Determination of nifedipine in human serum by gas chromatography-mass spectrometry: validation of the method and its use in bioavailability studies

Utility of N-Bromosuccinimide-Water Combination as a Green Reagents for a Validated Indirect Spectrophotometric Determination of Some Antihypertensive Drugs: An Application to Their Monitoring in Marketed Tablets and Capsules

BACKGROUND

Analytical tests were conducted to investigate the use of N-bromosuccinimide (NBS) as an important, safe analytical reagent for the spectrophotometric detection of therapeutically significant dihydropyridine-based calcium antagonists (DHP), namely nifedipine (NIF) and amlodipine (AML), which have been demonstrated to possess antioxidant activity in vivo and to reduce the intracellular production of reactive oxygen species (ROS). Following the reaction of DHP and NBS in acidic media, the excess NBS was evaluated for the first time by its interaction with P-aminophenol (PAP), which produced a violet-colored product that was detected at 556 nm.

OBJECTIVE

The analytical method was performed and validated since different variables disturbing the reaction (concentration of reagent, type and concentration of the selected acid, reaction time and the diluting solvents) were carefully studied and optimized.

METHODS

The stoichiometry of the applied reaction was determined by Job's method of continuous variation. Monitoring of these drug dosage forms' content uniformity is a first tool or evidence for their efficacy and safety after their administration.

RESULTS

Beer's law was obeyed in the concentration range 1.25-11.0 µg/mL for NIF and 1.25-10.0 µg/mL for AML. The calculated limit of detection (LODs) and limit of quantification (LOQs) for NIF and AML were 0.220, 0.155 µg/mL and 0.519, 0.735 µg/mL, respectively. The precision of the applied method was satisfactory; the RSDs did not exceed 2%. Two greenness assessment tools, the Green Analytical Procedure Index (GAPI) and Analytical Greenness Metric for Sample Preparation (AGREEprep) were used for measuring the environmental friendliness of the recommended method.

CONCLUSION

The micro-determinations of content uniformity for NIF and AML in their pharmaceutical dosage forms were extremely comparable with those from official and validated procedures.

HIGHLIGHTS

A validated indirect spectrophotometric method for accurate quantification of some 1,4-dihydropyridine drugs using NBS with the aid of PAP. Monitoring of NIF and AML dosage forms' content uniformity as a first tool or evidence for their efficacy and safety after their administration. Greenness evaluation tools, GAPI and AGREEprep, for measuring the environmental friendliness of the recommended method.

Analysis of nifedipine in human plasma and amniotic fluid by liquid chromatography-tandem mass spectrometry and its application to clinical pharmacokinetics in hypertensive pregnant women

Nifedipine is a dihydropyridine calcium channel blocker used for the treatment of hypertension in pregnant women. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for analysis of nifedipine in human plasma and amniotic fluid. Separation of nifedipine and nitrendipine (IS) was performed using a LiChroCART(®) RP-Select B column and a mixture of water:acetonitrile:glacial acetic acid (30:70:0.5 v/v) as the mobile phase. Aliquots of 500μL of biological samples were extracted at pH 13 using dichloromethane:n-pentane (3:7 v/v). The validated method was applied to a study of the pharmacokinetics of nifedipine in human plasma and amniotic fluid samples collected up to 12h after administration of the last slow-release nifedipine (20mg/12h) dose to 12 hypertensive pregnant women. The estimated pharmacokinetic parameters of nifedipine showed a mean AUC(0-12) of 250.2ngh/mL, ClT/F of 89.2L/h, Vd/F of 600.0L and t1/2 5.1h. The mean amniotic fluid/plasma concentration ratio was 0.05. The methods proved to be highly sensitive by showing a lower quantification limit of 0.1ng/mL for both matrices. And this study reports for the first time the complete development and validation of the method to quantify nifedipine in amniotic fluid using LC-MS-MS.

Determination of nifedipine in human plasma by ultra performance liquid chromatography-tandem mass spectrometry and its application in a pharmacokinetic study

A fast, sensitive and selective ultra performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method was developed for the determination of nifedipine in human plasma. Nitrendipine was used as the internal standard. The sample preparation employed liquid-liquid extraction with a mixture of n-hexane-diethyl ether (1:3, v/v). Chromatographic separation was performed on an ACQUITY UPLC™ BEH C(18) column. The mobile phase was composed of acetonitrile-10 mmol/L ammonium acetate (75:25, v/v) with a flow rate of 0.20 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. A high throughput was achieved with a run time of 1.4 min per sample. The linear calibration curves were obtained in the concentration range of 0.104-52.0 ng/mL (r(2)≥ 0.99) with a lower limit of quantification (LLOQ) of 0.104 ng/mL. The intra- and inter-day precision (relative standard deviation, RSD) values were below 15% and the accuracy (relative error, RE) was -4.0% to 6.2% at three quality control levels. The method was fully validated and successfully applied to a clinical pharmacokinetic study of nifedipine sustained-release tablet in healthy male volunteers.

Rapid and simultaneous determination of nifedipine and dehydronifedipine in human plasma by liquid chromatography-tandem mass spectrometry: Application to a clinical herb-drug interaction study

Nifedipine (NIF), a calcium channel antagonist, is metabolized primarily by cytochrome P450 (CYP3A4) to dehydronifedipine (DNIF). As such, NIF is often used as a probe drug for determining CYP3A4 activity in human studies. A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated to simultaneously determine NIF and DNIF in human plasma using nitrendipine as the internal standard (IS). After extraction of the plasma samples by ether-n-hexane (3:1, v/v), NIF, DNIF and the IS were subjected to LC/MS/MS analysis using electro-spray ionization (ESI). Chromatographic separation was performed on a Hypersil BDS C(18) column (50 mm x 2.1 mm, i.d., 3 microm). The method had a chromatographic running time of approximately 2.5 min and linear calibration curves over the concentrations of 0.5-100 ng/mL for NIF and DNIF. The recoveries of the one-step liquid extraction method were 81.3-89.1% for NIF and 71.6-80.4% for DNIF. The lower limit of quantification (LLOQ) of the analytical method was 0.5 ng/mL for both analytes. The intra- and inter-day precision was less than 15% for all quality control samples at concentrations of 2, 10, and 50 ng/mL. The validated LC/MS/MS method has been successfully used to study pharmacokinetic interactions of NIF with the herbal antidepressant St. John's wort in healthy volunteers. These results indicated that the developed LC/MS/MS method was efficient with a significantly shorter running time (2.5 min) for NIF and DNIF compared to those methods previously reported in the literature. The presented LC/MS/MS method had acceptable accuracy, precision and sensitivity and was used in a clinical pharmacokinetic interaction study of NIF with St. John's wort, a known herbal inducer of CYP3A4. St. John's wort was shown to induce NIF metabolism with increased plasma concentrations of DNIF.

Photostability studies for micellar liquid chromatographic determination of nifedipine in serum and urine samples

Nifedipine is a photosensitive compound that is converted into its 4-(2-nitrophenyl) pyridine and 4-(2-nitrosophenyl) pyridine homologue. In order to obtain the most adequate conditions for handling nifedipine solutions in the analytical laboratory, a number of studies on the decomposition of this compound were performed. A simple micellar liquid chromatographic procedure was described to determine nifedipine in different biological matrices such as serum and urine, and to control its decomposition. To perform the analysis, nifedipine was dissolved in 0.1 m SDS at pH 3 and chromatographed using a mobile phase containing 0.125 m SDS-3% pentanol, pH 3 on a C18 column and UV detection at 235 nm. The chromatographic analysis time was 8 min. The response of the drug for both biological matrices was linear in the 1-100 microg/mL range, with r2>0.997 at all times. Repeatability, intermediate precision (CV, %) and limits of quantification and detection (ng/mL) were 0.19, 4.3, 104 and 31 in serum and 0.81, 2.1, 136 and 41 in urine. The method developed here does not show interferences or matrix effects produced by endogenous compounds. Micellar media and mobile phases have the advantage of stabilising the compounds, thus preventing photodegradation and allowing the direct injection of biological samples.

Extractive spectrophotometric methods for the determination of nifedipine in pharmaceutical formulations using bromocresol green, bromophenol blue, bromothymol blue and eriochrome black T

Four simple, sensitive and accurate spectrophotometric methods have been developed for the determination of nifedipine in pharmaceutical formulations. These methods are based on the formation of ion-pair complexes of amino derivative of the nifedipine with bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB) and eriochrome black T (EBT) in acidic medium. The coloured products are extracted with chloroform and measured spectrophotometrically at 415 nm (BCG, BPB and BTB) and 520 nm (EBT). Beer's law was obeyed in the concentration range of 5.0-32.5, 4.0-37.5, 6.5-33.0 and 4.5-22.5 microg ml(-1) with molar absorptivity of 6.41 x 10(3), 4.85 x 10(3), 5.26 x 10(3) and 7.69 x 10(3) l mol(-1) cm(-1) and relative standard deviation of 0.82%, 0.72%, 0.66% and 0.68% for BCG, BPB, BTB and EBT methods, respectively. These methods have been successfully applied for the assay of drug in pharmaceutical formulations. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.

Cathodic adsorptive stripping square-wave voltammetric determination of nifedipine drug in bulk, pharmaceutical formulation and human serum

Nifedipine is a calcium-channel antagonist drug used in the management of angina pectoris and hypertension through inhibition of calcium influx. A fully validated sensitive cathodic adsorptive stripping square-wave voltammetry procedure was optimized for the determination of the drug at trace levels. The procedure was based on the reduction of the nitrophenyl group after the interfacial accumulation of the drug onto a hanging mercury drop electrode in Britton-Robinson buffer of pH 11.0. The optimal conditions of the procedure were found to be: accumulation potential=-0.9 V vs. Ag/AgCl/KCl(s)), accumulation time=30 s, scan increment=10 mV, pulse amplitude=50 mV and frequency=120 Hz. Under these conditions, a well-defined peak was obtained; its peak current showed a linear dependence on drug concentration in the range of 2x10(-9)-2x10(-7) mol L(-1) bulk nifedipine. The mean recoveries based on eight replicate measurements for 1x10(-8) and 5x10(-8) mol L(-1) bulk nifedipine solutions were 98.46+/-0.86% and 98.23+/-0.92%, respectively. A detection limit of 3.42x10(-10) mol L(-1) bulk nifedipine was achieved. The procedure was successfully applied for assay of the drug in tablets and spiked human serum with mean recoveries of 101.95+/-1.42% and 98.70+/-0.63%, respectively. The limit of detection of the drug in spiked human serum was found to be 3.90x10(-10) mol L(-1).

Determination of nifedipine in human plasma by square wave adsorptive stripping voltammetry

A simple, sensitive and selective square-wave adsorptive stripping voltammetric method has been developed and validated for the determination of nifedipine (NIF) in plasma. The assay was performed after single extraction of NIF from alkalinised plasma into organic phase. The adsorption behaviour of NIF on a hanging mercury drop electrode (HMDE) was explored by square-wave and cyclic voltammetry. The drug was accumulated at HMDE and a well-defined peak was obtained at -730 mV versus Ag/AgCl in borate buffer of pH 9.0 including 0.01 M KCl. The linear concentration range was 2.89 x 10(-9) M-3.61 x 10(-7) M (1.00-125.01 ng ml(-1)) when using 30 s accumulation time at -300 mV. Limit of detection and limit of quantification were 1.21 x 10(-9) M (0.42 ng ml(-1)) and 2.89 x 10(-9) M (1.00 ng ml(-1)) respectively. The intra-day relative standard deviation (RSD) ranged from 1.93 to 4.12% at three concentrations and the inter-day RSDs varied from 2.53 to 6.68%. The method was applied, to the plasma of pregnant women suffering from pregnancy induced hypertension, for the determination of NIF. The percentage recoveries varied from 96.26 to 99.49%. It has been shown that NIF could be determined in the presence of its main metabolite (dehydronifedipine) by the developed method.

Hydrolytic degradation of nitrendipine and nisoldipine

The development of a new HPLC-UV diode array procedure applied to follow the hydrolytic degradation of two well-known 4-nitrophenyl-1,4-dihydropyridine derivatives, nitrendipine and nisoldipine is reported. Hydrolysis of each drug were carried out in ethanol/Britton-Robinson buffer at different pHs, stored into amber vials at controlled temperatures of 40, 60 and 80 degrees C and periodically sampled and assayed by HPLC. Nitrendipine degradation in different parenteral solutions was also evaluated. The HPLC procedure exhibited an adequate selectivity, repeatability (<1%) and reproducibility (<2%). The recoveries were higher than 98% with CV of 1.13 and 1.54% for nitrendipine and nisoldipine, respectively. A significant degradation was observed at alkaline pH (>pH 8) with a first order kinetic for both drugs. At pH 12, 80 degrees C, k values of 3.56x10(-2) x h(-1) and 2.22x10(-2) for nitrendipine and nisoldipine, respectively were obtained. Also, activation energies of 16.8 and 14.7 kcal x mol(-1) for nitrendipine and nisoldipine, respectively, were calculated. Furthermore, from the results obtained from hydrolytic degradation in different solutions for parenteral use, we can affirm that solutions significantly increased the degradation of nitrendipine. In conclusion, the HPLC proposed procedure exhibited adequate analytical requirements to be applied to the hydrolytic degradation studies of nitrendipine and nisoldipine. Furthermore, all tested parenteral solutions significantly increased the hydrolytic degradation of nitrendipine, the composition of solution being a relevant factor.

Spectrophotometric method for the determination of nifedipine with 4-(methylamino)phenol and potassium dichromate

A new simple, sensitive and reproducible spectrophotometric method for the determination of nifedipine in pure and dosage forms has been proposed. It is based on the reduction of nifedipine with Zn/NNH4Cl, followed by coupling with N-methyl-1,4-benzoquinoneimine--the oxidation product of 4-(methylamino)phenol, to give a chromophore which absorbed maximally at 525 nm. The experimental conditions were optimised and Beer's law was obeyed over the concentration range of 5-175 microg ml(-1). The molar absorptivity, detection limit, recovery and RSD were found to be 1.9 x 10(3) l mol(-1) cm(-1), 1.1 microg ml(-1), 99.7-100.5% and 0.3-0.8%, respectively. The proposed method was compared favourably with the official B.P. method.

High-performance liquid chromatography with amperometric detection applied to the screening of 1,4-dihydropyridines in human plasma

A high-performance liquid chromatographic method with electrochemical detection has been developed for the determination of six 1,4-dihydropyridines: nifedipine, nimodipine, nisoldipine, nicardipine, felodipine and lacidipine. The chromatographic separation was performed using a Supelcosil LC-ABZ+Plus C18 column. A mobile phase of methanol-water (70:30), containing 2 mM CH3COOH-CH3COONa at a flow-rate of 1 ml/min and a pH of 5.0, was used. The temperature was optimized at 30+/-0.2 degrees C. The amperometric detector, equipped with a glassy carbon electrode, was operated at 1000 mV versus Ag/AgCl in the direct current mode. The method was applied to the determination of these compounds at ng/ml concentrations, obtaining intra-day reproducibilities of lower than 5.0% in terms of relative standard deviations and detection limits ranging from 16 to 44 ng/ml. The method was applied to the screening of 1,4-dihydropyridines in spiked plasma samples, with a total elution time of lower than 18 min, obtaining the best recoveries for nimodipine and felodipine (91 and 88%, respectively). These recoveries together with the low detection limits achieved allow its application to the analysis of these drugs in human plasma.

Simultaneous determination of nifedipine and dehydronifedipine in human plasma by liquid chromatography-tandem mass spectrometry

Quantitative analysis of therapeutic compounds and their metabolites in biological matrix (such as plasma, serum or urine) nowadays requires sensitive and selective methods to allow the determination of concentrations in the ng/ml range. A new on-line LC-MS-MS method using atmospheric pressure chemical ionisation (APCI) as interface for the simultaneous determination of nifedipine (NIF) and its metabolite in human plasma, dehydronifedipine (DNIF) has been developed. The compounds were extracted from plasma using solid-phase extraction (SPE) on disposable extraction cartridges (DECs). The SPE operations were performed automatically by means of a sample processor equipped with a robotic arm (ASPEC system). The DEC filled with phenyl modified silica was first conditioned with methanol and water. The washing step was performed with water. Finally, the analytes were successively eluted with methanol and water. The liquid chromatographic (LC) separation of NIF and DNIF was achieved on a RP-18 stationary phase (4 microm). The mobile phase consisted of methanol-50 mM ammonium acetate solution (50:50, v/v). The LC was then coupled to tandem mass spectrometry with an APCI interface in the positive ion mode. The method developed was validated. The absolute recoveries evaluated over the whole concentration range were 95+/-2% and 95+/-4% for NIF and DNIF, respectively. The method was found to be linear in the 0.5-100 ng/ml concentration range for the two analytes (r2 = 0.999 for both NIF and DNIF). The mean R.S.D. values for repeatability and intermediate precision were 2.9 and 3.0% for NIF and 2.2-4.7% for the metabolite. The method developed was successfully used to investigate the plasma concentration of NIF and DNIF in the pharmacokinetic studies.

Determination of nifedipine in human plasma by flow-injection tandem mass spectrometry

For use in clinical studies, a fast and sensitive assay method was developed for the determination of nifedipine in human plasma samples. The assay method is based on tandem mass spectrometry detection (HPLC-MS-MS). The effect of flow injection as well as HPLC separation on the results of the nifedipine determination were evaluated. The limit of quantification is 0.5 ng/ml and the accuracy (as determined by spiking recovery) was found to be good.

Involvement of the calcium inward current in cardiac impulse propagation: induction of unidirectional conduction block by nifedipine and reversal by Bay K 8644

In general, the fast sodium inward current (INa) is regarded as the main inward current ensuring fast and safe excitation of the normally polarized working myocardium. However, under conditions of locally delayed excitation in the millisecond range, the slow inward current (ICa) might additionally contribute to the success of impulse propagation. This hypothesis was tested in patterned growth cultures of neonatal rat ventricular myocytes, which consisted of narrow cell strands connected to large rectangular cell monolayers, where INa or ICa could be modified in the narrow cell strand adjacent to the expansion by a microsuperfusion system. As assessed during antegrade (strand-->expansion) propagation under control conditions using a system for multiple site optical recording of transmembrane voltage (MSORTV), this cell pattern gave either rise to local activation delays at the expansion ranging from 0.5 to 4 ms (dcontrol), or it induced undirectional conduction blocks (UCBs) in the antegrade direction. Irrespective of the size of dcontrol, suppression of the sodium current with tetrodotoxin confined to the cell strand adjacent to the expansion invariably induced UCB in the antegrade direction. If dcontrol was > 1 ms, UCB could also be elicited by suppression of ICa alone with nifedipine. Conversely, if UCB was present under control conditions, the inclusion of Bay K 8644 in the microsuperfusion established successful bidirectional conduction. These results suggest that ICa can be critically important for the success of impulse propagation across abrupt expansions of excitable tissue even if INa is not concurrently depressed.