Incidence of acute decreases in peak expiratory flow following the use of metered-dose inhalers in asthmatic patients.

This study aimed to investigate and compare the incidence of metered-dose inhaler (MDI)-associated bronchoconstriction in an asthmatic population, following the use of three different MDIs. Two different placebo metered-dose inhaler preparations containing the same chlorofluorocarbons but differing in dispersant chemicals, one containing oleic acid (MDI-OA) and the other lecithin NF (MDI-L), were compared with a MDI containing salmeterol xinafoate (25 micrograms) and lecithin NF (MDI-S). The study population comprised 11,850 asthmatic patients, who were assigned to receive two puffs from one of the three inhalers: MDI-S (n = 3,948); MDI-L (n = 3,942); or MDI-OA (n = 3,960). Peak expiratory flow (PEF) was measured before and 5 min after inhalation. A 20% fall in PEF was defined as a clinically significant bronchoconstriction. Overall 180 (1.5%) patients demonstrated bronchoconstriction, 43 (1.1%) in the MDI-S group, 67 (1.7%) in the MDI-L group and 70 (1.8%) in the MDI-OA. A significantly lower incidence of bronchoconstriction was seen with the salmeterol xinafoate MDI compared to either of the other two preparations. The risk of acute bronchoconstriction was also shown to increase with age and with decreasing pretreatment PEF. The study has shown that acute bronchoconstriction is an uncommon adverse reaction following the use of metered-dose inhalers. In addition, the study suggests that one of the inert constituents currently within metered-dose inhalers is the likely source of the irritant leading to bronchoconstriction.