The role of titratable acidity in acid aerosol-induced bronchoconstriction

Bile acids-induced lung injury: update of reverse translational biology

The presence of bile acids in lung tissue is associated with some clinical features observed in various medical specialties, but it took time to understand that these are due to a "bile acid-induced lung injury" since specific translational studies and cross-disciplinary awareness were lacking. We used a reverse translational approach to update and summarize the current knowledge about the mechanisms of bile acid-induced lung injury. This has been done in a cross-disciplinary fashion since these conditions may occur in patients of various age and in different medical fields. We here define these clinical conditions, then we review the physiopathology of these conditions and the animal models used to mimic them and, finally, their pathobiology. Mechanisms of bile acid-induced lung injury have been partially clarified overtime and are represented by: 1) the interaction with secretory phospholipase A2 pathway, 2) the effect on surfactant function and structure, 3) the biological effects on inflammation and local immunity, 4) the direct cellular toxicity. These mechanisms are schematically illustrated and histological comparisons between ARDS induced by bile acids and other triggers are also provided. Based on these mechanisms we propose possible direct therapeutic applications and, finally, we discuss further research steps to improve the understanding of processes that generate pathological clinical conditions.

A randomized clinical trial of nebulized magnesium sulfate in addition to albuterol in the treatment of acute mild-to-moderate asthma exacerbations in adults

STUDY OBJECTIVE

We sought to compare the efficacy and safety of nebulized magnesium sulfate (MgSO(4)) plus albuterol with that of albuterol alone in adult patients with mild-to-moderate acute asthma exacerbations.

METHODS

Patients were randomized to receive nebulized MgSO(4) (384 mg in 6 mL of sterile water) or an equal volume of placebo (normal saline solution) in a double-blind fashion after each dose of nebulized albuterol administered (2.5 mg/3 mL) every 20 minutes for the first hour of the study. Spirometry was performed at baseline and every 20 minutes for 2 hours. Monitoring for safety included vital signs, pulse oximetry, and serum magnesium levels. Improvement in percent predicted forced expiratory volume in 1 second was chosen as a primary efficacy end point.

RESULTS

Among 74 patients enrolled, 37 were randomized to each of 2 study groups. There were no statistically or clinically significant differences between the 2 study groups in percent predicted forced expiratory volume in 1 second at any point during the trial or overall. There were no significant differences in vital signs, pulse oximetry, or serum magnesium levels at any point during the study.

CONCLUSION

The combination of nebulized MgSO(4) and albuterol provides no benefit in addition to that provided by therapy with albuterol in adult patients with mild-to-moderate asthma exacerbations. The efficacy of nebulized MgSO(4) in patients with severe asthma exacerbations remains unknown.

Stability of frozen methacholine solutions in unit-dose syringes for bronchoprovocation

OBJECTIVE

Methacholine solutions < 0.25 mg/mL must be prepared fresh daily, while concentrations > or = 0.25 mg/mL must be prepared at 2-week intervals according to US Food and Drug Administration-required labeling. The purpose of this report was to determine whether freezing methacholine solutions in unit-dose syringes would allow less frequent preparation.

DESIGN

Diluent containing 0.5% sodium chloride, 0.275% sodium bicarbonate, and 0.4% phenol was used to prepare 11 concentrations of methacholine ranging from 0.031 to 32.0 mg/mL. Three milliliters of each dilution was placed into 5-mL polypropylene syringes and immediately frozen. Methacholine concentrations were determined using a validated high-performance liquid chromatography assay after preparation (time zero) and at 0.5, 1, 1.5, 2, 3, 4, 5, and 6 months. On the day of analysis, the samples were allowed to thaw to room temperature. An additional set of each dilution was stored at room temperature for 24 h after thawing and then analyzed for methacholine.

RESULTS

Samples > or = 0.062 mg/mL analyzed immediately after thawing retained > or = 90% of labeled potency for at least 6 months, while the 0.031-mg/mL sample retained 90% potency for 4 months. Most samples analyzed 24 h after thawing lost potency.

CONCLUSION

If prepared and stored in unit-dose syringes frozen, methacholine solutions containing 0.062 to 32.0 mg/mL can be prepared at 6-month intervals, and solutions containing 0.031 mg/mL can be prepared at 4-month intervals. Once thawed, unused methacholine solutions should be discarded.

Airway surface liquid pH in well-differentiated airway epithelial cell cultures and mouse trachea

Airway surface liquid (ASL) pH has been proposed to be important in the pathophysiology of cystic fibrosis, asthma, and cough. Ratio image analysis was used to measure pH in the ASL after staining with the fluorescent pH indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)-dextran. ASL pH in bovine airway cell cultures grown at an air-liquid interface was 6.98 +/- 0.06 in the absence and 6.81 +/- 0.04 in the presence of HCO/CO(2). Steady-state ASL pH changed in parallel to changes in bath pH and was acidified by Na(+) or Cl(-) replacement but was not affected by the inhibitors amiloride, glibenclamide, or 4,4'-dinitrostilbene-2,2'-disulfonic acid. In response to sudden acidification or alkalization of the ASL by approximately 0.4 pH units by HCl/NaOH, ASL pH recovered to its initial value at a rate of 0.035 pH units/min (-HCO) and 0.060 pH units/min (+HCO); the pH recovery rate was reduced by amiloride and H(2)DIDS. In anesthetized mice in which the trachea was surgically exposed for measurement of BCECF-dextran fluorescence through the translucent tracheal wall, ASL pH was 7.14 +/- 0.01. ASL pH was sensitive to changes in blood pH created by metabolic (HCl or NaHCO(3) infusion) or respiratory (hyperventilation, hypoventilation) mechanisms. ASL pH is thus primarily determined by basolateral fluid pH, and H(+)/OH(-) transport between the ASL and basolateral fluid involves amiloride-sensitive Na(+)/H(+) exchange and stilbene-sensitive Cl(-)/HCO exchange. The rapid response of ASL pH to changes in systemic acid-base status may contribute to airway hypersensitivity in asthma and other airway diseases.

Health effects of sulfur-related environmental air pollution. IV. Respiratory lung function

Recently concern has been raised about health effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on respiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to 1-microm neutral sulfite aerosol with a particle-associated sulfur(IV) concentration of 0.32 mg m(-3) and for 6 h/day to 1.1-microm acidic sulfate aerosol providing an hydrogen ion concentration of 15.2 micromol m(-3) for inhalation. Prior to exposure the dogs were kept under clean air conditions for 16 mo to establish physiological baseline values for each dog. A second group of eight dogs (control) was kept for the entire study under clean air conditions. Before and at the end of exposure, respiratory lung function was evaluated in both groups in anesthetized and mechanically ventilated animals. Lung volumes as well as static and dynamic lung compliances were measured. Series dead-space volumes and slopes of the alveolar plateau for respiratory (O2, CO2) and inert test gases (He, SF6) were determined from single-breath washout tracings. Monodisperse 0.9-microm DEHS droplets were used to assess convective mixing in the lungs and to evaluate airway dimensions in vivo. Gas exchange across the alveolar-capillary layer was characterized by membrane diffusing capacity for carbon monoxide and alveolar-arterial pressure differences for respiratory gases. A bronchial challenge with carbachol was used to assess airway responsiveness. In comparison to the control group, dogs exposed to sulfur(IV) and acidic aerosol exhibited no significant changes in any respiratory lung function parameter. Also the responsiveness of the bronchial airways to carbachol was not affected. In view of the results obtained in this and previous studies, we conclude that anticipated synergistic effects of the two air pollutants on pulmonary lung function were not observed. It is hypothesized that antagonistic effects of the air pollutants on the activity of phospholipase A2 play an important role and account for counteracting physiological compensatory mechanisms. The results emphasize the complexity of health effects on lung function in response to the complex mixtures of ambient air pollutants and witness the precariousness in the risk assessment of air pollutants for humans.

Effect of nebulizer type and antibiotic concentration on device performance

We compared the performance of selected ultrasonic and jet nebulizers when aerosolizing several antibiotic formulations to determine optimum combinations for delivery of a respirable antibiotic aerosol. Three ultrasonic devices were tested: the UltraNeb 99/100, the UltraAIR and the Aerosonic. The reusable jet nebulizers were the Dura ProNeb, Pari-LL and the Sidestream. The six disposable jet nebulizers were Marquest Acorn II, Hudson T Updraft II, Baxter MistyNeb, Pari-LC, Pari IS-2, and a disposable Sidestream. Each jet was tested with four compressors: a DeVilbiss AP-50, a Pulmo-Aide, a DuraNeb and a PariMaster. All nebulizing systems were initially tested with normal saline. From the initial data, six jet nebulizers and one ultrasonic device were tested with varying concentrations of tobramycin, gentamicin, ceftazidime, ciprofloxacin and colistin. Output was assessed by measuring volume (milliliters per minute), and amount of drug (milligrams per minute) nebulized. We then measured mean particle size of the antibiotic aerosol with seven jet nebulizers and two different compressors, Pulmo-Aide and PariMaster, and two ultrasonic devices. The rate of nebulization of saline and antibiotic solutions (milliliters per minute) was greater with the ultrasonic device(s) than all jet nebulizer systems tested. Increasing the reservoir antibiotic concentration increased the drug output (milligrams per minute) with the jet nebulizers to a maximum, followed by decreasing output. When antibiotic concentrations were increased the output decreased more precipitously with the ultrasonic devices than with the jet nebulizers. At the highest antibiotic concentrations tested, the ultrasonic devices had the lowest output. Particle size distribution was most dependent on the specific jet device, with particle size distribution less affected by a specific antibiotic or its concentration. Higher reservoir concentrations can be utilized for increasing output of respirable antibiotic aerosols by jet nebulizers. We conclude that antibiotic output is dependent upon both the nebulizing system and the reservoir concentration of antibiotic.

Roxithromycin attenuates acid-induced cough and water-induced bronchoconstriction in children with asthma

In the present study, we evaluated the effect of roxithromycin, a semisynthetic macrolide antibiotic, on the cough response to inhaled acetic acid (AA) and on the bronchoconstriction induced by ultrasonically nebulized distilled water (UNDW) in children with asthma. Ten hospitalized asthmatic children (8 boys and 2 girls, mean +/- SEM age 12.6 +/- 0.4 years) were enrolled in this study. They were treated with 150 mg of roxithromycin once a day orally for 8 weeks without any side effects. All the patients underwent AA inhalation challenge before and 2, 4, and 8 weeks after the administration of roxithromycin. Seven of the 10 patients, who had a fall in FEV1 of at least 20% after UNDW inhalation, underwent UNDW inhalation challege at the same time. The cough threshold values, the lowest concentrations of AA eliciting coughs, and UNDW provocative dose producing a 20% fall in FEV1 (UNDW PD20) values 4 or 8 weeks after the administration of roxithromycin increased significantly over the initial values (p < 0.05). No significant change was observed in baseline FEV1 or serum theophylline concentrations throughout the study. These results support the notion that administration of roxithromycin may have favorable results in the treatment of childhood asthma.

Hydrochloric acid inhalation: who needs admission?

Nine pharmaceutical workers were exposed to hydrochloric acid (HCl) fumes. Four were discharged with no symptoms after a 4 h observation period in the accident and emergency (A&E) department. The remaining five were admitted to the medical unit because of severe symptoms, reduced peak expiratory flow rate (PEFR), or hypoxaemia. Treatment was symptomatic and discharge followed 24 h later. Only one patient, discharged from the medical unit, developed long term airway hyper-reactivity, superimposed on a background of chronic obstructive airways disease. Thus patients who are minimally symptomatic with normal PEFR and oxygen saturation values can be safely discharged from the A&E department after a short observation period of 4 h with advice to return if dyspnoea occurs. Caution should be employed in severely symptomatic patients, those with pre-existing lung pathology or reduced PEFR, and hypoxaemic patients, where observation for at least 24 h is recommended.

Inhaled lysine acetylsalicylate (L-ASA) attenuates histamine-induced bronchoconstriction in asthma

When administered by inhalation, histamine provokes dose-related bronchoconstriction in asthmatic subjects mainly by a direct activation of histamine H1-receptors on airway smooth muscle. However, little is known of the change in airway responsiveness to histamine after cyclooxygenase blockade. The aim of the study was to investigate the effect of the potent cyclooxygenase inhibitor, lysine acetylsalicylate (L-ASA), administered by inhalation on histamine-induced bronchoconstriction in a group of 16 asthmatic subjects. The subjects studied attended the laboratory on four separate occasions to receive nebulized L-ASA (solution of 90 mg/ml) or matched placebo (glycine solution of 30 mg/ml) 15 min before bronchoprovocation tests with histamine and methacholine in a randomized, double-blind order. Changes in airway caliber were followed as forced expiratory volume in 1 s (FEV1), and agonist responsiveness was expressed as the provocative concentration causing a 20% fall in FEV1 from baseline (PC20). Administration of both L-ASA and glycine solution caused a small but significant acute fall in FEV1 from baseline, which returned to normal within 15 min. When compared to placebo, inhaled L-ASA reduced the airway responsiveness to histamine in 13 of the 16 subjects studied, the geometric mean (range) values fro PC20 histamine increasing significantly (P < 0.001) from 1.72 (0.13-5.49) mg/ml to 3.31 (0.36-12.00) mg/ml after placebo and L-ASA, respectively. No significant change in airway responsiveness to methacholine was recorded after L-ASA. Acute administration of L-ASA by inhalation protects the asthmatic airways against histamine-induced bronchoconstriction, thus suggesting that endogenous prostaglandins may play a contributory role in the airways response to histamine in human asthma.

Relationship between the acid-induced cough response and airway responsiveness and obstruction in children with asthma

BACKGROUND

In children with asthma little is known about the direct effect of the bronchoconstrictor and bronchodilator response on the cough threshold, or the relationship between bronchial responsiveness and the cough threshold. A study was undertaken to determine the effect of histamine-induced bronchoconstriction and salbutamol-induced bronchodilatation on the cough threshold in response to inhaled acetic acid, and to examine the relationship between the acetic acid cough threshold and bronchial hyperresponsiveness to histamine in children with asthma.

METHODS

Nineteen children with asthma (16 boys) of mean (SE) age 10.6 (0.6) years were enrolled in the study. On day 1 each underwent a histamine inhalation challenge to determine the provocative concentration causing a fall in forced expiratory volume in one second (FEV1) of more than 20% (PC20) as an index of individual bronchial hyperresponsiveness. On day 2 the acetic acid cough threshold was determined before and just after the inhalation of the PC20 concentration of histamine, and then salbutamol (1 mg/m2) was inhaled to relieve the bronchoconstriction. Ten of the 19 patients (eight boys) of mean age 12.2 (0.7) years also tried acetic acid inhalation challenge just after salbutamol inhalation.

RESULTS

There was no relationship between the bronchial responsiveness to histamine and acetic acid cough threshold in these patients. The acetic acid cough threshold after histamine inhalation was similar to that before histamine, although FEV1 decreased after histamine. In the 10 patients who also tried acetic acid inhalation challenge after salbutamol the cough threshold did not change.

CONCLUSIONS

These findings suggest that acid-induced cough sensitivity and bronchomotor tone are independently regulated in children with asthma.

Inhaled diuretics attenuate acid-induced cough in children with asthma

To evaluate the effect of inhaled diuretics, furosemide and amiloride, on cough induced by acid inhalation challenge in asthmatic children, a double-blind, randomized, placebo-controlled study was conducted. On separate days, 12 asthmatic children (10.3 +/- 0.7 [SEM] years) underwent acetic acid (AD) inhalation challenge after inhalation of furosemide (10 mg/m2 of body) amiloride (0.3 mg/m2 of body), or placebo (0.9% saline solution). Bronchoconstriction was not observed after administration of furosemide and amiloride. Both inhaled furosemide and amiloride exerted a protective effect against AA-induced cough in asthmatic children (p < 0.01 and p < 0.05, respectively), while there was little correlation between the individual protective potency of furosemide and amiloride against AA-induced cough (rs = 0.344, p = 0.255). These results demonstrate that both furosemide and amiloride can attenuate AA-induced cough, although, this protective effect of inhaled diuretics may not necessarily be dependent on Na(+)-K(+)-Cl- cotransporter or Na+ channel in airway epithelial cells.

Comparison of sulphur dioxide and metabisulphite airway reactivity in subjects with asthma

BACKGROUND

In asthmatic subjects bronchoconstriction is induced by inhalation of the common food preservatives sulphur dioxide (SO2) and metabisulphite (MBS). SO2 and MBS challenges share many similarities, but it is not known whether they are equivalent. In this study of subjects with mild clinical asthma equivalence was assessed by comparing SO2 and MBS reactivity by estimating the total dose of SO2 inhaled during SO2 and MBS challenges, and by calculating SO2 uptake during both challenges. In addition, as the MBS solutions inhaled were acidic and hyperosmolar, the effect of these factors on MBS responsiveness was investigated.

METHODS

Fifteen subjects were challenged on separate days with doubling (0.5 to 8.0 ppm) concentrations of SO2 gas inhaled during three minute periods of isocapnic hyperventilation and MBS administered in doses ranging from 0.1 to 12.8 mumol using the Wright protocol. On two other days SO2 and MBS challenges were preceded by a challenge with phosphate buffered saline (PBS) solutions of pH and osmolarity similar to MBS solutions. Response was measured as the dose or concentration causing a 20% fall in FEV1 (PD20 or PC20).

RESULTS

All subjects reacted to MBS and 14 responded to SO2. Geometric mean histamine PD20 was 1.61 mumol (95% confidence interval 0.72 to 3.60). MBS and SO2 airway responsiveness were not significantly related. Estimates of the mean concentration of SO2 inhaled during SO2 and MBS challenges differed, as did estimates of the mean SO2 uptake during both challenges. MBS and SO2 reactivity were not affected by prior challenge with PBS solutions.

CONCLUSIONS

SO2 and MBS challenges are not comparable. MBS reactivity was not affected by the hyperosmolar, acidic nature of its solutions.

Acute exposure to acid fog. Effects on mucociliary clearance

Submicrometric sulfuric acid (H2SO4) aerosol can affect mucociliary clearance without eliciting irritative symptoms or changes in pulmonary function. The effect of larger fog droplets containing H2SO4 on mucociliary clearance is unknown. We quantified mucociliary clearance from the trachea (n = 4) and small airways (n = 7) of young healthy male adults after an acute exposure to H2SO4 fog (MMAD = 10.3 microns; pH = 2.0; liquid water content = 481 +/- 65 mg/m3; osmolarity = 30 mOsm). Acid fog (AF) or saline fog (SF) (10.9 microns; 492 +/- 116 mg/m3; 30 mOsm) was administered for 40 min of unencumbered breathing (no mouth-piece) at rest and for 20 min of exercise sufficient to produce oronasal breathing. Fog exposures were followed by a methacholine (MCh) challenge (a measure of airway reactivity) or inhalation of technetium-99M radioaerosol (MMAD = 3.4 microns) on 2 study days each. Changes in symptoms and forced ventilatory function were also assessed. Clearance was quantified from computer-assisted analyses of gamma camera images of the lower respiratory tract in terms of %removal/min of the radiolabel from the trachea 25 min after inhalation and from the outer zone of the right lung after 1.9 to 3 h. Symptoms, forced ventilatory function, and MCh response were unaffected by either fog. Tracheal clearance was more rapid in four of four subjects after AF (0.83 +/- 1.58% removal/min) compared with that after SF (-0.54 +/- 0.85% removal/min). Outer zone clearance was more rapid in six of seven subjects after AF (0.22 +/- 0.15% removal/min) compared with that after SF (0.01 +/- 0.09% removal/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Workshop on the health effects of HCl in ambient air

This article presents a summary of the proceedings of the Workshop on the Health Effects of HCl in Ambient Air, held in Detroit, Michigan, on October 15, 1990. Participants addressed three topic areas: sources, levels, and chemistry of HCl in ambient air; toxicity of atmospheric HCI to humans and animals; and the need for future research on toxicity and exposure. Consensus conclusions related to each of these topic areas, arising form the deliberations of the workshop participants, are presented. These include: (1) atmospheric HCl will most commonly exist in the gaseous form; (2) long-range transport of HCl is probably of limited importance; (3) ambient HCI levels are in the low parts per billion range; (4) irritation of the upper airways appears to be the most sensitive indicator of exposure; (5) such effects are likely to occur only at exposure levels much greater than those measured in ambient air; and (6) future health research should focus on occupationally exposed populations and potentially sensitive subgroups, e.g., asthmatics.

Hypoxaemia after nebulised salbutamol in wheezy infants: the importance of aerosol acidity

The effect of nebulised iso-osmolar, preservative free, but acidic salbutamol solution was studied in 34 acutely wheezing infants aged 1-17 months. Transcutaneous oxygen pressure (TcPO2) and oxygen saturation (SO2) fell significantly during the first five minutes after nebulisation with further deterioration at 15-20 minutes. Ten of these infants were followed up for another two hours and showed slight improvement. Even after the second hour TcPO2 had not reached baseline values. Three months later the response to salbutamol and a placebo of equal acidity (pH 3.9) was studied in 11 infants from the same group, now free of symptoms. Lung function tests were included and showed no significant changes in specific conductance and volume corrected maximum expiratory flows (Vmax at functional residual capacity/thoracic gas volume). However, hypoxaemia occurred after the acidic placebo with a significant drop of TcPO2 (mean 0.9 kPa); SO2 decreased similarly but this did not reach significance. After salbutamol there was a further significant deterioration of mean TcPO2 (1.4 kPa) and of SO2. These results show that beside a possible pharmacological effect of salbutamol the acidity of the aerosol also induces hypoxaemia in infants.

Asthmatic responses to airborne acid aerosols

BACKGROUND

Controlled exposure studies suggest that asthmatics may be more sensitive to the respiratory effects of acidic aerosols than individuals without asthma. This study investigates whether acidic aerosols and other air pollutants are associated with respiratory symptoms in free-living asthmatics.

METHODS

Daily concentrations of hydrogen ion (H+), nitric acid, fine particulates, sulfates and nitrates were obtained during an intensive air monitoring effort in Denver, Colorado, in the winter of 1987-88. A panel of 207 asthmatics recorded respiratory symptoms, frequency of medication use, and related information in daily diaries. We used a multiple regression time-series model to analyze which air pollutants, if any, were associated with health outcomes reported by study participants.

RESULTS

Airborne H+ was found to be significantly associated with several indicators of asthma status, including moderate or severe cough and shortness of breath. Cough was also associated with fine particulates, and shortness of breath with sulfates. Incorporating the participants' time spent outside and exercise intensity into the daily measure of exposure strengthened the association between these pollutants and asthmatic symptoms. Nitric acid and nitrates were not significantly associated with any respiratory symptom analyzed.

CONCLUSIONS

In this population of asthmatics, several outdoor air pollutants, particularly airborne acidity, were associated with daily respiratory symptoms.

Pulmonary tolerance of prophylactic aerosolized pentamidine in human immunodeficiency virus-infected patients

The effects of primary and secondary long-term prophylaxis of Pneumocystis carinii pneumonia with aerosolized pentamidine on pulmonary function in HIV+ patients were evaluated. Eighty-one patients, none of whom were drug addicts or had pulmonary Kaposi's sarcoma, were studied. Fifty patients were receiving AP as secondary prophylaxis, 36 monthly and 14 twice-monthly; eight patients with a history of PCP served as control subjects. Twenty-three patients were receiving AP as primary prophylaxis, 12 monthly and 11 twice-monthly. Pulmonary function tests, including spirometry, lung transfer capacity for carbon monoxide (Tlco) and alveolar-arterial oxygen gradient (P[A-a]O2) were evaluated at M1, ie, one month after the diagnosis of PCP, or at the beginning of the AP prophylaxis, and then at three-month intervals (M4 to M13). No differences were observed in the results of spirometry or P(A-a)O2. Among the patients receiving secondary prophylaxis, a significant increase (paired Student's t-test) in Tlco occurred at M7 compared to M1 in the group receiving monthly administrations (p less than 0.01) and in the untreated control group (p less than 0.05); there was no significant difference in Tlco at M13 compared to M1 in the 12 patients who received monthly administrations for this period or at M7 in the 14 patients receiving AP twice-monthly. No significant difference in Tlco was observed at M7 in the primary prophylaxis groups. These results indicate that pulmonary tolerance of AP, as reflected by pulmonary function tests, is good.

Paradoxical bronchospasm after use of inhalation aerosols: a review of the literature

Various formulations of beta-agonists and other bronchodilators have been associated with unexpected bronchoconstriction in certain individuals. Even though the number of affected individuals represents a relatively small percentage and the etiologies may differ among patients, it is important for the public to be aware of the potential for paradoxical bronchospasm and for the physician to investigate each case accordingly.

Osmolality and pH of anti-asthmatic drug solutions

Mixtures of different drugs are frequently used in aerosol solution for treatment of asthma. These drugs have different pH and osmolality values as stock solutions. It has been suggested that acidity and osmolality interact in provoking bronchoconstriction and cough. Therefore, pH and osmolality of anti-asthmatic drug solutions and mixtures were measured in the nebulizer at 0, 1, 2, 5, 10 and 15 minutes of nebulisation, pH of fenoterol, ipratropium bromide, salbutamol and disodium cromoglycate ranged between 2.0 and 5.7 and did not change during nebulisation. Nearly all drug solutions were hypoosmolar and the osmolality increased during nebulisation with 11 to 62%. Therefore, it is suggested to dilute these drugs with saline 0.9% and to restrict nebulisation time to 10 minutes, since the most striking increase of osmolality was noted after 10 minutes.