The bioavailability of intranasal lignocaine

Six healthy males participated in a single-dose two-way crossover study of the bioavailability of intranasal vs intravenous administration of lignocaine (lidocaine) hydrochloride. Subjects received a single 100 mg dose of lignocaine HCl intranasally from a gel preparation on one occasion and intravenously by a 3 min infusion on another occasion. Multiple plasma samples drawn during 8 h following each dose were analysed for lignocaine by gas chromatography using nitrogen phosphorous detection. The mean (+/- s.e. mean) peak plasma concentration of lignocaine following intranasal administration was 144 +/- 48 ng ml-1, and the time to peak was 0.92 +/- 0.12 h. The mean AUC values for intranasal and intravenous routes were 421 +/- 121 vs 1616 +/- 30 ng ml-1 h, respectively, and the mean bioavailability of the intranasal formulation (AUC ratio) was 0.26 +/- 0.08. In all subjects, intranasal absorption was less than 50% complete, and bioavailability varied from 0.05 to 0.48 between individuals. Thus lignocaine is variably and incompletely absorbed when administered by the intranasal route, in the dosage formulation and according to the method used in this study.