Combination therapies of antihypertensive drugs are recommended in cases where hypertension is not controlled by monotherapy. This study aimed to compare the pharmacokinetics (PKs) between fixed-dose combination (FDC) of fimasartan/amlodipine 60/10 mg and the corresponding loose combination. Because of the high intra-subject variability for maximum plasma concentration (C(max)) of fimasartan, a randomized, open-label, 3×3 partial replicated crossover design was adopted. Subjects received a single dose of FDC of fimasartan/amlodipine 60/10 mg or the corresponding loose combination in each period. Blood samples for PK analysis were collected up to 48 hours for fimasartan and 144 hours for amlodipine, respectively. Geometric mean ratios (GMRs) and its 90% confidence intervals (CIs) of the FDC to the loose combination for C(max) and area under the concentration-time curve from time 0 to the last quantifiable time point (AUC(last)) were calculated. Sixty healthy subjects were randomized, and 57 subjects completed the study. The concentration-time profiles of fimasartan and amlodipine were similar between the FDC and loose combination. The GMRs (90% CIs) of the FDC to the loose combination for C(max) and AUC(last) were 1.0440 (0.9202–1.1844) and 1.0412 (0.9775–1.1090) for fimasartan, and 1.0430 (1.0156–1.0711) and 1.0339 (1.0055–1.0631) for amlodipine, respectively. The GMRs and its 90% CIs for C(max) and AUC(last) of fimasartan and amlodipine were included not only in the scaled bioequivalence criteria but also in the conventional bioequivalence criteria. In conclusion, FDC of fimasartan/amlodipine 60/10 mg showed comparable PK profiles with the corresponding loose combination, which suggests their bioequivalence.
Amlodipine ; Antihypertensive Agents ; Cross-Over Studies ; Healthy Volunteers ; Hypertension ; Pharmacokinetics ; Plasma ; Therapeutic Equivalency

The paper is aimed to investigate the pharmacokinetic (PK) and the pharmacodynamic (PD) properties of carvedilol using indirect response and effect-compartment link models, and compare the fitness of PK-PD models. Twenty male healthy Chinese volunteers received a single oral dose of 20 mg of carvedilol. The plasma concentrations of carvedilol were determined by reversed-phase HPLC method with fluorescence detection, and the pharmacokinetic parameters were calculated by DAS2.0. The mean arterial blood pressure was measured and the pharmacodynamics of carvedilol was characterized by tail-cuff manometry. The main pharmacokinetic parameters of carvedilol were as follows, t1/2 (4.56 +/- 2.56) h, Cmax (46.29 +/- 21.07) ng x mL(-1), AUC(0-infinity) (173.76 +/- 87.36) ng x mL(-1) x h. The estimated Kin was (0.41 +/- 0.31)% h(-1), Kout was (0.40 +/- 0.26) h(-1), the IC50 value was (24.40 +/- 21.10) ng x mL(-1) and the area under the effect curve (AUE) was (3.82 +/- 1.46)% h for the indirect response PD model. The Ke0 was (0.35 +/- 0.27) h(-1), the EC50 was (24.30 +/- 24.30) ng x mL(-1), and the AUE was (5.65 +/- 2.54)% h for the effect-compartment model. The HPLC method can be used for the pharmacokinetic study of carvedilol. The proposed effect-compartment link model provided more appropriate and better-fitting PK/PD characteristics than the indirect response model in Chinese healthy volunteers according to Akaike's information criterion values.
Antihypertensive Agents ; pharmacokinetics ; pharmacology ; Area Under Curve ; Blood Pressure ; drug effects ; Carbazoles ; blood ; pharmacokinetics ; pharmacology ; Humans ; Male ; Models, Cardiovascular ; Propanolamines ; blood ; pharmacokinetics ; pharmacology

AIMTo determine clonidine in rabbit plasma by LC-MS.

METHODSThe LC-MS system consisted of Waters Alliance 2790 HPLC and Micromass ZQ-4000 MS. The HPLC was performed by using XTerra C18 (150 mm x 2.1 mm ID, 5 microm). The mobile phase, consisting of acetonitrile/ammonium hydrogen carbonate solution, was maintained to a flow-rate of 0.2 mL x min(-1) and the linear gradient elution was adopted. Mass spectrum was obtained by using electrospray ionization interface and the m/z of SIM was 230.

RESULTSThe average recovery was high and the method was reproducible. The calibration curve showed good linearity in the range of 1 - 80 microg x L(-1), the lowest limit of detection was 0.05 microg x L(-1). The Cmax, AUC0-t, and Tmax value of the pharmacokinetics parameter were (27 +/- 9) microg x L(-1), (5,352 +/- 1,121) microg x L(-1), (79 +/- 17) h.

CONCLUSIONThe results demonstrated that the method had high sensitivity, good selectivity, accuracy and precision. It is used to determine the clonidine concentration in plasma. The transdermal patch can deliver clonidine to the surface of rabbit skin stably for periods of up to 1 week after a single application.

Administration, Cutaneous ; Animals ; Antihypertensive Agents ; administration & dosage ; blood ; pharmacokinetics ; Area Under Curve ; Chromatography, High Pressure Liquid ; methods ; Clonidine ; administration & dosage ; blood ; pharmacokinetics ; Rabbits ; Spectrometry, Mass, Electrospray Ionization ; methods

AIMTo investigate the preparation of pulsatile release tablets, the release of the drug in vitro and the pharmacokinetics in vivo.

METHODSDiltiazem hydrochloride (DIL) was used as model drug. The pulsatile release tablets were prepared by film-coated method using ethylcellulose and Eudragit L. The effect of formulation on pulsatile release of diltiazem hydrochloride was investigated under release rate test. The mechanism of pulsatile release of drug was proved by the test of water-uptake. The pharmacokinetic and bioavailability study in eight human subjects was performed by HPLC method.

RESULTSThe release of diltiazem hydrochloride effected by the formulation of the core tablets and the composition and thickness of the coating film. In vitro, the delayed-release time T10 was 4.4 h, the maximum release time Trm was 8.0 h and the pulsed-release time Trm-10 was 3.6 h. In vivo, the delayed-release time Tlag was 4.9 h, the peak time was 8.0 h and the pulsed-release time was 3.1 h. The relative bioavailability was 105%.

CONCLUSIONThe release of drug from pulsatile release tablets of diltiazem hydrochloride was shown to be in pulsed way both in vitro and in vivo.

Adult ; Antihypertensive Agents ; administration & dosage ; pharmacokinetics ; Biological Availability ; Chemistry, Pharmaceutical ; Delayed-Action Preparations ; Diltiazem ; administration & dosage ; pharmacokinetics ; Drug Delivery Systems ; Fluorocarbons ; chemistry ; Humans ; Male ; Polymethacrylic Acids ; chemistry

To investigate the disposition and tissue distribution of ML12 after intravenous (iv) administration in rats, the compound in plasma or in tissue was extracted into ethyl acetate under basic condition and was determined by HPLC after extracted by dilute sulfuric acid. Excitation wavelength and emission wavelength of fluorescence detection were 278 nm and 307 nm, respectively. The data were processed with the software 3P97 to calculate the main pharmaceutical parameters of ML12. At dose of 5 and 10 mg/kg, the elimination of the drug from plasma was found to be kinetically linear, but when the dosage was 20 mg/kg, a non-linear feature was observed. The highest level of ML12 was found in the kidney. Distribution of ML12 after iv administration was extensive and the concentration-time profile was found to be fitted to an open two-compartment model.
Antihypertensive Agents/*pharmacokinetics ; Biological Availability ; Chromatography, High Pressure Liquid/methods ; Kinetics ; Pharmaceutical Preparations ; Rats, Sprague-Dawley ; Spectrometry, Fluorescence/methods ; Sulfuric Acids/chemistry ; Tissue Distribution

This study aims to save cost of sampling for estimating the area under the amlodipine plasma concentration versus time curve in 24 hours (AUC(0-24 h)). Limited sampling strategy (LSS) models was developed and validated by mutiple regression model within 4 or fewer amlodipine concentration values. Absolute prediction error (APE), root of mean square error (RMSE) and visual predict check were used as criterion. The results of Jackknife validation showed that fifteen (9.4%) of the 160 LSS based on regression analysis were not within an APE of 15% by using one concentration-time point. 156 (97.5%), 159 (99.4%) and 160 (100%) of the 160 LSS model were capable of predicting within an APE 15% by using 2, 3, 4 points, separately. Limited sampling strategies have been developed and validated for estimating AUC(0-24 h) of amlodipine. The present study indicated that the implemention of both 5 mg and 10 mg dosage could enable accurate predictions of AUC(0-24 h) by the same LSS model. This study shows that 12, 4, 24, 2 h after administration are key sampling time points. The combination of (12, 4), (12, 4, 24) or (12, 4, 24, 2 h) might be chosen as sampling hours for predicting AUC(0-24 h) in practical application according to requirement.
Administration, Oral ; Adult ; Amlodipine ; administration & dosage ; blood ; pharmacokinetics ; Antihypertensive Agents ; administration & dosage ; blood ; pharmacokinetics ; Area Under Curve ; Asian Continental Ancestry Group ; Calcium Channel Blockers ; administration & dosage ; blood ; pharmacokinetics ; Humans ; Male ; Models, Biological ; Regression Analysis ; Sample Size ; Vasodilator Agents ; administration & dosage ; blood ; pharmacokinetics ; Young Adult

Scutellarin is the main effective constituent of breviscapine, a flavonoid mixture isolated from the dried whole plant of Erigeron breviscapus (Vant.) Hand-Mazz, and valsartan is used as an antihypertensive drug. These two drugs have already been clinically used together to treat diabetic nephropathy (DN) in China, and the combined medications showed some enhanced protection against DN. The aim of this study is to investigate the potential pharmacokinetic interaction between scutellarin and valsartan in rats. Breviscapine injection (20 mg x kg(-1), i.v.) and valsartan (15 mg x kg-, i.g.), either alone or together were given to 18 male Sprague-Dawley rats. Concentrations of scutellarin and valsartan were quantified by HPLC, and pharmacokinetic parameters were calculated by non-compartmental methods. We found that the pharmacokinetic parameters of scutellarin altered significantly after co-administration of oral valsartan. The plasma clearance (CL(p)) and the bile clearance (CL(b)) of scutellarin were reduced significantly in the presence of valsartan. After oral administration of valsartan with or without intravenous scutellarin, however, the pharmacokinetic parameters of valsartan were comparable. In conclusion, our data suggests that the concurrent use of valsartan reduces the biliary excretion of scutellarin, and this may be due to the inhibitory effect of valsartan on the biliary excretion of scutellarin mediated by Mrp2 (Multidrug resistance-associated protein 2).
Administration, Intravenous ; Administration, Oral ; Animals ; Antihypertensive Agents ; administration & dosage ; blood ; pharmacokinetics ; Apigenin ; administration & dosage ; blood ; isolation & purification ; pharmacokinetics ; Bile ; metabolism ; Chromatography, High Pressure Liquid ; Drug Interactions ; Erigeron ; chemistry ; Glucuronates ; administration & dosage ; blood ; isolation & purification ; pharmacokinetics ; Male ; Metabolic Clearance Rate ; Multidrug Resistance-Associated Proteins ; metabolism ; Plants, Medicinal ; chemistry ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Valsartan ; administration & dosage ; blood ; pharmacokinetics

The study aims to evaluate the bioequivalence of valsartan hydrochlorothiazide tablets, and to investigate the potential cause of bioinequivalence. This was a single-center study with an open, randomized double-way crossover design. Test and reference preparations containing 160 mg of valsartan and 25 mg of hydrochlorothiazide were given to 36 healthy male volunteers. Plasma concentrations of valsartan and hydrochlorothiazide were determined simultaneously by LC-MS/MS. The pharmacokinetic parameters and relative bioavailability were calculated, while the bioequivalence between test and reference preparations were evaluated. The dissolution profiles of test and reference preparations in four different mediums were determined via dissolution test and HPLC. The similarity was investigated according to the similarity factors (f2). The F(o-t) and F(0-infinity) were (139.4 +/- 65.2)% and (137.5 +/- 61.2)% for valsartan of test preparations. It led to get the conclusion that test and reference preparations were not bioequivalent for valsartan. A significant difference was observed between test and reference tablets in the valsartan dissolution test of pH 1.2 hydrochloric acid solution. The key factor of the bioinequivalence might be that dissolution of valsartan in acid medium has marked difference between two preparations.
Administration, Oral ; Adolescent ; Adult ; Angiotensin II Type 1 Receptor Blockers ; administration & dosage ; adverse effects ; blood ; pharmacokinetics ; Antihypertensive Agents ; administration & dosage ; adverse effects ; blood ; pharmacokinetics ; Area Under Curve ; Chromatography, Liquid ; Cross-Over Studies ; Drug Liberation ; Humans ; Hydrochlorothiazide ; administration & dosage ; adverse effects ; blood ; pharmacokinetics ; Male ; Tablets ; Tandem Mass Spectrometry ; Therapeutic Equivalency ; Valsartan ; administration & dosage ; adverse effects ; blood ; pharmacokinetics ; Young Adult

To prepare transdermal drug delivery system (TDDS) of felodipine and metoprolol and to study its pharmaceutical characteristics, pharmacokinetics and bioavailability in rabbits, an HPLC assay was established for the simultaneous determination of felodipine and metoprolol in the permeation receptor and patch. The permeation rate and permeation mechanism of felodipine-metoprolol-TDDS through rabbit skin in vitro was examined. The determination of drug content, the examination of content uniformity and stability of the TDDS were carried out. GC-ECD assays were established for the determination of felodipine and metoprolol in plasma separately and then employed to study the pharmacokinetics and bioavailability of felodipine and metoprolol after a single dose of oral or transdermal administration in rabbits. The results indicated that the permeation of flodipine and metoprolol from the patch through excised rabbit skin exhibited zero-order kinetic characteristics. The determination of drug content and the quality control of content uniformity of the patch accorded with Pharmacopoeia of the People's Republic of China of 2005 edition and the pharmaceutical characterization showed good stability. In contrast to oral delivery, relatively constant, sustained blood concentration with minimal fluctuation and prolonged peak time were observed over a long period after transdermal administration. The relative bioavailability of felodipine and metoprolol were 275.37% and 189.76% versus oral administration respectively. It was evident that the felodipine-metoprolol-TDDS exhibited good controlled release properties that satisfied the demands of original design that enhancing bioavailability and maintaining appropriate blood levels for a prolonged time without adverse effects associated with frequent oral administration.
Administration, Cutaneous ; Animals ; Antihypertensive Agents ; administration & dosage ; blood ; pharmacokinetics ; Area Under Curve ; Azepines ; chemistry ; Biological Availability ; Cyclohexanols ; chemistry ; Delayed-Action Preparations ; Drug Delivery Systems ; Drug Stability ; Felodipine ; administration & dosage ; blood ; pharmacokinetics ; Female ; Male ; Metoprolol ; administration & dosage ; blood ; pharmacokinetics ; Monoterpenes ; chemistry ; Propylene Glycols ; chemistry ; Rabbits ; Skin Absorption

Reasonable sampling scheme is the important basis for establishing reliable population pharmacokinetic model. It is an effective method for estimation of population pharmacokinetic parameters with sparse data to perform population pharmacokinetic analysis using the nonlinear mixed-effects models. We designed the sampling scheme for amlodipine based on D-optimal sampling strategy and Bayesian estimation method. First, optimized sample scenarios were designed using WinPOPT software according to the aim, dosage regimen and visit schedule of the clinical study protocol, and the amlodipine population model reported by Rohatagi et al. Second, we created a NONMEM-formatted dataset (n = 400) for each sample scenario via Monte Carlo simulation. Third, the estimation of amlodipine pharmacokinetic parameters (clearance (CL/F), volume (V/F) and Ka) was based on the simulation results. All modeling and simulation exercises were conducted with NONMEM version 7.2. Finally, the accuracy and precision of the estimated parameters were evaluated using the mean prediction error (MPE) and the mean absolute error (MAPE), respectively. Among the 6 schemes, schemes 6 and 3 have good accuracy and precision. MPE is 0.1% for scheme 6 and -0.6% for scheme 3, respectively. MAPE is 0.7% for both schemes. There is no significant difference in MPE and MAPE of volume among them. Therefore, we select scheme 3 as the final sample scenario because it has good accuracy and precision and less sample points. This research aims to provide scientific and effective sampling scheme for population pharmacokinetic (PK) study of amlodipine in patients with renal impairment and hypertension, provide a scientific method for an optimum design in clinical population PK/PD (pharmacodynamics) research.
Adult ; Age Factors ; Alanine Transaminase ; blood ; Amlodipine ; pharmacokinetics ; pharmacology ; Antihypertensive Agents ; pharmacokinetics ; pharmacology ; Bayes Theorem ; Body Weight ; Calcium Channel Blockers ; pharmacokinetics ; pharmacology ; Humans ; Hypertension ; metabolism ; Metabolic Clearance Rate ; Middle Aged ; Models, Biological ; Monte Carlo Method ; Nonlinear Dynamics ; Renal Insufficiency ; metabolism ; Software