Br. J. clin. Pharmac. (1990), 30, 371-376
Inhaled sodium metabisulphite induced bronchoconstriction: inhibition by nedocromil sodium and sodium cromoglycate CAROLINE M. S. DIXON & PHILIP W. IND Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, DuCane Road, London W12 OHS
1 The effects of nedocromil sodium and sodium cromoglycate on bronchoconstriction induced by inhaled sodium metabisulphite have been studied in eight atopic subjects, three of whom had mild asthma. 2 Nedocromilsodium (4mg, 7.8 x lo-6M), sodiumcromoglycate (10mg, 24.1 x 10-6M) and matched placebo were administered by identical metered dose inhalers 30 min before a dose-response to sodium metabisulphite (5-100 mg ml-') was performed. 3 Maximum fall in sGaw after placebo pre-treatment was -43.9 ± 3.3% baseline (mean ± s.e. mean). At the same metabisulphite concentration maximum fall in sGaw after sodium cromoglycate was -13.0 ± 3.6% and after nedocromil sodium was +4.3 ± 6.8%. Nedocromil sodium prevented any significant fall in sGaw even after higher concentrations of metabisulphite. 4 Both nedocromil sodium, 4 mg, and sodium cromoglycate, 10 mg, inhibited sodium metabisulphite induced bronchoconstriction but nedocromil sodium was significantly more effective. Relative in vivo potency of the two drugs is broadly in line with other in vivo and in vitro studies.
Keywords nedocromil sodium sodium cromoglycate sodium metabisulphite bronchoconstriction Introduction
Sulphiting agents including metabisulphites are among the most widely used-preservatives in the food and pharmaceutical industries. Sensitivity to metabisulphites may explain severe bronchospasm reported after parenteral drug administration (Baker et al., 1982) and paradoxical bronchoconstriction reported in a few asthmatic patients after inhalation of bronchodilator solutions containing these agents (Koepke et al., 1984; Sher et al., 1985; Twarog et al., 1982; Werth et al., 1982). Certain individuals appear highly sensitive to food additives, and after ingestion may develop urticaria, angioedema (Supramaniam et al., 1986), flushing, bronchospasm and even anaphylaxis (Prenner et al., 1976). Recently attention has been focused on exacerbations of asthma after metabisulphite
ingestion (Delohery et al., 1984; Schwartz et al., 1983; Simon et al., 1982; Stevenson & Simon, 1981). The mechanism of bronchoconstriction after ingestion of metabisulphite is unclear. No evidence for an allergic mechanism was found (Stevenson & Simon, 1981) and a metabolic defect has been postulated (Jacobsen etal., 1984). The characteristic rapidity of onset (Delohery et al., 1984; Stevenson & Simon, 1981) and the similarity of asthmatic responses to orange drinks containing sulphur dioxide (SO2) (Freedman, 1977) led to the suggestion that SO2 liberation might be involved (Stevenson & Simon, 1981). The demonstration of SO2 generation from several bronchodilator preparations containing metabisulphite supports this (Koepke et al.,
Correspondence: Ms Caroline M. S. Dixon, Department of Medicine, Royal Postgraduate Medical School, London W12 OHS
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1984). It is generally accepted that SO2 induces bronchoconstriction, in a variety of species, by a parasympathetic reflex mechanism (Boushey et al., 1974; Nadel etal., 1965; Roberts etal., 1983; Widdicombe, 1954). However, nedocromil sodium and sodium cromoglycate are also effective in preventing SO2 induced bronchoconstriction in both asthmatic and atopic, non-asthmatic subjects (Snashall et al., 1983; Tan et al., 1982; Altounyan et al., 1986; Dixon et al., 1987a). We have recently investigated bronchoconstriction induced by inhaled metabisulphite in atopic and asthmatic subjects and shown inhibition by nedocromil sodium (Dixon et al., 1986b). We have now compared the effect of sodium cromoglycate and the more recent antiallergic compound, nedocromil sodium, on bronchoconstriction induced by inhaled sodium metabisulphite, to dissect further the mechanism of action of metabisulphite induced bronchoconstriction.
Study design Subjects were studied on 5 days. On days 1 and 2, which were randomised, methacholine and metabisulphite responses were examined. Specific airways conductance (sGaw) was determined by computerised body plethysmography (Chowienczyk et al., 1981). Each measurement was taken as the mean of six readings. Sodium metabisulphite (Sigma, Poole, Dorset) was dissolved in 0.9% normal saline. Normal saline was also used as the control solution. The sodium metabisulphite and methacholine solutions were administered by a breath actuated dosimeter (Mefar, Brescia, Italy). Each dose is given as five breaths, each breath delivering 0.024 ml. The mass median diameter of the particles is 3-5 ,u. Metabisulphite solutions 5, 10, 25, 50, 100 mg ml-l (3-120 p.M) had pH of 3.64.0 and an osmolality of 373-1968 mOsm kg-'. Methacholine chloride was freshly made up and dissolved in 0.9% normal saline to final doubling concentrations of 0.03-16 mg ml-1 (0.01919 FLM).
Methods
Subjects Eight atopic subjects were studied, three were mild asthmatics and five non-asthmatic. The subjects were non-selected volunteers. Subject characteristics are shown in Table 1. All gave written, informed consent to the studies which had the approval of the hospital Ethics Committee. Atopic status was determined by positive skin weal and flare reactions to five common allergens. Asthma was defined according to the classification criteria of the American Thoracic Society (American Thoracic Society, 1962). Asthmatic subjects used only inhaled ,-adrenoceptor agonists as necessary.
Increasing concentrations of metabisulphite and methacholine were inhaled until a greater than 35% fall in sGaw was obtained. Log doseresponses were constructed and from these the PD35, that is the cumulative dose of metabisulphite and methacholine causing a 35% fall, was calculated by interpolation. The subjects then entered the double-blind, randomised, placebo controlled trial to assess the effects of nedocromil sodium (4 mg) and sodium cromoglycate (10 mg). On study days 3-5, after baseline measurement of sGaw, nedocromil sodium (2 mg per puff), sodium cromoglycate (5 mg per puff) or placebo were given by identical metered dose inhalers, according to a double-blind, randomised, crossover design. The dose-response to sodium
Table 1 Subject details
Subject 1 2 3 4 5 6 7 8
PD35 MBS PD35 MCh
Age (years)
Sex
Atopy
Smoking history
(PM)
(>xM)
40 29 28 34 36 26 27 23
F F F M M F F M
+ + + + + + + +
X Y N N N Y N N
43.2 19.1 9.6 17.7 19.9 8.3 5.3 7.3
2.0 1.7 7.5 1.2 8.5 14.6 4.6 15.4
Inhaled metabisulphite-induced bronchoconstriction metabisulphite was repeated 30 min later to determine PD35 values or until the maximum tolerated concentration had been inhaled. There was an interval of at least 3 days between visits. Subjects were naive to the two active treatments. Data analysis
The comparison of the pre-study and placebo treatment cumulative PD35 data was made by the non-parametric Wilcoxon rank sign test, and the Altman Bland test to determine the coefficient of variation. For the assessment of drug treatment all data were logarithmically transformed to normalise distribution, and were analysed by two way analysis of variance. PD35 values are expressed by geometric mean and 95% confidence interval (CI). After nedocromil pre-treatment where a 35% fall in sGaw was not achieved a censored value of 120 FLM was assigned. Results
Inhaled metabisulphite produced dose dependent bronchoconstriction in all atopic nonasthmatic and all atopic asthmatic subjects who were non-selected volunteers. Inhaled metabisulphite had a metallic taste and caused cough at concentrations above 25 mg ml-1. Nedocromil appeared to reduce the cough associated with inhalation of the higher concentrations. Baseline sGaw did not differ significantly on the different study days and neither nedocromil
It
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sodium nor sodium cromoglycate showed any bronchodilator effect. Cumulative PD35 values were calculated for each metabisulphite dose-response on the prestudy day and after placebo and sodium cromoglycate. After nedocromil 35% falls in sGaw were not achieved at the highest dose of metabisulphite administered and values of 120 FJM were assigned. Pre-study metabisulphite PD35 geometric mean (CI) was 13.2 F±M (7.4 - 23.4) compared with 14.8 FM (9.9 - 2w2.1) after placebo. Individual results are shown in Figure 1. The Altman Bland coefficient of variation is -3 (1 ± 4) FM. These results demonstrate that the reproducibility of response to inhaled metabisulphite is very good. PD35 metabisulphite increased to 44.0 FM (23.4 - 82.0) after sodium cromoglycate showing significant inhibition (P < 0.05). However, after nedocromil sodium a 35% fall in sGaw after inhalation of the maximum metabisulphite concentration (100 mg ml-1) was not seen in any subject (Figure 2) therefore showing significant protection. Mean maximum fall in sGaw at the highest metabisulphite concentration reached after placebo was -43.9 ± 3.3%. After sodium cromoglycate, mean maximum fall, at this same concentration was -13.0 ± 3.6% and after nedocromil +4.3 ± 6.8%. Nedocromil sodium was significantly N 100
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t 1 Figure Individual cumulative PD35 sodium metabisulphite after pre-treatment with nedocromil sodium, 4 mg (N), sodium cromoglycate, 10 mg (C), and placebo (P). P
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Figure 2 Mean cumulative PD35 sodium metabisulphite after pre-treatment with nedocromil sodium, 4 mg (N), sodium cromoglycate, 10 mg (C), or placebo (P). * P < 0.05.
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more effective than sodium cromoglycate at the doses studied in preventing metabisulphite induced bronchoconstriction (P < 0.05). Similar protection occurred with nedocromil and cromoglycate in atopic subjects with or without asthma as in a previous study (Dixon et al., 1986b).
Discussion Inhaled nedocromil sodium and sodium cromoglycate both significantly inhibited the bronchoconstriction induced by metabisulphite inhalation. The reproducibility of metabisulphite bronchoprovocation was assessed by comparing the PD35 metabisulphite on the pre-study day with that on the placebo day. There was good agreement. Inhaled sodium metabisulphite induced bronchoconstriction in all these unselected atopic subjects with or without mild asthma. Inhaled sodium metabisulphite has previously been shown to induce bronchoconstriction in selected asthmatics in a small number of reports
(Koepke et al., 1984; Schwartz et al., 1984; Werth et al., 1982). We are however, unaware of any other workers reporting bronchoconstriction induced by inhaled sodium metabisulphite in non-asthmatic atopic subjects. The mechanism of bronchoconstriction induced by inhaled sodium metabisulphite is unknown. It is distinct from bronchoconstriction induced by ingested sodium metabisulphite which is only found in 8% of the asthmatic population (Simon et al., 1982). Furthermore, no correlation was found between bronchoconstriction after ingested metabisulphite and after inhaled sulphur dioxide (Delohery et al., 1984). We have shown that sulphur dioxide gas is generated when sodium metabisulphite is nebulised (Dixon et al., submitted 1989, J. Allergy clin. Immunol.). Asthmatic and atopic subjects are well known to be sensitive to concentrations of SO2 as low as 3 ppm (Sheppard et al., 1980). Others have reported SO2 measurements of 1.2 up to 40 ppm on nebulisation of metabisulphite containing solutions (Delohery et al., 1984; Schwartz, 1983). We have demonstrated concentrations of 3481 ppm sulphur dioxide at the nebuliser outlet (Dixon et al., submitted 1989, J. Allergy clin. Immunol.) but it is unknown how these relate to airway concentrations. Classical work in animals and in man has suggested that sulphur dioxide gas represents a parasympathetic cholinergic stimulus (Nadel etal., 1965). S02-induced bronchoconstriction is inhibited by nedocromil sodium
and sodium cromoglycate (Allistone et al., 1985; Dixon et al., 1987a) as we have shown for inhaled sodium metabisulphite. Furthermore, sulphur dioxide in solution at airway pH 6.6 (Bodem et al., 1983) probably exists mainly as metabisulphite, and this chemical species may be the main constrictor stimulus when SO2 is inhaled. However, anticholinergic blockade is only partially effective in inhibiting metabisulphite induced bronchoconstriction (Dixon et al., 1987b). The pH of our sodium metabisulphite solutions varied from 3.5-4.1 and this may constitute a stimulus to bronchoconstriction. Fine et al (1987) have recently reported pH-dependent bronchoconstriction in nine out of ten asthmatics inhaling sodium sulphite. At pH 4 99% of sodium sulphite would be present in solution as bisulphite. Sodium metabisulphite solutions are also hyperosmolar and it is not clear to what extent this too will contribute to bronchoconstriction (Eschenbacher et al., 1984). Response to inhaled sodium metabisulphite is probably not just another expression of non-specific bronchial hyperresponsiveness as we found no correlation with methacholine sensitivity though the numbers studied are small. Since sodium cromoglycate and nedocromil sodium both inhibit bronchoconstriction induced by metabisulphite comparison of the two has not helped unravel the mechanism. Nedocromil sodium and sodium cromoglycate both stabilise mast cells and act on other inflammatory cells to prevent the release of inflammatory mediators in vitro. Nedocromil sodium appears to have a more selective action on mucosal mast cells than on connective tissue mast cells at least in primates (Eady et al., 1985). Mucosal mast cells are thought to be the relevant mast cell type in human asthma. Both drugs also inhibit specific bronchial challenges such as allergen and exercise and also adenosine monophosphate, which may involve mast cells, but also non-specific bronchial provocation by fog, cold air and sulphur dioxide (Allistone et al., 1986; Breslin et al., 1980; Dixon et al., 1987a; Harries et al., 1981; Richards et al., 1989; Robuschi et al., 1985). This therefore suggests an action of sodium cromoglycate and nedocromil sodium in addition to mast cell stabilisation. There is no evidence to implicate mast cells in S02-induced bronchoconstriction. Terfenadine is a very potent specific histamine Hl-receptor antagonist and has been advocated as an indicator of mast cell involvement (Rafferty & Holgate, 1987). It has been shown to be effective in blocking bronchoconstriction caused by allergen (Curzen et al., 1987) and adenosine (Phillips et al., 1987). However we found no
Inhaled metabisulphite-induced bronchoconstriction effect of a high dose of terfenadine on metabisulphite induced bronchoconstriction (Dixon & Ind, 1988). This does not support the involvement of histamine in the mechanism of sodium metabisulphite induced bronchoconstriction. The rapid time course of onset of bronchoconstriction after sodium metabisulphite inhalation also favours a direct action rather than mast cell involvement. Nedocromil sodium and sodium cromoglycate both inhibit a number of bronchoconstrictor responses which act, at least in part, via neural reflexes (Dixon & Barnes, 1988). Sodium cromoglycate, when given intravenously, at plasma concentrations well below that required to inhibit mast cell activity, in vitro, inhibits S02-induced bronchoconstriction (Allistone et al., 1985). Sodium cromoglycate inhibits unmyelinated afferent nerve vagal pathways in dogs (Dixon et al., 1980). Inhaled bradykinin produces bronchoconstriction partially inhibited by parasympathetic blockade (Fuller et al., 1987) but also by nedocromil sodium and sodium cromoglycate (Dixon & Barnes, 1988). Bradykinin causes the release of sensory neuropeptides. Possibly metabisulphite may act similarly and stimulate C fibres or rapidly adapting receptors. Nedocromil and cromoglycate could then act by inhibition of afferent nerve activity (Dixon et al., 1987a,b). Nedocromil, 4 mg, was found to be significantly more effective than sodium cromoglycate, 10 mg, in blocking sodium metabisulphite in-
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duced bronchoconstriction. This is in line with its increased potency in a variety of in vitro studies (Gonzalez et al., 1987). Little information is available regarding the relative potency of nedocromil sodium and sodium cromoglycate in vivo. However, nedocromil sodium has recently been shown to be 4 to 8 times more potent, on a molar basis, than cromoglycate in protecting against AMP-induced bronchoconstriction (Richards et al., 1989). Though we have compared only one dose of each drug we chose the clinically relevant doses which could each be conveniently administered as two puffs from metered dose inhalers. Although we are unable to calculate individual dose ratios for nedocromil we have shown that nedocromil is more than three times more potent than cromoglycate in protecting against inhaled metabisulphite. In conclusion, inhaled sodium metabisulphite produces bronchoconstriction which is blocked more effectively by nedocromil sodium, 4 mg, than by sodium cromoglycate, 10 mg. The generation of large amounts of sulphur dioxide, the rapid onset of bronchoconstriction and the partial antagonism by anticholinergic blockade suggest that nedocromil sodium and sodium cromoglycate antagonise inhaled sodium metabisulphite by an effect on neural pathways. Inhalation of sodium metabisulphite may represent a convenient model for examining nonmast cell activity of these compounds in man, in vivo.
References Allistone, A., Collier, J. G., Davidson, R. N., Fuller, R. W. & Richardson, P. S. (1985). The effect of intravenous sodium cromoglycate on the bronchoconstriction induced by sulphur dioxide inhalation in man. Clin. Sci., 68, 227-232. Altounyan, R. E. C., Cole, M. & Lee, T. B. (1986). Inhibition of sulphur-dioxide induced bronchoconstriction by nedocromil sodium and sodium cromoglycate in non-asthmatic atopic subjects. Eur. J. resp. Dis., 69 (Suppl. 147), 274-276. American Thoracic Society (1962). Definition and classification of chronic bronchitis, asthma and pulmonary emphysema. Am. Rev. resp. Dis., 85, 762-768. Baker, G. J., Collett, P. & Allen, D. H. (1982). Bronchospasm induced by metabisulfite containing foods and drugs. Med. J. Aust., 2, 614. Bodem, C. R., Lampton, L. M., Miller, D. P., Tarka, E. F. & Everett, E. D. (1983). Endobronchial pH. Am. Rev. resp. Dis., 127, 39-44. Boushey, H. A., Richardson, P. S., Widdicombe, J. G. & Wise, J. C. M. (1974). The response
of laryngeal afferent fibres to mechanical and chemical stimuli. J. Physiol. (Lond.), 240, 153. Breslin, F. J., McFadden, E. R. & Ingram, R. H. (1980). The effects of cromolyn sodium on the airway response to hyperpnoea and cold air in asthma. Am. Rev. resp. Dis., 122, 11-15. Chowienczyk, P. J., Rees, P. J., Payne, J. & Clark, T. J. H. (1981). A new method for computer assisted determination of airways resistance. J. appl. Physiol., 50, 672. Curzen, N., Rafferty, P. & Holgate, S. T. (1987). Effects of a cyclo-oxygenase inhibitor, flurbiprofen, and an H1 receptor antagonist, terfenadine, alone and in combination on allergen induced immediate bronchoconstriction in man. Thorax, 42, 946-952. Delohery, J., Simmul, R., Castle, W. D. & Allen, D. (1984). The relationship of inhaled sulfur dioxide reactivity to ingested metabisulfite sensitivity in patients with asthma. Am. Rev. resp. Dis., 130, 1027-1032. Dixon, C. M. S. & Barnes, P. J. (1988). Bradykinin induced bronchoconstriction: inhibition by nedo-
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cromil sodium and sodium cromoglycate. Thorax, 43, 225. Dixon, C. M. S., Chilvers, E. R. & Ind, P. W. (1987b). The effect of nedocromil sodium and oxitropium bromide on sodium metabisulphite induced bronchoconstriction. Clin. Sci., 73 (Suppl. 17), 5. Dixon, C. M. S., Fuller, R. W. & Barnes, P. J. (1987a). Effect of nedocromil sodium on sulphur dioxide induced bronchoconstriction. Thorax, 42, 462. Dixon, C. M. S. & Ind, P. W. (1988). Metabisulphite induced bronchoconstriction: mechanisms. Am. Rev. resp. Dis., 137, 238. Dixon, M., Jackson, D. M. & Richards, I. M. (1980). The action of sodium cromoglycate on 'C' fibre endings in dog lung. Br. J. Pharmac., 70, 11-13. Eady, R. P., Greenwood, B., Jackson, D. M., Orr, T. S. C. & Wells, E. (1985). The effect of nedocromil sodium and sodium cromoglycate on antigen-induced bronchoconstriction in the Ascaris-sensitive monkey. Br. J. Pharmac., 85, 323-325. Eschenbacher, W. L., Boushey, H. A. & Sheppard, D. (1984). Alteration in osmolarity of inhaled aerosols causes bronchoconstriction and cough, but absence of a permanent anion causes cough alone. Am. Rev. resp. Dis., 129, 211-215. Fine, J. M., Gordon, T. & Sheppard, D. (1987). The roles of pH and ionic species in sulfur dioxide- and sulfite-induced bronchoconstriction. Am. Rev. resp. Dis., 136, 1122-1126. Freedman, B. J. (1977). Asthma induced by sulfur dioxide, benzoate and tartrazine contained in orange drinks. Clin. Allergy, 7, 407. Fuller, R. W., Dixon, C. M. S., Cuss, F. M. C. & Barnes, P. J. (1987). Bradykinin-induced bronchoconstriction in humans. Am. Rev. resp. Dis., 135, 176-180. Gonzalez, J. P. & Brogden, R. N. (1987). Nedocromil sodium: A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in the treatment of irreversible obstructive airways disease. Drugs, 34, 560-577. Harries, M. G., Parkes, P. E. G., Lessof, M. K. & Off, T. S. C. (1981). Role of bronchial irritant receptors in asthma. Lancet, i, 5-7. Jacobsen, D. W., Simon, R. A. & Singh, M. (1984). Sulfite oxidase deficiency and cobalmin protection in sulfite sensitive asthmatics (Abstract). J. Allergy clin. Immunol., 73, 133. Koepke, G. W., Selner, J. C., Christopher, K. & Glover, G. (1984). Inhaled metabisulfite sensitivity (Abstract). J. Allergy clin. Immunol., 73, 135. Koepke, J. W., Staudenmayer, H. & Selner, J. C. (1985). Inhaled metabisulfite sensitivity. Ann. Allergy, 54, 213-215. Nadel, J. A., Salem, H., Tamplin, B. & Tokiwa, Y. (1965). Mechanism of bronchoconstriction during inhalation of sulfur dioxide. J. appl. Physiol., 20, 164. Prenner, B. M. & Stevens, J. J. (1976). Anaphylaxis after ingestion of sodium bisulfite. Ann. Allergy, 37, 180.
Phillips, G. D., Rafferty, P., Beasley, R. & Holgate, S. T. (1987). Effect of oral terfenadine on the bronchoconstrictor response to inhaled histamine and adenosine 5'monophosphate in non-atopic asthma. Thorax, 42, 939-945. Rafferty, P. & Holgate, S. T. (1987). Terfenadine (Seldane) is a potent and selective histamine H1receptor antagonist in asthmatic airways. Am. Rev. resp. Dis., 135, 181-184. Richards, R., Phillips, G. D. & Holgate, S. T. (1989). Nedocromil sodium is more potent than sodium cromoglycate against AMP-induced bronchoconstriction in atopic asthmatic subjects. Clin. exp. Allergy, 19, 285-291. Roberts, A. M., Hahn, H. L., Schulz, H. D., Nadel, J. A., Coleridge, H. M. & Coleridge, J. C. G. (1983). Afferent vagal C-fibres are responsible for the reflex airway constriction and secretion evoked by pulmonary administration of SO2 in dogs. Physiologist, 25, 226. Robuschi, M., Simone, P., Vaghi, A. & Bianco, S. (1986). Prevention of fog-induced bronchoconstriction by nedocromil sodium. Eur. J. resp. Dis., 69 (Suppl.), 286-288. Sheppard, D., Wong, W. S., Uehara, C. F., Nadel, J. A. & Boushey, H. A. (1980). Lower threshold and greater bronchomotor responsiveness of asthmatic subjects to sulfur dioxide. Am. Rev. resp. Dis., 122, 873-878. Schwartz, H. J. (1983). Sensitivity to ingested metabisulfite: variations in clinical presentation. J. Allergy clin. Immunol., 71, 487-489. Sher, T. H. & Schwartz, H. J. (1985). Bisulfite sensitivity manifesting as an allergic reaction to aerosol therapy. Ann. Allergy, 54, 224-226. Simon, R. A., Green, L. & Stevenson, D. D. (1982). The incidence of ingested metabisulfite sensitivity in an asthmatic population (Abstract). J. Allergy clin. Immunol., 69, 118. Snashall, P. D. & Baldwin, C. (1983). Mechanisms of sulphur dioxide induced bronchoconstriction in normal and asthmatic man. Thorax, 37, 118. Stevenson, D. D. & Simon, R. A. (1981). Sensitivity to ingested metabisulfites in asthmatic subjects. J. Allergy clin. Immunol., 68, 26-32. Supramaniam, G. & Warner, J. 0. (1986). Artificial food additive intolerance in patients with angiooedema and urticaria. Lancet, ii, 907. Tan, W. C., Cripps, E., Douglas, N. & Sudlow, M. F. (1982). Protective effect of drugs on bronchoconstriction induced by sulphur dioxide. Thorax, 37, 671. Trautlein, J., Allegra, J., Field, J. & Gillin, M. (1976). Paradoxic bronchospasm after inhalation of isoproterenol. Chest, 70, 711-714. Twarog, F. J. & Leung, D. Y. M. (1982). Anaphylaxis to a component of isoetharine (sodium bisulfite). J. Am. med. Ass., 248, 2030. Werth, G. E. (1982). Inhaled metabisulfite sensitivity. J. Allergy clin. Immunol., 70, 143. Widdicombe, J. C. (1954). Receptors in the trachea and bronchi of the cat. J. Physiol. (Lond.), 123, 242. (Received 20 March 1989,
accepted 12 February 1990)
Inhaled sodium metabisulphite induced bronchoconstriction: inhibition by nedocromil sodium and sodium cromoglycate CAROLINE M. S. DIXON & PHILIP W. IND Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, DuCane Road, London W12 OHS
1 The effects of nedocromil sodium and sodium cromoglycate on bronchoconstriction induced by inhaled sodium metabisulphite have been studied in eight atopic subjects, three of whom had mild asthma. 2 Nedocromilsodium (4mg, 7.8 x lo-6M), sodiumcromoglycate (10mg, 24.1 x 10-6M) and matched placebo were administered by identical metered dose inhalers 30 min before a dose-response to sodium metabisulphite (5-100 mg ml-') was performed. 3 Maximum fall in sGaw after placebo pre-treatment was -43.9 ± 3.3% baseline (mean ± s.e. mean). At the same metabisulphite concentration maximum fall in sGaw after sodium cromoglycate was -13.0 ± 3.6% and after nedocromil sodium was +4.3 ± 6.8%. Nedocromil sodium prevented any significant fall in sGaw even after higher concentrations of metabisulphite. 4 Both nedocromil sodium, 4 mg, and sodium cromoglycate, 10 mg, inhibited sodium metabisulphite induced bronchoconstriction but nedocromil sodium was significantly more effective. Relative in vivo potency of the two drugs is broadly in line with other in vivo and in vitro studies.
Keywords nedocromil sodium sodium cromoglycate sodium metabisulphite bronchoconstriction Introduction
Sulphiting agents including metabisulphites are among the most widely used-preservatives in the food and pharmaceutical industries. Sensitivity to metabisulphites may explain severe bronchospasm reported after parenteral drug administration (Baker et al., 1982) and paradoxical bronchoconstriction reported in a few asthmatic patients after inhalation of bronchodilator solutions containing these agents (Koepke et al., 1984; Sher et al., 1985; Twarog et al., 1982; Werth et al., 1982). Certain individuals appear highly sensitive to food additives, and after ingestion may develop urticaria, angioedema (Supramaniam et al., 1986), flushing, bronchospasm and even anaphylaxis (Prenner et al., 1976). Recently attention has been focused on exacerbations of asthma after metabisulphite
ingestion (Delohery et al., 1984; Schwartz et al., 1983; Simon et al., 1982; Stevenson & Simon, 1981). The mechanism of bronchoconstriction after ingestion of metabisulphite is unclear. No evidence for an allergic mechanism was found (Stevenson & Simon, 1981) and a metabolic defect has been postulated (Jacobsen etal., 1984). The characteristic rapidity of onset (Delohery et al., 1984; Stevenson & Simon, 1981) and the similarity of asthmatic responses to orange drinks containing sulphur dioxide (SO2) (Freedman, 1977) led to the suggestion that SO2 liberation might be involved (Stevenson & Simon, 1981). The demonstration of SO2 generation from several bronchodilator preparations containing metabisulphite supports this (Koepke et al.,
Correspondence: Ms Caroline M. S. Dixon, Department of Medicine, Royal Postgraduate Medical School, London W12 OHS
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1984). It is generally accepted that SO2 induces bronchoconstriction, in a variety of species, by a parasympathetic reflex mechanism (Boushey et al., 1974; Nadel etal., 1965; Roberts etal., 1983; Widdicombe, 1954). However, nedocromil sodium and sodium cromoglycate are also effective in preventing SO2 induced bronchoconstriction in both asthmatic and atopic, non-asthmatic subjects (Snashall et al., 1983; Tan et al., 1982; Altounyan et al., 1986; Dixon et al., 1987a). We have recently investigated bronchoconstriction induced by inhaled metabisulphite in atopic and asthmatic subjects and shown inhibition by nedocromil sodium (Dixon et al., 1986b). We have now compared the effect of sodium cromoglycate and the more recent antiallergic compound, nedocromil sodium, on bronchoconstriction induced by inhaled sodium metabisulphite, to dissect further the mechanism of action of metabisulphite induced bronchoconstriction.
Study design Subjects were studied on 5 days. On days 1 and 2, which were randomised, methacholine and metabisulphite responses were examined. Specific airways conductance (sGaw) was determined by computerised body plethysmography (Chowienczyk et al., 1981). Each measurement was taken as the mean of six readings. Sodium metabisulphite (Sigma, Poole, Dorset) was dissolved in 0.9% normal saline. Normal saline was also used as the control solution. The sodium metabisulphite and methacholine solutions were administered by a breath actuated dosimeter (Mefar, Brescia, Italy). Each dose is given as five breaths, each breath delivering 0.024 ml. The mass median diameter of the particles is 3-5 ,u. Metabisulphite solutions 5, 10, 25, 50, 100 mg ml-l (3-120 p.M) had pH of 3.64.0 and an osmolality of 373-1968 mOsm kg-'. Methacholine chloride was freshly made up and dissolved in 0.9% normal saline to final doubling concentrations of 0.03-16 mg ml-1 (0.01919 FLM).
Methods
Subjects Eight atopic subjects were studied, three were mild asthmatics and five non-asthmatic. The subjects were non-selected volunteers. Subject characteristics are shown in Table 1. All gave written, informed consent to the studies which had the approval of the hospital Ethics Committee. Atopic status was determined by positive skin weal and flare reactions to five common allergens. Asthma was defined according to the classification criteria of the American Thoracic Society (American Thoracic Society, 1962). Asthmatic subjects used only inhaled ,-adrenoceptor agonists as necessary.
Increasing concentrations of metabisulphite and methacholine were inhaled until a greater than 35% fall in sGaw was obtained. Log doseresponses were constructed and from these the PD35, that is the cumulative dose of metabisulphite and methacholine causing a 35% fall, was calculated by interpolation. The subjects then entered the double-blind, randomised, placebo controlled trial to assess the effects of nedocromil sodium (4 mg) and sodium cromoglycate (10 mg). On study days 3-5, after baseline measurement of sGaw, nedocromil sodium (2 mg per puff), sodium cromoglycate (5 mg per puff) or placebo were given by identical metered dose inhalers, according to a double-blind, randomised, crossover design. The dose-response to sodium
Table 1 Subject details
Subject 1 2 3 4 5 6 7 8
PD35 MBS PD35 MCh
Age (years)
Sex
Atopy
Smoking history
(PM)
(>xM)
40 29 28 34 36 26 27 23
F F F M M F F M
+ + + + + + + +
X Y N N N Y N N
43.2 19.1 9.6 17.7 19.9 8.3 5.3 7.3
2.0 1.7 7.5 1.2 8.5 14.6 4.6 15.4
Inhaled metabisulphite-induced bronchoconstriction metabisulphite was repeated 30 min later to determine PD35 values or until the maximum tolerated concentration had been inhaled. There was an interval of at least 3 days between visits. Subjects were naive to the two active treatments. Data analysis
The comparison of the pre-study and placebo treatment cumulative PD35 data was made by the non-parametric Wilcoxon rank sign test, and the Altman Bland test to determine the coefficient of variation. For the assessment of drug treatment all data were logarithmically transformed to normalise distribution, and were analysed by two way analysis of variance. PD35 values are expressed by geometric mean and 95% confidence interval (CI). After nedocromil pre-treatment where a 35% fall in sGaw was not achieved a censored value of 120 FLM was assigned. Results
Inhaled metabisulphite produced dose dependent bronchoconstriction in all atopic nonasthmatic and all atopic asthmatic subjects who were non-selected volunteers. Inhaled metabisulphite had a metallic taste and caused cough at concentrations above 25 mg ml-1. Nedocromil appeared to reduce the cough associated with inhalation of the higher concentrations. Baseline sGaw did not differ significantly on the different study days and neither nedocromil
It
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sodium nor sodium cromoglycate showed any bronchodilator effect. Cumulative PD35 values were calculated for each metabisulphite dose-response on the prestudy day and after placebo and sodium cromoglycate. After nedocromil 35% falls in sGaw were not achieved at the highest dose of metabisulphite administered and values of 120 FJM were assigned. Pre-study metabisulphite PD35 geometric mean (CI) was 13.2 F±M (7.4 - 23.4) compared with 14.8 FM (9.9 - 2w2.1) after placebo. Individual results are shown in Figure 1. The Altman Bland coefficient of variation is -3 (1 ± 4) FM. These results demonstrate that the reproducibility of response to inhaled metabisulphite is very good. PD35 metabisulphite increased to 44.0 FM (23.4 - 82.0) after sodium cromoglycate showing significant inhibition (P < 0.05). However, after nedocromil sodium a 35% fall in sGaw after inhalation of the maximum metabisulphite concentration (100 mg ml-1) was not seen in any subject (Figure 2) therefore showing significant protection. Mean maximum fall in sGaw at the highest metabisulphite concentration reached after placebo was -43.9 ± 3.3%. After sodium cromoglycate, mean maximum fall, at this same concentration was -13.0 ± 3.6% and after nedocromil +4.3 ± 6.8%. Nedocromil sodium was significantly N 100
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t 1 Figure Individual cumulative PD35 sodium metabisulphite after pre-treatment with nedocromil sodium, 4 mg (N), sodium cromoglycate, 10 mg (C), and placebo (P). P
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Figure 2 Mean cumulative PD35 sodium metabisulphite after pre-treatment with nedocromil sodium, 4 mg (N), sodium cromoglycate, 10 mg (C), or placebo (P). * P < 0.05.
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C. M. S. Dixon & P. W. Ind
more effective than sodium cromoglycate at the doses studied in preventing metabisulphite induced bronchoconstriction (P < 0.05). Similar protection occurred with nedocromil and cromoglycate in atopic subjects with or without asthma as in a previous study (Dixon et al., 1986b).
Discussion Inhaled nedocromil sodium and sodium cromoglycate both significantly inhibited the bronchoconstriction induced by metabisulphite inhalation. The reproducibility of metabisulphite bronchoprovocation was assessed by comparing the PD35 metabisulphite on the pre-study day with that on the placebo day. There was good agreement. Inhaled sodium metabisulphite induced bronchoconstriction in all these unselected atopic subjects with or without mild asthma. Inhaled sodium metabisulphite has previously been shown to induce bronchoconstriction in selected asthmatics in a small number of reports
(Koepke et al., 1984; Schwartz et al., 1984; Werth et al., 1982). We are however, unaware of any other workers reporting bronchoconstriction induced by inhaled sodium metabisulphite in non-asthmatic atopic subjects. The mechanism of bronchoconstriction induced by inhaled sodium metabisulphite is unknown. It is distinct from bronchoconstriction induced by ingested sodium metabisulphite which is only found in 8% of the asthmatic population (Simon et al., 1982). Furthermore, no correlation was found between bronchoconstriction after ingested metabisulphite and after inhaled sulphur dioxide (Delohery et al., 1984). We have shown that sulphur dioxide gas is generated when sodium metabisulphite is nebulised (Dixon et al., submitted 1989, J. Allergy clin. Immunol.). Asthmatic and atopic subjects are well known to be sensitive to concentrations of SO2 as low as 3 ppm (Sheppard et al., 1980). Others have reported SO2 measurements of 1.2 up to 40 ppm on nebulisation of metabisulphite containing solutions (Delohery et al., 1984; Schwartz, 1983). We have demonstrated concentrations of 3481 ppm sulphur dioxide at the nebuliser outlet (Dixon et al., submitted 1989, J. Allergy clin. Immunol.) but it is unknown how these relate to airway concentrations. Classical work in animals and in man has suggested that sulphur dioxide gas represents a parasympathetic cholinergic stimulus (Nadel etal., 1965). S02-induced bronchoconstriction is inhibited by nedocromil sodium
and sodium cromoglycate (Allistone et al., 1985; Dixon et al., 1987a) as we have shown for inhaled sodium metabisulphite. Furthermore, sulphur dioxide in solution at airway pH 6.6 (Bodem et al., 1983) probably exists mainly as metabisulphite, and this chemical species may be the main constrictor stimulus when SO2 is inhaled. However, anticholinergic blockade is only partially effective in inhibiting metabisulphite induced bronchoconstriction (Dixon et al., 1987b). The pH of our sodium metabisulphite solutions varied from 3.5-4.1 and this may constitute a stimulus to bronchoconstriction. Fine et al (1987) have recently reported pH-dependent bronchoconstriction in nine out of ten asthmatics inhaling sodium sulphite. At pH 4 99% of sodium sulphite would be present in solution as bisulphite. Sodium metabisulphite solutions are also hyperosmolar and it is not clear to what extent this too will contribute to bronchoconstriction (Eschenbacher et al., 1984). Response to inhaled sodium metabisulphite is probably not just another expression of non-specific bronchial hyperresponsiveness as we found no correlation with methacholine sensitivity though the numbers studied are small. Since sodium cromoglycate and nedocromil sodium both inhibit bronchoconstriction induced by metabisulphite comparison of the two has not helped unravel the mechanism. Nedocromil sodium and sodium cromoglycate both stabilise mast cells and act on other inflammatory cells to prevent the release of inflammatory mediators in vitro. Nedocromil sodium appears to have a more selective action on mucosal mast cells than on connective tissue mast cells at least in primates (Eady et al., 1985). Mucosal mast cells are thought to be the relevant mast cell type in human asthma. Both drugs also inhibit specific bronchial challenges such as allergen and exercise and also adenosine monophosphate, which may involve mast cells, but also non-specific bronchial provocation by fog, cold air and sulphur dioxide (Allistone et al., 1986; Breslin et al., 1980; Dixon et al., 1987a; Harries et al., 1981; Richards et al., 1989; Robuschi et al., 1985). This therefore suggests an action of sodium cromoglycate and nedocromil sodium in addition to mast cell stabilisation. There is no evidence to implicate mast cells in S02-induced bronchoconstriction. Terfenadine is a very potent specific histamine Hl-receptor antagonist and has been advocated as an indicator of mast cell involvement (Rafferty & Holgate, 1987). It has been shown to be effective in blocking bronchoconstriction caused by allergen (Curzen et al., 1987) and adenosine (Phillips et al., 1987). However we found no
Inhaled metabisulphite-induced bronchoconstriction effect of a high dose of terfenadine on metabisulphite induced bronchoconstriction (Dixon & Ind, 1988). This does not support the involvement of histamine in the mechanism of sodium metabisulphite induced bronchoconstriction. The rapid time course of onset of bronchoconstriction after sodium metabisulphite inhalation also favours a direct action rather than mast cell involvement. Nedocromil sodium and sodium cromoglycate both inhibit a number of bronchoconstrictor responses which act, at least in part, via neural reflexes (Dixon & Barnes, 1988). Sodium cromoglycate, when given intravenously, at plasma concentrations well below that required to inhibit mast cell activity, in vitro, inhibits S02-induced bronchoconstriction (Allistone et al., 1985). Sodium cromoglycate inhibits unmyelinated afferent nerve vagal pathways in dogs (Dixon et al., 1980). Inhaled bradykinin produces bronchoconstriction partially inhibited by parasympathetic blockade (Fuller et al., 1987) but also by nedocromil sodium and sodium cromoglycate (Dixon & Barnes, 1988). Bradykinin causes the release of sensory neuropeptides. Possibly metabisulphite may act similarly and stimulate C fibres or rapidly adapting receptors. Nedocromil and cromoglycate could then act by inhibition of afferent nerve activity (Dixon et al., 1987a,b). Nedocromil, 4 mg, was found to be significantly more effective than sodium cromoglycate, 10 mg, in blocking sodium metabisulphite in-
375
duced bronchoconstriction. This is in line with its increased potency in a variety of in vitro studies (Gonzalez et al., 1987). Little information is available regarding the relative potency of nedocromil sodium and sodium cromoglycate in vivo. However, nedocromil sodium has recently been shown to be 4 to 8 times more potent, on a molar basis, than cromoglycate in protecting against AMP-induced bronchoconstriction (Richards et al., 1989). Though we have compared only one dose of each drug we chose the clinically relevant doses which could each be conveniently administered as two puffs from metered dose inhalers. Although we are unable to calculate individual dose ratios for nedocromil we have shown that nedocromil is more than three times more potent than cromoglycate in protecting against inhaled metabisulphite. In conclusion, inhaled sodium metabisulphite produces bronchoconstriction which is blocked more effectively by nedocromil sodium, 4 mg, than by sodium cromoglycate, 10 mg. The generation of large amounts of sulphur dioxide, the rapid onset of bronchoconstriction and the partial antagonism by anticholinergic blockade suggest that nedocromil sodium and sodium cromoglycate antagonise inhaled sodium metabisulphite by an effect on neural pathways. Inhalation of sodium metabisulphite may represent a convenient model for examining nonmast cell activity of these compounds in man, in vivo.
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accepted 12 February 1990)
