Fimasartan is a nonpeptide angiotensin II receptor blocker. In a previous study that compared the pharmacokinetics (PK) of fimasartan between patients with hepatic impairment (cirrhosis) and healthy subjects, the exposure to fimasartan was found to be higher in patients, but the decrease of blood pressure (BP) was not clinically significant in those with moderate hepatic impairment. The aims of this study were to develop a population PK-pharmacodynamic (PD) model of fimasartan and to evaluate the effect of hepatic function on BP reduction by fimasartan using previously published data. A 2-compartment linear model with mixed zero-order absorption followed by first-order absorption with a lag time adequately described fimasartan PK, and the effect of fimasartan on BP changes was well explained by the inhibitory sigmoid function in the turnover PK-PD model overlaid with a model of circadian rhythm (NONMEM version 7.2). According to our PD model, the lower BP responses in hepatic impairment were the result of the increased fimasartan EC₅₀ in patients, rather than from a saturation of effect. This is congruent with the reported pathophysiological change of increased plasma ACE and renin activity in hepatic cirrhosis.
Absorption ; Blood Pressure ; Circadian Rhythm ; Colon, Sigmoid ; Healthy Volunteers ; Humans ; Linear Models ; Liver Cirrhosis* ; Liver* ; Pharmacokinetics ; Plasma ; Receptors, Angiotensin ; Renin

Data handling and tabulation are a time-consuming job when writing appendices for clinical study reports. The authors have developed an automated appendix generation system (ARGUS) conforming to the CDISC/SDTM standard using SAS (version 9.3) and R (version 3.3.1: for PK plot generation). It consists of the one main program and three subprograms. The program runs to convert a database file into an appendix document with about 100 tables and plots in MS Word format within one min after pressing the submit button under common desktop environments. We found that tasks of constructing appendices for a typical 2×2 crossover design study that have taken our team about 8 days were completed within 6 or 7 hours using the ARGUS system.
Appendix* ; Clinical Study* ; Cross-Over Studies ; Writing

Diuretic therapy for the treatment of edema in patients with end-stage renal disease (ESRD) is unsatisfactory, and a combination of thiazide and loop diuretics may produce better clinical effects. To evaluate the influence of thiazide on loop diuretic therapy for ESRD, we performed a crossover study of furosemide versus hydrochlorothiazide plus furosemide treatment. The diuretic effects of furosemide (160 mg i.v.) alone versus a combination of hydrochlorothiazide (100 mg p.o.) and furosemide were studied in ten ESRD patients with proteinuria greater than 1 g/day. The diuretic effects were compared for 24 h urine volume and electrolyte excretion. To detect the influence of thiazide that may have been obscured in the widely dispersed data, pharmacodynamic analysis of urine furosemide excretion rate versus fractional excretion of sodium (FeNa) was also performed using mixed-effect modeling. Combination therapy was not significantly different from furosemide monotherapy in terms of 24 h urine volume, chloride, or sodium excretion. Hydrochlorothiazide was not a significant covariate in the furosemide effect for the pharmacodynamic model. In patients with ESRD and severe proteinuria (>1,000 mg/day), the combination of hydrochlorothiazide with furosemide therapy did not increase the diuretic effect of furosemide.
Cross-Over Studies ; Diuretics ; Edema ; Furosemide ; Humans ; Hydrochlorothiazide* ; Kidney Failure, Chronic* ; Proteinuria ; Sodium ; Sodium Potassium Chloride Symporter Inhibitors

A simple, rapid, and reliable UPLC-MS/MS method was developed and validated for the determination of tadalafil in human plasma. The plasma samples were deproteinized with acetonitrile. Chromatographic separation was performed on a Shiseido C18 (100 × 2.1 mm, 2.7 µm) column with isocratic elution using 2.0 mM ammonium acetate and acetonitrile (55:45, v/v) with 0.1% formic acid at a flow rate of 0.7 mL/min. The total run time was 1 min per sample. The quantitative analysis was performed using multiple reaction monitoring at transition of m/z 390.4 → 268.3 for tadalafil and m/z 475.3 → 283.3 for sildenafil as an internal standard. The method was fully validated over a concentration range of 5–1,000 ng/mL with a lower quantification limit of 5 ng/mL. Intra- and inter-day precision (relative standard deviation, %RSD) were within 8.4% and accuracy (relative error, %RE) was lower than -3.2%. The developed and validated method was successfully applied to a pharmacokinetic study of tadalafil (20 mg) in Korean healthy male subjects (n = 12).
Ammonium Compounds ; Humans* ; Male ; Methods* ; Pharmacokinetics ; Plasma* ; Sildenafil Citrate ; Tadalafil*

This study was performed to evaluate the use of vibrating microneedles for the transdermal delivery of vitamin C. The microneedles were designed to vibrate at three levels of intensity. In vitro permeation by vitamin C was evaluated according to the specific conditions such as vibration intensity (levels 1, 2 and 3), application time (1, 3, 5, 7 and 10 min), and application power (500, 700 and 1,000 g). The highest permeation of vitamin C was observed at level 3 of vibration intensity, 5 min of application, and 1,000 g of application power. Vitamin C gel showed no cytotoxic effect against Pam212 cells or skin irritation effects. A pharmacokinetic study of the gel in rats was conducted under optimized conditions. The AUC₀-∞ and C(max) increased 1.35-fold and 1.44-fold, respectively, compared with those after vitamin C gel without application with vibrating microneedles. The present study suggests that vibrating microneedles can be used to facilitate the skin permeability of vitamin C under optimal conditions.
Animals ; Ascorbic Acid* ; In Vitro Techniques ; Permeability ; Pharmacokinetics ; Rats ; Skin* ; Vibration ; Vitamins*

Simvastatin is used to reduce plasma cholesterol by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and is primarily used to treat hypercholesterolemia. This study was conducted to assess the bioequivalence between the generic formulation of simvastatin 20 mg and the branded formulation of simvastatin 20 mg. A generic formulation of simvastatin 20 mg tablet was developed and the pharmacokinetics of the generic formulation were compared with those of the branded formulation of simvastatin 20 mg tablet in 33 healthy male volunteers after a single oral dose in a randomized, open-label, two-period, two-sequence, crossover study. The reference (Zocor®, MSD Korea LTD.) and test (Simvarotin®, Korea Arlico Pharm Co., Ltd.) formulations, two 20 mg tablets each, were administered to all subjects in fasting status. The serial blood samples for pharmacokinetic analysis were collected before dosing and up to 24 hours post-dose, and plasma concentrations of simvastatin were determined by liquid chromatography-tandem mass spectrometry. The pharmacokinetic parameters including T(max), C(max), AUC(last), AUC(inf) and t½ were calculated for both formulations by non-compartmental method, and the log-transformed C(max) and AUC(last) were compared statistically. Geometric mean ratios (90% confidence intervals) of the test to the reference formulation in C(max) and AUC(last) were 0.9652 (0.8302–1.1223) and 0.9891 (0.8541–1.1455), respectively. No significant differences in tolerability profiles were noted between the two formulations. The two formulations of simvastatin 20 mg tablets exhibited comparable pharmacokinetic profiles and 90% confidence intervals were within the acceptable range of bioequivalence criteria.
Cholesterol ; Coenzyme A ; Cross-Over Studies ; Fasting ; Humans ; Hypercholesterolemia ; Korea ; Male* ; Mass Spectrometry ; Methods ; Oxidoreductases ; Pharmacokinetics ; Plasma ; Simvastatin* ; Tablets ; Therapeutic Equivalency ; Volunteers*

Drunk driving is a serious social problem. We estimated the blood alcohol concentration of a defendant on the request of local prosecutor's office in Korea. Based on the defendant's history, and a previously constructed pharmacokinetic model for alcohol, we estimated the possible alcohol concentration over time during his driving using a Bayesian method implemented in NONMEM®. To ensure generalizability and to take the parameter uncertainty of the alcohol pharmacokinetic models into account, a non-parametric bootstrap with 1,000 replicates was applied to the Bayesian estimations. The current analysis enabled the prediction of the defendant's possible blood alcohol concentrations over time with a 95% prediction interval. The results showed a high probability that the alcohol concentration was ≥ 0.05% during driving. The current estimation of the alcohol concentration during driving by the Bayesian method could be used as scientific evidence during court trials.
Bayes Theorem ; Blood Alcohol Content ; Driving Under the Influence ; Forensic Sciences* ; Korea ; Pharmacology, Clinical* ; Social Problems ; Uncertainty

Clearance is a key concept in pharmacokinetics, but it is not easy to understand for beginners. This tutorial aims to help beginners by using the analogy of a vacuum cleaner clearing the dust from the air in a room. The air, the volume of the air, the dust and the vacuum cleaner are used to represent the plasma, the volume of distribution, the drug and the eliminating organ, respectively, in the human body. Because the capacity of a vacuum cleaner (eliminating organ) is an inherent feature that is independent of the concentration of dust (drug), the elimination rate (eliminated amount/time) of dust (drug), which is proportional to its concentration in the air (plasma), cannot reflect this inherent capacity correctly. Clearance estimates the volume of the solvent (air or plasma) cleared by the organ per unit time rather than the amount of the solute (dust or drug) removed. Therefore, clearance has the unit of volume/time. Just as the air is cleared of dust, but is not eliminated by the vacuum cleaner, the plasma is cleared of drug, but is not eliminated from the human body.
Dust ; Human Body ; Pharmacokinetics ; Plasma ; Vacuum*

The structural complexity of crossover studies for bioequivalence test confuses analysts and leaves them a hard choice among various programs. Our study reviews PROC GLM and PROC MIXED in SAS and compares widely used SAS codes for crossover studies. PROC MIXED based on REML is more recommended since it provides best linear unbiased estimator of the random between-subject effects and its variance. Our study also considers the covariance structure within subject over period which most PK/PD studies and crossover studies ignore. The QT interval data after the administration of moxifloxacin for a fixed time point are analyzed for the comparison of representative SAS codes for crossover studies.
Cross-Over Studies* ; Therapeutic Equivalency

The Vietnamese-Koreans, especially offspring between a Vietnamese mother and a Korean father constituted the highest proportion (64.2%) of total Kosian population according to a census in 2014. To evaluate genetic characteristics in the Vietnamese-Koreans, a total of 25 alleles from CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 were genotyped using SNaPshot method with DNA samples of 127 Vietnamese-Koreans. The previous reports on the CYPs of Korean and Vietnamese populations were also analyzed for the comparative studies for the frequencies of CYP alleles. The statistical significances in allele and genotype frequencies among the ethnics were analyzed by Chi-square or Fisher's exact probability test. Although most of variants analyzed in 5 CYPs did not reach the statistically significant difference between the Vietnamese-Koreans and Vietnamese, some alleles were only found in Vietnamese-Koreans. Compared with Korean population, frequencies of CYP2D6*1 and CYP2D6*10B were statistically different from Vietnamese-Koreans (p<0.05). This is the first report to describe the CYP genotype profiles of Vietnamese-Koreans, which may provide important insight for the genotype based prediction of CYP activities of this admixture of Korean and Vietnamese.
Alleles ; Asian Continental Ancestry Group ; Censuses ; Cytochrome P-450 CYP2D6* ; Cytochrome P-450 Enzyme System ; DNA ; Fathers ; Genotype ; Humans ; Mothers ; Polymorphism, Genetic*