Effect of inhaled salmeterol on sulfur dioxide-induced bronchoconstriction in asthmatic subjects

This study tested the capability of a single 42-microgram dose of inhaled salmeterol xinafoate, a long-acting beta 2-agonist, to protect against bronchoconstrictive effects of exposure to 0.75 ppm sulfur dioxide (SO2) during exercise, for up to 24 h. Ten SO2-responsive adult volunteers with stable asthma were studied under 4 conditions of drug pretreatment/exposure, administered in random order, double-blind: salmeterol/SO2, placebo/SO2, salmeterol/clean air, and placebo/clean air. Each subject underwent 10-min exposure/exercise challenges in a chamber 1, 12, 18, and 24 h after pretreatment. Exercise ventilation rates averaged 29 L/min. Response was measured as the decrement in FEV1 between preexposure and postexposure (lowest value within 30 min). After salmeterol, mean decrement post-SO2 was 7% at 1 h and 12% at 12 h. At 18 and 24 h after salmeterol, and at all times after placebo, mean decrements were 25 to 30%. After 18 and 24 h, salmeterol still improved base-line FEV1 relative to placebo, although improvement was not statistically significant at 24 h. Acute symptom increases accompanied FEV1 decrements.

In our asthmatic subjects, pretreatment with salmeterol imparted clinically and statistically significant (p < 0.01) protection against bronchoconstriction induced by SO2/exercise for at least 12 h, and maintained an improvement in lung function for as much as 18 h.