INTRAVENOUS LIDOCAINE AND ORAL MEXILETINE BLOCK REFLEX BRONCHOCONSTRICTION IN ASTHMATIC SUBJECTS

Stimulation of the airways of asthmatic individuals causes severe bron choconstriction, which is in part neurally mediated via the vagus nerv e. Local anesthetics are commonly administered to prevent this reflex- induced bronchoconstriction. Therefore, in a double-blind, placebo-con trolled prospective study, we tested the effectiveness of oral mexilet ine and intravenous lidocaine at blocking histamine-induced reflex bro nchoconstriction. Fifteen subjects with mild asthma were selected (for whom the provocative concentration of histamine aerosol causing a 20% decrease in FEV(1) (PC20) was less than 18 mg/ml). Subsequently, the subjects were pretreated with oral mexiletine, intravenous lidocaine, or placebo, and the histamine challenges were repeated. The baseline P C20 for histamine was 8.8 +/- 1.8 mg/ml. Mexiletine and lidocaine at t herapeutic serum concentrations blocked reflex bronchoconstriction. Or al mexiletine increased the PC20 to 21.1 +/- 5.0 mg/ml (serum concentr ation: 0.7 +/- 0.05 mu g/ml). Likewise, intravenous lidocaine increase d the PC20 to 24.5 +/- 4.9 mg/ml (serum concentration: 2.6 +/- 0.15 mu g/ml). Oral mexiletine and intravenous lidocaine block reflex-induced bronchoconstriction. Furthermore, mexiletine may have additional airw ay benefits when selected for the treatment of dysrhythmias or chronic pain in patients with coexisting lung diseases.