Allopurinol modulation of fluorouracil toxicity

Preparation and Evaluation of Rebamipide Colloidal Nanoparticles Obtained by Cogrinding in Ternary Ground Mixtures

Aphthous stomatitis is one of the side effects of chemotherapy and radiotherapy in cancer treatment. Rebamipide (RB) mouthwash for stomatitis acts as a radical scavenger. However, RB is poorly soluble in water, which leads to aggregation and precipitation of the dispersoid. The particle size of the drug needs to be less than 100 nm for the particles to reach the mucus layer in the oral cavity. In this study, we attempted to prepare nanoparticles of RB by cogrinding with polyvinylpyrrolidone (PVP) or hydroxypropyl cellulose (HPC) and sodium dodecyl sulfate (SDS) using a mixer ball mill, and evaluated the physicochemical properties of RB nanoparticles, the stability of dispersion in water, and permeation of the mucus layer in vitro. By cogrinding, the particle size decreased to around 110 nm, and powder X-ray diffraction (PXRD) of the particles showed totally broad halo patterns, which suggested a decreased crystalline region. Furthermore, the solubility of RB nanoparticles increased by approximately fourfold compared with RB crystals, and the water dispersibility and permeation of the mucus layer were improved. The results suggest that in a ternary ground mixture of RB, PVP or HPC, and SDS, the RB nanoparticles obtained can be applied as a formulation for stomatitis.

Clinical relevance of biochemical modulation of 5-fluorouracil

Biochemical modulation is a special type of combination chemotherapy which aims to selectively improve the therapeutic index by increasing the antitumor effect and protecting against toxic side effects. Biochemical modulation seems to be an attractive way to circumvent quantitative and qualitative heterogeneity of tumors. In the past decade a number of biochemical modulation approaches have been tested to improve the activity of 5-fluorouracil (5FU). 5FU itself has only modest anticancer activity but has been shown to be a very attractive target for biochemical modulation. A number of the combinations have been ineffective in the clinic despite extensive testing in a number of schedules. Some other combinations were initially tested in an inappropriate schedule, but were active when applied in another schedule. The latter was made possible by a systematic preclinical development of combinations with a proper translation to the clinic accompanied by pharmacodynamic evaluation. This review describes a number of biochemical modulation combinations, both inactive and active. The main conclusion is that properly applied biochemical modulation schedules may lead to successful use in the clinic.

A phase II trial of cisplatin and 5-fluorouracil with allopurinol for recurrent or metastatic carcinoma of the uterine cervix: a Southwest Oncology Group trial

On the strength of recent evidence of the activity of the combination of cisplatin and 5-fluorouracil against squamous malignancies of the esophagus and head and neck, this regimen was evaluated in a phase II trial against metastatic or recurrent squamous carcinoma of the uterine cervix. Cisplatin was administered at a dosage of 100 mg/m2 iv bolus and 5-fluorouracil was continuously infused iv at a dosage of 1000 mg/m2/day for 4 days. In an effort to determine whether the toxicities of 5-fluorouracil could be ameliorated by coadministration of allopurinol, patients were randomized to receive allopurinol, 900 mg orally, an odd or even courses of therapy beginning 5 days before 5-fluorouracil administration and continuing until conclusion of the infusion. Fifty-two eligible patients received 177 evaluable courses of treatment. The overall response rate was 28% (8 complete responses and 6 partial responses). Toxicity was confined to nausea and vomiting (81% of courses), anemia (47%), leukopenia (37%), oral mucositis (15%), diarrhea (6%), and thrombocytopenia (4%). Allopurinol produced no improvement in treatment-related toxicities. Allopurinol did not permit substantial increases in 5-fluorouracil dosage.

Randomized phase II study of a combination of cisplatin (DDP), 5-fluorouracil (5-FU), and allopurinol (HPP) versus 5-FU in advanced colorectal carcinoma. An EORTC Gastrointestinal Tract Cancer Cooperative Group study

In order to improve the therapeutic index of fluorouracil (5-FU), it has been combined with cisplatin (DDP) as synergistic agent and with allopurinol (HPP) as toxicity modulator. Patients with measurable colorectal carcinoma, previously untreated by chemotherapy, were randomized to receive either 5-FU alone 500 mg/m2 push iv days 1-5 or HPP 3 x 300 mg po, days 1-5, 5-FU 800 mg/m2 push iv, days 3-5 and DDP 50 mg/m2 d6. Treatment was repeated every 4 weeks. Of 104 patients randomized, 82 were evaluable for response and survival. Six partial responses were seen in each treatment group (15%) and the median survival time was 7 months. Hematologic toxicities were comparable in both treatment groups, with a mean nadir white blood cell count of 3500/ vs. 3800/mm3 and a mean nadir platelet count of 148,000/ vs, 203,000/mm3 for HPP-5-FU-DDP and 5-FU, respectively. This study suggests that the addition of both HPP and DDP does not improve the activity of 5-FU.

5-Fluorouracil with folinic acid is not effective against metastatic adenocarcinoma of the lung

Thirty patients with a diagnosis of metastatic adenocarcinoma of the lung were entered on a trial to evaluate the antitumor efficacy of 5-fluorouracil 370 mg/m2 daily for 5 days every four weeks in combination with folinic acid 200 mg/m2, 60 min prior to 5FU. All patients had a good performance status, bidimensionally measurable disease, and weight loss less than or equal to 5% of preillness weight. Of the 29 evaluable patients, only two (7%) had partial responses (95% confidence limits 1-24%). Eleven (38%) had stable disease and 16 (55%) progressed. The two responding patients survived 12 and 60+ weeks. The median survival of all evaluable patients was 25 weeks (range 7-60+) and that of the stable patients was 26 weeks. The principal toxicities observed were diarrhea and stomatitis. Myelosuppression was rarely dose limiting. In contrast to the results of treatment with 5FU and folinic acid in metastatic colorectal cancer and breast cancer, the results of treatment with this combination of agents have been much less encouraging in adenocarcinoma of the lung.

Pharmacokinetic modulation of plasma 5-fluorouracil concentrations to potentiate the antitumor activity of continuous venous infusion of 5-fluorouracil

Methods for pharmacokinetic modulation of the plasma 5-fluorouracil (5-FU) level to increase antitumor activity during continuous venous infusion (CVI) of low doses of 5-FU were examined in Yoshida sarcoma-bearing rats. These methods were additional infusion of 5-FU for a short period (4 h) or oral administration of UFT or Tegafur during long-term CVI of 5-FU that alone gave a plasma 5-FU level of about 50 ng/ml. The antitumor effect on Yoshida sarcoma was markedly potentiated when an additive dose of 5-FU combined with 3-cyano-2,6-dihydroxypyridine (CNDP), a potent inhibitor of 5-FU degradation, giving a plasma level of about 500 ng/ml, was infused for 4 h. A similar increase in the antitumor effect was observed with oral administration of a conventional dose of UFT during CVI of 5-FU without CNDP, giving a plasma level of 30 to 60 ng/ml. These results suggest that the antitumor effect of CVI of 5-FU can be potentiated by pharmacokinetic modulation of the 5-FU concentration in the blood.

Effects of the plasma concentration of 5-fluorouracil and the duration of continuous venous infusion of 5-fluorouracil with an inhibitor of 5-fluorouracil degradation on Yoshida sarcomas in rats

The correlations of the 5-fluorouracil (5-FU) level in the plasma and the duration of continuous 5-FU infusion with the antitumor activity of 5-FU on Yoshida sarcomas in rats were examined. The circadian variation in the plasma level of 5-FU during continuous infusion was prevented by treatment with 3-cyano-2,6-dihydroxypyridine (CNDP), which strongly inhibits 5-FU degradation. On continuous venous infusion of 2 to 30 mg/kg of 5-FU over 24 h with CNDP at a molar ratio of 1:10 into normal rats, the 5-FU level in the blood was linearly proportional to the dose of 5-FU. The optimum schedule for antitumor activity on Yoshida sarcomas in rats was found to be infusion of 5-FU at 5 mg/kg over 24 h for 6 consecutive days, which gave a plasma 5-FU level of 176 ng/ml. Continuous infusion of 5-FU to give a plasma level of 300 ng/ml for 6 consecutive days from day 5 after implantation of tumor cells, when the tumors weighed about 1.0 g, resulted in complete regression of the tumors in all rats.

Neoadjuvant therapy for advanced head and neck cancer with allopurinol-modulated high dose 5-fluorouracil and cisplatin. A phase I-II study

The combination of cisplatin (100 mg/m2) and 5-fluorouracil (5-FU) by continuous infusion (1 g/m2/day for 5 days) has been reported to produce a high response rate as neoadjuvant therapy for advanced squamous cell head and neck cancer. We sought to improve the response rate by increasing the dose of 5-FU to 1.5 g/m2/day and 2.0 g/m2/day with allopurinol modulation to reduce toxicity. The overall response rate in the 30 patients who received three courses of chemotherapy was 100% with a 50% complete response (CR) rate. A 50% CR rate was observed in patients with T3 (six of 12) and N3 (four of eight) disease. Six patients (four with CR) did not complete subsequent treatment as planned. Seven of 11 (63.6%) chemotherapy complete responders and three of 12 (25%) partial responders (one lost to follow-up) who received all planned treatment are free of disease. The major toxicity encountered was stomatitis (severe in 32%) followed by leukopenia. The maximum tolerated dose of 5-FU in this combination with allopurinol protection was 1.5 g/m2/day. Cisplatin plus high dose 5-FU does not appear to be associated with a higher CR rate than that reported with conventional doses of 5-FU and is more toxic.

Concurrent allopurinol and 5-fluorouracil: 5-fluoro-2'-deoxyuridylate formation and thymidylate synthase inhibition in rat colon carcinoma and in regenerating rat liver

The formation of FdUMP and the inhibition of TS were studied in a subcutaneously growing transplantable rat colon carcinoma and in regenerating rat liver following bolus administration of 5-FU, with or without HPP pretreatment. In tumor, peak levels of FdUMP at 30 min following bolus 5-FU, 100 mg/kg, averaged 4931 +/- 587 pmol/g. Pretreatment with HPP, 50 mg/kg, 24 h and 1 h before 5-FU, reduced the peak FdUMP level to 2085 +/- 387 pmol/g. The inhibition of TS by 5-FU treatment was greater than 95% by 30 min, and after 48 h residual enzyme inhibition averaged 40%. No effect on TS inhibition by 5-FU treatment could be observed as a result of HPP pretreatment. The levels of TStot increased linearly after 5-FU treatment and doubled within 48 h. In regenerating rat liver, neither FdUMP levels nor TS inhibition, studied at 1 h after bolus 5-FU, were affected by HPP pretreatment.

5-fluorocytosine susceptibility of pathogenic fungi in the presence of allopurinol: potential for improving the therapeutic index of 5-fluorocytosine

The minimal inhibitory concentration of 5-fluorocytosine in 18 pathogenic fungal isolates was not altered by either allopurinol (100 microM) or oxypurinol (100 microM). Since allopurinol at this level clinically has been demonstrated to interfere with 5-fluorouracil anabolism, thereby reducing toxicity owing to 5-fluorouracil, allopurinol may be useful in counteracting the 5-fluorouracil-induced myelotoxicity observed in patients being treated with 5-fluorocytosine without interfering with the antifungal activity of 5-fluorocytosine.

Elucidation of pathways of 5-fluorouracil metabolism in xenografts of human colorectal adenocarcinoma

Hypoxanthine (Hx) and allopurinol (HPP) have been shown experimentally to reduce the conversion of 5-fluorouracil (FUra) to FUMP by orotate phosphoribosyltransferase (OPRTase). This study was designed to elucidate the major pathway by which FU ra was metabolized to ribonucleotides by human colorectal tumors. Consequently, the effect of Hx and HPP on the metabolism of [6-3H]-FUra was examined in 5 human colorectal adenocarcinomas maintained as xenografts in immune-deprived mice. In 2 tumors the formation of ribonucleotides from FUra was depressed by Hx and HPP in combination during the first hour after treatment, while in 3 other lines ribonucleotide concentrations were not reduced. The data suggested that these 5 xenograft lines may be divided into 2 groups: (1) group 1 tumors formed relatively high levels of FUrd and low levels of fluorinated ribonucleotides after the injection of FUra, with no decrease in ribonucleotide concentrations after the administration of Hx and HPP. These tumors possessed high ratios of uridine (Urd) phosphorylase/orotate phosphoribosyltransferase (OPRTase: 7-24) and ribose-1-phosphate (R-1-P)/5-phosphoribosyl-1-pyrophosphate (PRPP;5), and thus appeared to metabolize FUra by the U rd phosphorylase and U rd kinase pathway; (2) group 2 tumors formed low levels of FU rd, higher concentrations of fluorinated ribonucleotides and a reduction in levels of these nucleotides after administration of the purine combination. Group 2 tumors demonstrated a lower enzyme ratio (1-2), higher endogenous levels of PRPP, a lower R-1-P/PRPP ratio (1) and appeared to metabolize FUra predominantly by the activity of OPRTase. Hypoxanthine and HPP, alone or in combination, caused a rapid depletion of PRPP in each tumor line examined. In group 2 tumors this may be responsible for the decreased formation of FUra ribonucleotides observed.

A rapid high-performance liquid chromatographic method for quantitation of 5-fluorouracil in plasma after continuous intravenous infusion

A fast, simple, precise, high-performance liquid chromatographic method for the assay of 5-fluorouracil in plasma from humans receiving continuous intravenous infusion is described. After a single extraction, underivatised 5-fluorouracil is assayed by high-performance liquid chromatography using a variable-wavelength ultraviolet detector. After extraction of 1 ml plasma, 0.3 mumol/l can be assayed. The assay is reproducible and linear up to at least 40 mumol/l. A single determination takes 3 hours and a batch of 40 specimens can be extracted and assayed in 4 working hours if automated equipment is used, enabling injections and calculations to be done overnight.