Simultaneous determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolite in dog plasma by high-performance liquid chromatography with electrochemical detection.

A rapid and sensitive high-performance liquid chromatographic analysis, with electrochemical detection, has been developed for the simultaneous determination of a new calcium-channel antagonist, (+/-)-methyl 2-oxopropyl-1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedi carboxylate (I, MPC-1304), and its active metabolite in dog plasma. The plasma extract with toluene was chromatographed on a reversed-phase column and detected by an electrochemical detector at + 0.92 V. Calibration curves were linear from 2.0 to 100.0 ng/ml, and the detection limit was ca. 0.25 ng/ml. This method is applicable to the simultaneous determination of I and its metabolite in dog plasma following the oral administration of I.     

Quantitation of clobazam in human plasma using high-performance liquid chromatography.

A rapid and simple reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of clobazam concentrations in human blood samples is developed and validated. Solid-phase column extraction is performed to clean up blood samples before running the analytical HPLC system. The chromatography is isocratic with a mobile phase consisting of acetonitrile (20%, v/v), methanol (23%, v/v), and 0.1 M potassium hydrogen phosphate buffer (pH 3.6; 57%, v/v) at a constant flow rate of 2 mL/min. Clobazam is detected at 226 nm. Chromatography is completed within less than 25 min. The recovery rate is greater than 95% and linear over a wide range of drug concentrations. The intra-assay coefficient of variation percentage varies between 4.3 and 12. This method is used for therapeutic drug monitoring in patients undergoing antiepileptic therapy with clobazam. Plasma levels of clobazam ranged from 21 to 663 ng/mL. Other antiepileptic compounds, such as clonazepam and phenobarbital, did not interfere with the detection of clobazam.     

Quantitation of homoharringtonine in plasma by high-performance liquid chromatography with amperometric detection

A high-performance liquid chromatographic procedure was developed for the quantitation of homoharringtonine in plasma. Harringtonine was used as an internal standard, and 1 ml of sample was required. The single-step extraction with dichloromethane resulted in almost 100% recovery for homoharringtonine and harringtonine. Analysis was performed on a reversed-phase CN column with amperometric detection. Chromatography was completed in 12 min. At an oxidation potential of +1.0 V, the detection limit was 1 ng/ml at a signal-to-noise ratio of 2. The mean analytical recovery for homoharringtonine was 99.5%. The within-run precision and between-run precision were both less than 11%. The method is equally applicable for plasma or serum, and it has been demonstrated to be applicable for study of the pharmacokinetics of homoharringtonine in patients suffering from acute non-lymphocytic leukaemia.     

Quantitation of zimelidine and norzimelidine in plasma using high-performance liquid chromatography

A method is described for the quantitation of new non-tricyclic antidepressant, zimelidine, and its pharmacologically active, N-demethylated metabolite, norzimelidine, in plasma. The method involves a single extraction of basified plasma with diethyl ether, concentration of the ethereal extract, chromatography on a high-performance liquid chromatograph and quantitation using a variable-wavelength UV detector. The respective geometric isomers of zimelidene and norzimelidine are used as internal standards for quantitation. Resolution is effected using a 5-micron silica gel column with an aqueous methanolic solution of ammonium nitrate as the mobile phase. The minimum quantitated amount was 25 ng and the coefficient of variation for the method did not exceed 7% in the range 25 to 1000 ng/ml for both compounds. The method has been applied in monitoring the plasma concentration of zimelidine and norzimelidine in plasma from depressed patients and an example of this application is presented.     

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C₂ and the analytes nifedipine and nitrendipine (internal standard) are separated on a C₁₈ column with a mobile phase consisting of acetonitrile–13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 μl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.     

Quantitation of insulin injection by high-performance liquid chromatography and high-performance capillary electrophoresis.

High-performance capillary electrophoresis (HPCE) was evaluated as a potential technique for the regulatory analysis of commercial dosage forms of insulin. A comparison was made to a liquid chromatographic analysis presently being proposed as an official monograph in the United States Pharmacopeia. The salient points of this comparison were accuracy, precision and ease of use. Both authentic (i.e. single blind, spiked) samples and commercial pharmaceutical formulations (injections) were examined. Chromatographic analyses of both commercial formulations and authentic samples were characterized by good precision, with accuracy being supported by results from authentic (spiked) samples. Conventional HPCE (by which is meant a non-micellar electrolyte used with an uncoated, unmodified fused-silica capillary) achieved reasonable accuracy, but less than impressive precision, when applied to authentic samples. When used for commercial formulations, this type of HPCE did not produce a level of accuracy suitable for regulatory purposes, even with the use of an internal standard.     

Determination of the anticonvulsant felbamate in beagle dog plasma by high-performance liquid chromatography.

An automated internal standard method for the determination of felbamate in 0.1 ml of plasma from pediatric and adult beagle dogs was developed. Plasma proteins are precipitated with acetonitrile and after centrifugation the supernatant is directly injected on a Spherisorb ODS2, 3 microns, 150 mm x 4.6 mm I.D. column with 25% acetonitrile in aqueous phosphate buffer, pH 6.50, as mobile phase with ultraviolet detection at 210 nm. The run time is 10 min, the linear range is 0.150-150 micrograms/ml felbamate, and the lower limit of quantitation is 0.150 microgram/ml.     

Quantitation of a novel antiemetic (ADR-851) in plasma and urine by reversed-phase high-performance liquid chromatography with fluorescence detection

A sensitive and specific bioanalytical method for quantitation of a novel antiemetic (ADR-851) in plasma and urine has been developed and validated. The drug and internal standard (metoclopramide) are extracted from the plasma matrix by solid-phase extraction on cyanopropyl bonded-phase columns. After extraction, samples are separated by isocratic reversed-phase high-performance liquid chromatography. The parent drug, internal standard and a yet unidentified metabolite are detected by fluorescence. The method requires 1.0 ml of plasma or 0.1 ml of urine and has a lower limit of quantitation of 2 ng/ml with 10.9% relative standard deviation (R.S.D.). Method linearity has been established over a 2-800 ng/ml range when 1.0 ml of plasma is used. The intra- and inter-day imprecisions for the method are typically better than 6% and 11% R.S.D., respectively, in both plasma and urine over the entire dynamic range. The pooled estimate of bias is less than 5% and attests to the excellent accuracy.     

Determination of apigenin in rat plasma by high-performance liquid chromatography

Apigenin (4′,5,7-trihydroxyflavone, AP) belongs to a less-toxic and non-mutagenic flavone subclass of flavonoids, the biotransformation and metabolism of which have been little studied until now. Therefore, this study is focussed on the determination of AP in free form. AP was administered to rats via the i.p. route (25 mg kg⁻¹) and then the blood was collected at 10, 15, 30 and 45 min after injection. Methanol was used for rat plasma deproteinization. The HPLC assay (mobile phase, 2% formic acid–acetonitrile–methanol, 40:35:25, v/v; flow-rate, 1 ml min⁻¹; UV detection at 349 nm) for AP determination was validated and used for the quantification of AP in rat plasma. The unknown concentration was calculated from the equation obtained by the least-squares regression analysis (y=0.521x+1.130, r²=0.998). The highest concentration of AP in plasma was found to be 30 min after injection. The concentration profile of AP obtained here may contribute to until known results about AP metabolism. They could be applied to other studies of AP or related flavonoids because of favourable effects on human health.