Discovery of Novel Aryl Triazolone Dihydropyridines (ATDPs) Targeting Highly Conserved Residue W229 as Promising HIV-1 NNRTIs.

NNRTI is an important component of the highly active antiretroviral therapy (HAART), but the rapid emergence of drug resistance and poor pharmacokinetics limited their clinical application. Herein, a series of novel aryl triazolone dihydropyridines (ATDPs) were designed by structure-guided design with the aim of improving drug resistance profiles and pharmacokinetic profiles. Compound 10n (EC50 = 0.009-17.7 µM) exhibited the most active potency, being superior to or comparable to that of doravirine (DOR) against the whole tested viral panel. Molecular docking was performed to clarify the reason for its higher resistance profiles. Moreover, 10n demonstrated excellent pharmacokinetic profile (T1/2 = 5.09 h, F = 108.96%) compared that of DOR (T1/2 = 4.4 h, F = 57%). Additionally, 10n was also verified to have no in vivo acute or subacute toxicity (LD50 > 2000 mg/kg), suggesting that 10n is worth further investigation as a novel oral NNRTIs for HIV-1 therapy.

Gellan gum based gastroretentive tablets for bioavailability enhancement of cilnidipine in human volunteers.

Cilnidipine, a fourth-generation both L-and N-type calcium channel blocker (CCB) is safe and effective in lowering blood-pressure without reflex tachycardia compared to other dihydropyridine CCBs. However, its low solubility coupled with extensive first-pass metabolism results in very low oral bioavailability. Thus the study aimed to improve oral bioavailability of Cilnidipine by increasing its gastrointestinal transit-time and mucoadhesion. Gastroretentive tablets were prepared by direct-compression technique using gellan gum as hydrogel forming polymer and sodium bicarbonate as gas-generating agent. Statistical optimization was carried out by design approach which showed that gellan gum has significant impact on floating lag time, mucoadhesive strength, % drug release at 1 h and time to release 90% of drug. Drug release study revealed that optimized tablets prolonged drug release for 12 h and followed anomalous-diffusion indicating drug release is by coupling of both diffusion and erosion mechanism. Intragastric behaviour of formulation in human volunteers revealed that radio-opaque tablets remain buoyant in stomach for more than 6 h with sufficient mucoadhesion. Comparative pharmacokinetic profiling in human subjects revealed that relative bioavailability of Cilnidipine GR tablets was enhanced compared to reference tablets. Thus concluded that gastroretentive tablets to be promising strategy for improved oral bioavailability of Cilnidipine for effective treatment of hypertension.

Exploratory Study on Lercanidipine Hydrochloride Polymorphism: pH-Dependent Solubility Behavior and Simulation of its Impact on Pharmacokinetics.

This work describes an exploratory experimental and in silico study of the influence of polymorphism, particle size, and physiology on the pharmacokinetics of lercanidipine hydrochloride (LHC). Equilibrium and kinetic solubility studies were performed on LHC forms I and II, as a function of pH and buffer composition. GastroPlus® was used to evaluate the potential effect of solubility differences due to polymorphism, particle size, and physiological conditions, on the drug pharmacokinetics. The results indicated that solubilities of LHC polymorphs are strongly dependent on the composition and pH of the buffer media. The concentration ratio (CI/CII) is particularly large for chloride buffer (CI/CII = 3.3-3.9) and exhibits a slightly decreasing tendency with the pH increase for all other buffers. Based on solubility alone, a higher bioavailability of form I might be expected. However, exploratory PBPK simulations suggested that (i) under usual fasted (pH 1.3) and fed (pH 4.9) gastric conditions, the two polymorphs have similar bioavailability, regardless of the particle size; (ii) at high gastric pH in the fasted state (e.g., pH 3.0), the bioavailability of form II can be considerably lower than that of form I, unless the particle size is < 20 µm. This study demonstrates the importance of investigating the effect of the buffer nature when evaluating the solubility of ionizable polymorphic substances. It also showcases the benefits of using PBPK simulations, to assess the risk and pharmacokinetic relevance of different solubility and particle size between crystal forms, for diverse physiological conditions.

Cilnidipine loaded poly (ε-caprolactone) nanoparticles for enhanced oral delivery: optimization using DoE, physical characterization, pharmacokinetic, and pharmacodynamic evaluation.

Cilnidipine (CND), an anti-hypertensive drug, possesses low oral bioavailability due to its poor aqueous solubility, low dissolution rate, and high gut wall metabolism. In the present study, an attempt has been made to prepare CND loaded polycaprolactone based nanoparticles (CND-PCL-NPs) by nanoprecipitation method applying the concepts of Design of Experiments. Critical factors affecting particle size and loading efficiency (LE%) were assessed by a hybrid design approach, comprising of Mini Run Resolution IV design followed by Box-Behnken design. Particle size, PDI, zeta potential and LE% of optimized formulations of CND-PCL-NPs were 220.3 ± 2.6 nm, 0.25 ± 0.1, -19.5 ± 0.9 mV, and 46.4 ± 1.8%, respectively. No significant changes were observed in the physical stability of nanoparticles when stored at 25 °C/60% RH over a period of 3 months. Oral pharmacokinetic studies revealed that Fabs of CND-PCL-NPs (0.55) were significantly higher than the CND suspension (0.26). Pharmacodynamic studies have revealed that the mean percent reduction in systolic blood pressure (% ΔSBP) was significantly higher in the case of CND-PCL-NPs (42%) as compared to CND suspension (24%). Optimized CND-PCL-NPs offer great potential in providing higher and sustained antihypertensive effect compared to conventional formulations of CND.

An Investigative Review for Pharmaceutical Analysis of 1,4-Dihydropyridine-3,5-Dicarboxylic Acid Derivative: Cilnidipine.

Hypertension is commonly a quiet condition, and it expands the risk of heart diseases and stroke. Calcium delivers a substantial role in cardiovascular functions and hence is essential for cardiac automaticity and functioning. Calcium channel antagonists are the choice of drugs for the management of cardiovascular diseases; they precisely stop the introduction of calcium through L-type calcium channels are existing channels in the heart. Cilnidipine belongs to the class 4th generation calcium channel blockers as a foremost therapeutic agent used in the treatment of hypertension and heart diseases. This review article focuses on an inclusive account of crucial analytical methodologies used for the pharmaceutical analysis of cilnidipine in pure forms, biological samples and pharmaceuticals. According to literature reports several analytical techniques such as hyphenated techniques, high-performance thin-layer chromatography, high-performance liquid-chromatography, capillary electrophoresis, voltammetry, UV/Vis-spectrophotometry, and Fourier-transform infrared spectroscopy approaches have been used for determination of cilnidipine alone or in the combined dosage form. We have also discussed the pharmacopeial assay methods, physicochemical properties, and also depict the stacked column chart for year wise publication count for cilnidipine. From literature, concluded that the high-performance liquid-chromatography and UV/Vis-spectrophotometry methods are the most prevailing methods for the analysis of cilnidipine. The data presented in this review may provide a very significant base for further studies on cilnidipine in the area of drug analysis.

In Vitro-In Vivo Correlation for Solid Dispersion of a Poorly Water-Soluble Drug Efonidipine Hydrochloride.

The aim of this present study was to investigate the ability of different dissolution methods to predict the in vivo performance of efonidipine hydrochloride (EFH). The solid dispersions of EFH were prepared by solvent evaporation method with HPMC-AS as matrix and urea as a pH adjusting agent. The paddle method, the open-loop, and the closed-loop flow-through cell methods were studied. In the study, Weibull's model was the best fit to explain release profiles. The pharmacokinetics behaviors of two kinds of solid dispersions with different release rate were investigated in comparison to the EFH after oral administration in rats. In vivo absorption was calculated by a numerical deconvolution method. In the study, the level A in vivo and in vitro correlation (IVIVC) was utilized. The correlation coefficient was calculated and interpreted by means of linear regression analysis (Origin.Pro.8.5 software). As a result, excellent IVIVC for solid dispersions and crude drug (r2 = 0.9352-0.9916) was obtained for the dissolution rate determined with flow-through cell open-loop system in phosphate buffer solution with 0.1% (w/v) polysorbate 80 at pH 6.5, the flow-rate of 4 mL/min. In addition, the self-assembled flow cell system had good repeatability and accuracy. The dissolution rate of the solid dispersion could be slowed down by the flow-through method, and the difference caused by preparation was significantly distinguished. The study demonstrated that flow-through cell method of the open-loop, compared with paddle method, was suitable for predicting in vivo performance of EFH solid dispersions.

Pharmacodynamic, pharmacokinetic and physical characterization of cilnidipine loaded solid lipid nanoparticles for oral delivery optimized using the principles of design of experiments.

Cilnidipine (CND), an anti-hypertensive drug, is known to have low oral bioavailability due to its poor aqueous solubility, low dissolution rate and high gut wall metabolism. In the present study, CND loaded compritol based nanoparticles (CND-CMP-NPs) were prepared by emulsification-solvent evaporation method applying the concepts of design of experiments. Critical factors affecting particle size and loading efficiency (LE%) were assessed by hybrid design approach, comprising of Mini Run Resolution IV design followed by Box-Behnken design. Particle size, PDI, zeta potential and LE% of optimized formulations of CND-CMP-NPs were 207.1 ± 2.9 nm, 0.27 ± 0.1, -22.2 ± 1.9 mV and 15.9 ± 1.3% respectively. No significant changes were observed in physical stability of NPs when stored at 25 °C/60% RH over a period of three months. Pharmacokinetic studies revealed that Fabs of CND-CMP-NPs (0.66) was significantly higher than the free CND (0.27). The Cmax and AUC0-∞ of CND-CMP-NPs (572.4 ± 25.3 ng/mL and 5588.6 ± 229.5 ng/mL × h) were significantly higher (Pcal < 0.0001) as compared to free CND (363.6 ± 23.5 ng/mL and 2316.1 ± 163.6 ng/mL × h). MRT of CND-CMP-NPs (9.8 ± 0.9 h) was significantly higher (Pcal < 0.0001) as compared to free CND (5.7 ± 0.5 h). Pharmacodynamic studies showed a maximum of 38% decrease in systolic blood pressure with more than 20% drop in systolic blood pressure sustained for a total duration of 64 h in the case of CND-CMP-NPs as compared to free CND. CND-CMP-NPs not only provide higher and sustained plasma levels of CND but also higher and sustained antihypertensive therapy as compared to free CND.

L-Type Calcium Channel Blocker Enhances Cellular Delivery and Gene Silencing Potency of Cell-Penetrating Asymmetric siRNAs.

The efficient delivery of small interfering RNAs (siRNAs) to the target cells is critical for the pharmaceutical success of RNA interference (RNAi) drugs. One of the possible strategies to improve siRNA delivery is to identify auxiliary molecules that augment their cellular uptake. Herein, we performed a chemical library screening in an effort to discover small molecules that enhance the potency of cholesterol-conjugated, cell-penetrating asymmetric siRNAs (cp-asiRNAs). Interestingly, three compounds identified from the screen share a common dihydropyridine (DHP) core and function as L-type calcium channel blockers (CCBs). Using confocal microscopy and quantitative analysis of small RNAs, we demonstrated that the L-type CCBs increased the endocytic cellular uptake of cp-asiRNAs. Furthermore, these small molecules substantially improved the potency of cp-asiRNAs, not only in vitro but also in vivo on rat skin. Collectively, our study provides an alternative pharmacological approach for the identification of small molecules that potentiate the effects of therapeutic siRNAs.

A novel transdermal nanoethosomal gel of lercanidipine HCl for treatment of hypertension: optimization using Box-Benkhen design, in vitro and in vivo characterization.

Poor bioavailability of drugs via oral route is the greatest challenge facing drug formulation. To overcome this obstacle, transdermal route was commonly used as an alternative route to improve bioavailability. Lercanidipine HCl (LER) is a vasoselective calcium-channel blocker that has a poor oral bioavailability of 10% due to its hepatic metabolism and low solubility. The main objective of this study was to develop nanoethosomal LER gel for transdermal delivery to increase its skin permeation and promote bioavailability. Nanoethosomes were prepared and optimized using a Box-Behnken design employing ethanol injection method. The design studied the influence of Phospholipon 90G (PL90G), LER, and ethanol concentrations on entrapment efficiency (EE%); vesicle size; % cumulative LER release (CLERR); and cumulative LER permeated per unit area at 24 h Q24 (µg/cm2). The pharmacokinetic parameters of the optimized formulation were determined in rats. Nanoethosomes showed a mean vesicle size between 210.87 and 400.57 nm and EE% ranging from 49.26 to 97.22%. The developed nanoethosomes enhanced % CLERR and Q24 values compared to drug suspension. The experimental parameters of optimized formulation were very close to those calculated by software. The pharmacokinetics study showed three times statistically significant (p < 0.05) enhancement in LER bioavailability following nanoethosomal LER gel transdermal application compared to that of oral LER suspension. Nanoethosomes can be considered as a promising carrier for LER transdermal delivery, thus will be fruitful therapy in hypertension management. Graphical abstract.

Effect of Lercanidipine on the Pharmacokinetics-Pharmacodynamics of Carvedilol Enantiomers in Patients With Chronic Kidney Disease.

This study evaluates the carvedilol-lercanidipine drug interaction, and the influence of chronic kidney disease (CKD) on both drugs. Patients with high blood pressure (8 with normal renal function [control] and 8 with CKD with estimated glomerular filtration rate categories of G3b to G5 [12-38 mL/min/1.73 m2 ]) were included and prescribed 3 different treatment regimens, a single oral dose of racemic carvedilol 25 mg (CAR), a single oral dose of racemic lercanidipine 20 mg (LER), and single oral doses of CAR plus LER. Blood samples were collected and variations in heart rate were assessed (using isometric exercise with handgrip) for up to 32 hours. Lercanidipine pharmacokinetics were not enantioselective, and were not affected by carvedilol and CKD. Carvedilol pharmacokinetics (data presented as median) were enantioselective with higher plasma exposure of (R)-(+)-carvedilol in both control (103.5 vs 46.0 ng ∙ h/mL) and CKD (190.6 vs 98.9 ng ∙ h/mL) groups. Lercanidipine increased the area under the plasma concentration-time curve of only (R)-(+)-carvedilol in the CKD group (190.6 vs 242.2 ng ∙ h/mL) but not in the control group (103.5 vs 98.7 ng ∙ h/mL). CKD increased plasma exposure (46.0 vs 98.9 ng ∙ h/mL) and effect-compartment exposure (5.5 vs 20.9 ng ∙ h/mL) to (S)-(-)-carvedilol, resulting in higher ß-adrenergic inhibition (10.0 vs 6.1 bpm). Therefore, carvedilol dose titration in CKD patients with estimated glomerular filtration rate categories of G3b to G5 should be initiated, with no more than half the dose used for patients with normal renal function.

Chronological Delivery of Antihypertensive Drugs in Bilayered Core-in-Cup Buccoadhesive Tablets: In Vitro and In Vivo Evaluation.

Hypertension shows circadian blood pressure rhythms (day-night pattern) that urge the delivery of antihypertensive drugs at the right time in the desired levels. Thus, a bilayered core-in-cup buccoadhesive tablet was formulated that immediately releases olmesartan, to give a burst effect, and controls azelnidipine release, to prolong its therapeutic effect. The main challenge was the poor bioavailability of azelnidipine due to its poor aqueous solubility and first-pass effect. Hence, liquisolid compact buccoadhesive tablets were prepared to enhance solubility, dissolution profiles, and bypass the oral route. Two factorial designs were conducted to study the type and concentration effect of the mucoadhesive polymers on the dissolution and mucoadhesion of olmesartan and azelnidipine. Characterization studies were conducted regarding drug content, surface pH, water uptake, mucoadhesive strength, in vitro release, and ex vivo permeability. The core-in-cup olmesartan/azelnidipine buccoadhesive tablet showed similar release profile to the statistically optimized formulae of each drug. In vitro dissolution study showed enhanced release of azelnidipine than the directly compressed tablets, to comply with the regulatory standards of controlled release systems. In vivo pharmacokinetic study of olmesartan and azelnidipine conducted on human volunteers against Rezaltas® 10/8 mg tablet showed percentage relative bioavailability of 106.12 and 470.82%, respectively. Graphical Abstract.

Exploration of supersaturable lacidipine ternary amorphous solid dispersion for enhanced dissolution and in vivo absorption.

Amorphous solid dispersion stands out among different formulation strategies for the improvement of dissolution rate and bioavailability via generating supersaturated drug solution, which provides a higher solubility than the crystalline counterpart, leading to a promoted intestinal absorption. Soluplus (SOL), termed as the fourth generation of solid dispersion carrier, presented a preferable effect on supersaturation maintaining and bioavailability enhancement for poorly water soluble drugs. However, some binary drug/SOL systems still suffer from insufficient dissolution and unsatisfied in vivo absorption. Thus, taking Lacidipine (LCDP) as a model drug, the aim of this study was to explore a ternary amorphous solid dispersion consisted of SOL and a surfactant to further increasing the dissolution rate and in vivo absorption. First of all, various surfactants were screened via equilibrium solubility enhancement and sodium dodecyl sulfate (SDS) was selected as the most effective candidate. Thereafter, the influence of SOL/SDS and drug/carrier weight ratio on the supersaturation maintaining was investigated. The supersaturated drug solutions were spray dried and the in vitro release, pharmacokinetic behavior as well as physical stability were investigated. It was found that although combination use of SOL and SDS did not present remarkable advantage in supersaturation maintenance in liquid state, 6-7 times higher dissolution rate under non-sink condition was noticed at SOL/SDS ratio 3:1 after spray drying, for LCDP/SOL/SDS based formulation compared to that of the binary LCDP/SOL system, which was maintained even after 92.5% humidity and 60 °C accelerated stability test. Moreover, compared to the LCDP/SOL formulation, approximately 3.3 and 3.7-fold increase in C max and AUC0-∞ was achieved with LCDP/SOL/SDS based formulation. In conclusion, the presented SDS could not only be regarded as solubility enhancer but also dissolution or bioavailability promoter, highlighting its potential application in ternary supersaturable amorphous solid dispersion for further increasing the dissolution and in vivo absorption of poorly water soluble drugs.

Improved bioavailability of Azelnidipine gastro retentive tablets-optimization and in-vivo assessment.

Azelnidipine, dihydropyridine based calcium channel blocker has been used for treating ischemic heart disease and cardiac remodeling after myocardial infarction but it is having a low bioavailability due to its poor solubility. The present study is to investigate the formulation and evaluation of floating tablets of Azelnidipine for controlled release and to increase bioavailability by increasing the gastrointestinal transit time and mucoadhesion of drug. The gastro retentive tablets were prepared by direct compression method using different concentrations of combination of Polyoxyethylene oxide WSR 303 as hydrophilic polymer and Potassium bicarbonate as gas generating agent. Main effects of the formulation variables were evaluated quantitatively using design approach showing that both independent variables have significant effects on floating lag time, % drug release at 1 h (D1 h) and time required to release 90% of the drug (t90). The statistically optimized formulation (F3) released 95.11 ±â€¯1.43% drug for 12 h followed K-Peppas drug release kinetics indicating release of drug by diffusion and erosion mechanism. Evaluation of the optimized formulation in vivo in human volunteers showed that the GFT was buoyant in gastric fluid and that its gastric residence time was enhanced. Pharmacokinetics studies carried out revealed significant (P < 0.05) equivalent Cmax, longer Tmax and higher AUC values for the optimized formula compared to the marketed oral product. From the results obtained it can be concluded that Azelnidipine Gastro retentive tablets with enhanced bioavailability and better release pattern is suitable for more effective treatment compared to marketed conventional tablets.

Synergetic effect of nucleation and crystal growth inhibitor on in vitro-in vivo performance of supersaturable lacidipine solid dispersion.

Limited supersaturation maintaining duration is the main challenge for amorphous solid dispersion design. Nucleation or crystal growth inhibitors may function in different ways but the combination use of nucleation and crystal growth inhibitors in supersaturated system is rarely explored. Thus, using Lacidipine (LCDP) as a Biopharmaceutical Classification System (BCS) II model drug, the aim of this study was to explore whether the combination use of nucleation and crystal growth inhibitors could provide a synergistic effect on the in vitro-in vivo performance of poorly water-soluble drugs. First of all, based on compatibility screening using solubility parameter (Δδ) and crystallization inhibition efficiency as criteria, soluplus (SOL) and gum arabic (GA) were selected as the most effective nucleation and crystal growth inhibitor respectively. Thereafter, the supersaturated drug solutions were spray dried and characterized. The in vitro release, physical stability as well as pharmacokinetic behavior were investigated. It was found that the combination use of SOL and GA did not present remarkable advantage in prolonging the supersaturation time in solution state. However, their synergistic effect in equilibrium solubility and dissolution enhancement was noticed at SOL/GA ratio 3:1, with 5-7 times higher dissolution rate observed for LCDP/SOL/GA based formulation compared with that of LCDP/SOL, which was maintained even after three months accelerated stability test under non-sink condition. Moreover, compared to the LCDP/SOL formulation, approximately 2.8 and 2.5-fold increase in the maximum plasma concentration (Cmax) and the area under the plasma-time curve (AUC0-∞) was achieved with LCDP/SOL/GA based formulation. Possible mechanism of the synergistic effect was elucidated, indicating GA may penetrate into SOL particles providing both electrostatic and steric stabilization. In conclusion, the combination use of screened nucleation and crystal growth inhibitors might be an efficient approach to design supersaturated drug delivery system.

Effect of rifampin on enantioselective disposition and anti-hypertensive effect of benidipine.

AIMS: In vitro study showed that benidipine is exclusively metabolized by cytochrome P450 (CYP) 3A. This study evaluated the effect of rifampin on the enantioselective disposition and anti-hypertensive effect of benidipine. METHODS: Benidipine (8 mg) was administered to healthy subjects with or without repeated rifampin dosing, in a crossover design. Plasma concentrations of (S)-(S)-(+)-α and (R)-(R)-(-)-α isomers of benidipine and blood pressure were measured for up to 24 h after dosing. In addition, CYP3A metabolic capacity was evaluated in each subject using oral clearance of midazolam. RESULTS: The exposure of (S)-(S)-(+)-α-benidipine was greater than that of (R)-(R)-(-)-α-benidipine by approximately three-fold following single dose of benidipine. Repeated doses of rifampin significantly decreased the exposure of both isomers. Geometric mean ratios (GMRs) (95% CI) of Cmax and AUC∞ for (S)-(S)-(+)-α-benidipine were 0.14 (0.10-0.18) and 0.12 (0.08-0.18), respectively. GMRs (95% CI) of Cmax and AUC∞ for (R)-(R)-(-)-α-benidipine were 0.10 (0.06-0.17) and 0.10 (0.06-0.17), respectively. Oral clearances of both isomers were increased equally by approximately 10-fold. There were no significant differences in cardiovascular effect following benidipine administration between control and rifampin treatment. CYP3A activity using midazolam did not appear to correlate with oral clearance of benidipine. CONCLUSIONS: After single administration of racemic benidipine, enantioselective disposition of (S)-(S)-(+)-α- and (R)-(R)-(-)-α-benidipine was observed. Treatments with rifampin significantly decreased the exposure of both isomers but appeared to marginally affect its blood pressure-lowering effect in healthy subjects. Impact of coadministration of rifampin on the treatment effects of benidipine should be assessed in hypertensive patients.

TP0463518, a novel inhibitor for hypoxia-inducible factor prolyl hydroxylases, increases erythropoietin in rodents and monkeys with a good pharmacokinetics-pharmacodynamics correlation.

Hypoxia-inducible factor prolyl hydroxylases (PHDs) inhibitor stabilizes hypoxia inducible factor alpha, which increases erythropoietin (EPO) expression via the hypoxia response element. Therefore, PHDs inhibitors have been developed as novel therapeutic agents for anemia. Here, we characterize the in vitro and in vivo pharmacological profiles of TP0463518, 2-[[1-[[6-(4-chlorophenoxy)pyridin-3-yl]methyl]-4-hydroxy-6-oxo-2,3-dihydropyridine-5-carbonyl]amino]acetic acid, a novel potent PHDs inhibitor. TP0463518 competitively inhibited human PHD2 with a Ki value of 5.3 nM. TP0463518 also inhibited human PHD1/3 with IC50 values of 18 and 63 nM as well as monkey PHD2 with an IC50 value of 22 nM. In normal mice and rats, TP0463518 significantly increased the serum EPO levels at doses of 5 and 20 mg/kg, respectively. The correlation factors for serum EPO and the serum TP0463518 levels were 0.95 in mice and 0.92 in rats. TP0463518 also increased the serum EPO level in 5/6 nephrectomized chronic kidney disease model rats at a dose of 10 mg/kg, with a correlation factor for serum EPO and the serum TP0463518 levels of 0.82. Finally, the effect of TP0463518 in monkeys was investigated. TP0463518 was promptly removed with a half-life of 5.2 h and increased the area under the curve (AUC) of EPO at a dose of 5 mg/kg. The EPO and TP0463518 levels were also correlated. These results suggest that TP0463518 induces endogenous EPO with a strong pharmacokinetic-pharmacodynamic correlation and may contribute to desirable hemoglobin control in patients with renal anemia.

Development and validation of two LC-MS/MS methods to assay urinary tylerdipine hydrochloride and its metabolites in healthy Chinese subjects.

For quantitative assaying tylerdipine hydrochloride, and its two primary metabolites (M2 and M4) in human urine, two sensitive and accurate LC-MS/MS methods were firstly developed and validated, where multiple reaction monitoring (MRM) was applied under positive electrospray ionization mode for tylerdipine and negative electrospray ionization mode for M2/M4, respectively. Urinary proteins were precipitated using acetonitrile, and deuterated isotopes of tylerdipine and M4 ([D5]­tylerdipine and [D6]-M4) were used as internal standards. Triton X-100, a good surfactant, was used to prevent the adsorption. An Agilent Poroshell 120 column was employed for chromatographic separation of the analytes with the mobile phases of 2 mM ammonium formate solution (containing 0.1% formic acid) and acetonitrile (45:55 for tylerdipine and 75:25 for the M2/M4, v/v). Flow rate was 0.3 mL/min. Calibration curves for tylerdipine, M2 and M4 in urine were linear over the ranges of 0.02-10 ng/mL, 2-1500 ng/mL and 0.5-200 ng/mL, respectively. The precision, accuracy, specificity and stability of two methods all evaluated and achieved the acceptable criteria. The LC-MS/MS methods were successfully applied to assay urinary excretion of tylerdipine and the metabolites in healthy Chinese subjects who orally received a single dose of 20 mg tylerdipine tablet. Generally, the urinary excretion of the two primary metabolites accounted for 11.7% of the total dose of tylerdipine in healthy Chinese subjects, while little tylerdipine was recovered in urine.

Determination of lacidipine in human plasma by LC-MS/MS: Application in a bioequivalence study
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OBJECTIVE: This study aimed to conduct a sensitive, simple, and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of lacidipine in human plasma. MATERIALS AND METHODS: In this method, the plasma samples were extracted from human plasma using methanol as the precipitant and nisoldipine as internal standard (IS). The analytes were separated on a Phenomenex Luna C18 column (150 mm × 2.0 mm, 3 µm) at 40 °C using isocratic mobile phase consisting of 0.2% formic acid-methanol (13 : 87, v/v) at a flow rate of 0.2 mL/min. The tandem mass detection was constructed on a triple-quadrupole tandem mass spectrometer with an electrospray ionization (ESI) source operating in positive-ion mode. The selected reaction monitoring of transitions was m/z 456.2 → 354.2 for lacidipine and m/z 389.2 → 315.0 for IS, respectively. Then, the established method was applied in a bioequivalence study comparing lacidipine dispersible tablet with commercial tablet in 20 healthy Chinese subjects. RESULTS: The calibration curve exhibited great linearity in the range of 0.10 - 10.00 ng/mL (r2 = 0.999). The intraday and interday precision and accuracy met the acceptance criteria, and no matrix effect was found. In addition, the 90% confidence intervals for the test/reference ratio of Cmax, AUC0-24, and AUC0-∞ fell within the bioequivalence acceptance criteria (80 - 125%). CONCLUSION: The method is suitable for quantification of lacidipine in human plasma. Moreover, the two preparations are bioequivalent.
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Increased bioavailability of efonidipine hydrochloride nanosuspensions by the wet-milling method.

The aim of this study was to improve the oral bioavailability of a practically insoluble drug, efonidipine hydrochloride (EFH), by agglomeration in acid solution/gastric fluid. The EFH nanosuspension was prepared by the wet-milling method with F68 as a dispersing agent, SDS as an auxiliary stabilizer and l-arginine as a pH adjusting agent. The EFH nanosuspension have been prepared in industrial scale-up. The dissolution rate of the EFH nanosuspension was greater than that of bulk EFH. An in vitro intestinal permeability study showed a clear increase in the apparent permeability of different intestinal segments compared with bulk EFH. Also, a pharmacokinetic study showed that the Cmax and AUC0-24h of the nanosuspensions were approximately 1.76-fold and 2.2-fold greater than that of bulk EFH, respectively, and there was no significant difference compared with commercial tablets. It appears that wet-milling offers an effective approach to improve the dissolution rate and oral absorption of this practically insoluble drug.

Pharmacokinetics and tissue distribution study of clevidipine and its primary metabolite H152/81 in rats.

This present study was designed to investigate the pharmacokinetic profiles and tissue distribution characteristics of clevidipine and its primary metabolite H152/81 in rats following a single intravenous administration of clevidipine butyrate injectable emulsion. For this study, a sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established and validated for the simultaneous quantitation of clevidipine and H152/81 in rat whole blood and various tissues. A Hedera ODS-2 column with two gradient elution programs was employed for the troubleshooting of matrix effect on the detection of analytes among different biological samples. The experimental data showed that clevidipine represented quick elimination from blood with a half-life of about 4.3 min and rapid distribution in all of the investigated tissues after administration; the highest concentration of clevidipine was found in the heart whereas the lowest concentration was detected in the liver. In addition, clevidipine was almost undetectable in most tissues except for heart and brain at 90 min post-dosing, suggesting that there was no apparent long-term accumulation in rat tissues. For H152/81, the peak concentration of 3714 ± 319 ng/mL occurred at 0.129 ± 0.048 h, the half-life was 10.08 ± 1.45 h and area under the concentration-time curve was 42091 ± 3812 ng h/mL after drug administration. In addition, H152/81 was found at significant concentration levels in all tissues, in descending order of lung, kidney, heart, liver, spleen and brain at each time point. The results of current study offer useful clues for better understanding the distribution and metabolism of clevidipine butyrate injectable emulsion in vivo.