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-d ose inhaler (MDI)-associated bronchoconstriction in an asthmatic popul ation, following the use of three different MDIs, Two different placeb o metered-dose inhaler preparations containing the same chlorofluoroca rbons 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 mu g) and lecithin NP (MDI-S). The study population comprised 11,850 asthmatic patients, who were assign ed 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) wa s measured before and 5 min after inhalation. A 20% fall in PEP was de fined 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 sig nificantly lower incidence of bronchoconstriction was seen with the sa lmeterol xinafoate MDI compared to either of the other two preparation s, The risk of acute bronchoconstriction was also shown to increase wi th age and with decreasing pretreatment PEF. The study has shown that acute bronchoconstriction is an uncommon adverse reaction following th e use of metered-dose inhalers, In addition, the study suggests that o ne of the inert constituents currently within metered-dose inhalers is the likely source of the irritant leading to bronchoconstriction.