Both intravenous and inhaled lidocaine attenuate reflex bronchoconstriction but at different plasma concentrations

Intravenous lidocaine can attenuate bronchial hyperreactivity. However, lid ocaine inhalation might yield the same or better results at higher airway a nd lower lidocaine plasma concentrations. Therefore, we tested in awake vol unteers with bronchial hyperreactivity the effect of lidocaine on histamine -induced bronchoconstriction administered either intravenously or as an aer osol. After approval of the local ethics committee, 15 volunteers were enro lled in this placebo-controlled, double-blinded, randomized study. Voluntee rs were selected by showing a decrease in FEV1 greater than 20% of baseline (PC20) in response to histamine inhalation. On three different days the ch allenge was repeated after pretreatment with either intravenous lidocaine, inhaled lidocaine, or placebo. Blood samples for determination of lidocaine plasma concentration were drawn. Comparisons were made using the Friedman and Wilcoxon signed-rank tests. Baseline PC20 was 6.4 +/- 1.1 mg ml(-1). Bo th inhalation of lidocaine and intravenous administration significantly inc reased PC20 to 14.8 +/- 3.5 mg.ml(-1) and 14.2 +/- 2.5 mg.ml(-1), respectiv ely (p = 0.0007). Peak plasma lidocaine concentrations at the end of challe nges were 0.7 +/- 0.1 mu g.ml(-1) (inhaled) and 2.2 +/- 0.1 mu g.ml(-1) (i. v.). However, 7 of 15 subjects showed an initial decrease of FEV1 greater t han 5% following lidocaine inhalation. While both intravenous as well as in haled lidocaine attenuate reflex bronchoconstriction significantly, lidocai ne plasma concentrations are significantly lower after inhalation. However, the high incidence of initial bronchoconstriction to lidocaine inhalation may limit its use in patients with asthma and thus offers therapeutic advan tages for intravenous lidocaine.