[A high performance liquid chromatographic method for the determination of teniposide in brain tissue using electro-chemical detection].

A reversed-phase HPLC method for the determination of teniposide in brain tissue is described. Teniposide can be separated on a Hypersil ODS column with a mobile phase of methyl alcohol-water-acetic acid (56:41:3, V/V) and flow rate of 0.8 mL/min (10 MPa). Column temperature was 35 degrees C and operating potentials for electrochemical detection was 0.70 V. To 50 mg brain tissue were 1 mL 50% ammonium sulfate and 4 mL ethyl acetate. The sample was vortexed for 5 min and ultrasonically agitated for 15 min, then centrifuged at 3000 r/min for 15 min. The upper (organic) layer was collected and the lower layer reextracted with 4 mL of ethyl acetate by vigorously vortexing, then centrifuged at 3000 r/min for 15 min. The organic layer was combined with the previously collected ethyl acetate layer. This organic extract was dried under a gentle nitrogen stream, and the residue was reconstituted with 1 mL internal standard of guaifenesinum before HPLC analysis. The linear range was 0.1-10.0 mg/L, and the detection limit 0.1 mg/L. Intra-day and inter-day RSD for assaying brain tissue sample were 0.87% and 1.41%, respectively. The average recovery was 92.87% with coefficient of variation of 2.35%.

Etoposide and teniposide. Bioanalysis, metabolism and clinical pharmacokinetics.

Etoposide (VP 16-213) and teniposide (VM 26) are semisynthetic epipodophyllotoxin derivatives active against a variety of tumours. The clinical efficacy has led to an increasing interest in these compounds. This review presents information on the mechanism of action, biochemical pharmacology, bioanalysis, metabolism and pharmacokinetics of etoposide and teniposide.

Improved HPLC-ECD analysis of mitomycin C, porfiromycin, VP 16-213 and VM 26 by implantation of software filters.

In high performance liquid chromatography with electrochemical detection (HPLC/ECD) much attention has been paid to the performance of the applied detection system with respect to reliability and sensitivity. In general, insufficient attention has been paid to relatively easy to implant devices for improved collection and handling of detection signals. Four models of software filtering are studied and compared with hardware filtering. In the investigated chromatographic-electrochemical system, off-line parabolic filtering after on-line averaging of sixteen measurements proved to be the system of first choice, with respect to execution time, noise level, signal to noise ratio, peak height and resolution.

Radioimmunoassay for etoposide and teniposide.

A radioimmunoassay for VP-16 or VM-26 was developed by using tritiated ligand and antisera produced from rabbits immunized with succinyl-VP-16 bovine serum albumin conjugates. Separate determinations of VP-16 and its hydroxy acid, a metabolite which cross-reacted with the VP-16 antisera, could be accomplished by extracting samples with chloroform in which the metabolite was insoluble. The assay was reproducible and sensitive. Extracted standard curves were linear from 0.025 to 5 micrograms for VP-16 and 0.1 to 10 micrograms for the hydroxy acid per 0.5 ml assay mixture. Fifty percent inhibition of binding was achieved at 0.066 and 0.55 microgram for VP-16 or VM-26 and the metabolite, respectively. Preliminary disposition studies in mice and dog, and human urinary excretion support the application of the assay in pharmacologic studies.

Ammonium acetate: a general purpose buffer for clinical applications of high-performance liquid chromatography.

The chromatographic properties of ammonium acetate have been studied, and its use as a general purpose buffer for reversed-phase chromatography has been investigated. Simple ammonium acetate systems can often replace complicated and expensive buffers, with or without ion-pairing agents, with improved column selectivity and efficiency. A wide range of clinically important compounds have been successfully separated by ammonium acetate buffer systems. These include creatinine, bilirubin, verapamil and its metabolites, etoposide and teniposide, vitamin A, biogenic amines and porphyrins.

High-performance liquid chromatographic analysis of the semisynthetic epipodophyllotoxins teniposide and etoposide using electrochemical detection.

A high-performance liquid chromatographic (HPLC) assay was developed for the quantitation of two structurally similar and highly active anticancer drugs, etoposide (I) and teniposide (II), and their potential metabolites (hydroxy acid, picrolactone, and aglycone). The assay utilizes electrochemical detection, which imparts specificity and sensitivity sufficient to detect greater than or equal to 20 ng/mL in plasma, urine, and CSF. The mean assay coefficients of variation were 5.1 and 8.1% for teniposide (10 micrograms/mL) and etoposide (5 micrograms/mL), respectively. The extraction efficiencies were 86% for etoposide, 70% for its hydroxy acid metabolite, 66% for teniposide, and 54% for the hydroxy acid of teniposide. The correlation coefficient of the multilevel standard curve was greater than or equal to 0.995 over the concentration range of 0.05-50 micrograms/mL for the parent drugs and metabolites extracted from plasma. This method has been used to determine the concentrations of the parent drugs and their metabolites in the plasma, urine, and CSF of patients with cancer.

Automated liquid chromatographic analysis of the anti-tumorigenic drugs etoposide (VP 16-213) and teniposide (VM 26).

A method is described for the fully automated analysis of large numbers of 1--2 ml serum and plasma or urine samples containing the anti-tumorigenic drugs etoposide and teniposide and their aglycone. The blood samples are hydrolysed by a proteolytic enzyme, subtilisin A, prior to preconcentration on a small precolumn. The hydrolysis step serves both to release the strongly protein-bound drugs and to prevent clogging of the chromatographic system. On-line preconcentration is carried out with precolumns packed with PRP1, a micro-particulate divinylbenzene-styrene copolymeric sorbent. Chromatography takes place, after column switching, in a C18/methanol--water system. After a post-column clean-up step using continuous extraction with dichloroethane in an autoanalyzer system, native fluorescence of these analytes is used for detection of the drugs. Recovery of etoposide and teniposide from spiked serum and plasma samples was 100%. Calibration curves of etoposide and teniposide typically show correlation coefficients of 0.9994 over a two-to-three order linear range. The detection limit of etoposide is approx. 8 ng per sample. Repeatability was found to be excellent. Unattended overnight routine analysis is possible without any problems. This method, considering optimal sample throughput, reliability and selectivity, competes favourably with existing techniques for the analysis of etoposide and teniposide.