Sensitive and effective method with 96-well plate for determination of levamlodipine in human plasma using LC-MS/MS

we developed an effective protein precipitation method for determination of levamlodipine in human plasma using LC-MS/MS. Sample extraction was carried out by using liquid-liquid extraction in 96-well plate format. (S)-Amlodipine-d4 was used as internal standard (IS). The chromatographic separation was achieved using Philomen Chiral MX (2) column (3 μm, 2.1 × 100 mm). Mobile phase A was comprised of Acetonitrile (ACN), Mono ethanol amine (MEA) and Iso-Propyl alcohol (IPA) (1000:1:10, v/v/v), Mobile phase B was IPA-ACN (2:1, v/v). The flow rate was 0.4 mL/min. The total run time of each sample was 4.0 min with gradient elution. LC-MS/MS spectra were generated in positive ion mode, and multiple reaction monitoring (MRM) was used to detect the following transitions: m/z 409.20 → 238.15 for levamlodipine and 415.25 → 240.20 for (S)-Amlodipine-d4 (the IS). The method was linear from 50 to 10000 pg/mL（R2＝0.9988489）,and the lower limit of quantification (LLOQ) was 50 pg/mL. This method was applied to a bioequivalence study of levamlodipine.

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.

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.

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 ± 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.

Detection of Maillard Reaction Product [5-(5,6-Dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol (F3-A) in Breads and Demonstration of Bioavailability in Caco-2 Intestinal Cells

[5-(5,6-Dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol, also called F3-A, has been isolated from hexose-lysine Maillard reaction (MR) models. Here we report on optimized conditions for the recovery of F3-A and concentrations found in bread. Recovery of F3-A was best achieved when samples were extracted with dichloromethane (DCM) at a solvent to sample ratio of 2:1 (v/v) after adjustment of the pH to 12. The amount of F3-A in whole wheat bread was significantly (P < 0.05) higher than that in white bread; bread crust contained a significantly (P < 0.05) higher amount of F3-A (0.9-7.8 μg/100 g) than the bread crumb (not detectable-3.5 μg/100 g); and toasting increased F3-A concentration with a range of not detectable to 6.0 μg/100 g in the control bread and 4.0 and 17.7 μg/100 g in the dark-toasted white sandwich bread and 100% whole wheat sandwich bread, respectively. The in vitro permeability of F3-A was measured using Caco-2 cell monolayer. The apparent permeability coefficient (P_app) of F3-A is (6.01 ± 0.35) × 10^-5 cm/s, which is similar to that of propranolol, a highly passive transcellular absorbed drug. In conclusion, the concentration of F3-A recovered in bread varies with the type of bread and degree of toasting, and F3-A is bioavailable.

A novel nanoproliposomes of lercanidipine: Development, in vitro and preclinical studies to support its effectiveness in hypertension therapy

AIM

The aim of the present study was to develop nanoproliposomes of lercanidipine, in order to overcome its poor biopharmaceutical properties and to improve its therapeutic efficacy in treating hypertension.

MAIN METHODS

The nanoproliposomes were prepared using a modified thin-film hydration method, and the formula was optimized by varying the ratio of lipids and the types of cryoprotectants. This optimized formulation was characterized in terms of its particle size, solid-state, drug release, in-situ absorption, in-vivo pharmacokinetics, and in-vivo anti-hypertensive activity in DOCA-salt induced hypertensive rats. Finally, a PK-PD correlation was established in order to understand the clinical implications of the developed novel nanoproliposomes.

KEY FINDINGS

The nanoproliposomes showed a particle size of 174.7nm and an entrapment efficiency of 85.4%. The in-vitro release displayed initial rapid release (19.33%) followed by a sustained release profile, releasing 88.37% of the encapsulated drug. The in-situ studies showed a significant increase in absorption rate across the rat intestinal membrane. The pharmacokinetics of this novel form indicated a 2.75-fold increase in the absolute bioavailability as compared to pure lercanidipine. In addition, the nanoproliposomes were found to be efficient in treating hypertension in DOCA-salt induced hypertensive rats. The PK-PD correlation demonstrated no time lag between effect and exposure, indicating that a direct PK-PD relationship can be expected in the clinic.

SIGNIFICANCE

These findings suggest that nanoproliposomes are promising carriers in improving the oral bioavailability and bioactivity of lercanidipine, and can be an effective therapy in the management of hypertension.

Simple and effective HPLC method development and its validation for Clindipine in human drug free plasma

Simple and effective high performance liquid chromatographic (HPLC) method was developed for estimation of Clindipine in drug free human drug free blank plasma. The internal standard used as Nifidipine (IS). The current method was used protein precipitating extraction of Clindipine from blank plasma. Separation was achieved on reversed-phase c18 column (25cm × 4.6mm, 5μ) and the detection was monitored by UV detector at 260 nm. The optimized mobile phase was used acetonitrile: 5mM potassium dihydrogen orthophosphate (pH 4.5), in the ratio of 60:40% v/v at a flow rate of 1.0 ml/min. This linearity was achieved in this method range of 10.0-125.0 ng/ml with regression coefficient range is 0.99. The present method is suitable in terms of precise, accurate and specific during the study. The simplicity of the method allows for application in laboratories that lack sophisticated analytical instruments such as LC-MS/MS or GC-MS/MS that are complicated, costly and time consuming rather than a simple HPLC-UV method. The present method was successfully applied for pharmacokinetic studies.

Pharmacokinetic drug-drug interaction of calcium channel blockers with cyclosporine in hematopoietic stem cell transplant children

BACKGROUND

Cyclosporine (CsA) is frequently responsible for hypertension in bone marrow transplant children. Calcium channel blockers (CCBs) are considered to be the best treatment for CsA-induced hypertension, but they may alter the exposure and the effect of CsA by inhibiting the CYP3A4 pathway of CsA metabolism or P-gp. However, the inhibitory effect on CYP3A4 may vary among CCBs.

METHODS

This study aimed to quantify the pharmacokinetic drug-drug interaction between CsA and nicardipine, amlodipine, and lacidipine. In all, 51 children who received CsA and CCB concomitantly were included.

RESULTS

Dose-normalized CsA trough blood concentrations significantly increased in patients treated with nicardipine and amlodipine, whereas they remained stable in patients treated with lacidipine.

CONCLUSIONS

Because lacidipine appears to have no effect on CsA exposure, it may be the best option among CCBs for treating high blood pressure caused by CsA in children.

Role of manidipine in the management of patients with hypertension

Manidipine is a third-generation dihydropyridine calcium antagonist, which causes systemic vasodilation by inhibiting the voltage-dependent calcium inward currents in smooth muscle cells. In clinical studies, manidipine has been shown to significantly lower office and 24-h blood pressure compared with placebo in patients with essential hypertension. The resulting reduction in blood pressure is maintained over 24 h, with preservation of the circadian blood pressure pattern; its blood pressure-lowering capacity appears to be similar to that of other calcium antagonists. In elderly patients with mild-to-moderate essential hypertension, manidipine is able to significantly decrease blood pressure compared with placebo for up to 3 years of treatment. The drug also significantly lowers blood pressure in patients with hypertension and concomitant Type 2 diabetes mellitus or renal impairment, and is devoid of adverse metabolic effects. It is well-tolerated with few untoward adverse effects related to vasodilation. In particular, manidipine appears to have less potential for pedal edema than other calcium channel blockers.

[The place of lercanidipine in the treatment of cardiovascular diseases]

The data are presented on using the first, second and third generation calcium antagonists in cardio-vascular pathology patients. The accent has been made on the improved pharmacokinetic profile of the third generation calcium antagonists where modern preparation lerkanidipin belongs to. It is shown that lerkanidipine has expressed antihypertensive effect with no significant impact on the cardiac contraction frequency and its metabolic neutrality enables using the said preparation with diabetes mellitus and other metabolic disorders patients. Besides, an improved pharmacokinetic lerkanidine profile leads to organoprotective and antiaterogeneous effect. Significantly fewer side reactions as connected with activised simpatico-adrenal system, and peripheral edemas are observed as compared against other representatives of the said preparations category.

Desferrithiocin analogue iron chelators: iron clearing efficiency, tissue distribution, and renal toxicity

The current solution to iron-mediated damage in transfusional iron overload disorders is decorporation of excess unmanaged metal, chelation therapy. The clinical development of the tridentate chelator deferitrin (1, Table 1) was halted due to nephrotoxicity. It was then shown by replacing the 4'-(HO) of 1 with a 3,6,9-trioxadecyloxy group, the nephrotoxicity could be ameliorated. Further structure-activity relationship studies have established that the length and the position of the polyether backbone controlled: (1) the ligand's iron clearing efficiency (ICE), (2) chelator tissue distribution, (3) biliary ferrokinetics, and (4) tissue iron reduction. The current investigation compares the ICE and tissue distribution of a series of (S)-4,5-dihydro-2-[2-hydroxy-4-(polyether)phenyl]-4-methyl-4-thiazolecarboxylic acids (Table 1, 3-5) and the (S)-4,5-dihydro-2-[2-hydroxy-3-(polyether)phenyl]-4-methyl-4-thiazolecarboxylic acids (Table 1, 8-10). The three most effective polyether analogues, in terms of performance ratio (PR), defined as mean ICE(primate)/ICE(rodent), are 3 (PR 1.1), 8, (PR 1.5), and 9, now in human trials, (PR 2.2). At the onset of the clinical trial on 9, no data were available for ligand 3 or 8. This is unfortunate, as 3 has many advantages over 9, e.g., the ICE of 3 in rats is 2.5-fold greater than that of 9 and analogue 3 achieves very high levels in the liver, pancreas, and heart, the organs most affected by iron overload. Finally, the impact of 3 on the urinary excretion of kidney injury molecule-1 (Kim-1), an early diagnostic biomarker for monitoring acute kidney toxicity, has been carried out in rats; no evidence of nephrotoxicity was found. Overall, the results suggest that 3 would be a far superior clinical candidate to 9.

Determination of azelnidipine by LC-ESI-MS and its application to a pharmacokinetic study in healthy Chinese volunteers

A simple, rapid and sensitive high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) assay for determination of azelnidipine in human plasma using perospirone as the internal standard (IS) was established. After adjustment to a basic pH with sodium hydroxide solution, plasma samples were extracted with diethyl ether and separated on a C18 column with a mobile phase of methanol-5 mM ammonium acetate solution (90:10, v/v). The lower limit of quantification (LLOQ) was 0.20 ng/ml. After administration of a single dose of azelnidipine 8mg and 16 mg, respectively; the area under the plasma concentration versus time curve from time 0 h to 96 h (AUC(0-96) were (186 +/- 47) ng ml(-1) h, (429 +/- 145) ng ml(-1) h, respectively; clearance rate (CL/F) were (45.94 +/- 11.61), (42.11 +/- 14.23) L/h, respectively; peak plasma concentration Cmax were (8.66 +/- 1.15), (19.17 +/- 4.13) ng/ml, respectively; apparent volume of distribution (Vd) were (1749 +/- 964), (2480 +/- 2212) L, respectively; time to Cmax (Tmax) were (2.8 +/- 1.2), (3.0 +/- 0.9) h, respectively; elimination half-life (t(1/2beta)) were (22.8 +/- 2.4), (23.5 +/- 4.2) h, respectively; and MRT were (25.7 +/- 1.3), (26.2 +/- 2.2) h, respectively; The essential pharmacokinetic parameters after oral multiple doses (8 mg, q.d.) were as follows: (Cmax) ss, (15.04 +/- 2.27) ng/ml; (Tmax) ss, (2.38 +/- 0.92) h; (Cmin) ss, (3.83 +/- 0.94) ng/ml; C(av), (7.05 +/- 1.54) ng/ml; DF, (1.62 +/- 0.26); AUCss, (169.19 +/- 36.87) ng ml(-1) h.

Determination of cilnidipine, a new calcium antagonist, in human plasma using high performance liquid chromatography with tandem mass spectrometric detection

A rapid, sensitive and reliable high performance liquid chromatographic method coupled with tandem mass spectrometry (HPLC-MS/MS) has been developed and validated for the determination of cilnidipine, a relatively new calcium antagonist, in human plasma. The reversed-phase chromatographic system was interfaced with a TurboIonSpray (TIS) source. Nimodipine was employed as the internal standard (IS). Sample extracts following protein precipitation were injected into the HPLC-MS/MS system. The analyte and IS were eluted isocratically on a C18 column, with a mobile phase consisting of CH(3)OH and NH(4)Ac (96:4, v/v). The ions were detected by a triple quadrupole mass spectrometric detector in the negative mode. Quantification was performed using multiple reaction monitoring (MRM) of the transitions m/z 491.2-->122.1 and m/z 417.1-->122.1 for cilnidipine and for the IS, respectively. The analysis time for each run was 3.0 min. The calibration curve fitted well over the concentration range of 0.1-10 ngmL(-1), with the regression equation Y=(0.103+/-0.002)X+(0.014+/-0.003) (n=5), r=0.9994. The intra-day and inter-day R.S.D.% were less than 12.51% at all concentration levels within the calibration range. The recoveries were between 92.71% and 97.64%. The long-term stability and freeze-thaw stability were satisfying at each level. The present method provides a modern, rapid and robust tool for pharmacokinetic studies of cilnidipine.

Impact of the 3,6,9-trioxadecyloxy group on desazadesferrithiocin analogue iron clearance and organ distribution

The impact of introducing a 3,6,9-trioxadecyloxyl group at various positions of the desazadesferrithiocin (DADFT) aromatic ring on iron clearance and organ distribution is described. Three DADFT polyethers are evaluated: (S)-4,5-dihydro-2-[2-hydroxy-4-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(HO)-DADFT-PE, 3], (S)-4,5-dihydro-2-[2-hydroxy-5-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid [(S)-5'-(HO)-DADFT-PE, 6], and (S)-4,5-dihydro-2-[2-hydroxy-3-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid [(S)-3'-(HO)-DADFT-PE, 9]. The iron-clearing efficiency (ICE) in rodents and primates is shown to be very sensitive to which positional isomer is evaluated, as is the organ distribution in rodents. The polyethers had uniformly higher ICEs than their corresponding parent ligands in rodents, consistent with in vivo ligand-serum albumin binding studies. Ligand 9 is the most active polyether analogue in rodents and is also very effective in primates, suggesting a higher index of success in humans. In addition, this analogue is also shown to clear more iron in the urine of the primates than many of the other chelators. If this trend were also observed in patients, it would facilitate iron-balance studies in a clinical setting.

Lercanidipine, enalapril and their combination in the treatment of elderly hypertensive patients: placebo-controlled, randomized, crossover study with four ABPM

This double-blind, placebo-controlled, four-way balanced design crossover study included hypertensive patients aged 60-85 years with mean office-measured sitting systolic blood pressure (SBP) 160-179 mm Hg and daytime SBP > or =135 mm Hg. After a 2-week run-in period, during which previous medications were discontinued, each patient received the following four treatments in randomized order for 4 weeks each: lercanidipine 10 mg (L), enalapril 20 mg (E), lercanidipine 10 mg plus enalapril 20 mg (L/E) and placebo (P). At the end of each treatment period, office trough blood pressure (BP) was measured and a 24-h Ambulatory Blood Pressure Monitoring (ABPM) was performed. Seventy-five patients (mean age 66 years, office BP 168/92 mm Hg, daytime SBP 151 mm Hg) were randomized and 62 completed the study with four valid post-baseline ABPMs. The administration of P, L, E and L/E was associated with a mean 24-h SBP of 144, 137, 133 and 127 mm Hg, respectively. All active treatments significantly reduced the mean 24-h SBP in comparison with placebo, but L/E was significantly more effective than L and E alone. Similarly, office SBP was significantly more reduced with L/E (-16.9 mm Hg) than with L (-5.0 mm Hg) or E (-5.9 mm Hg). A BP <140/90 mm Hg was recorded in 18% of patients with L, 19% with E and 45% with L/E. Two patients on P and two on L/E were withdrawn from the study due to adverse events. In conclusion, combination therapy with L/E has additive antihypertensive effects on both ambulatory and office BP in elderly patients and is well tolerated.

Enantioselective determination of azelnidipine in human plasma using liquid chromatography–tandem mass spectrometry

A sensitive and simple method was developed for determination of the enantiomers of azelnidipine, (R)-(-)-azelnidipine and (S)-(+)-azelnidipine, in human plasma using chiral liquid chromatography with positive ion atmospheric pressure chemical ionization tandem mass spectrometry. Plasma samples spiked with stable isotope-labeled azelnidipine, [(2)H(6)]-azelnidipine, as an internal standard, were processed for analysis using a solid-phase extraction in a 96-well plate format. The azelnidipine enantiomers were separated on a chiral column containing alpha(1)-acid glycoprotein as a chiral selector under isocratic mobile phase conditions. Acquisition of mass spectrometric data was performed in multiple reaction monitoring mode, monitoring the transitions from m/z 583-->167 for (R)-(-)-azelnidipine and (S)-(+)-azelnidipine, and from m/z 589-->167 for [(2)H(6)]-azelnidipine. The standard curve was linear over the studied range (0.05-20 ng/mL), with r(2)>0.997 using weighted (1/x(2)) quadratic regression, and the chromatographic run time was 5.0 min/injection. The intra- and inter-assay precision (coefficient of variation), calculated from the assay data of the quality control samples, was 1.2-8.2% and 2.4-5.8% for (R)-(-)-azelnidipine and (S)-(+)-azelnidipine, respectively. The accuracy was 101.2-117.0% for (R)-(-)-azelnidipine and 100.0-107.0% for (S)-(+)-azelnidipine. The overall recoveries for (R)-(-)-azelnidipine and (S)-(+)-azelnidipine were 71.4-79.7% and 71.7-84.2%, respectively. The lower limit of quantification for both enantiomers was 0.05 ng/mL using 1.0 mL of plasma. All the analytes showed acceptable short-term, long-term, auto-sampler and stock solution stability. Furthermore, the method described above was used to separately measure the concentrations of the azelnidipine enantiomers in plasma samples collected from healthy subjects who had received a single oral dose of 16 mg of azelnidipine.

Characterization of benidipine and its enantiomers' metabolism by human liver cytochrome P450 enzymes

Benidipine is a dihydropyridine calcium antagonist that has been used clinically as an antihypertensive and antianginal agent. It is used clinically as a racemate, containing the (-)-alpha and (+)-alpha isomers of benidipine. This study was performed to elucidate the metabolism of benidipine and its enantiomers in human liver microsomes (HLMs) and to characterize the cytochrome P450 (P450) enzymes that are involved in the metabolism of benidipine. Human liver microsomal incubation of benidipine in the presence of NADPH resulted in the formation of two metabolites, N-desbenzylbenidipine and dehydrobenidipine. The intrinsic clearance (CL(int)) of the formation of N-desbenzylbenidipine and dehydrobenidipine metabolites from (-)-alpha isomer was similar to those from the (+)-alpha isomer (1.9 +/- 0.1 versus 2.3 +/- 2.3 microl/min/pmol P450 and 0.5 +/- 0.2 versus 0.6 +/- 0.6 microl/min/pmol P450, respectively). Correlation analysis between the known P450 enzyme activities and the rate of the formation of benidipine metabolites in the 15 HLMs showed that benidipine metabolism is correlated with CYP3A activity. The P450 isoform-selective inhibition study in liver microsomes and the incubation study of cDNA-expressed enzymes also showed that theN-debenzylation and dehydrogenation of benidipine are mainly mediated by CYP3A4 and CYP3A5. The total CL(int) values of CYP3A4-mediated metabolite formation from (-)-alpha isomer were similar to those from (+)-alpha isomer (17.7 versus 14.4 microl/min/pmol P450, respectively). The total CL(int) values of CYP3A5-mediated metabolite formation from (-)-alpha isomer were also similar to those from (+)-alpha isomer (8.3 versus 11.0 microl/min/pmol P450, respectively). These findings suggest that CYP3A4 and CYP3A5 isoforms are major enzymes contributing to the disposition of benidipine, but stereoselective disposition of benidipine in vivo may be influenced not by stereoselective metabolism but by other factors.

Fixed-dose combination lercanidipine/enalapril

Lercanidipine, a dihydropyridine calcium channel blocker, and enalapril, an ACE inhibitor, are established antihypertensive agents. A fixed-dose tablet formulation of lercanidipine/enalapril is approved in Germany for the treatment of hypertension in patients not responding to monotherapy. Lercanidipine/enalapril 10mg/10mg once daily significantly reduced sitting diastolic blood pressure and sitting systolic blood pressure, relative to lercanidipine 10mg once daily, in a 12-week, randomised, double-blind trial in patients with mild to moderate hypertension who had previously not responded to 4 weeks' treatment with lercanidipine. In a similarly designed trial, lercanidipine/enalapril 10mg/20mg once daily was significantly more effective than enalapril 20mg once daily in hypertensive patients who had previously not responded to enalapril monotherapy. Fixed-dose lercanidipine/enalapril was generally well tolerated, with a tolerability profile similar to that of either of the individual drugs alone or placebo. Cough was reported in <or=5.2% and peripheral oedema in <or=1.5% of lercanidipine/enalapril recipients.

Lercanidipine in the treatment of hypertension

OBJECTIVE

To review the literature regarding the efficacy, tolerability, and utility of lercanidipine in the treatment of hypertension.

DATA SOURCES

A search of the literature was performed using MEDLINE (1966-September 2006), EMBASE Drugs and Pharmacology (1980-September 2006), and Current Contents/Clinical Medicine (week 24, 2005-week 30, 2006). Package inserts from lercanidipine, nifedipine, felodipine, and amlodipine were also reviewed for comparison of adverse effects.

STUDY SELECTION AND DATA EXTRACTION

Articles were limited to clinical trials, abstracts, and review articles published in English.

DATA SYNTHESIS

Lercanidipine is a novel dihydropyridine (DHP) calcium-channel blocker indicated for the treatment of mild-to-moderate hypertension. Although it is not yet available in the US, lercanidipine has been utilized extensively in other countries. In 2 randomized controlled trials of approximately 400 patients with mild-to-moderate hypertension, lercanidipine showed efficacy similar to that of 2 other DHPs, felodipine and slow-release nifedipine, in significantly reducing systolic blood pressure and diastolic blood pressure (DBP) after 4 weeks. In a longer trial (12 mo), lercanidipine 10 mg/day led to normalized blood pressure in 49% of patients after 4 weeks. A postmarketing trial of 9050 patients corroborated the results observed in previous clinical trials, with 64% of patients achieving a DBP of less than 90 mm Hg and 32% attaining blood pressure control (<140/90 mm Hg). In elderly patients, lercanidipine was found comparable with lacidipine and nifedipine, showing similar decreases in DBP when compared with nifedipine (-18.3 vs -17.7 mm Hg, respectively). What distinguishes lercanidipine from other members of the DHP class is its lower incidence of adverse effects, particularly edema. One study showed that fewer patients withdrew secondary to adverse drug reactions in the lercanidipine (0.9%) and nifedipine (3.8%) group compared with the felodipine (4.5%) group. Lercanidipine has also shown efficacy similar to that of other antihypertensives, including atenolol, captopril, and losartan.

CONCLUSIONS

Lercanidipine may be an option in the treatment of hypertension, as current literature suggests comparable antihypertensive efficacy and better tolerability. Further randomized, double-blind clinical trials must be conducted in order to clarify its position among other antihypertensive medications.

Determination and pharmacokinetics of manidipine in human plasma by HPLC/ESIMS

A sensitive HPLC/ESIMS method was established for the determination of manidipine in human plasma and pharmacokinetics study. After basified plasma with ammonia, manidipine and the internal standard (IS) (felodipine) were extracted with n-hexane and separated on a Hypersil ODS2 column with a mobile phase of methanol-5 mm ammonium acetate solution containing 0.1% acetic acid (85:15, v/v). MS determination was performed by electrospray ionization in the selected ion monitoring mode. Manidipine was monitored at m/z 611.4 and IS at m/z 384. The assay had a calibration range from 0.2 to 20 ng/mL and a lower limit of quantification of 0.1 ng/mL. The method has been successfully applied to the pharmacokinetic study in healthy volunteers.

Determination of azelnidipine in human plasma by liquid chromatography–electrospray ionization-mass spectrometry

A liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the determination of azelnidipine in human plasma was established. Nicardipine was used as the internal standard (IS). After adjustment to a basic pH with sodium hydroxide solution (0.1 M), plasma samples were extracted with cyclohexane-diethyl ether (1:1, v/v) and separated on a C(18) column with a mobile phase of 20 mM ammonium acetate solution-methanol-formic acid (25:75:0.5, v/v). The electrospray ionization was employed in a single quadrupole mass spectrometer for the determination. The method was linear over the concentration range of 0.05-40 ng/ml. The lower limit of quantification (LLOQ) was 0.05 ng/ml. The intra- and inter-run standard deviations were less than 9.5% and 11.0%, respectively. The method was successfully applied to study the pharmacokinetics of azelnidipine in healthy Chinese volunteers.

Effect of grapefruit juice on the disposition of manidipine enantiomers in healthy subjects

AIM

To examine the effect of grapefruit juice, an inhibitor of CYP3A4 in the small intestine, on the disposition of manidipine enantiomers in healthy subjects.

METHODS

A randomized cross-over study with at least a 2-week wash-out period was performed. Seven healthy male volunteers received an oral 40-mg dose of racemic manidipine after an overnight fast with either grapefruit juice (GFJ) or water, as a control study. Plasma concentrations of (S)- and (R)-manidipine were monitored up to 10 h after the dosing.

RESULTS

The plasma concentrations of (S)-manidipine were significantly higher (P<0.001) than those of (R)-manidipine in the control phase with an S/R ratio for the AUC0-infinity of 1.62 (95% confidence interval 1.52, 1.73). GFJ significantly increased Cmax and AUC0-infinity of (S)-manidipine by 2.4-fold (P<0.01) and 2.3-fold (P<0.01), respectively, and Cmax and AUC0-infinity of (R)-manidipine were increased by 3.4-fold (P<0.01) and 3.0-fold (P<0.01), respectively. There were significant differences (P<0.01) in GFJ-mediated percentage increases in Cmax and AUC0-infinity of (S)-manidipine compared with those of (R)-manidipine. The S/R ratio for AUC0-infinity was significantly decreased from 1.6 to 1.2 during the GFJ phase (P<0.01).

CONCLUSION

These results indicate that the stereoselective disposition of manidipine was altered by GFJ, as an inhibitor of CYP3A4. GFJ appears to affect this metabolic disposal of (R)-manidipine to a greater extent than that of (S)-manidipine.

Tumour-specific cytotoxicity and MDR-reversal activity of dihydropyridines

The ability of 41 1,4-diphenyl-1,4-dihydropyridine derivatives to inhibit the transport activity of P-glycoprotein were studied by flow cytometry in a multidrug-resistant human colon cancer cell line (COLO320) and in human mdr1 gene-transfected mouse lymphoma cells (L 5178 Y). The cytotoxicities of these compounds were also examined against human normal and cancer cell lines. The majority of the tested compounds proved to be effective inhibitors of rhodamine 123 outward transport, but their cytotoxicities were not negligible. Some dihydropyridine derivatives displayed cytotoxic activity against four human oral tumour cell lines and against three normal human oral cell lines. There was no clear-cut relationship between the multidrug-resistance activity or cytotoxicity and the chemical structures of the compounds. New ring substituents could prevent the oxidation of the ring of the aromatic compound.

Studies on condensed 1,4-dihydropyridine derivatives and their calcium modulatory activities

Hexahydroquinoline and furoquinoline derivatives were synthesized and their calcium modulatory activity was investigated on isolated rat ileum and lamb carotid artery. In addition, the in vitro hepatic microsomal biotransformation of one hexahydroquinoline derivative was studied in rat microsomes.

Pharmacokinetics and pharmacodynamics of benidipine using a slow receptor-binding model

PURPOSE

This study examined the relationship between the plasma concentration of benidipine, a long-lasting antihypertensive agent with Ca(2+)-channel-blocking properties, and its cardiovascular effects (reduction in blood pressure and increase in heart rate) in order to assess the usefulness of pharmacokinetic-pharmacodynamic (PK-PD) modelling in describing this relationship.

METHODS

Two groups of 24 healthy volunteers received either a 4- or 8-mg benidipine hydrochloride tablet; 11 additional subjects received a placebo. Serial blood sampling and PD measurements were performed over 8 h thereafter. Plasma concentrations of benidipine were measured with a validated LC/MS/MS system, and the effects on blood pressure and heart rate were assessed during the same period. A two-compartment open model with lag time was used to explain the PK properties, and the PD model was characterized by slow receptor binding, reflecting the binding of benidipine to the ion-channel receptor.

RESULTS

Benidipine reached mean peak plasma concentrations of 1.04 and 3.85 ng/mL at 0.5 and 0.75 h after 4 and 8 mg doses, respectively. Peak cardiovascular effects were detected approximately 2 h after the administration of either dose. Maximal decreases in diastolic blood pressure with 4 and 8 mg of benidipine were 7.79 and 14.75 mmHg, respectively, and maximal increases in heart rate were 7.32 and 17.56 bpm, respectively. No significant changes in systolic blood pressure were observed. The cardiovascular effects were analysed according to a slow receptor-binding model.

CONCLUSIONS

The tested PK-PD model successfully described the relationship between the plasma concentration of benidipine and its cardiovascular effects.

HPLC method for analysis of a new 1,4-dihydropyridine: Application to pharmacokinetic study in rabbit

A high sensitive HPLC assay for plasma analysis of a new 1,4-dihydropyridine (nitrimidodipine) was developed to support the subsequent preclinical development of the compound. To 1 ml of rabbit plasma was added internal standard (3-(4-nitrooxy butyl)-5-ethyl-1,4-dihydro-2,6-dimethyl-4-(1-methyl-5-nitro-2-imidazolyl)-3,5-pyridine dicarboxylate) and 0.5 ml of 1M HCl. The plasma was extracted using 5 ml ethyl acetate which evaporated under gentle stream of nitrogen. The residue was reconstituted in 200 microl mobile phase and 100 microl of aliquots were injected to HPLC system. Chromatographic separation was accomplished on octadecyl column (250 mm x 4.6mm) using a mobile phase consisting of acetonitrile-water (45:55, v/v). The method was sensitive to 2.5 ng/ml in plasma (LOD), acceptable within- and between day reproducibility and a linearity (r2>0.9957) over a concentration range from 5 to 400 ng/ml. The mean extraction efficacy was 90.6% and no interfering peaks of the blank plasma chromatograms were observed. By using the above procedure, a simple, sensitive and convenient HPLC assay for determination, stability evaluation and pharmacokinetic study of nitrimidodipine was developed.

Pharmacological, Pharmacokinetic, and Clinical Properties of Benidipine Hydrochloride, a Novel, Long-Acting Calcium Channel Blocker

Benidipine is a dihydropyridine-derived calcium channel blocker developed in Japan, with several unique mechanisms of action, that is, triple calcium channels (L, N, and T) blocking action with a membrane approach. Benidipine has relatively high vascular selectivity and is expected to show protective effects on vascular endothelial cells. Renal protective effects of benidipine also have been shown in several basic and clinical studies. Moreover, anti-oxidative action and enhancing nitric oxide production have been noted with this drug, following its cardio-protective effects in patients with ischemic heart diseases. In fact, benidipine exerted a better prognostic effect than other calcium channel blockers in the therapy for patients with vasospastic angina. In addition, benidipine showed reliable antihypertensive, renoprotective effects if used in combination with angiotensin II type 1 receptor blockers (ARBs) when adequate anti-hypertensive effects are not achieved by ARBs alone, indicating that benidipine is an useful calcium channel blocker in combination therapy for hypertension. Benidipine was launched on the Japanese market 14 years ago, but few severe side effects have been reported, suggesting that this is a drug with established safety and long-acting pharmacological effects.

[Metabolic kinetics of MN9202 in Beagle dog liver microsomes]

AIM

To study the metabolic kinetics of MN9202 in Beagle dog liver microsome.

METHODS

Beagle dog liver microsomes were prepared by using ultracentrifuge method. After incubating 0.4 micromol x L(-1) MN9202 with 1 g x L(-1) microsomes for 30 min at 37 degrees C, the reaction was terminated by adding 0.5 mL alkalization. The RP-HPLC was used to determine the drug in the incubation mixture. The Michaelis-Menten parameters Km, and Vmax in Beagle dog liver microsomes were initially estimated by analyzing Lineweave-Brurk plot. Various selective CYP inhibitors were used to investigate their inhibitory effect on the metabolism of MN9202.

RESULTS

The Km, Vmax and CLint of MN9202 were (22.6 +/- 8.0) micromol x L(-1), (0.54 +/- 0.17) micromol x g(-1) x min(-1) and (0.0242 +/- 0.0009) L x g(-1) x min(-1), respectively. The metabolism of MN9202 was significantly inhibited by ketoconazole (Ket) and troleandomycin (Tro) in Beagle dog liver microsomes. Tranylcypromine (Tra) could inhibit the metabolism of drug as well. While other inhibitors showed little inhibitory effect on the metabolism of MN9202.

CONCLUSION

It was shown that CYP3A and CYP2C19 were involved in MN9202 metabolism. The inhibitors of human CYP3A and CYP2C19 may have potential interaction with MN9202, and this can reduce the metabolism rate and increase the toxicity of MN9202.

Quantitative structure-activity relationship and quantitative structure-pharmacokinetics relationship of 1,4-dihydropyridines and pyridines as multidrug resistance modulators

PURPOSE

The aim of this study was to develop quantitative structure-activity/pharmacokinetic relationships (QSAR/QSPKR) for a series of synthesized 1,4-dihydropyridines (DHPs) and pyridines as P-glycoprotein (P-gp) inhibitors.

METHODS

Molecular descriptors of test compounds were generated by 3D molecular modeling using SYBYL and KowWin programs. Forward inclusion coupled with multiple linear regression (MLR) was used to derive a QSAR equation for Ca2+ channel binding. A multivariate statistical technique, partial least square (PLS) regression, was applied to derive a QSAR model for P-gp inhibition and QSPKR models. Cross-validation using the "leave-one-out" method was performed to evaluate the predictive performance of models.

RESULTS

For Ca2+ channel binding, the MLR equation indicated a good correlation between observed and predicted values (R2 = 0.90), and cross-validation confirmed the predictive ability of the model (Q2 = 0.67). For P-gp reversal, the model obtained by PLS could account for most of the variation in P-gp inhibition (R2 = 0.76) with fair predictive performance (Q2 = 0.62). Nine structurally related 1,4-DHP drugs were used for QSPKR analysis. The models could explain the majority of the variation in clearance (R2 = 0.90), and cross-validation confirmed the prediction ability (Q2 = 0.69).

CONCLUSION

QSAR/QSPKR models were developed, and the QSAR models were capable of identifying synthesized 1,4-DHPs and pyridines with potent P-gp inhibition and reduced Ca2+ channel binding. The QSPKR models provide insight into the contribution of electronic, steric, and lipophilic factors to the clearance of DHPs.

Lercanidipine in hypertension

Lercanidipine is a lipophilic, dihydropyridine calcium antagonist with a long receptor half-life. Its slow onset of action helps to avoid reflex tachycardia associated with other dihydropyridines (DHPs). It produces even and sustained blood pressure lowering with once-daily dosing. It has equivalent antihypertensive efficacy to many other agents and is effective as initial monotherapy or in combination. Efficacy has been demonstrated in elderly as well as younger patients and also in the presence of other risk factors. Lercanidipine is well tolerated with DHP-associated adverse effects occurring early in treatment. The incidence of pedal edema and subsequent withdrawals has been found to be lower with lercanidipine than with amlodipine or nifedipine gastrointestinal transport system. Preclinical and preliminary clinical findings suggest lercanidipine may have beneficial effects on atherosclerosis and left ventricular hypertrophy. The efficacy and tolerability profiles of lercanidipine make it a suitable choice for treating hypertension in a wide range of affected patients.

Dihydropyridines, felodipine, and PHARMAC

Calcium antagonists have evolved as useful drugs in the treatment of hypertension and angina. Dihydropyridines are the largest subgroup and various products have been marketed. Safety concerns have largely been allayed by comparative outcome trials but concern remains over short-acting products. In New Zealand, many patients requiring fully subsidised dihydropyridines have had several changes of product imposed due to successive reference pricing and sole-supply arrangements, along with deregistering and reregistering of generic felodipine. Some narrowly avoided a complete loss of access to a suitable low dose of any dihydropyridine. Generic substitution and sole-supply arrangements may make useful savings but can leave the supply of key pharmaceuticals vulnerable and impose significant loss in quality of healthcare from multiple changes in pharmaceutical preparation.

Analysis of benidipine enantiomers in human plasma by liquid chromatography-mass spectrometry using a macrocyclic antibiotic (Vancomycin) chiral stationary phase column

We used a novel chromatographic method to rapidly and simply characterize the pharmacokinetics of benidipine enantiomers in human plasma. The stereoisomers of benidipine were extracted from plasma using diethylether under alkaline conditions. After evaporating the organic layer, the residue was reconstituted in the mobile phase (methanol:acetic acid:triethylamine, 100:0.01:0.0001, v/v/v). The enantiomers in the extract were separated on a macrocyclic antibiotic (Vancomycin) chiral stationary phase column. The mobile phase was eluted at 1 ml/min and was split by an interface. One-fifth of the eluent was used to quantify both isomers in a tandem mass spectrometer in multiple reaction-monitoring mode. The coefficient of variation of the precision of the assay was less than 8%, the assay accuracy was between 93.4 and 113.3%, and the limit of detection was 0.05 ng/ml for 1 ml of plasma. The method described above was used to measure the concentration of both benidipine enantiomers in plasma from healthy subjects who received a single oral dose of a racemate of 8 mg benidipine. The C(max) and AUC(inf) values of (+)-alpha benidipine were higher than those of (-)-alpha benidipine by 1.96- and 1.85-fold, respectively (p<0.001), whereas, the T(max) and t(1/2) for each of the benidipine stereoisomers were not significantly different.

Partition-variant desferrithiocin analogues: organ targeting and increased iron clearance

Altering the lipophilicity (log P(app)) of desferrithiocin analogues can change the organ distribution of the chelators and lead to enhanced iron clearance. For example, alkylation of (S)-2-(2,4-dihydroxyphenyl)-4,5-dihydro-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(HO)-DADFT] and its analogues to more lipophilic compounds, such as (S)-4,5-dihydro-2-(2-hydroxy-4-methoxyphenyl)-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(CH3O)-DADFT], provides ligands that achieved between a 3- and 8-fold increase in chelator concentrations in the heart, liver, and pancreas (the organs most at risk in iron-overload disease) of treated rodents. The 4'-O-methylated compounds are demethylated to their hydroxylated counterparts in rodents; furthermore, this O-demethylation takes place in both rodent and human liver microsomes. The relationship between chelator lipophilicity and iron-clearing efficacy in the iron-overloaded Cebus apella primate is further underscored by a comparison of the iron-clearing efficiency of (S)-2-(2,3-dihydroxyphenyl)-4,5-dihydro-4-methyl-4-thiazolecarboxylic acid [(S)-3'-(HO)-DADFT] and its 3'-(CH3O) counterpart. Finally, these DFT analogues are shown to be both inhibitors of the iron-mediated oxidation of ascorbate as well as effective radical scavengers.

Dioleoyl phosphatidylethanolamine and PEG-lipid conjugates modify DNA delivery mediated by 1,4-dihydropyridine amphiphiles

Complexes of amphiphilic cationic 1,4-dihydropyridines with DNA (lipoplexes) can be used for nonviral gene delivery. In order to achieve serum-resistant transfection system, DOPE and PEG-lipid conjugates were used to modify 1,4-dihydropyridine amphiphile DHP-12 complexes with DNA. The ability to bind DNA was examined by ethidium bromide displacement assay. Cellular uptake, transfection efficacy and intracellular trafficking of the lipoplexes were assessed using FACS, betagalactosidase gene transfection and confocal laser microscopy, respectively. Cytotoxicity was determined by MTT assay. DHP-12 lipoplexes that included DOPE showed enhanced cell uptake and transfection efficacy both in the absence and presence of serum. PEG-lipid conjugates, in contrast, impaired transfection. In conclusion, combination of DHP-12 with DOPE appears to be a promising transfection system.

Intracellular metabolism and pharmacokinetics of 5'-hydrogenphosphonate of 3'-azido-2',3'-dideoxythymidine, a prodrug of 3'-azido-2',3'-dideoxythymidine

5'-Hydrogenphosphonate of 3'-azido-2',3'-dideoxythymidine (HpAZT), a novel anti-HIV drug approved for the treatment of HIV-infected patients in Russia, displays some clinical advantages over azidothymidine (AZT). Metabolism in the HL-60 cell culture and pharmacokinetics in mice of [6-3H]-HpAZT (in comparison with [6-3H-AZT) were studied to elucidate the metabolic basis of its lower clinical toxicity. Accumulation of [6-3H]-HpAZT-derived products in cells with time, distribution of its radioactive metabolites among blood and different mouse organs and dependence of drug accumulation on the route of administration were investigated. The rate of accumulation of [3H]-HpAZT metabolites in cells was slower than the rate of accumulation of [3H]-AZT metabolites. [3H]-AZTMP was the dominating metabolite at all time points, achieving the level of 15 +/- 3 pmol/10(6) cells after 25 h incubation. After oral or intravenous administrations of [3H]-HpAZT, the (radioactive) metabolites were rapidly distributed among blood, stomach, intestine and liver and were not found in brain, muscles and spleen. [3H]-HpAZT underwent rapid and extensive metabolism, [3H]-AZT being the dominating product at all time points. Administration of 180 nmol of [3H]-HpAZT resulted in an AZT concentration in blood of 1-3 microM after 5 min, which remained practically constant during the next 25 min and did not depend on the route of administration.

Assessing the bioequivalence of 4- and 8-mg benidipine tablets in healthy volunteers after a single oral dose

OBJECTIVE

To assess the bioequivalence of a new tablet formulation of benidipine hydrochloride with reference to a marketed product.

METHODS

Two groups, consisting of 24 healthy volunteers each, received a 4- or 8-mg (one or two tablets) reference benidipine hydrochloride tablet and one or two test tablets in a 2 x 2 cross-over study. There was a 6-day washout period between doses. The plasma benidipine concentration was monitored using LC/MS/MS for 8 h after the dose. The area under the plasma concentration-time curve from time 0 to the last sampling time (AUCt) was calculated using the linear-log trapezoidal rule. The maximum plasma drug concentration (Cmax) and the time to reach Cmax (Tmax) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed AUCt and Cmax, and untransformed Tmax.

RESULTS

The geometric mean AUCt was 2.23 ng/mL/h (test medication) and 2.47 ng/mL/h (reference medication) for the 4-mg tablet, and 9.57 and 9.97 ng/mL/h for the 8-mg tablet, respectively. A Cmax of 1.94 and 2.01 ng/mL was achieved for the test and reference medication for the 4-mg tablet, and 5.94 and 6.53 ng/mL for the 8-mg tablet, respectively. The 90% confidence intervals for AUCt and Cmax were 0.8441-1.0481 and 0.8739-1.2037 for the 4-mg tablet, and 0.8559-1.1273 and 0.9926-1.2176 for the 8-mg tablet, respectively, satisfying the bioequivalence criteria of the US Food and Drug Administration Guidelines, and the Korea Food and Drug Administration Guidelines. These results indicate that the 4- and 8-mg tablets of benidipine are bioequivalent to the reference formulations.

SCH00013, a novel Ca(2+) sensitizer with positive inotropic and no chronotropic action in heart failure

We investigated the effects of the agent SCH00013 on Ca(2+)-induced force generation in rabbit skinned cardiac muscle fibers and in vivo cardiac function in high-pacing-induced heart failure dogs. The Ca(2+)-induced force generation in skinned cardiac muscle fibers was determined at pH 6.2 - 7.4, and SCH00013 was found to have a significant Ca(2+) sensitizing effect at pH 7.2 to 7.4. There was no significant difference in the Ca(2+) sensitizing action between the enantiomers of SCH00013. The Ca(2+) sensitizing effect of SCH00013 was dependent on the sarcomere length, being significant only at a long sarcomere length. SCH00013 elicited a positive inotropic effect at more than 0.3 and 1 mg/kg, i.v. in normal and heart failure dogs, respectively, with no chronotropic action. These results strongly suggested that SCH00013 is a novel Ca(2+) sensitizer that elicits a positive inotropic and no chronotropic effect in heart failure, probably through enhancing the Frank-Starling mechanism.

A comparison between calcium channel blocking drugs with different potencies for T- and L-type channels in preventing atrial electrical remodeling

Calcium overload plays a key role in the development of atrial electrical remodeling. The effect of an L-type Ca channel blocker in preventing this remodeling has been reported to be short lasting, partly due to down-regulation of this channel and persisting Ca entry through the T-type Ca channel. To prove if efonidipine, a dual L- and T-type Ca channel blocker exerts a greater effect than an L-type Ca channel blocker verapamil, 21 dogs underwent rapid atrial pacing at 400 bpm for 14 days, pretreatment with efonidipine in 7 (E), verapamil in 7 (V), and none in 7 (C). We measured the atrial effective refractory period (ERP) serially during 14 days of rapid pacing. In response to rapid pacing, ERP decreased progressively in C. In contrast, in E and V, ERP remained greater than ERP in C (P < 0.01) on days 2 through 7. However, on the 14th day, ERP in V decreased to the level seen in C, whereas ERP in E remained significantly longer than ERPs in C or V (P < 0.01). The blockade L-type Ca channel alone is not sufficient, but the addition of a T-type Ca channel blockade shows a more sustained effect to prevent atrial electrical remodeling.

A high-performance liquid chromatographic method for determination of the niguldipine analogue DHP-014

A simple and reliable reversed-phase high-performance liquid chromatography method was developed and validated for the determination of DHP-014, a niguldipine analogue with potent P-glycoprotein inhibitory and negligible calcium channel blocking properties, in rat plasma. DHP-014 and niguldipine hydrochloride (the internal standard) were extracted from rat plasma by liquid extraction using hexane. DHP-014 was then separated by HPLC on a C18 column and quantified by ultraviolet detection at 238 nm. The mobile phase consisted of acetonitrile-aqueous 5 mM phosphate buffer (65:35, v/v) containing 0.4% (v/v) triethylamine adjusted to pH 7.0. The mean extraction efficiency of DHP-014 was 109.0 +/- 12.9, 97.7 +/- 8.0 and 102.9 +/- 7.5% for DHP-014 concentrations of 10, 50 and 100 nM, respectively (n = 5). The method was linear over the concentration range 2.5-200 nM with a regression coefficient of 0.998. The limit of detection of DHP-014 in rat plasma was 1.0 nM. The intra- and inter-day coefficients of variation for DHP-014 in rat plasma were 4.7-7.9 and 6.9-9.9%, respectively. The intra- and inter-day accuracy was 98.2-99.5 and 97.9-103%, respectively. The bioanalytical technique was used to determine DHP-014 in plasma samples in a pharmacokinetic study of DHP-014 administered to female Sprague-Dawley rats.

Pharmacokinetics and bioavailability of a newly synthesized dihydropyridine compound with multidrug resistance reversal activity

(+/-)3-(3-(4,4-diphenylpiperidin-1-yl)propyl) 5-methyl 4-(3,4-dimethoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate ((+/-)-DHP-014), is a new 4-aryl-1,4-dihydropyridine that can reverse multidrug resistance mediated by the ATP-binding cassette (ABC) transport proteins, P-glycoprotein, multidrug resistance-associated protein 1 and breast cancer resistance protein; it exhibits negligible calcium channel blocking activity. The objective of this work was to investigate the pharmacokinetics of this new compound in rats. Three intravenous (1, 2 and 5 mg/kg) and two oral (25 and 50 mg/kg) doses were administered to female Sprague-Dawley rats. A two-compartment model with nonlinear elimination best characterized the pharmacokinetic profiles after intravenous and oral administration in rats. The terminal half-life of (+/-)-DHP-014 increased and the systemic clearance significantly decreased at higher doses, indicating nonlinear elimination. The dose-dependent clearance is likely due to saturation of metabolism. The apparent volume of distribution of (+/-)-DHP-014 was 2.0 L/kg in rats and was unchanged with increasing intravenous doses of (+/-)-DHP-014. The estimated oral bioavailability of (+/-)-DHP-014 was 8.2%. The poor bioavailability is likely due to the poor solubility of the compound, as well as to substantial first-pass elimination.

Enantioselective pharmacokinetics of lercanidipine in healthy volunteers

OBJECTIVE

The enantioselective kinetic disposition of lercanidipine, a dihydropyridine type of third-generation calcium antagonist, was investigated in six healthy male volunteers following a single 20 mg racemic oral dose.

METHODS

Serial plasma samples were obtained from 0 to 24 h after drug administration. Lercanidipine enantiomers were analysed using a chiral LC-MS-MS method.

RESULTS

The following differences (p < 0.05, Wilcoxon test) between (S) and (R) enantiomers were found (median): C(max) 2.071 ng mL(-1) versus 1.681 ng mL(-1); AUC(0-24)12.352 ng h mL(-1) versus 10.063 ng h mL(-1) and Cl/f 732.16 L h(-1) versus 1891.84 L h(-1). The AUC(0-infinity) values for (S)-LER were 1.21-fold higher than those for (R)-LER.

CONCLUSION

The pharmacokinetics of LER was enantioselective in healthy volunteers following a single dose of 20 mg of the unlabeled racemic drug.

Determination of benidipine in human plasma using liquid chromatography–tandem mass spectrometry

We developed a method for determining benidipine, a dihydropyridine analogue calcium-channel blocker, in plasma using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Benidipine and benidipine-d5, an internal standard, were extracted from plasma using diethyl ether in the presence of 5M NaOH. After drying the organic layer, the residue was reconstituted in acetonitrile and injected onto a reversed-phase C18 column. The isocratic mobile phase (acetonitrile-5mM ammonium acetate, 90:10, v/v) was eluted at 0.2 ml/min. The ion transitions monitored in multiple reaction-monitoring mode were m/z 506-174 for benidipine and m/z 511-179 for the internal standard. The coefficient of variation of the assay precision was less than 13%, and the accuracy exceeded 92%, except at the limit of quantification, 0.05 ng/ml with 1ml of plasma, when it was 85%. This method was used to measure the benidipine concentration in plasma from healthy subjects after a single 4-mg oral dose of benidipine. This method is a very simple, sensitive, and accurate way to determine the plasma benidipine concentration.

Azelnidipine

Azelnidipine is a new dihydropyridine calcium channel antagonist with selectivity for L-type calcium channels that has recently been approved in Japan for the treatment of patients with hypertension. Results from clinical trials showed that, in 95 patients with mild-to-moderate hypertension, long-term treatment with azelnidipine effectively controls blood pressure (BP). The mean reduction from baseline in sitting systolic/diastolic BP after 1 year of treatment was 27.8/16.6 mm Hg. Among 172 patients with uncontrolled hypertension receiving non-calcium channel antagonist antihypertensive agents, the addition of azelnidipine therapy significantly reduced mean BP in a noncomparative, 1-year study (a reduction from 165.7/95.4 mm Hg at baseline to 138.2/79.9 mm Hg at study end). The antihypertensive efficacy of azelnidipine in patients with mild-to-moderate hypertension was shown to be similar to that of amlodipine or nitrendipine in randomised, double-blind studies. Azelnidipine and amlodipine controlled 24-hour BP to a similar extent. Azelnidipine is generally well tolerated; vasodilator adverse events such as as headache and hot facial flushes account for most of the adverse events. Its use is not associated with reflex tachycardia.

Lercanidipine : a review of its efficacy in the management of hypertension

Lercanidipine (Zanidip) is a vasoselective dihydropyridine calcium channel antagonist that causes systemic vasodilation by blocking the influx of calcium ions through L-type calcium channels in cell membranes. It is a highly lipophilic drug that exhibits a slower onset and longer duration of action than other calcium channel antagonists. Furthermore, lercanidipine may have antiatherogenic activity unrelated to its antihypertensive effect. In two large, nonblind, noncomparative studies involving approximately 16 000 patients with mild-to-moderate hypertension, systolic blood pressure (BP) [SBP] and diastolic BP (DBP) were significantly reduced after 12 weeks' treatment with lercanidipine 10-20 mg/day. Furthermore, in the largest study, 64% of patients were responders (DBP <90 mm Hg) after 12 weeks of treatment and an additional 32% had their BP normalised (BP <140/90 mm Hg). In comparative trials, lercanidipine 10-20 mg/day was as effective as nifedipine slow release (SR) 20-40 mg twice daily, amlodipine 10 mg/day, felodipine 10-20 mg/day, nifedipine gastrointestinal therapeutic system (GITS) 30-60 mg once daily or verapamil SR 240 mg/day at reducing SBP and DBP in patients with mild-to-moderate hypertension after 2-16 weeks of therapy. In addition, 4 weeks of lercanidipine therapy (10 mg/day) was as effective as captopril 25mg twice daily, atenolol 50 mg/day or hydrochlorothiazide 12.5 mg/day. Lercanidipine 5-30 mg/day effectively decreased BP in elderly patients (aged >60 years) with mild-to-moderate hypertension or isolated systolic hypertension to the same extent as amlodipine 5-10 mg/day, nifedipine GITS 30-60 mg/day or lacidipine 2-4 mg/day after 24-26 weeks of therapy. In addition, a limited number of studies suggest that lercanidipine may have antihypertensive efficacy in patients with severe or resistant hypertension, in hypertensive patients with type 2 diabetes mellitus and in postmenopausal women with mild-to-moderate essential hypertension. Lercanidipine is well tolerated, with most treatment-emergent events related to vasodilation. Common adverse events included headache, flushing and peripheral oedema. Importantly, the incidence of vasodilatory oedema was significantly lower in patients receiving lercanidipine than in those receiving some other calcium channel antagonists.

CONCLUSION

Once-daily lercanidipine is an effective and well tolerated antihypertensive agent in patients with mild-to-moderate hypertension.

Single oral dose pharmacokinetic interaction study of manidipine and delapril in healthy volunteers

OBJECTIVE

The objective of the study was to assess potential pharmacokinetic interactions between delapril, an angiotensin conversion enzyme inhibitor, and manidipine, a calcium channel antagonist, prior to the development of a fixed combination drug product.

METHODS

Eighteen healthy male volunteers received a single oral dose of 10 mg manidipine dihydrochloride (CAS 89226-75-5), or 30 mg delapril hydrochloride (CAS 83435-67-0), or both simultaneously, according to a fully balanced three-way cross-over design. The three treatments were separated by a one-week washout period. Blood samples were collected during 24 h for plasma determination of manidipine and metabolite M-XIII and/or of delapril and metabolites M1, M2 and M3, using specific LCMS/MS methods.

RESULTS

The bioavailability of manidipine and M-XIII was slightly decreased by concomitant administration of delapril (manidipine: Cmax-19% and AUC infinity-11% M-XIII: Cmax-17% and AUCt-18%). The bioavailability of delapril was not influenced by co-administration with manidipine (Cmax-7% and AUC infinity +4%). The effect on delapril pharmacologically active metabolites M1 and M3 was negligible. The inactive metabolite M2 underwent a 13% reduction of Cmax and AUC infinity. The 90% confidence intervals were confined within limits of acceptance (70-143% for Cmax and 80-125% for AUC). Mean residence times and apparent elimination half-lives were unaltered. Blood pressure and heart rate versus time profiles were similar during the three treatments.

CONCLUSIONS

Simultaneous oral administration of 10 mg manidipine and 30 mg delapril does not significantly alter the pharmacokinetics of either drug or that of their principal metabolites.

Enantioselective determination of lercanidipine in human plasma for pharmacokinetic studies by normal-phase liquid chromatography–tandem mass spectrometry

We describe here the first method for the enantioselective analysis of the calcium antagonist lercanidipine in human plasma by high performance liquid chromatography (HPLC) employing tandem mass spectrometric (MS) detection. Routine determination of lercanidipine enantiomers in human plasma in the working range of 0.025-50.0 ng ml(-1) plasma for each enantiomer with an accuracy and precision less than 15% was possible. Application of the method to a stereospecific study of the pharmacokinetics showed that plasma levels after an oral dose of rac-lercanidipine administered to a healthy volunteer were found to be higher for the (S)-enantiomer.

Pharmacokinetics and tolerability of a new manidipine and delapril fixed oral combination in young and elderly subjects

OBJECTIVES

The aim of the present study was to compare the pharmacokinetic and pharmacodynamic properties of a fixed combination tablet containing 10 mg of manidipine dihydrochloride (CAS 89226-75-5), a calcium channel antagonist, and 30 mg of delapril hydrochloride (CAS 83435-67-0), an angiotensin converting enzyme (ACE) inhibitor, during once daily repeated dosing in young and elderly subjects and to assess the bioequivalence of the fixed combination tablet and the single ingredient tablets taken simultaneously in young healthy subjects after a single dose administration.

METHODS

Eighteen young healthy male volunteers received a single oral dose of 10 mg manidipine and 30 mg delapril as two separate tablets or a fixed combination tablet, followed by a week of once daily dosing with the fixed combination. Eight male and eight female elderly volunteers also received a week of once daily dosing with the fixed combination. Blood samples were collected during 24 h on the first and last treatment day for plasma determination of manidipine, delapril and their main metabolites, using specific LC-MS/MS methods. Blood pressure and heart rate were also recorded during 24 h.

RESULTS

Bioequivalence was strictly demonstrated between the extemporaneous and the fixed combination tablet after single dose administration. At steady-state in young subjects, manidipine AUC and Cmax were lower (-8 and -12%) and t1/2 was longer (+45%), while delapril and metabolites were little affected as compared to single dose. In elderly subjects, manidipine Cmax was 4% lower than after single dose, AUC was 13% higher, and t1/2 was increased 2.4-fold. For delapril and active metabolites, Cmax and AUC increased modestly. Blood pressure and heart rate versus time profiles after single dose and at steady-state were almost superimposable. In elderly compared to young subjects at steady-state, peak concentrations of manidipine and delapril changed by +35% and -15% while AUCs increased by +70% and +9.7%.

CONCLUSION

The fixed combination tablet of 10 mg manidipine and 30 mg delapril is bioequivalent to mono-ingredient tablets. At steady-state, the pharmacokinetic and pharmacodynamic profiles in young and elderly subjects undergo minor changes and indicate negligible accumulation. Drug exposure is higher in elderly subjects.