Determination of diltiazem and its main metabolites in human plasma by automated solid-phase extraction and high-performance liquid chromatography: a new method overcoming instability of the compounds and interference problems

Detection limit enhancement of antiarrhythmic drugs in human plasma using capillary electrophoresis with dispersive liquid–liquid microextraction and field-amplified sample stacking method

Background: A new capillary zone electrophoresis (CZE) with ultraviolet detection method has been developed and validated for the analysis of four antiarrhythmic drugs in human plasma samples. Methods: In this study, a dispersive liquid–liquid microextraction (DLLME) coupled with field-amplified sample stacking (FASS) was employed for biological samples clean-up and sensitivity enhancement in CZE. Results: Under optimum DLLME-FASS-CZE conditions, enhancement factors were in the range of 157–314. The method was validated over the concentration range of 20–800 ng/ml in human plasma. Inter- and intra-day precision and the accuracy were less than 20%; the detection limits ranged from 2.5 to 4.7 ng/ml. Furthermore, the validated method was successfully applied to the detection of studied drugs in patients’ plasma samples.

An Overview of Analytical Determination of Diltiazem, Cimetidine, Ranitidine, and Famotidine by UV Spectrophotometry and HPLC Technique

This review article recapitulates the analytical methods for the quantitative determinations of diltiazem and three H2receptor antagonists (cimetidine, ranitidine, and famotidine) by one of the spectroscopic technique (UV spectrophotometery) and separation technique such as high-performance liquid chromatography (HPLC). The clinical and pharmaceutical analysis of these drugs requires effective analytical procedures for quality control, pharmaceutical dosage formulations, and biological fluids. An extensive survey of the literature published in various analytical and pharmaceutical chemistry-related journals has been compiled in its review. A synopsis of reported spectrophotometric and high-performance liquid chromatographic methods for individual drug is integrated. This appraisal illustrates that majority of the HPLC methods reviewed are based on the quantitative analysis of drugs in biological fluids, and they are appropriate for therapeutic drug monitoring purpose.

Nonlinear calibrations on the assay of dilitiazem and two of its metabolites from plasma samples by means of liquid chromatography and ESI/MS(2) detection: application to a bioequivalence study

The assay of diltiazem (DLTZ) and its active metabolites desacetyldiltiazem (DAcD) and desmethyldiltiazem (DMeD) in plasma samples was achieved by means of an HPLC/(ESI)MS(2) method. The diastereoisomer of diltiazem, namely {(2R,3S)-5-[2-(dimethylamino)ethyl]-2-(4-methoxyphenyl)-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepin-3-yl acetate} was used as internal standard (IS). Sample preparation was based on protein precipitation by means of organic solvent addition (acetonitrile). The isocratic elution based on a reversed-phase mechanism allows good separation of the analytes within 15 min. Atmospheric pressure electrospray ionization was used. All analytes were monitored in the MS(2)-MRM mode. A fragmentation schema is proposed for the target compounds. As the method was designed for bioequivalence purposes, a full validation procedure was considered. On validation, nonlinear calibrations were observed. Consequently, concentration intervals requiring nonlinear calibrations are discussed. Low limits of quantification in the 0.6-1 ng/mL concentration range were obtained. The analytical method was successfully applied to a single dose (120 mg), open-label, randomized, two-period, two-sequence, crossover bioequivalence study of two commercially available solid oral dosage pharmaceutical formulations (tablets).

High-performance liquid chromatography-mass spectrometry analysis of diltiazem and 11 of its phase I metabolites in human plasma

The aim of the present work was to develop a high-performance liquid chromatography-mass spectrometry method for analysis of diltiazem (DTZ) and metabolites in human plasma after single dose administration (120 mg). Human plasma samples (1 ml) were cleaned up by a solid phase extraction procedure (C18 cartridges) using codeine as an internal standard. Reconstituted extracts were separated on a reversed-phase C8 column with a linear gradient mobile phase system. The run time per sample analysis was 11 min. Detection was performed using selected ion monitoring following atmospheric pressure chemical ionization. The lower limit of quantification was estimated to be 1 microg/l (in spiked plasma) for all available reference compounds (i.e. DTZ and five metabolites). Validation of the method showed good linearity, precision and accuracy for quantification of these six reference compounds. In addition, tandem MS analyses of human plasma sampled from healthy individuals after peroral intake of 120 mg DTZ revealed that the method enabled detection of six additional metabolites for which reference compounds were not available.

Simultaneous enantioseparation of cis-diltiazem hydrochloride and its metabolite cis-desacetyldiltiazem using high-performance liquid chromatography and capillary electrophoresis

Two alternative methods were developed using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) for a simultaneous enantioselective determination of Ca(2+) blocking chiral drug cis-diltiazem hydrochloride (DLT) and its degradation product and metabolite cis-desacetyldiltiazem (Desac-DLT). The methods were compared from the viewpoint of analytical performance. The identification of HPLC peaks were performed using off-line electrospray ionization mass spectrometry. In addition, CE method was evaluated for quantitative determination of minor enantiomeric impurities in pharmacologically active (+)-cis-DLT.

Adsorptive stripping voltammetric determination of antihypertensive agent: diltiazem

Adsorptive stripping voltammetry was used to determine the antihypertensive agent diltiazem in phosphate buffer (pH 7.0). The adsorptive cathodic peak was observed at -1.72 V vs. Ag/AgCl. The peak response was characterized with respect to pH, preconcentration time, possible interferences, accumulation potential and supporting electrolytes. The obtained results were analyzed and the statistical parameters were calculated. The proposed method was applied to determine the mentioned drug in pharmaceutical formulation (capsule) and urine. The detection limit is 1x10(-8) M (4.5 ng ml(-1)) using 180 s preconcentration time, whereas the lower limit of detection is 6x10(-9) M (2.7 ng ml(-1)).

A simple and sensitive high-performance liquid chromatography assay of diltiazem and main metabolites in renal transplanted patients

A sensitive and specific reversed-phase high-performance liquid chromatographic method was developed for determination of the benzothiazepine calcium channel blocker diltiazem and three of its main metabolites in human plasma. A solid-phase extraction method (C18) is described for isolating diltiazem and the metabolites N-demethyl-diltiazem (M(A)), deacetyldiltiazem (M1) and N-demethyl-deacetyl-diltiazem (M2) from human plasma spiked with trans-diltiazem as internal standard. Chromatographic analysis of the eluate was accomplished using a reversed-phase column (C8) and a mobile phase consisting of acetonitrile, potassium dihydrogen phosphate-buffer (pH 2.9), triethylamine and methanol (280:598:2:90 v/v/v/v). The limit of detection was 5 ng/ml for diltiazem and 2.5 ng/ml for the metabolites (UV detection). Recoveries were > 75% for all substances. Precision analysis indicated a coefficient of variation below 5% for both diltiazem and metabolites at plasma concentrations ranging from 30 to 120 ng/ml for diltiazem and from 15 to 60 ng/ml for the metabolites. The accuracy was < 3% for diltiazem at all concentrations investigated. Metabolites showed an accuracy of < 7% at higher concentrations, however at low concentration the accuracy was < 16%. A pilot study has been performed in order to study whether the method was applicable to patients and volunteers. Plasma samples from renal transplanted patients treated with cyclosporin A and healthy volunteers did not show any interference by cyclosporin A with the determination of diltiazem and metabolites.