Pharmacokinetics and Safety of Dapoxetine Hydrochloride in Healthy Chinese Men: Impact of Dose and High-Fat Meal

Bioequivalence Assessment of Two Dapoxetine Hydrochloride Formulations in Healthy Chinese Males Under Fasted and Fed Conditions

This study evaluated the bioequivalence of the newly developed dapoxetine hydrochloride tablet relative to the marketed reference product by comparing their pharmacokinetic profiles under fasted and fed conditions. A total of 60 healthy Chinese male subjects participated in a single-center, 2-period, 2-sequence, randomized, open-label, self-crossover study with a washout period of 14 days, 30 in the fasted group and 30 in the fed group. Following a single 30-mg oral dose of the test or reference dapoxetine formulation, blood samples were collected before dosing to 72 hours after dosing. Liquid chromatography-tandem mass spectrometry was performed to measure plasma concentration of dapoxetine and determine pharmacokinetic parameters through noncompartmental analysis. The vital signs and adverse events were also monitored during the study. The 90% confidence intervals of the geometric mean ratios for maximum plasma concentration, area under the plasma concentration-time curve from time 0 to the last concentration time, and area under the plasma concentration-time curve from time 0 extrapolated to infinity of the 2 dapoxetine formulations completely fell within the regulatory criteria for bioequivalence of 80%-125%. In addition, both dapoxetine hydrochloride formulations were generally well tolerated. The generic dapoxetine hydrochloride tablet was bioequivalent to the marketed reference product in healthy Chinese men with no discernible safety differences.

Effects of CYP2D6 *10 and *41 Variants in Healthy Chinese Men on the Pharmacokinetics of Dapoxetine

Dapoxetine is a selective serotonin reuptake inhibitor (SSRI) used to treat premature ejaculation (PE), and is mainly metabolized by CYP2D6, CYP3A4, and flavin-containing monooxygenase 1. The purpose of the study was to evaluate the effect of CYP2D6 polymorphism on the pharmacokinetics of dapoxetine in healthy Chinese men. Thirty-nine subjects who received a single oral dose of 30 mg dapoxetine hydrochloride were classified based on their CYP2D6 genotype: *1/*1 (n = 9), *1/*41 (n = 1), *1/*10 (n = 12), *10/*41 (n = 3), or *10/*10 (n = 14). The difference in pharmacokinetic parameters between different genotype groups was analyzed and then scored according to the activity score system. Compared with the wild-type subjects of CYP2D6 *1/*1, the peak plasma concentration (Cmax) and the area under the plasma drug concentration-time curve (AUCinf) of dapoxetine in the *10/*10 and *10/*41 groups were notably increased (P ≤ .05). Significant differences in Cmax, AUC, volume of distribution/bioavailability (V/F) and clearance/bioavailability (CL/F) were observed among dapoxetine activity score groups (P ≤ .05). The AUCinf was increased significantly (154% and 89.73%, P ≤ .05) and the Cmax was increased significantly (73.45% and 42.67%, P ≤ .05) in CYP2D6 *10/*41 subjects, compared with CYP2D6 *1/*1 and *1/*10 subjects. The results obtained indicated that CYP2D6 *10 and *41 polymorphisms have significant effects on the pharmacokinetic properties of dapoxetine.

Pharmacokinetics and Safety Study of HN0037, a Novel Anti-Human Herpes Simplex Virus Inhibitor, in Healthy Volunteers

HN0037 is a helicase-primase inhibitor developed to treat herpes simplex virus (HSV) infection. This study evaluated the safety, tolerability, and pharmacokinetics of HN0037, following oral administration in healthy volunteers. This double-blind, placebo-controlled, phase 1 study comprised two parts. In part 1, a single escalating dose of 10, 30, 60, 120, 200, 300, and 400 mg was assessed, and the food effect was evaluated in the 200-mg cohort. In part 2, a multiple dose evaluation involving 30 and 100 mg once a day was conducted for 14 days. Following single oral doses, the systemic exposure of HN0037 increased in a proportional manner over the lower dose range (10-120 mg) and in a subproportional manner over the higher dose range (200-400 mg). Following multiple oral doses, significant drug accumulation of systemic exposure was found at steady state, and the half-life ranged 50.4-61.0 h. The food effect study results indicated that a high-fat meal had a marginal impact on HN0037's pharmacokinetics. No differences were observed in the incidence of adverse events between HN0037 and placebo groups in either study. These results demonstrate that HN0037 is safe and well-tolerated, supporting further clinical development.

Determination of Dapoxetine Hydrochloride in Human Plasma by HPLC–MS/MS and Its Application in a Bioequivalence Study

Dapoxetine is used for the treatment of premature ejaculation. The present study developed an HPLC–MS/MS method to determine the levels of dapoxetine in human plasma processed using simple protein precipitation. Dapoxetine-d₇ was selected as the internal standard. The established method was performed using a mass spectrometer equipped with an electrospray ionization source in multiple positive ion reactions to monitor the mode using the precursor-to-product ion transitions of m/z 306.2–157.2 and m/z 313.2–164.2 for dapoxetine-d7 and dapoxetine, respectively. The method was evaluated based on its selectivity, linearity, limit of quantification, precision, accuracy, matrix effects, dilution integrity, stability, and extraction recovery. As a result of the model used in the present study, the validated linear ranges of dapoxetine were determined to be 2.00~1000 ng/mL in plasma, and the selectivity, precision, accuracy, dilution integrity, stability, and extraction recovery met the accepted standard. No matrix interference was observed. The method was successfully validated and applied to pharmacokinetic studies in healthy Chinese volunteers during the fasting and postprandial periods, respectively.