Hwa Yoon

Pharmacokinetics and Bioequivalence of Two Formulations of Rebamipide 100-mg Tablets: A Randomized, Single-Dose, Two-Period, Two-Sequence Crossover Study in Healthy Korean Male Volunteers

BACKGROUND Rebamipide is a quinolinone-derived gastroprotective agent approved in Korea for the treatment of gastric ulcers, acute gastritis, and exacerbated chronic gastritis. OBJECTIVES The aims of this study were to evaluate the pharmacokinetics and bioequivalence of a reference (branded) and test (generic) formulation of rebamipide 100-mg tablets in healthy Korean male volunteers for the purposes of generic substitution and to evaluate the relationship between genetic polymorphisms in the ABCB1 gene (exons 21 and 26) and rebamipide pharmacokinetics. METHODS This study had a 2-period crossover design, with a 7-day washout between formulations. Healthy Korean male volunteers were randomly assigned to receive a single 100-mg dose of the test or reference formulation, administered with 240 mL of water after a 12-hour overnight fast. Serum concentrations of rebamipide up to 12 hours after administration were determined using a validated HPLC method with fluorescence detection. Vital signs (temperature, blood pressure, and heart rate) were measured before and after dosing in both periods. Adverse events were monitored by clinic staff on the days of study drug administration and were recorded for up to 1 week after the last dose of study medication. Pharmacokinetic parameters were determined using a noncompartmental method. The formulations were considered bioequivalent if the log-transformed ratios of AUC(0-t), AUC(0-infinity)), and C(max) were within the predetermined bioequivalence range (80%-125%) established by the US Food and Drug Administration and Korean legislation. The in vitro dissolution profiles of the 2 formulations were examined, and the influence on rebamipide pharmacokinetics of genetic polymorphisms in the ABCB1 gene (P-glycoprotein) was investigated. RESULTS Thirty healthy Korean male volunteers (mean [SD] age, 22.97 [1.67] years [range, 20-27 years]; height, 174.56 [6.27] cm [range, 159.1-184.8 cm]; and weight, 69.44 [8.32] kg [range, 54.7-90.2 kg]) were enrolled in and completed the study. No adverse events were reported. The 2 formulations had comparable in vitro dissolution profiles. The mean AUC(0-t) for the test and reference formulations was 831.09 (329.52) and 903.46 (419.17) ng/mL/h, respectively; the AUC(0-infinity) was 851.68 (332.62) and 923.58 (423.21) ng/mL/h; the C(max) was 218.12 (93.90) and 220.57 (107.48) ng/mL; the T(max) was 2.05 (1.15) and 2.10 (0.76) hours; and the t((1/2)) was 1.96 (0.52) and 1.93 (0.49) hours. No significant sequence, subject, formulation, or period effects were detected for any pharmacokinetic parameter. The point estimates for AUC(0-t), AUC(0-infinity), and C(max) were 0.95 (90% CI, 0.84-1.06), 0.95 (90% CI, 0.84-1.06), and 1.01 (90% CI, 0.89-1.15), respectively, satisfying the criterion for bioequivalence. There was no statistically significant difference in T(max). No significant differences in rebamipide AUC(0-t), AUC(0-infinity), or C(max) were found among the ABCB1 2677 GG, GT, or TT groups, or among the ABCB1 3435 CC, CT, or TT groups. There was no evidence that genetic polymorphisms in the ABCB1 gene influenced the pharmacokinetics of rebamipide. CONCLUSIONS The results of this study in healthy Korean male volunteers suggest that the 2 rebamipide 100-mg tablet formulations administered in the fasted state met the regulatory criterion for bioequivalence. There was no evidence that rebamipide pharmacokinetic parameters were influenced by genetic polymorphisms in the ABCB1 gene (exons 21 and 26). ClinicalTrials.gov identifier: .

Pharmacokinetics and bioequivalence evaluation of gliclazide/metformin combination tablet and equivalent doses of gliclazide and metformin in healthy Korean subjects.

OBJECTIVE To evaluate the bioequivalence of a gliclazide/metformin combination tablet (at dose of 80/500 mg) with co-administration of metformin (500 mg) and gliclazide (80 mg) as individual tablets in healthy male Korean volunteers. SUBJECTS, MATERIALS AND METHODS The study was conducted as an open-label, randomized, 2-period crossover design in 32 healthy male Korean volunteers who received a combination tablet of gliclazide/metformin at a dose of 80/500 mg or co-administration of gliclazide and metformin as individual tablets in each study period. There was a 7-day washout period between doses. Serum concentrations of gliclazide and metformin up to 32 hours after administration were determined using a validated HPLC method with UV detection. The pharmacokinetic parameters such as AUC0-t (the area under the curve from zero to the time), AUC0- yen (the area under the curve from zero to infinity), Cmax (maximum serum concentration), tmax (time to reach Cmax) and t1/2 (terminal half-life), were analyzed by non-compartmental analysis. Analysis of variance (ANOVA) was carried out using logarithmically transformed AUC0-t, AUC0- yen and Cmax, and untransformed tmax. In addition, blood glucose concentration was also logarithmically transformed and analyzed. Tolerability and safety profiles were also investigated. RESULTS There were no significant differences between the single combination tablet and the individual tablets in AUC0-t, AUC0- yen, Cmax and blood glucose concentration. The point estimates (90% confidence intervals) for AUC0-t, AUC0- yen and Cmax were 1.0293 (0.9476 - 1.1178), 1.0253 (0.9185 - 1.1443) and 1.0425 (0.9986 - 1.0883) for gliclazide, and 0.9887 (0.9137 - 1.0697), 0.9915 (0.9189 - 1.0697) and 0.9882 (0.9295 - 1.0505) for metformin, respectively, satisfying the bioequivalence criteria of 80 - 125% as proposed by the US FDA and the Korean legislation. Significant F test values were found between the subjects and subject nested sequence (SEQ) for AUC0-t and Cmax, indicating substantial inter-subject variation in the pharmacokinetics of gliclazide and metformin. However, a SEQ effect in the two-way crossover design did not impair the bioequivalence conclusion. No statistically significant differences were found for tmax and blood glucose concentration between two treatments. CONCLUSION The combination tablet of gliclazide/metformin is bioequivalent to co-administration of individual tablets. As a result, the combination tablets are regarded therapeutically equivalent and exchangeable to the co-administration of individual tablets in clinical practice. Moreover, the combination tablets are expected to improve convenience and adherence to prescribed therapy and to contribute to better blood glucose control for patients with Type 2 diabetes.

Haplotype Analysis and Single Nucleotide Polymorphism Frequency of Organic Cation Transporter Gene (OCT1 and 2) in Korean Subjects

Organic cation transporters (OCTs) are important for absorption, elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. This gene is located in a cluster on chromosome 6 and OCTs are in major organs such as intestine, liver, kidney, brain and placenta. Therefore, expression levels and function of OCTs directly affect plasma levels and intracellular concentrations of drugs and thereby determine therapeutic response. The aim of this study was to investigate the frequency of the SNPs on OCT1 (C181T and C1022T) and OCT2 (G808T) to analyze haplotype frequency in healthy Korean population. Human subjects have been genotyped for OCT1 (C181T for 195 subjects and C1022T for 825 subjects), using polymerase chain reaction-based diagnostic tests (RFLP). And for OCT2 (G808T), a total of 861 subjects have been genotyped, using pyrosequencing method. Haplotype was statistically inferred using an algorithm based on the expectation-maximization (EM). OCT1 C181T genotyping showed 100% homozygous wild-type (C/C). OCT1 C1022T genotyping showed wild-type (C/C), heterozygous (C/T) and homozygous mutant-type (T/T) and each accounted for 72.1, 24.5 and 3.4%, respectively. OCT2 G808T genotyping results also showed homozygous wild-type (G/G), heterozygous (G/T) and homozygous mutant-type (T/T) and each took 81.8, 17.9 and 0.3%, respectively. Based on these genotype data, haplotype analysis between OCT1 C181T and OCT1 C1022T has proceeded. The result has revealed that linkage disequilibrium between alleles is not obvious (P=0.0122).

Determination of ibudilast in human serum by high-performance liquid chromatography for pharmacokinetic study

A simple, accurate, precise and cost effective reversed-phase HPLC method was developed to determine the concentration of ibudilast in human serum. Ibudilast and an internal standard, butyl 4-hydroxybenzoate, were extracted by liquid-liquid extraction with methyl tert-butyl ether. HPLC analysis was carried out under the following conditions: a Luna C(18)(2) 5 microm column, a mobile phase of acetonitrile-0.02% phosphoric acid (50 : 50, v/v, adjusted to pH 6.0 with triethylamine) and a UV detector at 319 nm. The chromatograms showed good resolution and sensitivity as well as no interference from the human serum. The calibration curves were linear over the concentration range, 1-100 ng/mL, for serum with correlation coefficients >0.999. The intra- and inter-day assay precision as well as the accuracy fulfilled the international requirements. The mean absolute recovery for human serum was 101.7 +/- 6.1%. The lower limit of quantitation in human serum was 1 ng/mL, which is sensitive enough for pharmacokinetic studies. Stability studies revealed that ibudilast in human serum was stable during storage as well as during the assay procedure. This method was applied successfully to an examination of the pharmacokinetics of ibudilast in human subjects following a single oral dose of an ibudilast (10 mg) capsule.

Bioequivalence of Famvir Tablet 750 mg to Famcivir Tablet 750 mg (Famciclovir 750 mg)

Famciclovir, 9-(4-hydroxy-3-hydroxymethylbut-1-yl) guanine, is an oral prodrug of the antiherpesvirus nucleoside analogue, penciclovir. In human, famciclovir is orally well absorbed and then undergoes extensive first pass metabolism to penciclovir and essentially no parent compound is recovered from plasma or urine. The purpose of the present study was to evaluate the bioequivalence of two famciclovir tablets, Famvir tablet 750 mg (Novartis Korea Ltd.) and Famcivir tablet 750 mg (Hanmi Pharmaceutical. Co., Ltd.), according to the guidelines of the Korea Food and Drug Administration (KFDA). The release of famciclovir from the two famciclovir formulations in vitro was tested using KP VIII Apparatus II method with water. Twenty six healthy male subjects, years in age and in body weight, were divided into two groups and a randomized cross-over study was employed. After a single tablet containing 750 mg as famciclovir was orally administered, blood samples were taken at predetermined time intervals and the concentrations of penciclovir in serum were determined using HPLC with UV detector. The dissolution profiles of two formulations ere similar at water. The pharmacokinetic parameters such as , and were calculated and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed , and untransformed . The results showed that the differences between two formulations based on the reference drug, tablet 750 mg, were -0.53%, 1.12% and -24.82% for , and , respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25 (e.g., and for and , respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating Famcivir tablet 750 mg was bioequivalent to Famvir tablet 750 mg.

Validation of an LC/MS/MS Method for the Pharmacokinetic Study of Lercanidipine

A rapid, simple and sensitive LC/MS/MS method for the determination of lercanidipine in human serum was validated and applied to the pharmacokinetic study of lercanidipine. Lercanidipine and internal standard, amlodipine, were extracted from human serum by liquid-liquid extraction with hexan-isoamyl alcohol (100: 1, v/v) and analyzed on a MS column with the mobile phase of acetonitrile-0.2% aqueous formic acid (70: 30, v/v). Using MS/MS with multiple reaction monitoring (MRM) mode, lercanidipine and amlodipine were detected without severe interferences from human serum matrix. Lercanidipine produced a protonated precursor ion () at m/z 612.3 and a corresponding product ion at m/z 280.0. Internal standard produced a protonated precursor ion (]) at m/z 409.0 and a corresponding product ion at m/z 238.0. The ruggedness of this method was investigated using quality control (QC) samples. This method showed linear response over the concentration range of 0.05-20 ng/mL with correlation coefficient greater than 0.999. The lower limit of quantitation using 0.5 mL of serum was 0.05 ng/mL, which was sensitive enough for pharmacokinetic studies. The overall accuracy of the developed method ranged from 85.51 to 112.2% for lercanidipine with overall precision (% C.V.) being 3.56-13.1%. This method showed good ruggedness (within 15% C.V.) and was successfully applied for the analysis of lercanidipine in human serum samples for the pharmacokinetic studies, demonstrating the suitability of the method.

Bioequivalence of S-napine Tablet 10 mg to Alesion Tablet(Epinastine HCl 10 mg)

Epinastine is an antiallergic drug effective for bronchial asthma, allergic rhinitis, urticaria and dermatitis. Epinastine is topically active, direct H1-receptor antagonist and an inhibitor of the release of histamine from the mast cell. The purpose of the present study was to evaluate the bioequivalence of two epinastine hydrochloride tablets, Alesion Tablet (Boehringer Ingelheim Korea Ltd.) and S-napine tablet 10 mg(Sam Chun Dang Pharm. Co., Ltd), according to the guidelines of the Korea Food and Drug Administration(KFDA). The release of epinastine from the two epinastine formulations in vitro was tested using KP VIII Apparatus II method with various dissolution media(pH 1.2, 4.0, 6.8 buffer solution and water). Twenty six healthy male subjects, years in age and in body weight, were divided into two groups and a randomized cross-over study was employed. After two tablets containing 20 mg as epinastine hydrochloride was orally administered, blood was taken at predetermined time intervals and the concentrations of epinastine in serum were determined using HPLC with UV detector. The dissolution profiles of two formulations were similar at all dissolution media. In addition, the pharmacokinetic parameters such as were calculated and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed and untransformed . The results showed that the differences between two formulations based on the reference drug, Alesion tablet, were 1.50, 1.46 and -13.48% for , respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25(e.g., log 0.95log 1.12 and log 0.93log 1.10 for , respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating S-napine tablet 10 mg was bioequivalent to Alesion tablet.

Validated HPLC Method for the Pharmacokinetic Study of Atenolol and Chlorthalidone Combination Therapy in Korean Subjects

A rapid, selective and sensitive reverse-phase HPLC methods for the determination of atenolol and chlorthalidone in human serum and whole blood were validated, and applied to the pharmacokinetic study of atenolol and chlorthalidone combination therapy. Atenolol and an internal standard, pindolol, were extracted from human serum by liquid-liquid extraction, and analyzed on a -Bondapak C18 column in a mobile phase of methanol-0.01 M potassium dihydrogenphosphate(30:70, v/v, adjusted to pH 3.5) and fluorescence detection(emission: 300 nm, excitation: 224 nm). Chlorthalidone and an internal standard, probenecid, were extracted form human whole blood by liquid-liquid extraction, and analyzed on a Luna C18 column in a mobile phase of acetonitrile containing 77% 0.01 M sodium acetate and UV detection at 214 nm. These analysis were performed at three different laboratories using the same quality control(QC) samples. The chromatograms showed good resolution, sensitivity, and no interference by human serum and whole blood, respectively. The methods showed linear responses over a concentration range of 10-1,000 ng/mL for atenolol and 0.05-20 for chlorthalidone, with correlation coefficients of greater than 0.999 at all the three laboratories. Intra- and inter-day assay precision and accuracy fulfilled international requirements. Stability studies(freeze-thaw, short-, long-term, extracted sample and stock solution) showed that atenolol and chlorthalidone were stable. The lower limit of quantitation of atenolol and chlorthalidone were 10 ng/mL and 0.05 , respectively, which was sensitive enough for pharmacokinetic studies. These methods were applied to the pharmacokinetic study of atenolol and chlorthalidone in human volunteers following a single oral administration of Hyundai tablet(atenolol 50 mg and chlorthalidone 12.5 mg) at three different laboratories.