 0.01). SCG, however, was most effective when it was used as the first drug, indicated by a significant increase in FVC in the first period (p less than 0.05). Neither in the first nor in the second period did SCG treatment influence the Ln (PC20) value positively, and the SCG treatment administered in the second period could not maintain the improvement in the pulmonary function (i.e., FEV1, FVC, and PEF) obtained initially with the BDP treatment. When the effect of BDP on FEV1, FVC, PEF, and Ln (PC20) was compared to the effect of SCG in the first 8-week treatment period, no significant difference was observed (p greater than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of inhaled salmeterol on methacholine responsiveness in subjects with asthma up to 12 hours.

The duration of the protective effect of 50 and 100 micrograms of inhaled salmeterol against methacholine-induced bronchoconstriction was compared with that of 200 micrograms of inhaled salbutamol in 12 patients with asthma with a baseline FEV1 of at least 70% and a provocative concentration of inhaled methacholine causing a 20% fall in FEV1 (PC20) greater than or equal to 8 mg/ml. The study was placebo controlled, double blind, randomized, and crossover. The bronchodilating effect was no longer significant 4 hours after inhalation of salbutamol, whereas the effect was still present 12 hours after administration of 50 and 100 micrograms of salmeterol. All active treatments caused PC20 to increase at 1 hour (p less than 0.05). PC20 (milligrams per milliliter) thus reached 3.7 +/- 0.8 after placebo, 13.8 +/- 3.0 after 50 micrograms of salmeterol, 23.2 +/- 4.7 after 100 micrograms of salmeterol, and 13.9 +/- 3.4 after 200 micrograms of salbutamol. The protective effect of 200 micrograms of salbutamol was no longer significant at 4 hours, whereas both doses of salmeterol protected against methacholine challenge up to 12 hours after inhalation (p less than 0.01). An increased incidence of tremor (2/12) and palpitations (2/12) was recorded after inhalation of 100 micrograms of salmeterol. We conclude that inhalation of 50 or 100 micrograms of salmeterol causes a long-lasting bronchodilatation and protects against methacholine-induced bronchoconstriction for at least 12 hours.