BACKGROUND Arbidol is an antiviral drug indicated for the prevention and treatment of all types of influenza infection and some other kinds of acute respiratory infections, specifically against influenza groups A and B, and severe acute respiratory syndrome. It is used to help prevent influenza infection as long as necessary with little risk for influenza mutation rendering it less effective. OBJECTIVE The aim of this study was to compare the pharmacokinetic properties and tolerability, and to determine bioequivalence, of a newly developed generic dispersible tablet formulation (test) and a branded capsule formulation (reference) of arbidol 200 mg in healthy Chinese fasted male volunteers. METHODS This open-label, single-dose, randomized-sequence, 2-period crossover study was conducted in healthy native Chinese male volunteers. Eligible subjects were randomly assigned in a 1:1 ratio to receive a single 200-mg dose of the test or reference formulation, followed by a 1-week washout period and administration of the alternate formulation. The study drugs were administered after a 12-hour overnight fast. After the study drug administration, serial blood samples were collected for 72 hours after administration. Plasma drug concentrations were determined using high-performance liquid chromatography coupled with tandem mass spectrometry. Several pharmacokinetic pararameters, including C(max), T(max), t((1/2)), AUC(0-t), and AUC(0-infinity), were determined from the plasma concentrations of the 2 formulations of arbidol using noncompartmental analysis. The formulations were to be considered bioequivalent if the log-transformed ratios of C(max) and AUC were within the predetermined bioequivalence range of 80% to 125% established by the State Food and Drug Administration (SFDA) of the People's Republic of China. Tolerability was assessed by monitoring vital signs (blood pressure, heart rate, temperature, and electrocardiography), laboratory analysis (hematology, blood biochemistry, hepatic function, and urinalysis), and subject interview on adverse events. RESULTS Twenty subjects were enrolled and completed the study (mean [SD] age, 21.1 [1.1] years; weight, 64.7 [5.1] kg; and height, 172.3 [3.1] cm). Neither period nor sequence effect was observed. The main pharmacokinetic properties with the test and reference formulations were as follows: C(max), 417.4 (107.6) and 414.8 (95.1) ng/mL, respectively (P = NS); median (range) T(max), 0.63 (0.25-1.0) and 0.75 (0.5-1.5) hours (P = 0.035); AUC(0-t), 2033.6 (564.9) and 1992.0 (483.3) ng/mL/h (P = NS); AUC(0-infinity), 2285.4 (597.7) and 2215.2 (604.0) ng/mL/h (P = NS); and t(1/2), 6.9 (4.2) and 6.1 (5.2) hours (P = NS). The 90% CIs for the log-transformed ratios of C(max), AUC(0-t), and AUC(0-infinity) were 91.7% to 109.7%, 91.0% to 112.8%, and 92.0% to 116.3%, respectively (all, P < 0.05), which were within the predetermined range for bioequivalence. No adverse events were found on analysis of vital signs or laboratory tests or reported by subjects in this study. CONCLUSIONS In this study in healthy Chinese male volunteers, the dispersible tablet formulation and the 200-mg capsule formulation of arbidol met the SFDA's regulatory definition of bioequivalence based on the rate and extent of absorption.