Approximately 15 million people in the United States have asthma. Of these, more than 75 percent have symptoms of gastroesophageal reflux. Multiple studies have established a link between asthma exacerbations and reflux, which may also be a precipitating factor in the development of asthma. Treatment of asthma includes medications that relax bronchial smooth muscle and reduce bronchoconstriction. One of the more common medications used to relax thesesmooth muscles is the inhaled beta2-adrenergic agonist albuterol. There is speculation that part of the response to this inhaled bronchodilator is a reduction in lower esophageal sphincter tone, which increases the risk of gastroesophageal reflux. This increase in reflux can increase the chance of exacerbating asthma. Crowell and associates studied the impact of inhaled albuterol on lower esophageal sphincter tone.
The study was a prospective, randomized, placebo-controlled, double-blind crossover trial in healthy volunteers. A nebulizer was used to administer albuterol at doses of 2.5 to 10 mg or placebo to the volunteers at two sessions one week apart. The protocol was 2.5 mg of albuterol per nebulizer treatment every 20 minutes until a cumulative dose of 10 mg had been administered. The esophagus was studied during the treatment sessions with a 6-cm manometry assembly and low-compliance pneumohydraulic pump at 5 cm, 10 cm, and 15 cm above the lower esophageal sphincter. The volunteers were given 5-mL water swallows, and esophageal measurements were taken at 20 and 50 minutes before the trial and at the end of each 20-minute dosing period.
The albuterol inhalation produced a dose-dependent reduction in lower esophageal sphincter tone and a cumulative dose of 7.5 mg reduced lower esophageal pressures. These were statistically significant reductions when compared with placebo. The use of albuterol also reduced the amplitude of esophageal contractions.
The authors conclude that inhaled albuterol has a significant impact on esophageal function and increases the risk for gastroesophageal reflux. This reflux could increase the risk for persistent asthma because of the potential impact of acid on bronchoconstriction. This result is particularly true at higher dosages. The authors do caution that because this study was done in healthy volunteers, further studies need to be performed in persons with asthma.