High-speed liquid chromatographic method for the monitoring of carbamazepine and its active metabolite, carbamazepine-10,11-epoxide, in human plasma

Implications of metabolic parameters of carbamazepine in the therapeutic monitoring of Tunisian patients with epilepsy

Carbamazepine (CBZ) is widely used in the control of simple and complex focal seizures and generalized tonic-clonic seizures in patients with epilepsy. The toxic effects of CBZ are not easily predicted, and this is due to the difficulty of delivering the optimal dose and/or plasma concentration of CBZ necessary to achieve beneficial effects, and especially to prevent the onset of toxicity associated with its use. Our study aimed to determine the relationship between the administered daily dose of CBZ and its pharmacokinetic parameters, including concentrations of CBZ and carbamazepine-10,11-epoxide (CBZ-E) plasma levels, and the metabolic ratio of CBZ-E to CBZ, in Tunisian patients with epilepsy. To accomplish this, a high-performance liquid chromatography method with ultraviolet detection was used for quantification in the simultaneous analysis of CBZ and one of its active metabolites, CBZ-E, in human plasma. A statistically significant positive correlation was found between the daily doses administered (mg/kg/day) and plasma concentrations of CBZ and CBZ-E, and the CBZ-E/CBZ ratio increased significantly as a function of the specific dose (in mg/kg/day). The increase in plasma concentrations of CBZ-E was non-linear in relation to plasma concentrations of CBZ, and there was no correlation between the CBZ-E/CBZ metabolic ratio and CBZ plasma concentrations. Our findings suggest that monitoring of CBZ as well as CBZ-E blood levels should be considered, as it may play a useful role in the therapeutic management of patients with epilepsy.

Quantitative bioanalytical and analytical method development of dibenzazepine derivative, carbamazepine: A review

Bioanalytical methods are widely used for quantitative estimation of drugs and their metabolites in physiological matrices. These methods could be applied to studies in areas of human clinical pharmacology and toxicology. The major bioanalytical services are method development, method validation and sample analysis (method application). Various methods such as GC, LC-MS/MS, HPLC, HPTLC, micellar electrokinetic chromatography, and UFLC have been used in laboratories for the qualitative and quantitative analysis of carbamazepine in biological samples throughout all phases of clinical research and quality control. The article incorporates various reported methods developed to help analysts in choosing crucial parameters for new method development of carbamazepine and its derivatives and also enumerates metabolites, and impurities reported so far.

Passive diffusion of polymeric surfactants across lipid bilayers

Self-assembling polymeric surfactant, mmePEG(750)P(CL-co-TMC) [monomethylether poly(ethylene glycol)(750)-poly(caprolactone-co-trimethylene carbonate)], increases drug solubility and crosses an enterocyte monolayer both in vitro and in vivo. The aims of the present work were to investigate whether mmePEG(750)P(CL-co-TMC) polymers can diffuse passively through lipid bilayer using parallel artificial membrane permeability assay (PAMPA) and affect membrane properties using liposomes as model. The mmePEG(750)P(CL-co-TMC) polymer was able to cross by passive diffusion an enterocyte-mimicking membrane in PAMPA at concentration which did not perturb membrane integrity. A weak rigidification associated with a low increase in permeability of liposomal lipid bilayers was observed. These data suggest that polymeric surfactants can cross the lipid membrane by passive diffusion and interact with lipid bilayers.

Simultaneous determination of zonisamide, carbamazepine and carbamazepine-10,11-epoxide in infant serum by high-performance liquid chromatography

This study developed a simple method for the simultaneous determination of zonisamide (ZNS), carbamazepine (CBZ) and its active metabolite, carbamazepine-10,11-epoxide (CBZE) in infant serum using reversed-phase high-performance liquid chromatograph (HPLC). The method involves a single-step protein precipitation procedure that uses no solid-phase or liquid-liquid extraction. The HPLC separation was carried out on a Cadenza CD-C18 column (3 microm, 4.6 mm x 150 mm) with potassium phosphate buffer (pH 4.6; 25 mM)-methanol-acetonitrile (65:20:15 (v/v/v)) as a mobile phase at a 1.0 ml/min flow rate: ZNS was detectable using a UV detector at 235 nm, and both CBZ and CBZE were at 215 nm. The quantification limits were established in accordance with each therapeutic range at 2.5 microg/ml for ZNS, 0.5 microg/ml for CBZ, and 0.25 microg/ml for CBZE. The respective coefficients of variation were 1.3-6.0% and 2.2-7.7% for the intra- and inter-assay.

Liquid chromatography/tandem mass spectrometry for the determination of carbamazepine and its main metabolite in rat plasma utilizing an automated blood sampling system

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous determination of carbamazepine and its main metabolite carbamazepine 10,11-epoxide in rat plasma is described. The method consists of a liquid-liquid extraction procedure and electrospray LC/MS/MS analysis. The chromatographic separation was achieved within 5 min using a C(8) (150 mm x 2.1mm) 5 microm column with a mobile phase composed of water/acetonitrile/acetic acid (69.5:30:0.5, v/v/v) at a flow rate of 0.4 ml/min. D(10)-carbamazepine is used as the internal standard for all compounds. Analytes were determined by electrospray ionization tandem mass spectrometry in the positive ion mode using selected reaction monitoring (SRM). Carbamazepine was monitored by scanning m/z 237-->194, carbamazepine 10,11-epoxide by m/z 253-->210 and d(10)-carbamazepine by m/z 247-->204. The lower limit of quantitation (LLOQ) is 5 ng/ml for each analyte, based on 0.1 ml aliquots of rat plasma. The extraction recovery of analytes from rat plasma was over 87%. Intra-day and inter-day assay coefficients of variations were in the range of 2.6-9.5 and 4.0-9.6%, respectively. Linearity is observed over the range of 5-2000 ng/ml. This method was used for pharmacokinetic studies of carbamazepine and carbamazepine 10,11-epoxide in response to two different blood sampling techniques (i.e., manual sampling versus automated sampling) in the rat. Several differences between the two sampling techniques suggest that the method of blood collection needs to be considered in the evaluation of pharmacokinetic data.

Octakis-6-sulfato-gamma-cyclodextrin as additive for capillary electrokinetic chromatography of dibenzoazepines: carbamazepine, oxcarbamazepine and their metabolites

Single isomer octakis-(2,3-dihydroxy-)6-sulfato-gamma-cyclodextrin used as pseudostationary phase of the background electrolyte interacts with dibenzo[b,f]azepines (consisting of a condensed 3-ring system) and forms negatively charged complexes. Hydroxygroups in position 2 and 3 at carbamazepine increase the extent of interaction, whereas substitution by oxygen at position 10 and/or 11 reduces it. The complex constants for the analytes are ranging from few tens L/mol (10-hydroxycarbamazepine, 10,11-dihydroxycarbamazepine, 10,11-epoxycarbamazepine, oxcarbazepine) to several hundreds L/mol (carbamazepine, 2-hydroxycarbamazepine, 3-hydroxycarbamazepine), and are much larger than those of the analytes with octakis-(2,3-dimethyl-)-6-sulfato-gamma-cyclodextrin. Full enantiomeric separation of the chiral metabolites of carbamazepine and oxcarbazepine is obtained at octakis-(2,3-dihydroxy-)-6-sulfato-gamma-cyclodextrin concentrations of about 10 mM (3 mM borate buffer, pH 8.5). Compared to heptakis-6-sulfato-beta-cyclodextrin, selectivity differs and stereoselectivity is more pronounced.

Separation of carbamazepine and five metabolites, and analysis in human plasma by micellar electrokinetic capillary chromatography

A rapid and feasible method was developed for the analysis of carbamazepine and its five metabolites (10,11-dihydro-10,11-epoxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine, 10,11-dihydro-10-hydroxycarbamazepine, 2-hydroxycarbamazepine and 3-hydroxycarbamazepine) in human plasma. Separation of the analytes is based on micellar electrokinetic chromatography, in untreated fused-silica capillary (48.5/40.0 cm length, 50 microm I.D.) with phosphate buffer (30 mM, pH 8.00) as background electrolyte, containing 50 mM sodium dodecylsulfate, and methanol (15%, v/v) as organic modifier. Clean up of human plasma samples was carried out by means of a solid-phase extraction procedure, which gave a high extraction yield for all six carbamazepines (>88%). The overall precision of the method gives a mean RSD of about 1.8%. The limit of quantitation for all analytes is < or = 0.30 microg ml(-1), the limit of detection < or = 0.12 microg ml(-1).

Determination of antiepileptic drugs in biological material

Current analytical methodologies applied to the determination of antiepileptic drugs in biological material are reviewed. The role of chromatographic techniques is emphasized. Special attention is focused on new chemical entities as well as current trends such as high-speed liquid chromatographic techniques, hyphenated techniques and electrochromatography techniques. A review with 542 references.

LC determination of carbamazepine in murine brain

A reversed phase HPLC method for the determination of carbamazepine (CBZ) in the brain of adult mice is described. CBZ was recovered from murine brain by solvent-extraction with ethyl acetate and resolved from imipramine (internal standard) and brain endogenous material using a Lichrospher RP select B column with a linear gradient of acetonitrile (40-80 v/v, 25 min) in ammonium acetate buffer (25 mM, pH 4.0) with UV detection at 285 nm. The method is selective, reproducible and precise with a limit detection of 45 ng/ml and is suitable for the determination of CBZ in murine brain after intra-peritoneal administration.

Simultaneous high-performance liquid chromatography determination of carbamazepine and five of its metabolites in plasma of epileptic patients

A high-performance liquid chromatographic method with UV detection for the simultaneous analysis of the antiepileptic drug carbamazepine and five of its metabolites in human plasma has been developed. The analysis was carried out on a reversed-phase column (C8, 150x4.6 mm I.D., 5 microm) using acetonitrile, methanol and a pH 1.9 phosphate buffer as the mobile phase. Under these chromatographic conditions, carbamazepine and its metabolites 10,11-dihydro-10,11-epoxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine, 2-hydroxycarbamazepine, 3-hydroxycarbamazepine and 10,11-dihydro-10-hydroxycarbamazepine are baseline separated in less than 18 min. The extraction of the analytes from plasma samples was performed by means of an original solid-phase extraction procedure using Oasis HLB cartridges. The method requires only 250 microl of plasma for one complete analysis. The repeatability (RSD%<2.4), intermediate precision (RSD%<3.5) and extraction yield (84.8-103.0%) were very good for all analytes. The method is suitable for reliable therapeutic drug monitoring of patients undergoing chronic treatment with carbamazepine and for kinetic-metabolic studies of this drug.

Comparative LC-MS and HPLC analyses of selected antiepileptics and beta-blocking drugs

A highly sensitive and specific assay procedure based on the combination of liquid chromatography and mass spectrometry (LC-MS) has been developed for the quantitative analysis of selected antiepileptics (carbamazepine and phenytoin) and beta-blocking drugs (acebutolol, atenolol, pindolol and propranolol) using APCI as an ionization process. The measured concentration range was 100-300 ng ml-1 for all drugs except phenytoin (0.5-1.5 micrograms ml-1). Analysis was based on direct injection of methanolic solutions of drugs into the mass spectrometer with the subsequent elution with a mobile phase consisting of methanol and 1% acetic acid solution (4:1) at a flow rate 1 ml min-1. The mass spectrometer was programmed to permit detection and determination of either fragment or molecular ions of carbamazepine, phenytoin, acebutolol, atenolol, pindolol and propranolol at m/e 194.3, 252.9, 337.2, 267.1, 249.1 and 260.1, respectively. The recorded chromatograms exhibited well-resolved peaks at retention times < 1 min. The peak area was correlated linearly to the drug concentration. Intraday precision gave relative standard deviations in the range 1.75-4.02%. Compared to HPLC, the described LC-MS was faster, more sensitive and specific. Unlike HPLC, LC-MS could be applied to analyze incompletely resolved mixtures. The absolute detection limits for LC-MS and HPLC were 0.2-0.5 and 10-25 ng, respectively. Recovery studies of the investigated compounds in pharmaceutical products using LC-MS and HPLC gave mean percentages of 97.5-102.0 and 98.4-103.3, respectively. Statistical analysis of the data using t- and F-tests showed insignificant differences between both methods for the analysis of carbamazepine, phenytoin, acebutolol and atenolol in pharmaceutical formulations. However, LC-MS gave more accurate results than HPLC for determination of pindolol in tablets. Propranolol could only be determined in tablets using LC-MS.