Adsorptive stripping voltammetry of nicardipine at a HMDE; determination of trace levels nicardipine in blood and urine

From mercury to nanosensors: Past, present and the future perspective of electrochemistry in pharmaceutical and biomedical analysis

Polarography was the first developed automated method of voltage-controlled electrolysis with dropping mercury electrode (DME). Then, hanging mercury drop and static mercury drop electrodes were added as an alternative indicator electrode. In this way, polarography turned formally into voltammetry with mercury electrodes in the electroreduction way. Solid electrodes such as noble metal and carbon based electrodes can be used for the investigation of the compounds for both oxidation and reduction directions, which is called voltammetry. The voltammetric and polarographic techniques are more sensitive, reproducible, and easily used electroanalytical methods that can be alternative to more frequently used separation and spectrometric methods. Furthermore, in some cases there is a relationship between voltammetry and pharmaceutical samples, and the knowledge of the mechanism of their electrode reactions can give a useful clue in elucidation of the mechanism of their interaction with living cells. The voltammetric and polarographic analysis of drugs in pharmaceutical preparations are by far the most common use of electrochemistry for analytical pharmaceutical problems. Recent trends and challenges in the electrochemical methods for the detection of DNA hybridization and pathogens are available. Low cost, small sample requirement and possibility of miniaturization justifies their increasing development.

Simultaneous determination of five 1,4-dihydropyridines in pharmaceutical formulations by high-performance liquid chromatography–amperometric detection

A high-performance liquid chromatographic method with electrochemical detection was developed for the simultaneous determination of five 1,4-dihydropyridines: amlodipine, nitrendipine, felodipine, lacidipine and lercanidipine. These drugs are widely used in the treatment of hypertension, angina pectoris and the therapy of cerebrovascular spasms of various origins. The chromatographic separation was performed on a Supelcosil LC ABZ + Plus C18 column with a mobile phase consisting of acetonitrile-10 mM acetate buffer (72:28, v/v) at a flow rate of 1 ml/min. The temperature was set at 30 +/- 0.2 degrees C. The amperometric detector, equipped with a glassy carbon electrode was operated at +1100 mV versus Ag/AgCl in the direct current mode. Under these chromatographic conditions, the drugs eluted in less than 12 min. The method showed to be linear over the range 4.5-15 microg/ml with a within-day and day-to-day repeatabilities in terms of R.S.D. lower than 15%, an accuracy greater than 98% and detection limits varying from 90 ng/ml (amlodipine) to 1.55 microg/ml (nitrendipine). The method was successfully applied to commercially available pharmaceuticals with relative errors lower than 5%. The validity of the method was examined comparing the results obtained with those of HPLC with photometric detection.

A simple method for nicardipine hydrochloride quantification in plasma using solid-phase extraction and reversed-phase high-performance liquid chromatography

A simple and sensitive reversed-phase liquid chromatography method was developed and validated for the determination of nicardipine hydrochloride (NC) in rabbit plasma. Nicardipine hydrochloride and nimodipine, used as internal standard, were initially extracted from plasma by a rapid solid-phase extraction using C(18) cartridges. After extraction, nicardipine hydrochloride was separated by HPLC on a C(18) column and quantified by ultraviolet detection at 254 nm. A mixture of acetonitrile-0.02 M sodium phosphate buffer-methanol (45:40:15) with 0.2% of triethylamine of pH of 6.1 was used as mobile phase. The mean (+/-SD) extraction efficiency of NC was 77.56 +/- 5.4, 84.23 +/- 4.32 and 83.94 +/- 3.87% for drug concentrations of 5, 25 and 100 ng/mL, respectively. The method proved to be linear in the range of 5-100 ng/mL with a regression coefficient of 0.9993. The relative standard deviations of intra- and inter-day analysis for NC in plasma were 3.26-6.52% (n = 5) and 4.71-9.38% (n = 5), respectively. The differences of the mean value measured from the concentration prepared, expressed in percentages (bias percentage), were only - 5.2, 0.4 and 0.8% at NC 5, 25 and 50 ng/mL, which confirmed the accuracy of the method. The analytical technique was used to determine NC plasma concentration after drug oral administration to rabbits. The results inferred that NC is rapidly absorbed in rabbits and has a short half-life (t(1/2) = 1.34 h).

A high-performance liquid chromatographic method for the determination of nicardipine in plasma and its application to pharmacokinetics in humans

A simple and sensitive reversed-phase liquid chromatographic method has been developed and validated for the analysis of nicardipine in human plasma and the study of the pharmacokinetics of the drug in human body. Nicardipine and nimodipine (internal standard) in plasma were extracted with hexane-butanol (12:1, v/v) after addition of borate buffer (0.5 mol/mL, pH = 9.0), and then measured by HPLC using a Hypersil C18 column as stationary phase and acetonitrile--KH2PO4 buffer (0.015 M, pH = 5.5)--triethylamine as mobile phase. Nicardipine was quantified by ultraviolet absorbance at 236 nm. The method proved to be linear in the clinical range of 5-200 ng/mL with a regression coefficient of 0.9998. The lower limit of detection of nicardipine in plasma was 2.5 ng/mL. Intra- and inter-day coefficients of variation of assay for nicardipine in plasma were 3.5-5.4% (n = 7) and 5.2-6.4% (n = 5), respectively. The recovery of nicardipine was 92.8-100.8% for plasma. The method has been used to determine nicardipine in plasma samples from 10 volunteers and provided data on the pharmacokinetics of the drug. The results inferred that nicardipine is absorbed rapidly and has a relatively short half-life in healthy individuals. The data obtained was fitted with a 3P87 program to study the pharmacokinetics. The results showed that the disposition of nicardipine was conformed to a two-compartment open model with Tmax = 1.6 +/- 0.3 h, Cmax = 109.8 +/- 38.7 ng/mL, T1/2 = 5.35 +/- 2.28 h and AUC0-->infinity = 322.1 +/- 69.6 ng/h/mI.