Simultaneous quantification method for 5-FU, uracil, and tegafur using UPLC-MS/MS and clinical application in monitoring UFT/LV combination therapy after hepatectomy.

Combination therapy of tegafur/uracil (UFT) and leucovorin (LV) is widely used to treat colorectal cancers. Although this therapy has a significant therapeutic effect, severe adverse effects occur frequently. Therapeutic drug monitoring (TDM) may help to prevent adverse effects. A useful assay that can quantitate plasma levels of 5-FU, uracil, and tegafur simultaneously for TDM has been desired, but such a method is not currently available. In this study, we aimed to develop a sensitive method for simultaneous quantification of 5-FU, uracil, and tegafur in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). After preparing plasma samples by protein precipitation and liquid extraction, 5-FU, uracil, and tegafur were analyzed by UPLC-MS/MS in negative electrospray ionization mode. Validation was performed according to US Food and Drugs Administration guidance. The calibration curves were linear over concentration ranges of 2-500 ng/mL for 5-FU, 20-5000 ng/mL for uracil, and 200-50,000 ng/mL for tegafur. The corresponding average recovery rates were 79.9, 80.9, and 87.8%. The method provides accuracy within 11.6% and precision below 13.3% for all three analytes. Matrix effects of 5-FU, uracil, and tegafur were higher than 43.5, 84.9, and 100.2%, respectively. This assay was successfully applied to assess the time courses of plasma 5-FU, uracil, and tegafur concentrations in two patients with colorectal liver metastasis who received UFT/LV therapy after hepatectomy. In conclusion, we succeeded to develop a sensitive and robust UPLC-MS/MS method for simultaneous quantification of 5-FU, uracil, and tegafur in human plasma. This method is potentially useful for TDM in patients receiving UFT/LV combination therapy.

Pharmacokinetic and bioequivalence study between two formulations of S-1 in Korean gastric cancer patients.

PURPOSE: S-1 is an oral fluoropyrimidine anticancer drug consisting of the 5-fluorouracil prodrug tegafur combined with gimeracil and oteracil. The purpose of this study was to evaluate the pharmacokinetic (PK), bioequivalence, and safety of a newly developed generic formulation of S-1 compared with the branded reference formulation, in Korean gastric cancer patients. METHODS: This was a single-center, randomized, open-label, single-dose, two-treatment, two-way crossover study. Eligible subjects were randomly assigned in a 1:1 ratio to receive the test formulation or reference formulation, followed by a one-week washout period and administration of the alternate formulation. Serial blood samples were collected at 0 hrs (predose), 0.25, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, and 48 hrs after dosing in each period. The plasma concentrations of tegafur, 5-FU, gimeracil, and oteracil were analyzed using a validated liquid chromatography-tandem mass spectrometry method. The PK parameters were calculated using a non-compartmental method. RESULTS: In total, 29 subjects completed the study. All of the 90% confidence intervals (CIs) of the geometric mean ratios (GMRs) fell within the predetermined acceptance range. No serious adverse events were reported during the study. CONCLUSION: The new S-1 formulation met the Korean regulatory requirement for bioequivalence. Both S-1 formulations were well tolerated in all subjects.Clinical trial registry: https://cris.nih.go.kr CRIS KCT0003855.

High-throughput method to analyze tegafur and 5-fluorouracil in human tears and plasma using hydrophilic interaction liquid chromatography/tandem mass spectrometry.

RATIONALE: We developed a new high-throughput method to analyze tegafur (FT) and 5-fluorouracil (5-FU) in tear and plasma samples using hydrophilic interaction liquid chromatography (HILIC)/tandem mass spectrometry (MS/MS). METHODS: The tear samples (10 µL) spiked with FT, 5-FU, and 5-chlorouracil (internal standard) were diluted using 40 µL of 2 M ammonium acetate and 250 µL of acetonitrile with 2% formic acid; 20 µL of plasma spiked with the two drugs and internal standard was diluted with 80 µL of 2 M ammonium acetate and 500 µL of acetonitrile with 2% formic acid. After centrifugation, the clear supernatant extract (15 µL) was directly injected into the HILIC/MS/MS instrument, and each drug was separated on a Unison UK-Amino column (50 mm × 3 mm i.d., 3 µm particle size) with a linear gradient elution system composed of 10 mM ammonium acetate (pH 6.8) and acetonitrile at a flow rate of 0.7 mL/min. We performed quantification by multiple reaction monitoring (MRM) with negative-ion atmospheric-pressure chemical ionization. RESULTS: Distinct peaks were observed for the drugs on each MRM channel within 2 min. The regression equations showed good linearity within the range 0.04-4.0 µg/mL for the tear and plasma samples with detection limits at 0.02-0.04 µg/mL. Recoveries for target analytes (FT and 5-FU) for the tear and plasma samples were in the 94-128% and 94-104% ranges, respectively. The intra- and inter-day coefficients of variation for the two drugs were lower than 10.8%. The accuracies of quantitation were 97-115% for both samples. CONCLUSIONS: We established a high-throughput, reproducible, and practical procedure for analyzing FT and 5-FU in human tear and plasma samples using HILIC/MS/MS analysis with an aminopropyl-bonded mixed-mode separation column. This method can be applied to the high-throughput routines used in clinical analyses.

Circadian variations in the pharmacokinetics of the oral anticancer agent tegafur-uracil (UFT) and its metabolites in rats.

Uracil-tegafur (UFT) is an oral anticancer drug containing uracil and 5­fluorouracil prodrug tegafur and is widely used for adjuvant chemotherapy of colorectal cancer. Although clinical data show circadian variations in plasma 5­fluorouracil concentrations during its long-term infusion, and feasibility studies of chronomodulated administration have been previously reported, the circadian pattern in plasma 5­fluorouracil concentration after UFT administrations remains unclear. The aim of this study was to identify factors causing circadian variations in UFT pharmacokinetics and estimate circadian patterns of plasma 5­fluorouracil concentration corresponding to UFT dosing time in rats. Rats were orally administered UFT (15 mg/kg as tegafur) at three different times of the day: 07:00 (23 h after light onset, HALO), 13:00 (5 HALO), or 19:00 (11 HALO), and then plasma concentrations of tegafur, 5­fluorouracil, and uracil were measured after UFT administration. We found that the area under the plasma concentration-time curves (AUC0-∞) of 5­fluorouracil depended on the UFT dosing time of day with a 2.4-fold difference between the peak (at 19:00: 13.7 ±â€¯1.4 µmol·h/L) and trough (at 13:00: 5.6 ±â€¯1.3 µmol·h/L). The simulated population mean clearance of 5­fluorouracil followed a 24-h cosine circadian curve, with the highest value in the early light phase being 2.2-fold higher than the lowest value in the early dark phase, which was an inverse circadian pattern compared to the plasma 5­fluorouracil concentration. The plasma tegafur levels suggested that circadian variation in tegafur absorption and conversion to 5­fluorouracil are factors causing variations in plasma 5­fluorouracil levels following UFT administration. In conclusion, the circadian pattern of 5­fluorouracil clearance and circadian variations in tegafur pharmacokinetics are important determinants of plasma 5­fluorouracil concentrations following UFT administration. This knowledge could help in developing a chronomodulated administration strategy of UFT for improving clinical outcomes.

A high throughput immunoassay for the therapeutic drug monitoring of tegafur.

Cancer is a group of diseases in which abnormal cells grow and divide without control, with the potential to invade other parts of the body. Chemotherapy is a type of treatment that uses chemical agents to treat cancer. These drugs are toxic and produce undesirable adverse drug reactions due to their narrow therapeutic window and highly variable pharmacokinetics, thus, they need to be monitored to establish personalized treatment to achieve maximal efficiency and reduce drug toxicity. Nowadays, therapeutic drug monitoring (TDM) is not routinely used for chemotherapy agents, however, TDM has the potential to improve the clinical benefit of chemotherapy drugs. Tegafur, a prodrug of 5-fluorouracil (5FU), is one of the main anti-cancer drugs used worldwide. Herein, a reproducible and sensitive indirect competitive ELISA has been developed and validated in plasma samples. The assay reports an IC50 of 35.6 nM, reaching a limit of detection of 2.7 nM. It is highly reproducible and does not show cross-reactivity with any related compound. In summary, this assay provides a sensitive, accurate and high throughput analytical method for tegafur quantification in plasma, which fits TDM requirements.

Postgastrectomy pharmacokinetic changes of S-1 in patients with localized advanced gastric cancer.

S-1 is an oral 5-fluorouracil agent containing tegafur, 5-chloro-2, 4-dihydroxypyridine (CDHP), and potassium oxonate. This study explored the pharmacokinetics of S-1 and pharmacokinetic changes after gastric surgery in patients with resectable gastric cancer who received pre- and postoperative S-1 plus docetaxel. Serial blood was drawn before and after gastrectomy from 37 patients for pharmacokinetic analysis. The pharmacokinetics of tegafur, 5-fluorouracil, and CDHP were analyzed by noncompartmental analysis (NCA) methods and by modeling. In modeling analysis, CHDP concentrations were incorporated in the model as a time-varying covariate that inhibits the clearance of 5-fluorouracil following an inhibitory Emax model. In NCA, the pharmacokinetics of tegafur and 5-FU before and after gastric surgery were similar, although average maximum concentrations of 5-FU were decreased with statistical significance after gastrectomy. Median Tmax of tegafur was shorter after surgery without statistical significance. In modeling analysis, tegafur was best fitted by mixed zero and first-order absorption. The only difference in the final pharmacokinetic model around gastrectomy was the presence of an absorption lag of 0.23 hours before surgery. Incorporation of CDHP concentrations significantly improved the model. Although some pharmacokinetic results showed statistically significant changes after gastrectomy, these differences seem to be too small to have any clinical implication.

Species variation in the enantioselective metabolism of tegafur to 5-fluorouracil among rats, dogs and monkeys.

OBJECTIVES: Tegafur (FT), a pro-drug of 5-fluorouracil (5-FU), is a racemate consisting of two enantiomers, R and S-FT. The aim of this study was to clarify interspecies variation in the enantioselective metabolism of FT. METHODS: Plasma concentrations of FT enantiomers were determined in rats, dogs and monkeys following intravenous and oral dosing of the racemate (5 mg/kg). In addition, the enzymatic conversion of FT enantiomers to 5-FU was assayed using hepatic preparations. KEY FINDINGS: Metabolic clearance of R-FT was higher than that of S-FT in rats and monkeys, but S-FT was the preferential substrate for dogs. An inhibition study revealed that cytochrome P450 is primarily responsible for the enantioselective metabolism of FT in rats and dogs. In contrast, in monkeys, thymidine phosphorylase was a determinant of the enantioselectivity in FT metabolism. Although oral bioavailability was not enantioselective, in-vitro and in-vivo kinetic studies suggested that the enantioselectivity in the hepatic intrinsic clearance of FT directly influences the body clearance in all animal species examined. CONCLUSIONS: The interspecies variations were observed in the enantioselective pharmacokinetics of FT, and the in-vivo enantioselectivity could be extrapolated from the in-vitro metabolic activities.

Phase II tailored S-1 regimen study of first-line chemotherapy in elderly patients with advanced and recurrent non-small cell lung cancer.

PURPOSE: We investigated the efficacy and toxicity of a novel oral 5-fluorouracil (5-FU) formulation (S-1), administered according to a tailored dose regimen. METHODS: S-1 was administered orally for 28 days, followed by 14 days of no treatment, in 23 patients who received a tailored dose of S-1, adjusted on the basis of individual creatinine clearance and body surface area. In 8 of the patients, pharmacokinetic study was performed on the 6 points on 7th day after S-1 administration. RESULTS: Of the 23 patients enrolled in this study, 2 (8.7 %) had a partial response and 14 (60.9 %) had stable disease. The disease control rate was 69.6 % (16/23) (95 % confidence interval, 50.8-88.4 %). Grade 3/4 hematologic and non-hematologic toxicities were minor. In the pharmacokinetic study group, the maximum plasma concentration (C (max)) and the area under the plasma concentration curve of 5-FU at all 6 points after administration of the tailored S-1 dose regimen were similar to the values reported in a previous study describing cancer patients with normal renal function who received a standard dose of S-1 (80 mg/m(2)/day). CONCLUSIONS: Our results suggest that tailored S-1 monotherapy is safe and therapeutically useful as first-line treatment for elderly patients with advanced and recurrent non-small cell lung cancer.

Development and utilization of a combined LC-UV and LC-MS/MS method for the simultaneous analysis of tegafur and 5-fluorouracil in human plasma to support a phase I clinical study of oral UFT®/leucovorin.

Tegafur is a 5-fluorouracil (5-FU) prodrug widely used outside the United States to treat colorectal cancer as well as cancers of the head and neck. The resulting plasma concentrations of tegafur are much higher than those of 5-FU; thus, analytical methods are needed that are sensitive enough to detect low plasma concentrations of 5-FU and robust enough to simultaneously analyze tegafur. Previous LC-MS/MS methods have either failed to demonstrate the ability to simultaneously measure low 5-FU and high tegafur plasma levels, or failed to be applicable in clinical studies. Our goal was to develop a method capable of measuring low concentrations of 5-FU (8-200 ng/ml) and high concentrations of tegafur (800-20,000 ng/ml) in human plasma and to subsequently evaluate the utility of the method in patient samples collected during a phase I clinical study where oral doses of either 200mg or 300 mg UF®/LV (uracil and tegafur in a 4:1 molar ratio plus leucovorin) were administered. A combined LC-MS/MS and LC-UV method was developed utilizing negative ion atmospheric pressure ionization (API). The method provides an accuracy and precision of <10% and <6%, respectively, for both analytes. Material recoveries from the liquid-liquid extraction technique were 97-110% and 86-91% for tegafur and 5-FU, respectively. Utilization of this method to determine tegafur and 5-FU plasma concentrations followed by noncompartmental pharmacokinetic analyses successfully estimated pharmacokinetic parameters (C(MAX), t(MAX) and AUC(0-10h)) in the clinical study patients. Overall, this method is ideal for the simultaneous bioanalysis of low levels of 5-FU and relatively higher levels of its prodrug, tegafur, in human plasma for clinical pharmacokinetic analysis.

[Pharmacokinetics of S-1 capsule in patients with advanced gastric cancer].

The study is to investigate the pharmacokinetics of S-1 capsule (tegafur, gimeracil and potassium oxonate capsule) in patients with advanced gastric cancer after single and multiple oral administration. Twelve patients with advanced gastric cancer were recruited to the study. The dose of S-1 for each patient was determined according to his/her body surface area (BSA). The dose for single administration was 60 mg every subject. The dose for multiple administration for one subject was as follows: 100 mg x d(-1) or 120 mg x d(-1), 28-days consecutive oral administration. The pharmacokinetic parameters of tegafur, 5-fluorouracil, gimeracil, potassium oxonate and uracil after single oral administration were as follows: (2,207 +/- 545), (220.0 +/- 68.2), (374.9 +/- 103.0), (110.5 +/- 100.8) and (831.1 +/- 199.9) ng x mL(-1) for Cmax; (11.8 +/- 3.8), (4.4 +/- 3.3), (7.8 +/- 5.1), (3.1 +/- 0.9) and (8.8 +/- 4.1) h for t1/2, respectively. After six days oral administration, the average steady state plasma concentrations (Cav) of tegafur, 5-fluorouracil, gimeracil, potassium oxonate and uracil were (2,425 +/- 1,172), (73.88 +/- 18.88), (162.6 +/- 70.8), (36.89 +/- 29.35) and (435.3 +/- 141.0) ng x mL(-1), respectively, and the degree of fluctuation (DF) were (1.0 +/- 0.2), (2.5 +/- 0.4), (3.1 +/- 0.8), (2.4 +/- 0.8) and (1.5 +/- 0.3), respectively. The cumulative urine excretion percentage of tegafur, 5-fluorouracil, gimeracil and potassium oxonate in urine within 48 h were (4.2 +/- 2.8) %, (4.7 +/- 1.6) %, (18.5 +/- 6.0) % and (1.7 +/- 1.2) %, repectively, after single oral administration of S-1. The results exhibited that tegafur had some drug accumulation observed, and gimeracil, potassium oxonate, 5-fluorouracil and uracil had no drug accumulation observed.

Determination of 2-hydroxyflutamide in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS): application to a bioequivalence study on Chinese volunteers.

A sensitive, simple and rapid ultra fast liquid chromatography (UFLC)-ESI-MS/MS method was developed for the determination of 2-hydroxyflutamide in human plasma using tegafur as the internal standard. The plasma sample was pretreated with methanol for protein precipitation and the analytes were separated on an Ultimate C18 column (5 microm, 2.1 mm x 50 mm, MD, USA) with the mobile phase consisted of acetonitrile and water (2:1, v/v). Detection was performed on a triple-quadrupole tandem mass spectrometer under a negative multiple reaction-monitoring mode (MRM). The mass transition ion-pair was followed as m/z 290.90-204.8 for 2-hydroxyflutamide and 198.9-128.8 for tegafur. Linear calibration curves were obtained in the concentration range of 1.742-1452 ng/ml with a lower limit of quantification of 1.742 ng/ml. The intra- and inter-batch precision values were less than 8.1% and 5.6%, respectively. The established method was successfully applied to a bioequivalence study of two flutamide preparations (250 mg) in 20 healthy male volunteers.

Plasma pharmacokinetics after combined therapy of gemcitabine and oral S-1 for unresectable pancreatic cancer.

BACKGROUND: The combination of gemcitabine (GEM) and S-1, an oral 5-fluorouracil (5-FU) derivative, has been shown to be a promising regimen for patients with unresectable pancreatic cancer. METHODS: Six patients with advanced pancreatic cancer were enrolled in this pharmacokinetics (PK) study. These patients were treated by oral administration of S-1 30 mg/m2 twice daily for 28 consecutive days, followed by a 14-day rest period and intravenous administration of GEM 800 mg/m2 on days 1, 15 and 29 of each course. The PK parameters of GEM and/or 5-FU after GEM single-administration, S-1 single-administration, and co-administration of GEM with pre-administration of S-1 at 2-h intervals were analyzed. RESULTS: The maximum concentration (Cmax), the area under the curve from the drug administration to the infinite time (AUCinf), and the elimination half-life (T1/2) of GEM were not significantly different between GEM administration with and without S-1. The Cmax, AUCinf, T1/2, and the time required to reach Cmax (Tmax) were not significantly different between S-1 administration with and without GEM. CONCLUSION: There were no interactions between GEM and S-1 regarding plasma PK of GEM and 5-FU.

Determination of tegafur, 5-fluorouracil, gimeracil and oxonic acid in human plasma using liquid chromatography-tandem mass spectrometry.

S-1 is an oral anticancer drug, which consists of tegafur (FT), gimeracil (CDHP) and potassium oxonate (Oxo) at a molar ratio of 1:0.4:1. Among these, tegafur is a prodrug, and is rapidly metabolized to the active drug, 5-fluorouracil (5-FU), in vivo. To evaluate the pharmacokinetics of S-1 in patients, LC-MS/MS methods were developed and validated for determination of FT, 5-FU, CDHP and Oxo in human plasma. FT, 5-FU and CDHP were extracted from plasma following protein precipitation, separated on a Synergi Hydro-RP column and simultaneously quantified by LC-MS/MS. The mobile phase consisted of methanol-water-ammonia-acetic acid (27:73:0.0018:0.018, v/v/v/v). The mass spectrometer was operated in negative mode using electrospray ionization. The calibration curves were linear in the range of 12.0-3000ng/mL for FT, and 2.00-500ng/mL for 5-FU and CDHP. The accuracy ranged from 93.1% to 110.7% and the precision ranged from 2.4% to 14.6% for each analyte. To determine Oxo in human plasma, an LC-MS/MS method employing pre-column derivatization was developed and validated. 4-Bromomethyl-7-methoxycoumarin was chosen as the derivatization reagent and [(13)C(2),(15)N(3)]-Oxo was used as the internal standard. The MS/MS detection was operated in positive mode using an APCI source. The calibration range was 2.00-150ng/mL. The accuracy and precision were within 95.9-99.1% and 4.4-10.0%, respectively. The validated methods were successfully applied to characterize the pharmacokinetic profiles of FT, 5-FU, CDHP and Oxo following oral administration of 60mg S-1 tablets to patients with solid gastrointestinal tract tumors.

Two dosages of oral fluoropyrimidine S-1 of 35 and 40 mg/m2 bid: comparison of the pharmacokinetic profiles in Korean patients with advanced gastric cancer.

OBJECTIVE: In this study, we compared the pharmacokinetic profiles of 5-fluorouracil (5-FU), tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo) after administration of S-1 at 35 or 40 mg/m(2) bid for 28 consecutive days, in Cycles 1 and 3, in patients with advanced gastric cancer. METHODS: Three patients were enrolled for each dosage. S-1 dosage was assigned based on body surface area (BSA), which is different from the Japanese dosing system. The median daily dose per BSA was 76 mg/m(2), ranging from 70 to 88 mg/m(2). RESULTS: Plasma levels of 5-FU, tegafur, CDHP and Oxo at 4 h post-dose reached steady-state on day 8. The estimated steady-state level was dependent on S-1 dosage. There were no intercyclic differences of pre-dose and 4 h post-dose levels between Cycles 1 and 3, implying no cumulative effect of S-1 was shown probably due to 2-week drug-resting period. Pharmacokinetic profiles on day 28 were similar to previous Japanese report. C(max) and AUC(0-48 h) values of each S-1 component increased depending on S-1 dosage. Pharmacokinetic parameters were not correlated with tumor response or toxicity. CONCLUSIONS: We suggest that these pharmacokinetic profiles of Asian population could provide a basis for schedule optimization and for additional studies on interaction with other antitumor drugs.

Simultaneous determination of tegafur and gimeracil in human plasma by liquid chromatography/tandem mass spectrometry.

We developed a rapid, simple and sensitive LC/MS/MS method for the simultaneous quantitation of tegafur (FT) and gimeracil (CDHP) in human plasma with a concentration range of 20-5000 and 2-500 ng/mL, respectively. Methanol was chosen as a precipitation agent for sample preparation. Chromatographic separation was performed on an inertsil ODS-3 C18 column using 1.0% formic acid in water and methanol (80/20, v/v) at a flow rate of 0.3 mL/min. The MS detection was operated with selected reaction monitoring (SRM) in the positive-ion mode. The matrix effect ranged from -8.9 to 7.8% for all analytes. The intra- and inter-day precisions were less than 8.6 and 9.5%, and the accuracy was within +/-7.5% for all analytes, respectively. The mean recoveries were 76.5 +/- 5.2 and 78.3 +/- 5.9% for FT and CDHP, respectively. The analytes were stable under all possible conditions of storing and handling for each compound.

Development of a pharmacokinetic model to optimize the dosage regimen of TS-1, a combination preparation of tegafur, gimeracil and oteracil potassium.

BACKGROUND: TS-1 is a combination preparation of tegafur, a prodrug of 5-fluorouracil (5-FU), with gimeracil, a potent inhibitor of dihydropyrimidine dehydrogenase (DPD), which mediates the inactivation of 5-FU. UFT is a combination preparation of tegafur with uracil, which also inhibits DPD, though less potently; UFT has a higher content of tegafur than that in TS-1. We aimed to develop a pharmacokinetic model to describe the kinetics of tegafur and 5-FU after the administration of TS-1 and UFT. METHODS: We developed a model incorporating the inhibition of DPD by gimeracil and uracil, and fitted the model to the observed kinetics of tegafur and 5-FU after the administration of TS-1 and UFT. Then, we simulated the plasma 5-FU profiles in patients with renal dysfunction and those after replacement of TS-1 with UFT and compared them with the observed profiles. RESULTS: The developed model could appropriately describe the plasma concentration profiles of 5-FU and tegafur after the administration of TS-1 in patients with normal and impaired renal function. CONCLUSION: The developed model may be useful to optimize the dosage regimen of TS-1 under various clinical conditions.

[A phase I study of postoperative combination therapy with TS-1 and low dose cisplatin against stage IV gastric carcinoma].

A dose-escalation study was conducted for postoperative patients with stage IV gastric cancer to determine the recommended dose of daily intravenous cisplatin combined with a fixed dose of TS-1. TS-1 was administered orally twice daily for 2 weeks followed by a 1-week rest. The dose of TS-1 was based on the body surface area (BSA) as follows: 80 mg/day for BSA less than 1.25, 100 mg/day for BSA 1.25 to less than 1.50, and 120 mg/day for BSA 1.5 or more. Three dose levels of cisplatin (2, 4, 6 mg/m(2)) were studied, and two courses were performed. Cisplatin was infused on day 1-5 and 8-12 for 30 minutes. The National Cancer Institute common toxicity criteria (NCI-CTC Version 3) were used to evaluate the grade of toxicity. Three patients enrolled in each level. Dose escalation was performed when dose-limiting toxicities (DLT) were seen in 0/3, and 3 more cases of the same level were added when DLTs were seen 1-2/3. Maximum-tolerated dose (MTD) were determined when DLTs were seen in 3 cases. DLTs were not recorded during the administration of CDDP up to 4 mg/m(2). However, DLTs were seen 3/3 at level 3. From these results, cisplatin of 4 mg/m(2)was determined to be the recommended dose (RD) in this protocol for postoperative stage IV gastric carcinoma.

Pharmacokinetics of S-1 in patients with peritoneal dissemination of gastric cancer.

The response of gastric cancer with peritoneal dissemination to systemic chemotherapy may be negatively affected by poor drug delivery due to the blood-peritoneal barrier. However, S-1 has been reported to be effective. We examined the pharmacokinetics of S-1 in 14 patients who had gastric cancer with peritoneal dissemination. S-1 was given from the morning of the day before surgery to the morning of surgery. Concentrations of 5-fluorouracil (5-FU) and gimeracil (CDHP) were measured in the serum, ascites, disseminated peritoneal nodes, and normal peritoneum. There was a strong correlation between 5-FU and CDHP concentrations in peritoneal tissues. The concentrations of 5-FU and CDHP in the serum were similar to those in ascites. The concentration of 5-FU was significantly higher in disseminated nodes than in the normal peritoneum. After administration of S-1 to gastric cancer patients with peritoneal dissemination, 5-FU and CDHP in the serum linearly pass through the peritoneum and enter the ascites. High concentrations of 5-FU selectively penetrate disseminated peritoneal cells.

Sensitive MS/MS-liquid chromatography assay for simultaneous determination of tegafur, 5-fluorouracil and 5-fluorodihydrouracil in plasma.

Ftorafur (FT), an oral prodrug of 5-FU, is part of UFT and S1, two oral prodrugs widely used in digestive tract cancer. We set up a liquid chromatography tandem mass spectrometry (LC/MS-MS) method, chosen for its specificity of detection, for simultaneously measuring in human plasma FT, 5-FU and 5-FUH2. Separation was performed on a Hypercarb column. Linearity, precision and accuracy were validated in the concentration range studied for each compound. This simple and reliable LC/MS-MS method allows specific, sensitive and reproducible quantification of FT, 5-FU and FUH2 in human plasma and can be applied to further pharmacokinetic studies in patients treated with FT-based prodrugs.