Simple and rapid high-performance liquid chromatographic analysis of cyclosporine in human blood and serum

Liquid chromatographic–electrospray mass spectrometric determination of cyclosporin A in human plasma

A rapid, sensitive and selective liquid chromatography-mass spectrometry (LC-MS) assay has been developed for determination of cyclosporin A (CyA) in human plasma; cyclosporin B (CyB) was used as internal standard (IS). The method utilized a combination of a column-switching valve and a reversed-phase symmetry column. The mobile phase was a 25:75 (v/v) mixture of 10% aqueous glacial acetic acid and acetonitrile. Running time per single run was less than 10 min. Sample preparation included C8 SPE of human plasma spiked with the analyte and internal standard, evaporation of the eluate to dryness at 50 degrees C under N2 gas, and finally reconstitution in the mobile phase. Detection of cyclosporin A and the IS was performed in selected ion-monitoring mode at m/z 601.3 and 594.4 Da for CyA and IS, respectively. Quantitation was achieved by use of the regression equation of relative peak area of cyclosporin to IS against concentration of cyclosporin. The method was validated according to FDA guideline requirements. The linearity of the assay in the range 5.0-400.0 ng mL(-1) was verified as characterized by the least-squares regression line Y = (0.00268+/-1.9 x 10(-4))X+(0.00078+/-1.8 x 10(-3)), correlation coefficient, r = 0.9986+/-1.1 x 10(-3) (n = 48). Intra and inter-day quality-control measurements in the range 5.0-350.0 ng mL(-1) revealed almost 100% accuracy and < or = 9% CV for precision. The mean absolute recovery of CyA was found to be 84.01+/-9.9% and the respective relative recovery was 100.3+/-9.19. The limit of quantitation (LOQ) achieved was 5 ng mL(-1). Eventually, stability testing of the analyte and IS in plasma or stock solution revealed that both chemicals were very stable when stored for long or short periods of time at room temperature or -20 degrees C.

Development of a HPLC method for the determination of cyclosporin-A in rat blood and plasma using naproxen as an internal standard

An isocratic reversed phase high-performance liquid chromatographic (HPLC) method with ultraviolet detection at 205 nm has been developed for the determination of cyclosporin-A (CyA) in rat blood and plasma. Naproxen was successfully used as an internal standard. Blood or plasma samples were pretreated by liquid-liquid extraction with diethyl ether. The ether extract was evaporated and the residue was reconstituted in acetonitrile-0.04 M monobasic potassium phosphate buffer (pH 2.5) solvent mixture. After washing with n-hexane, 30 microl of the reconstituted solution was injected into HPLC system. Good chromatographic separation between CyA and internal standard peaks was achieved by using a stainless steel analytical column packed with 4 microm Nova-Pak Phenyl material. The system was operated at 75 degrees C using a mobile phase consisting of acetonitrile-0.04 M monobasic potassium phosphate (pH 2.5) (65:35 v/v) at a flow rate of 1 ml/min. The calibration curve for CyA in rat blood was linear over the tested concentration range of 0.0033-0.0166 M with a correlation coefficient of 0.989. For rat plasma, the range of the concentrations tested were between 0.002 and 0.0166 M and showed linearity with a correlation coefficient of 0.953. The intra- and inter-run precision and accuracy results were 1.24-21.87 and 3.1-12.23%, respectively. The low volume of blood or plasma needed (200 microl), simplicity of the extraction process, short run time (5 min) and low injection volume (30 microl) make this method suitable for quick and routine analysis.

Optimization of sampling time for cyclosporine monitoring in transplant patients

Cyclosporine (CsA) dosing is based on CsA plasma or blood concentrations measured 12 to 24 hours after drug administration (trough levels). This study evaluated the relationship between the timing of CsA concentrations and subsequent pharmacokinetic parameters to predict an optimal sampling period. Plasma samples were obtained from 22 patients before their morning dose of CsA and at 2, 4, 6, 8, 10, and 12 hours after the dose on the 7th and on the 21st day after heart transplantation. The plasma samples were assayed by both HPLC and FPIA. The Cmax for CsA was achieved over a period ranging from 2 to 6 hours (mean/median = 4.7/4.0) during the day 7 and the day 21 studies. The mean (+/- SD) half-life was 3.2 (1.0) hours on day 7 and 2.9 (1.1) hours on day 21, (P > 0.05); the mean apparent oral clearance was 276 (117) L/hr on the day 7 and 269 (209) L/hr on day 21, (P > 0.05). When CsA plasma concentration by either FPIA and HPLC was monitored, the drug concentration best correlated with AUC was found to correspond to the plasma samples taken 4 to 8 hours after drug administration. The authors conclude that through blood sampling for therapeutic drug monitoring of CsA is not optimal, and that further studies are necessary to correlate concentration monitoring during the dosing interval with pharmacologic and toxicologic parameters.

Chromatographic methods as tools in the field of mycotoxins

Achievements in the applications of chromatographic techniques in mycotoxicology are reviewed. Historically, column chromatography (CC) and paper chromatography (PC) were applied first, followed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and gas chromatography (GC). Although PC techniques are no longer used in the analysis of mycotoxins, selected applications of PC are included to underline historical continuity. The most important achievements published from 1980 onwards are described. They include clean-up methods, TLC, CC, HPLC and GC of mycotoxins in environmental samples, foods, feeds, body fluids and in studies on biosynthesis and biotransformations of mycotoxins. Advantages and disadvantages of chromatographic techniques used in mycotoxicology are also evaluated.

Determination of cyclosporin A in the serum of kidney transplant patients by rapid-flow fractionation and normal-phase high-performance liquid chromatography

High-performance liquid chromatography was used to determine cyclosporin A (CsA) concentrations in the serum of kidney transplant patients by rapid-flow fractionation (RFF) followed by silica gel normal-phase high-performance liquid chromatography (HPLC). The extraction of CsA from serum was achieved by RFF using a short diatomaceous earth column eluted with diethyl ether-n-hexane (50:50, v/v). The recovery was more than 80% at concentrations of 50-150 micrograms/l. The concentration of this compound was determined by HPLC using a conventional silica gel column with 3.3 M ammonia solution-ethanol-n-hexane (0.31:10.69:89, v/v) as eluent. Concentration calibration was made on the basis of the peak-height ratio of CsA to CsD as the internal standard. The coefficient of variation of this assay was less than 6.5% and the results were used for the therapeutic drug monitoring of CsA administered to kidney transplant patients. Measurements of the CsA concentrations in 160 serum specimens were also made by conventional radioimmunoassay (RIA) using commercial kits. The data obtained by RIA were on average 2.5 times those obtained by HPLC. Higher values in RIA were observed characteristically with patients with severe disfunction resulting from CsA hepatotoxicity. From the results, it appeared that HPLC rather than RIA provides more precise and reliable values for the concentration of this drug.

A simple improved method for the measurement of cyclosporin by liquid-liquid extraction of whole blood and isocratic HPLC

The current HPLC methods of cyclosporin measurement have been reviewed and all aspects assessed. A simple isocratic C-18 reverse phase HPLC method with improved efficiency is described for the routine measurement of cyclosporin in whole blood. An alkaline ether extraction is followed by an acid wash, solvent evaporation and two hexane washes of the reconstituted extract. The turn-round time for a single sample is 1 h. Daily batches of up to 40 patient samples can be easily measured with this method. The results are compared with those from the Sandoz radioimmunoassay (RIA) method.

Cyclosporin: pharmacokinetics and detailed studies of plasma and erythrocyte binding during intravenous and oral administration

On the basis that unbound concentration better correlates with response than total plasma or blood concentration, the inter- and intra-subject variability in the distribution of cyclosporin within blood and to plasma components was studied in renal transplant patients. Pharmacokinetic aspects were also studied. Blood samples were analysed from patients who received the drug both by a 72-h i.v. infusion and orally (7 mg.kg-1 twice daily). Steady-state was reached within 18 h of starting the i.v. infusion; the plasma data were best fitted by a biexponential equation with half-times of 0.13-1.02 h and 4.3-13.9 h, associated with the two phases. The mean plasma clearance was 700 ml/min. Concentrations during the infusions measured by RIA and HPLC were comparable. Oral profiles showed rapid and extensive absorption. The peak plasma concentrations were 1460-1880 micrograms.l-1 and occurred 2-4 h after dosing, with bioavailability estimates of 41-113%. Concentrations measured by RIA were higher than by HPLC. Blood-to-plasma concentration ratio measurements of cyclosporin at 37 degrees C decreased with increasing plasma concentration and increased with haematocrit. Fraction unbound, measured by ultra-centrifugation, was in the range 0.042-0.122 with an average of 0.068, and varied little in some patients but showed systematic changes with time in others. Cyclosporin binding was found to be related not only to the triglyceride but, more particularly, to the cholesterol-related lipoproteins in plasma. Monitoring cholesterol may be helpful in identifying patients with extremes in binding or with widely varying binding.

New automated high-performance liquid chromatographic analysis of cyclosporin A and G in human serum

An automated isocratic high-performance liquid chromatographic (HPLC) method is described for the determination of cyclosporin A and G in human serum. This method involves the use of an automated solid-liquid extraction procedure following rapid protein precipitation with acetonitrile. The use of a disposable C8 extraction cartridge allows a good recovery of cyclosporine (87%) from serum and a detection limit of 20 ng/ml with good reproducibility using 0.5 ml of sample. This method can also be adapted to whole blood measurements. The choice of a 3-micron cyano analytical column and of the mobile phase hexane-isopropanol (85:15) permitted a low column temperature (50 degrees C), a low flow-rate (0.6 ml/min) and a short run time (14 min). This method allows the accurate and fast routine monitoring of cyclosporine by HPLC, which is particularly important in hepatic transplantations.

Liquid chromatographic determination of cyclosporin A in serum with use of a solid-phase extraction. Comparison between high-performance liquid chromatography and radioimmunoassay levels in clinical investigations

A simple reliable liquid chromatographic method for assay of cyclosporin A in serum or urine is described. Samples were cleaned up on a solid-phase extraction system (cyanopropyl column). The system involved a reversed-phase C18 Ultrasphere column maintained at 72 degrees C and an acetonitrile linear gradient (65 to 95%) in 0.14% triethylammonium phosphate. Liquid chromatographic analysis of radioimmunoassay standards shows that some samples contain a contaminant peak. Comparison of cyclosporin A levels obtained by radioimmunoassay and high-performance liquid chromatography in clinical investigations show that the former values are generally, but not always, higher than the latter, and that cyclosporin A is very differently metabolized depending on the patient, disease and treatment.

Measurement of cyclosporin A and of four metabolites in whole blood by high-performance liquid chromatography

A high-performance liquid chromatographic procedure using cyclosporin D as internal standard for the routine measurement of cyclosporin A and four of its metabolites is described. Whole-blood samples were purified on refillable solid-phase glass extraction columns. The chromatographic method includes a gradient elution using acetonitrile and water (pH 3.0) as eluents and an RP-8 analytical column. More than 1000 samples have already been analysed without any loss. The inter-assay variation was 6.3% and the intra-assay variation 4.9%. A linear correlation was found over a range of 0-3000 ng cyclosporin A per ml whole blood. The detection limit was 20 ng and the recovery was found to be 80-90%. Metabolites 1, 17, 18 and 21 could be characterized.

Liquid chromatographic determination of cyclosporine in whole blood with the advanced automated sample processing unit

We describe a rapid, precise, cost-effective, and accurate isocratic liquid chromatographic (LC) procedure for determining cyclosporine in whole blood. The cyclosporine is extracted from 0.5 ml of whole blood together with 200 micrograms of cyclosporin D, added per liter as internal standard, by using an Advanced Automated Sample Processing (AASP) unit. The on-line solid-phase extraction is performed on an octasilane sorbent cartridge which is interfaced with a Perkin-Elmer 83 X 4.6 mm I.D. cartridge column, packed with 3-micron octadecyl packing. The column is eluted with a mobile phase containing acetonitrile-water (13:7) at a flow-rate of 1.0 ml/min at a column temperature of 70 degrees C. The column effluent is monitored at 210 nm. The absolute recovery of cyclosporine exceeded 87% and the linearity extended up to 2000 micrograms/l. Within-run and day-to-day coefficients of variation were less than 8%. The correlation between AASP-LC and manual Bond-Elut extraction-LC method was excellent (r = 0.97).

Cyclosporine: structure, pharmacokinetics, and therapeutic drug monitoring

Cyclosporine is an 11-amino acid cyclic peptide immunosuppressant that has revolutionized organ transplantation. Alone or in combination with prednisone and azathiaprine, it is preferred in hepatic, cardiac, and high-risk renal transplantation. Its unusual primary structure of hydrophobic, N-methylated amino acids results in a compact conformation in the crystal which changes to multiple conformations in hydrophilic solvents. The unusual structure produces unusual pharmacokinetic behavior which is still poorly understood. The metabolism occurs predominately in the liver and is affected by several drugs known to alter hepatic metabolism. At least ten metabolites have been identified but are inadequately characterized. The unique behavior of cyclosporine necessitates therapeutic drug monitoring (TDM) for individualization of therapy. Cyclosporine has been monitored in both whole blood and plasma by both RIA and HPLC with significantly different results for each combination. When cyclosporine is assayed by HPLC in a compulsive regimen of TDM, a correlation is observed between immunosuppression, toxicity, and concentration. To distinguish renal or hepatic toxicity from rejection, biopsies, clinical status, and blood concentrations of cyclosporine must be simultaneously analyzed. After extensive experimental and clinical study, cyclosporine remains an enigma with clear clinical benefit.

Determination of cyclosporin A in whole blood by high-performance liquid chromatography using automated column switching

A fully automated high-performance liquid chromatographic column-switching system is presented for the determination of cyclosporin A in whole blood. After blood proteins were precipitated with acetonitrile, the supernatant was automatically loaded on to a cyanopropyl column for initial separation, and then the fraction containing cyclosporin A was loaded on to a trimethylsilica column for final separation and quantitation. Cyclosporin A was detected by ultraviolet absorption at 205 nm. The minimum detectable concentration of cyclosporin A was 5 ng/ml in 100 microliter of blood. The coefficient of variation of the method was 1.755, 1.748 and 0.655% in whole blood when spiked at the 170, 425 and 850 ng/ml levels, respectively. One assay was completed in 15 min.

Cyclosporine serum concentrations soon after heart or heart-lung transplantation

The accumulation of cyclosporine was evaluated in 11 patients following either heart or heart-lung transplantation. Blood samples were drawn frequently for the first few postoperative days, and the plasma was analyzed by both radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC). The levels determined by RIA were higher than those assessed by HPLC, and it is hypothesized that the difference is due to antibody reactive metabolites of cyclosporine, which are measured by the RIA procedure. We did not find any consistent trends in the accumulation of these metabolites. Analysis of early clinical data did not suggest any relationship between levels of cyclosporine or its metabolites and clinical outcome.

Cyclosporine blood concentrations determined by specific versus nonspecific assay methods

Cyclosporine blood concentrations were simultaneously determined by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) at multiple points in time in two patients receiving cyclosporine for immunosuppression following liver transplantation. Radioimmunoassay levels always exceed those determined by HPLC; however, the divergence between the two methods increased as serum bilirubin concentration increased, with HPLC:RIA ratios generally less than 0.3 when serum bilirubin concentrations exceeded 10.0 mg/dL. These preliminary results suggest that retention of immunoactive cyclosporine metabolites due to imparied liver function may account for RIA-determined cyclosporine concentrations that greatly exceed those measured by HPLC.

Semi-automated high-performance liquid chromatographic determination of cyclosporine A in whole blood using one-step sample purification and column-switching

A highly sensitive and semi-automated high-performance liquid chromatographic method, utilizing acetonitrile protein precipitation and column-switching, is described for the determination of cyclosporine A in whole blood. Following a rapid manual acetonitrile treatment of the blood samples, the supernatant is loaded automatically onto a 5-micron high-speed protein separation column without any further clean-up operations. The fraction containing cyclosporine A is switched to a 3-micron C18 reversed-phase high-speed column by a microprocessor-controlled column-switching unit for final separation and detection by absorption at 214 nm. Minimal sample handling and efficient separation resulted in a high recovery (75 +/- 3%) of cyclosporine A from blood and a detection limit as low as 2 micrograms/l with a highly reproducible and linear response up to 2500 micrograms/1 using 0.5 ml of sample. A separation cycle including regeneration of the first column is finished in 15 min, and this system was used continuously for ca. 1000 blood samples from heart, liver, kidney, pancreas and bone marrow recipients without change in separation parameters or material replacement. The method described allows accurate and very fast daily routine monitoring of cyclosporine A in large numbers of blood samples from transplant recipients.