Single- and multiple-dose pharmacokinetics of the peripheral non-narcotic antitussive moguisteine in healthy Chinese volunteers

Background: Moguisteine is a non-narcotic peripheral antitussive drug that has been effective and well-tolerated in clinical studies. The aim of the present work was to investigate the pharmacokinetics of moguisteine given as single or multiple doses to healthy Chinese subjects. Methods: In Stages 1-3 of this study, 12 healthy Chinese subjects (6 males and 6 females) participated in a randomized, open-label, single-dose, 3-period, 3-way crossover study, with a 24-h washout period between each treatment. Eligible subjects were randomized to receive a single dose of 100, 200 or 400 mg moguisteine. Blood was sampled before and up to 10 h after administration. In those receiving 200 mg moguisteine, urine was sampled at intervals of 0-2, 2-4, 4-6, 6-10, and 10-24 h. In Stage 4, subjects received a moguisteine tablet containing 200 mg three times daily for five consecutive days. Blood was sampled for up to 10 h after the last dose. HPLC-tandem mass spectrometry was used to determine concentrations of the moguisteine metabolite M1 in serum, while HPLC-UV was used to determine concentrations of M1 in urine. Safety of the dosing schedules was assessed based on physical examination, recording of adverse events, 12-lead electrocardiography, and laboratory tests. Results: All subjects completed all four stages of the study. M1 was detectable at the shortest time points after moguisteine administration; the time to achieve peak concentration was 0.5-1.0 h in single dosing and 1.5 h in multiple dosing. Elimination half-life (t(1/2)) was 0.91-1.54 h in single dosing and 1.57 h in multiple dosing. AUC increased roughly proportionally with dose, while C(max )increased much more gradually with dose. During 5-day dosing of three tablets per day, a steady state concentration was reached on day 3, and the mean accumulation ratio was 0.87. At 24 h after a single dose of 200 mg moguisteine, approximately 34.0% of the resulting M1 was recovered in urine. Pharmacokinetics of moguisteine did not differ significantly between men and women, except among those receiving a single dose of 100 mg (P < 0.05). Mild adverse events (nausea, loose stool, abdominal distention, or dizziness) occurred in six subjects and resolved without treatment, while no serious adverse events were observed. Conclusion: Moguisteine was safe and well-tolerated by our healthy subjects, and it exhibited dose linearity but not proportionality when a single dose of 100-400 mg was given. M1 did not accumulate in subjects after multiple doses of moguisteine.