Effect of Smoking on the Pharmacokinetics of Inhaled Loxapine

BACKGROUND: Loxapine inhalation powder delivered by a hand-held device as a thermally generated aerosol (ADASUVE) was recently approved in the United States and European Union for use in the acute treatment of agitation in patients with bipolar disorder or schizophrenia. As smokers comprise a large subpopulation of these patients, and many antipsychotic drugs require dose adjustments for smokers, the objective of this study was to compare the pharmacokinetics of inhaled loxapine administered to smokers and nonsmokers. METHODS: Pharmacokinetics and sedation pharmacodynamics using a visual analog scale were studied in 35 male and female adult subjects (18 nonsmokers and 17 smokers) following a single dose of 10 mg of inhaled loxapine. Blood samples were drawn at predose, 30 seconds, 1, 2, 3, 10, 30, and 60 minutes, and 2, 6, 12, and 24 hours after dosing. Loxapine and 8-OH-loxapine were analyzed using reverse-phase liquid chromatography coupled with a tandem mass spectrometer. Pharmacokinetic parameters assessed included C(max), T(max), AUC(inf), and T(1/2) for loxapine and 8-OH-loxapine. Geometric mean ratios (GMRs) were determined for smokers to nonsmokers. RESULTS: Loxapine C(max) was similar in smokers and nonsmokers with a GMR of 99.0%. The median loxapine T(max) was 1.88 and 1.01 minutes for nonsmokers and smokers, respectively. Loxapine AUC(inf) and AUC(last) values in nonsmokers were comparable with smokers (GMRs of 85.3% and 86.7%, respectively). A slight decrease in the observed mean terminal half-life values was observed for smokers (6.52 hours for smokers and 7.30 hours for nonsmokers). CONCLUSIONS: Sedation profiles and visual analog scale scores at each time point were similar for nonsmokers and smokers. It was concluded that inhaled loxapine does not require dosage adjustment based on smoking behavior.