10 Sep

Effect of Long-term Salmeterol Therapy Compared With As-Needed Albuterol Use on Airway Hyperresponsiveness: Patients

Female and male patients a 12 years of age with a diagnosis of asthma were enrolled in the study. Patients were excluded if they had any clinically significant disease other than asthma, had an upper or lower respiratory infection within 6 weeks of the screening visit, or were hospitalized for asthma within 3 months of the screening visit. Patients were required to have a baseline FEV1 of a 70% of predicted values after asthma medications had been withheld. Reversibility of disease was demonstrated by an increase in FEV1 of at least 15% above baseline within 30 min after the inhalation of two puffs (180 μg) of albuterol. The provocative dose of methacholine required to reduce the FEV1 by 20% from baseline (PD20) was used to assess bronchial hyperreactivity. During the run-in period, patients had to have demonstrated two PD20 values of < 55.5 cumulative dosage units (512 cumulative μg) of methacholine (equivalent to a provocative concentration of methacholine necessary for a a 20% decrease in FEV1 from saline solution control value of 7.5 mg/mL of methacholine) that were within a threefold change of one another. Each PD20 value was obtained at visits that were separated by at least 3 days; patients were given three visits to obtain the required PD20 values. birth control

Methacholine Challenge Testing
All study sites used a standardized methacholine challenge pro-cedure and methacholine challenge equipment consisting of a spirometer (PDS Research; Louisville, CO), a breath-actuated dosimeter (PDS Research), and calibrated nebulizers (DeVilbiss model 646; Sunrise Medical; Somerset, PA). The baffle and straw of each nebulizer were fixed in place. Inhalation rates were held constant at 0.5 L/s using a valve (Rosenthal Flow Regulator; PDS Research) fitted to the inport of the nebulizer. Dosimeter actuation was repeated at intervals of 0.6 s with 3 mL of solution in the nebulizer bowl. Air supply was at a constant 30 pounds per square inch, and inspiratory flow rate was fixed at 0.5 L/s. Under these conditions, the output of all nebulizers was characterized to allow calculation of the absolute amount (in micrograms) of the metha-choline delivered to the patient. The methacholine concentration sequence is provided in Table 1. Fresh solutions of methacholine (Methapharm; Brantford, Ontario, Canada) were prepared daily in preservative-free 0.9% inhalation saline solution. Challenges were performed between 6:00 am and 9:00 am and before taking morning study medications.
Table 1—Methacholine Concentration Sequence

Stage Concentration,*mg/mL No. of Breaths Cumulative Dosage Unitsf
1 0.025 5 0.125
2 0.075 5 0.50
3 0.25 5 1.75
4 0.75 5 5.50
5 2.5 5 18.0
6 7.5 5 55.5
7 25.00 5 180.5
8 75.00 5 555.5

Categories: Airway
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