Objectives

An important question in current asthma research is whether regularly scheduled treatment with inhaled Beta-agonists in asthmatics produces adverse effects on asthma control. Because an estimated 60-70% of patients with asthma have mild disease and are treated only with inhaled Beta2-adrenergic agonists of medium duration, a firm basis upon which to make treatment recommendations for this large number of patients was critically needed. Therefore, the ACRN developed a protocol to test the following null hypothesis: In patients with mild asthma, whose only asthma treatment is inhaled Beta-agonists, addition of regular inhaled Beta-agonist treatment to treatment on an "as needed only" basis will result in no effect on asthma control.

Design

Patients with mild asthma, and with an FEV1 >= 70% predicted using Beta-agonists as their sole therapy, were recruited and followed for a 6-week single-blind run-in period during which they took a coded placebo inhaler, 2 puffs QID. A Chronolog TM recording device was used to assure compliance and all patients were provided "open label" albuterol for rescue use. If, after the run-in period, patients were compliant and still met entry criteria, they were randomized to receive either albuterol or placebo, 2 puffs QID via the Chronolog TM during a 16-week double-blind treatment period, which was followed by a 4-week "run-out" period during which patients received single-blind QID placebo. The primary outcome variable was AM peak expiratory flow (PEF) (measured using a Mini-Wright TM peak flow meter), with multiple secondary outcome variables including PM PEF, AM-PM PEF variability, asthma symptom scores, rescue albuterol use, FEV1, including response to albuterol, methacholine PC20, quality of life, asthma exacerbations, and treatment failures. Power analysis had indicated that 200 subjects would be required for an 80% chance of detecting a difference in AM peak flow of 25 L/min. Enrollment began in December 1994 with a target of 250 randomized patients (allowing for 20% withdrawal). The last subject was enrolled in July 1995, and the trial ended in February 1996. Of the 319 subjects recruited, 255 (33% minority, 56% female) were eligible for randomization to receive double-blind treatment (126 in the regular use group and 129 in the as-needed group). Groups were well matched for all inclusion criteria. Twenty-five patients dropped out of the trial, yielding 230 subjects who completed it. Compliance with inhaled medication was > 80%, and more than 99% of the scheduled clinic visits were kept.

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