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 â†’ 238.15 for levamlodipine and 415.25 â†’ 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.

Fixed Dose Single Tablet Formulation with Differential Release of Amlodipine Besylate and Simvastatin and Its Pharmacokinetic Profile: QbD and Risk Assessment Approach.

PURPOSE: A differential release fixed dose matrix tablet of amlodipine besylate (AML-B) and simvastatin (SIM) was formulated to enhance patient compliance. MATERIAL AND METHOD: In the first phase, release controlling parameters of AML-B and SIM granules were identified and in the second phase a fixed dose AML-B and SIM tablet formulation was prepared and optimized for a differential release of the drugs using a quality by design (QbD) and risk assessment approach. A validated HPLC method was employed for simultaneous determination of AML-B and SIM for FDC formulation. A pharmacokinetics of the above drugs was studied in healthy dogs in the third phase. RESULTS: In QbD-based optimized formulation, Eudragit® RSPO-dicalcium phosphate (DCP) blend controlled the release of AML-B over 8 h, though this diffusion-controlled release assumed first order kinetics. DCP and Eudragit® RS 100 also retarded release of SIM causing SIM release over 8 h after AML-B release from the optimized FDC tablet formulation. The HPLC retention times of AML-B and SIM were 2.10 and 15.52 min, respectively. Linearity for AML-B was 5.0-50 ng/mL and 0.01-2.0 µg/mL for SIM with percent recoveries of 92.85-101.53% and 94.51-117.75% for AML-B and SIM. AUC0-∞ of AML-B was increased 3 fold, while AUC0-∞ of SIM was decreased 2 fold. The tmax values for AML-B and SIM were 12 and 6 h, respectively. AML-B was absorbed without any lag time (tlag) while tlag was 6.33 ± 0.81 h for SIM, thus met the study objective. CONCLUSION: The pharmacokinetic study showed an immediate absorption of AML-B while that of SIM was withheld for 6 h, close to the desired delay time of 8 h.

Determination of amlodipine, indapamide and perindopril in human plasma by a novel LC-MS/MS method: Application to a bioequivalence study.

A robust and rapid UPLC-MS/MS method has been developed, optimized and validated for determination of amlodipine (AML), indapamide (IND) and perindopril (PRN) in human plasma. A positive electrospray ionization mode was used in a Xevo TQD LC-MS/MS instrument. A single sample preparation step using extraction technique was applied to extract the three analytes from plasma samples. There was no need to extract indapamide from blood samples in a further step. Extraction of the three drugs and internal standards was done using a solvent mixture composed of methyl tertiary butyl ether, dichloromethane and ethyl acetate. The prepared samples were analyzed using an Acquity UPLC HSS C18 (100 × 2.1 mm, 1.7 µm) column. Ammonium acetate and methanol, pumped at a flow rate of 0.3 ml/min, were used as a mobile phase. Method validation was done as per the US Food and Drug Administration guidelines. Linearity was achieved in the range of 0.2-15 ng/ml for AML, 0.5-50 ng/ml for IND and 0.5-120 ng/ml for PRN. Accuracy and precision were estimated and found to be within the acceptable ranges. The rapid chromatography permits analysis of many samples per batch, making the method suitable for clinical and pharmacokinetic investigations. The developed and validated method was applied to estimate AML, IND, and PRN in a fasting bioequivalence study in healthy human volunteers.

UHPLC-MS/MS assay for simultaneous determination of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin with its active metabolites in human plasma, for population-scale drug-drug interactions studies in people living with HIV.

Thanks to highly active antiretroviral treatments, HIV infection is now considered as a chronic condition. Consequently, people living with HIV (PLWH) live longer and encounter more age-related chronic co-morbidities, notably cardiovascular diseases, leading to polypharmacy. As the management of drug-drug interactions (DDIs) constitutes a key aspect of the care of PLWH, the magnitude of pharmacokinetic DDIs between cardiovascular and anti-HIV drugs needs to be more thoroughly characterized. To that endeavour, an UHPLC-MS/MS bioanalytical method has been developed for the simultaneous determination in human plasma of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin and its active metabolites. Plasma samples were subjected to protein precipitation with methanol, followed by evaporation at room temperature under nitrogen of the supernatant, allowing to attain measurable plasma concentrations down to sub-nanogram per milliliter levels. Stable isotope-labelled analytes were used as internal standards. The five drugs and two metabolites were analyzed using a 6-min liquid chromatographic run coupled to electrospray triple quadrupole mass spectrometry detection. The method was validated over the clinically relevant concentrations ranging from 0.3 to 480 ng/mL for amlodipine, atorvastatin and p-OH-atorvastatin, and 0.4 to 480 ng/mL for pravastatin, 0.5 to 480 ng/mL for rosuvastatin and o-OH-atorvastatin, and 3 to 4800 ng/mL for metoprolol. Validation performances such as trueness (95.4-110.8%), repeatability (1.5-13.4%) and intermediate precision (3.6-14.5%) were in agreement with current international recommendations. Accuracy profiles (total error approach) were lying within the limits of ±30% accepted in bioanalysis. This rapid and robust UHPLC-MS/MS assay allows the simultaneous quantification in plasma of the major currently used cardiovascular drugs and offers an efficient analytical tool for clinical pharmacokinetics as well as DDIs studies.

Analysis of secondary care data to evaluate the clinical relevance of the drug-drug interaction between amlodipine and simvastatin.

BACKGROUND: Pharmacokinetic analyses revealed an increase in the bioavailability of simvastatin when co-administered with amlodipine [Nishio S et al. Hypertensin research 2005; Son H et al. Drug metabolism and pharmacokinetics 2014]. This may induce an increased risk of muscle toxicity for patients who receive this combination. So far, no in vivo data on the clinical relevance of this interaction exist. The objective of the present analysis was to determine the number of patients with concomitant treatment of amlodipine and simvastatin. Subsequently, the data was analyzed for the indication of muscular discomfort. Patients with combined prescription of amlodipine and another hydroxymethylglutaryl-CoA-reductase inhibitor except simvastatin or patients receiving simvastatin without amlodipine served as control groups. METHODS: The present analysis used secondary data from the health insurance company AOK PLUS including information regarding diagnosis and drug prescriptions. RESULTS: In total, 67.081 patients corresponding to 4.93% of the analyzed collective received a combined prescription of amlodipine and simvastatin. The absolute frequency increased continuously over time. Muscular discomfort was detected in a) 6.20% of the patients receiving amlodipine and simvastatin, b) 6.60% of the patients receiving amlodipine and another hydroxymethylglutaryl-CoA- reductase inhibitor and c) 8.04% of the patients with simvastatin only. CONCLUSIONS: The present analysis shows an increasing trend of combined prescriptions of amlodipine and simvastatin. Evidence for simvastatin dose adaptation or therapy switch to another hydroxymethylglutaryl-CoA-reductase inhibitor, however, was not found. Muscular discomfort does not occur more often in patients with amlodipine and simvastatin compared to the two control groups. The results of the present analysis reveal no evidence for a clinically relevant interaction between amlodipine and simvastatin.

Study of Interactions between Amlodipine and Quercetin on Human Serum Albumin: Spectroscopic and Modeling Approaches.

The aim of this study was to analyze the binding interactions between a common antihypertensive drug (amlodipine besylate-AML) and the widely distributed plant flavonoid quercetin (Q), in the presence of human serum albumin (HSA). Fluorescence analysis was implemented to investigate the effect of ligands on albumin intrinsic fluorescence and to define the binding and quenching properties. Further methods, such as circular dichroism and FT-IR, were used to obtain more details. The data show that both of these compounds bind to Sudlow's Site 1 on HSA and that there exists a competitive interaction between them. Q is able to displace AML from its binding site and the presence of AML makes it easier for Q to bind. AML binds with the lower affinity and if the binding site is already occupied by Q, it binds to the secondary binding site inside the same hydrophobic pocket of Sudlow's Site 1, with exactly the same affinity. Experimental data were complemented with molecular docking studies. The obtained results provide useful information about possible pharmacokinetic interactions upon simultaneous co-administration of the food/dietary supplement and the antihypertensive drug.

Reliable and easy-to-use LC-MS/MS-method for simultaneous determination of the antihypertensives metoprolol, amlodipine, canrenone and hydrochlorothiazide in patients with therapy-refractory arterial hypertension.

BACKGROUND: Therapy-refractory arterial hypertension is defined as a blood pressure (BP) in a subset of patients who fail to achieve BP control despite a three-drug regimen (including a diuretic). Various factors have impact on loss of therapy response. Drug-drug-interactions (DDIs) may cause altered pharmacokinetics (PK) of antihypertensive drugs. Upregulation of activity and expression of cytochrome P450 (CYP) enzymes can result in decreased plasma drug levels. Besides these PK considerations a significant problem could be nonadherence to drug therapy. In this regard Therapeutic Drug Monitoring (TDM) is a useful tool for detecting nonadherence. Therefore a LC-MS/MS-method for determination of Metoprolol (MET), Amlodipine (AML), Canrenone (CAN) and Hydrochlorothiazide (HCT) was developed. METHODS: An UHPLC-MS/MS method was developed and validated for simultaneous determination of MET, AML, CAN and HCT in plasma matrix. Extraction of serum samples consisted of simple protein precipitation using acetonitrile. Stable isotope labeled analogues for each antihypertensive were obtained for internal standardization and quantitative analysis ([2H7]-MET, ([13C6]-AML, [2H4]-CAN, [13C6]-HCT). Calibrators and quality controls were prepared in plasma matrix of normal individuals. Sample preparation: protein precipitation with acetonitrile and addition of internal standard-mix. RESULTS: All analytes were eluted within a runtime of 2.5 min. Linearity experiments were demonstrated in plasma over following concentration ranges: MET: 5-750 µg/l, AML: 1-50 µg/l, CAN: 10-500 µg/l, HCT: 5-500 µg/l (R2 > 0.993). Chromatographic separation was achieved using a C18 column (50 × 2.1 mm, 1.9 µm particle size) and an isocratic elution. LC-MS/MS analyses were performed on a triple quadrupole mass spectrometer using positive and negative electrospray ionization in selected reaction monitoring (SRM) mode. Ion transitions monitored for quantitation were m/z 268.2 → 74.1 for MET, m/z 409.1 → 238.0 for AML, m/z 341.2 → 91.0 for CAN and m/z 296.0 → 205.1 for HCT. For all analytes, inter- and intra-day precision (CV, %) varied between 1.7 and 14.0 and inter- and intra-day accuracy values ranged from -2.5 to 7.1%. The lower limits of detection and quantification were: 0.08 and 0.23; 0.05 and 0.15; 2.82 and 8.54; and 0.02 and 0.05 µg/l for MET, AML, CAN and HCT, respectively. Results of stability experiments were within the required range of +/- 15%. CONCLUSIONS: Although the level of recommendation of TDM of antihypertensive drugs in patients with refractory hypertension is not yet established, the present LC-MS/MS-method can serve as an effective tool for detection of PK-alterations/nonadherence and may help to monitor antihypertensive pharmacotherapy.

Quantification of amlodipine and atorvastatin in human plasma by UPLC-MS/MS method and its application to a bioequivalence study.

A robust, rapid and sensitive UPLC-MS/MS method has been developed, optimized and validated for the determination of amlodipine (AML) and atorvastatin (ATO) in human plasma using eplerenone as an internal standard (IS). Multiple-reaction monitoring in positive electrospray ionization mode was utilized in Xevo TQD LC-MS/MS. Double extraction was used in sample preparation using diethyl ether and ethyl acetate. The prepared samples were analyzed using an Acquity UPLC BEH C18 (50 × 2.1 mm, 1.7 µm) column. Ammonium formate and acetonitrile, pumped isocraticaly at a flow rate of 0.25 mL/min, were used as a mobile phase. Method validation was done as per the US Food and Drug Administration guidelines. Linearity was achieved in the range of 0.1-10 ng/mL for AML and 0.05-50 ng/mL for ATO. Intra-day and inter-day accuracy and precision were calculated and found to be within the acceptable range. A short run time, of <1.5 min, permits analysis of a large number of plasma samples per batch. The developed and validated method was applied to estimate AML and ATO in a bioequivalence study in healthy human volunteers.

High-throughput LC-MS/MS method with 96-well plate precipitation for the determination of arotinolol and amlodipine in a small volume of rat plasma: Application to a pharmacokinetic interaction study.

A rapid, sensitive, and selective liquid chromatography with tandem mass spectrometry method was developed and fully validated for the simultaneous quantification of arotinolol and amlodipine in rat plasma. Two internal standards were introduced with metoprolol as the internal standard of arotinolol and (S)-amlodipine-d4 as the internal standard of amlodipine. The analytes were isolated from 50.0 µL plasma samples by a simple protein precipitation using acetonitrile. The chromatographic separation was achieved in 5 min on a C18 column. The mobile phase consisted of phase A 5% methanol and phase B 95% methanol (both containing 0.5% formic acid and 5 mM ammonium acetate) and was delivered in gradient elution at 0.300 mL/min. Quantification was performed in multiple reaction monitoring mode with the transition m/z 372.1 â†’ 316.1 for arotinolol, m/z 268.2 â†’ 116.2 for metoprolol, m/z 409.1 â†’ 238.1 for amlodipine and m/z 413.1 â†’ 238.1 for (S)-amlodipine-d4. Linearity was obtained over the range of 0.200-40.0 ng/mL for arotinolol (r2  = 0.9988) and 0.500-100 ng/mL for amlodipine (r2  = 0.9985) in rat plasma. The validated data have met the acceptance criteria in FDA guideline. This method was successfully applied to a pharmacokinetic interaction study in rats, and the results indicated that there was no significant drug-drug interaction between arotinolol and amlodipine.

VLDL/LDL acts as a drug carrier and regulates the transport and metabolism of drugs in the body.

Only free drugs have been believed to be carried into tissues through active or passive transport. However, considering that lipoproteins function as carriers of serum lipids such as cholesterol and triglycerides, we hypothesized that lipoproteins can associate with certain drugs and mediate their transport into tissues in lipid-associated form. Here, in vitro and in vivo studies with low density lipoprotein receptor (LDLR)-overexpressing or -knockdown cells and wild-type or LDLR-mutant mice were used to show the association of various drugs with lipoproteins and the uptake of lipoprotein-associated drugs through a lipoprotein receptor-mediated process. In clinical studies, investigation of the effect of lipoprotein apheresis on serum drug concentrations in patients with familial hypercholesterolemia demonstrated that lipoprotein-mediated drug transport occurs in humans as well as in mice. These findings represent a new concept regarding the transport and metabolism of drugs in the body and suggest that the role of lipoprotein-mediated drug transport should be considered when developing effective and safe pharmacotherapies.

Pharmacokinetic drug-drug interaction assessment between LCZ696, an angiotensin receptor neprilysin inhibitor, and hydrochlorothiazide, amlodipine, or carvedilol.

LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor in development for treatments of hypertension and heart failure indications. In 3 separate studies, pharmacokinetic drug-drug interactions (DDIs) potential was assessed when LCZ696 was coadministered with hydrochlorothiazide (HCTZ), amlodipine, or carvedilol. The studies used a open-label, single-sequence, 3-period, crossover design in healthy subjects. Blood samples were collected to determine the pharmacokinetic parameters of LCZ696 analytes (AHU377, LBQ657, and valsartan), HCTZ, amlodipine, or carvedilol (R[+]- and S[-]-carvedilol) for statistical analysis. When coadministered LCZ696 with HCTZ, the 90% CIs of the geometric mean ratios of AUCtau,ss of HCTZ and that of LBQ657 were within a 0.80-1.25 interval, whereas HCTZ Cmax,ss decreased by 26%, LBQ657 Cmax,ss increased by 19%, and the AUCtau,ss and Cmax,ss of valsartan increased by 14% and 16%, respectively. Pharmacokinetics of amlodipine, R(+)- and S(-)-carvedilol, or LBQ657 were not altered after coadministration of LCZ696 with amlodipine or carvedilol. Coadministration of LCZ696 400 mg once daily (qd) with HCTZ 25 mg qd, amlodipine 10 mg qd, or carvedilol 25 mg twice a day (bid) had no clinically relevant pharmacokinetic drug-drug interactions. LCZ696, HCTZ, amlodipine, and carvedilol were safe and well tolerated when given alone or concomitantly in the investigated 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.

Development of a pharmacokinetic interaction model for co-administration of simvastatin and amlodipine.

A model for drug interaction between amlodipine and simvastatin was developed using concentration data obtained from a multiple-dose study consisting of single- and co-administration of amlodipine and simvastatin conducted in healthy Koreans. Amlodipine concentrations were assumed to influence the clearance of simvastatin and simvastatin acid, which as well as the oral bioavailability was allowed to vary depending on genetic polymorphisms of metabolic enzymes. Covariate effects on drug concentrations were also considered. The developed model yielded a 46% increase in simvastatin bioavailability and a 13% decrease in simvastatin clearance when amlodipine 10 mg was co-administered. When CYP3A4/5 polymorphisms were assessed by a mixture model, extensive metabolizers yielded a decrease in simvastatin bioavailability of 81% and a decrease in simvastatin clearance by 4.6 times as compared to poor metabolizers. Sixty percent of the usual dose was the optimal simvastatin dose that can minimize the interaction with amlodipine 10 mg. Age and weight had significant effects on amlodipine concentrations. In conclusion, this study has quantitatively described the pharmacokinetic interaction between simvastatin and amlodipine using a modeling approach. Given that the two drugs are often prescribed together, the developed model is expected to contribute to more efficient and safer drug treatment when they are co-administered.

Rapid quantification of amlodipine enantiomers in human plasma by LC-MS/MS: application to a clinical pharmacokinetic study.

A rapid, simple, specific and sensitive LC-MS/MS method has been developed and validated for the enantiomeric quantification of amlodipine (AML) isomers [R-amlodipine (R-AML) and S-amlodipine (S-AML)] with 200 µL of human plasma using R-AML-d4 and S-AML-d4 as corresponding internal standards as per regulatory guidelines. A simple liquid-liquid extraction process was used to extract these analytes from human plasma. The total run time was 3.5 min and the elution of R-AML, S-AML, R-AML-d4 and S-AML-d4 occurred at 1.62, 2.51, 1.63 and 2.53 min, respectively. This was achieved with a mobile phase consisting of 0.2% ammonia-acetonitrile (20:80, v/v) at a flow rate of 1 mL/min on a Chiralcel OJ RH column. A linear response function was established for the range of concentrations 0.1-10 ng/mL (r >0.998) for each enantiomer. The intra- and inter-day precision values for both enantiomers met the acceptance criteria. Both enantiomers were stable in a set of stability studies, viz. bench-top, auto-sampler, freeze-thaw cycles and long-term. The current assay was successfully applied to a pharmacokinetic study to quantitate AML enantiomers following oral administration of 10 mg AML tablet to humans.

Simultaneous determination of atorvastatin, amlodipine, ramipril and benazepril in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

A rapid, simple, sensitive and specific LC-MS/MS method has been developed and validated for the simultaneous estimation of atorvastatin (ATO), amlodipine (AML), ramipril (RAM) and benazepril (BEN) using nevirapine as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. Analytes and IS were extracted from plasma by simple liquid-liquid extraction technique using ethyl acetate. The reconstituted samples were chromatographed on C(18) column by pumping 0.1% formic acid-acetonitrile (15:85, v/v) at a flow rate of 1 mL/min. A detailed validation of the method was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 0.26-210 ng/mL for ATO; 0.05-20.5 ng/mL for AML; 0.25-208 ng/mL for RAM and 0.74-607 ng/mL for BEN with mean correlation coefficient of ≥0.99 for each analyte. The intra-day and inter-day precision and accuracy results were well with in the acceptable limits. A run time of 2.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The developed assay method was successfully applied to a pharmacokinetic study in human male volunteers.

[Percutaneous penetration ability of dexamethasone-amlodipine besylate compound gel and its effect on survival of ischemic random skin flap].

OBJECTIVE: Dexamethasone (DXM) can regulate the balance of neutrophil and cytokine and enhance the ischemia-reperfusion tolerance of the skin flap; amlodipine besylate (AB) can selectively expand the peripheral blood vessels and relieve the vascular smooth muscle spasm. To investigate the percutaneous penetration ability of DXM/AB compound gel and evaluate its effect on survival of ischemic skin flap. METHODS: Sodium carboxymethylcellulose was used to make blank gel, which was mixed in DXM, AB, azone (AZ), and propylene glycol (PG) respectively to make the compound gel containing 0.3%DXM/0.5%AB only (group D), the compound gel containing 3%AZ/2%PG, 3%AZ, and 2%PG (groups A, B, and C), the 0.3%DXM gel containing 3%AZ/2%PG (group E), the 0.5%AB gel containing 3%AZ/2%PG (group F). The accumulative penetration of DXM and AB in compound gel, 0.3%DXM gel, 0.5%AB gel through excised rat skin and its penetration within flap tissue were investigated by ultraviolet spectrophotometry. Fifty SD rats were selected to make 100 mm x 10 mm random flap at the back, and were randomly divided into 5 groups according to different gels which were used to treat flaps (n = 10): compound gel group (group A1), 0.3%DXM gel group (group B1), 0.5%AB gel group (group C1), blank gel group (group D1), and peritoneal injection of DXM (5 mg/kg) and AB (2 mg/kg) (group E1). The survival area of ischemic random skin flap was measured on the 7th day by planimetry. Twenty-four SD rats were selected to make 100 mm x 10 mm random flap at the back, and were randomly divided into 2 groups (n = 12). The accumulative penetration of DXM and AB within skin flap were also detected at 2 and 6 hours after application of 2 g of compound gel containing 3%AZ/2%PG (group A2) and peritoneal injection AB (2 mg/kg) / DXM (5 mg/kg) (group B2). RESULTS: The accumulative penetration of DXM and AB in compound gel were increased in time-dependent manner (P < 0.05), and it was the highest in group A, and was significantly higher than that in group B and group C (P < 0.01), but there was no significant difference when compared with group E or group F (P > 0.05). The accumulative penetration of DXM and AB in groups A, B, and C were significant higher than that in group D (P < 0.05). After 7 days, the survival area of flaps in groups A1, B1, C1, D1, and E1 were (695.0 +/- 4.6), (439.3 +/- 7.1), (477.5 +/- 14.5), (215.2 +/- 3.8), and (569.4 +/- 9.7) mm2, respectively; group A1 was significantly higher than other groups (P < 0.05). After 2 and 6 hours, the quantities of DXM and AB in skin flap of group A2 were significantly higher than that of group B2 (P < 0.05). CONCLUSION: In 0.3%DXM/0.5%AB compound gel, DXM and AB might penetrate into skin tissue, which could significantly increase the survival area of ischemic skin flap.

Direct quantitative determination of amlodipine enantiomers in urine samples for pharmacokinetic study using on-line coupled isotachophoresis-capillary zone electrophoresis separation method with diode array detection.

The present work illustrates possibilities of column-coupling capillary electrophoresis (CE-CE) combined with chiral selector (2-hydroxypropyl-beta-cyclodextrin, HP-beta-CD) and fiber-based diode array detection (DAD) for the direct quantitative enantioselective determination of trace drug (amlodipine, AML) in biological multicomponent ionic matrices (human urine). Capillary isotachophoresis (ITP) served as an ideal injection technique in CE-CE. Moreover, the ITP provided an effective on-line sample pretreatment prior to the capillary zone electrophoresis (CZE) separation. Enhanced separation selectivity due to the combination of different separation mechanisms (ITP vs. CZE-HP-beta-CD) enabled to obtain pure zones of the analytes, suitable for their detection and quantitation. The DAD, unlike single wavelength UV detection, enabled to characterize the purity (i.e. spectral homogeneity) of the analytes zones. A processing of the raw DAD spectra (the background correction and smoothing procedure) was essential when a trace analyte signal was evaluated. Obtained results indicated pure (i.e. spectrally homogeneous) zones of interest confirming effective ITP-CZE separation process. The proposed ITP-CZE-DAD method was characterized by favorable performance parameters (sensitivity, linearity, precision, recovery, accuracy, robustness, selectivity) and successfully applied to an enantioselective pharmacokinetic study of AML.

Effect of ABCB1 (MDR1) haplotypes derived from G2677T/C3435T on the pharmacokinetics of amlodipine in healthy subjects.

AIM: We aimed to investigate the effect of the ABCB1 gene on the pharmacokinetics of amlodipine. METHODS: Based on polymorphisms of the ABCB1 gene at positions 2677 and 3435, 26 healthy male participants were divided into three groups: subjects with 2677GG/3435CC (n = 9), 2677GT/3435CT (n = 9) and 2677TT/3435TT (n = 8). After a single-dose administration of 5 mg amlodipine, plasma concentrations of amlodipine were measured and its pharmacokinetic characteristics were compared according to ABCB1 genotype. RESULTS: The area under the plasma concentration-time curve was significantly lower in subjects with 2677TT/3435TT (140.8 +/- 35.6 ng h(-1) ml(-1)) and 2677GT/3435CT (149.8 +/- 40.1 ng h(-1) ml(-1)) than in those with 2677GG/3435CC (208.6 +/- 39.2 ng h(-1) ml(-1)) [95% confidence interval (CI) on the difference, 2677GG/3435CC vs. 2677GT/3435CT 12.0, 105.6, P < 0.01; 2677GG/3435CC vs. 2677TT/3435TT 19.6, 116.0, P < 0.01; 2677GT/3435CT vs. 2677TT/3435TT - 39.2, 57.2, P > 0.05]. The peak plasma concentrations were highest in subjects with 2677GG/3435CC (3.8 +/- 0.5 ng ml(-1)), lower in subjects with 2677GT/3435CT (3.2 +/- 0.5 ng ml(-1)) and 2677TT/3435TT (2.7 +/- 0.5 ng ml(-1)) in rank and showed a significant difference between those with 2677GG/3435CC and with 2677TT/3435TT (95% CI on the difference 0.4, 2.0, P < 0.01). However, the oral clearance was higher in subjects with 2677TT/3435TT (37.7 +/- 10.2 l h(-1)) than in those with 2677GT/3435CT (35.7 +/- 9.9 l h(-1)) and with 2677GG/3435CC (24.8 +/- 5.4 l h(-1)) and exhibited a significant difference between ABCB1 genotype groups (95% CI on the difference, 2677GG/3435CC vs. 2677GT/3435CT - 21.5, - 0.3, P < 0.05; 2677GG/3435CC vs. 2677TT/3435TT - 23.8, - 2.0, P < 0.05). CONCLUSION: Amlodipine pharmacokinetics was affected by the genetic polymorphisms of the ABCB1 gene in humans. These findings may provide a plausible explanation for interindividual variation in the disposition of amlodipine, although our study could not explain the exact mechanism(s) by which the polymorphic ABCB1 gene paradoxically reduces the plasma levels of amlodipine. Further evaluation is thus warranted.

Effect of stealthy liposomal topotecan plus amlodipine on the multidrug-resistant leukaemia cells in vitro and xenograft in mice.

BACKGROUND: Multidrug resistance (MDR) is a major obstacle to successful cancer chemotherapy as the over-expressed MDR protein acts as an efflux pump, which leads to a reduction in the uptake of the anticancer agent by tumour cells. We combined topotecan and amlodipine together into the stealthy liposomes, in which amlodipine was applied as a MDR reversing agent to overcome the resistance. MATERIALS AND METHODS: Cytotoxicity, apoptosis and the signalling pathway assays were performed on human chronic myelogenous leukaemia K562, promyelocytic leukaemia HL-60 and MDR HL-60 cells, respectively. Pharmacokinetics and antitumour activity studies were performed on normal Kunming mice and female BALB/c nude mice with MDR HL-60 xenografts, respectively. RESULTS: Topotecan alone was effective in inhibiting the growth of non-resistant leukaemia cells, K562 and HL-60 cells but not the growth of MDR HL-60 cells. The resistance of topotecan in MDR HL-60 cells was potently reversed by the addition of amlodipine. Moreover, amlodipine enhanced the apoptosis-inducing effect of topotecan synergistically. Apoptosis was through activating caspases in a cascade: first, the initiator caspase 8 and then effectors caspase 3/7 (total activity of caspases 3 and 7) were activated. Being encapsulated into the stealthy liposomes with an acidic internal medium, topotecan existed dominantly in an active lactone species, which was reversibly changed from an inactive carboxylate form via a pH-dependent reaction. After administration of stealthy liposomes to mice, the blood exposure of the lactone form was evidently increased and extended. The antitumour effects in the MDR HL-60 xenografted tumour were stealthy liposomal topotecan (SLT) plus amlodipine > SLT > un-encapsulated topotecan > blank control. CONCLUSIONS: The enhanced antitumour activity in the MDR HL-60 cells by the SLT plus amlodipine could be owing to multiple reasons: (a) synergistic apoptosis inducing effect, (b) reversing MDR by amlodipine and (c) increasing the availability of active lactone of topotecan by the stealthy liposomes. The apoptosis induced by amlodipine is through caspase 8 and then the 3/7 signalling pathway.

Population analyses of amlodipine in patients living in the community and patients living in nursing homes.

OBJECTIVE: Our objective was to determine the effects of age, sex, and morbidity on the apparent oral clearance (CL/F) of amlodipine. METHODS: Population pharmacokinetic analyses were performed on data from 211 patients receiving oral racemic amlodipine (dose of 7.2 +/- 3.6 mg/d [mean +/- SD]) on a long-term basis. Of the patients, 105 were men, with a mean age of 72 +/- 13 years and lean body weight (LBW) of 60.7 +/- 7.6 kg, and 106 were women, with a mean age of 79 +/- 11 years and LBW of 44.2 +/- 6.0 kg; 119 lived in the community, 20 in assisted living facilities, and 72 in nursing homes. Amlodipine was measured by liquid chromatography-tandem mass spectrometry. Population analyses were performed by use of NONMEM with sex, age, race, living site, alcohol intake, and concomitant medications considered as covariates. The significance of covariates was determined by likelihood ratio tests. RESULTS: Female sex and living in a nursing home were associated with a faster CL/F compared with men and community-dwelling patients, respectively. The mean CL/F was 7.83 +/- 0.50 mL.min(-1).kg(-1) (LBW) in women compared with 6.31 +/- 1.01 in men and 8.68 +/- 1.00 mL.min(-1).kg(-1) in nursing home residents compared with 6.32 +/- 1.17 in community-dwelling patients. Increasing age was associated with decreasing CL/F only in community-dwelling patients and residents of assisted living facilities. CONCLUSIONS: In middle-aged and very old (>80 years) patients, amlodipine CL/F was faster in women compared with men and was faster in nursing home residents compared with community-dwelling patients, with increasing age decreasing CL/F only in community-dwelling patients and residents of assisted-living facilities.