Modulation of 5-fluorouracil toxicity by uridine, deoxyuridine, orotate and dipyridamole in normal tissues of rats with liver adenocarcinoma

The cytotoxicity of 5-FU, given by the hepatic artery, was measured by its incorporation into the acid soluble fraction, RNA and DNA in normal tissues and an adenocarcinoma transplanted into the liver in rats. Other substances were simultaneously administered by the portal vein to modulate the cytotoxicity. None of them had any significant influence on the incorporation of 5-FU into tumor. Dipyridamole decreased the incorporation of 5-FU into liver RNA and increased the nucleotide/DNA and RNA/DNA ratios so that the incorporation into mg RNA per liver cell was unchanged. Dipyridamole decreased the incorporation into the acid soluble fraction, RNA and DNA of the small intestine and also into RNA per mg DNA. It increased the nucleotide/RNA and RNA/DNA ratios in the bone marrow. Orotate decreased the incorporation into liver and intestinal RNA. Uridine increased the incorporation into liver RNA. The results obtained with dipyridamole were the most pronounced. Studies are continuing with this and other membrane transport inhibitors.     

5-fluorouracil toxicity with severe bone marrow suppression in a dog

This report describes 5-fluorouracil (5-FU) toxicity in a dog that resulted in severe bone marrow suppression. The dog initially was presented with neurologic and gastrointestinal signs and developed pancytopenia characterized by severe neutropenia and thrombocytopenia. Examination of bone marrow aspirate showed aplasia. The dog also had marked echinocytosis, which has been previously associated with in vitro 5-FU exposure. The patient was given aggressive supportive care and recovered within 25 d of exposure. To the authors' knowledge, this is the first report of a case of 5-FU toxicity in a dog to include results of bone marrow examination, as well as the first to describe echinocytosis related to 5-FU toxicity.     

氨甲喋呤联合5-氟尿嘧啶在恶性滋养细胞肿瘤中的临床疗效分析

目的分析氨甲喋呤联合5-氟尿嘧啶在恶性滋养细胞肿瘤中的临床疗效。方法回顾性分析氨甲喋呤联合5-氟尿嘧啶治疗48例恶性滋养细胞肿瘤患者的近期疗效、中近期疗效及副反应。结果在本组48例病例中侵蚀性葡萄胎30例,其中25例单一以本方案治愈;绒癌为18例,其中16例单一以本方案治愈;本组侵蚀性葡萄胎近期治愈率为83.3%,半年及1年无复发率为100%及88%;绒癌的近期治愈率为89%,半年及1年无复发率为100%及87.5%。结论氨甲喋呤联合5-氟尿嘧啶是治疗恶性滋养细胞肿瘤的有效化疗方案。     

Dihydropyrimidine dehydrogenase gene as a major predictor of severe 5-fluorouracil toxicity

The importance of polymorphisms in the dihydropyrimidine dehydrogenase (DPD) gene (DPYD) for the prediction of severe toxicity in 5-fluorouracil (5-FU) based chemotherapy has been controversially debated. As a key enzyme in the catabolism of 5-FU, DPD is the top candidate for pharmacogenetic studies on 5-FU toxicity, since a reduced DPD activity is thought to result in an increased half-life of the drug, and thus, an increased risk of toxicity. Here, we review the current knowledge on well-known and frequently studied DPYD variants such as the c.1905+1G>A splice site variant, as well as the recent discoveries of important functional variation in the noncoding regions of DPYD. We also outline future directions that are needed to further improve the risk assessment of 5-FU toxicity, in particular with respect to metabolic profiling and in the context of different combination therapeutic regimens, in which 5-FU is used today.     

Inhibition by methotrexate of the stable incorporation of 5-fluorouracil into murine bone marrow DNA

As a consequence of the inhibition of de novo purine synthesis by methotrexate (MTX) there is an increase in 5-phosphoribosyl-1-pyrophosphate (PRPP) concentration. In cells where 5-fluorouracil (FUra) is activated via orotate phosphoribosyltransferase (OPRtase), increased PRPP results in greater conversion of FUra to nucleotides. In the murine CD8F1 breast tumor system, MTX markedly enhances the antitumor activity of FUra, increasing both the activation of FUra to FUMP and the incorporation of FUTP into RNA. However, in contrast to reported tumor tissue culture studies, MTX pretreatment in vivo prevents the stable incorporation of FUra into CD8F1 bone marrow DNA. Pretreatment with MTX (300 mg/kg) 2.5 hr prior to [3H]FUra (100 mg/kg), with a 2-hr labeling, reduced the level of FUra in DNA from 921 pmol to 66 pmol/mg of DNA. Without MTX pretreatment, 59% of the total incorporation of FUra into nucleic acids was into DNA when FUra was administered. After MTX the percentage of incorporation into DNA was reduced to 9%. Additionally, the ratio of [3H]FUra to 32P in DNA when both were given simultaneously was reduced by greater than 90%, suggesting that MTX must be specifically blocking the incorporation of FUra rather than nonspecifically preventing its incorporation by inhibiting DNA synthesis. In contrast, MTX failed to reduce the formation of DNA containing fluorouracil residues from FdUrd. To test whether MTX prevents the initial incorporation of FUra into DNA, or acts to enhance removal by the DNA glycosylase repair system, DNA was prelabeled in vivo with [3H]FUra, and MTX or MTX plus dThd was then administered. The level of FUra in bone marrow DNA was not reduced by subsequent treatment with MTX, or MTX plus dThd, indicating that MTX does not enhance the removal of FUra from DNA. The level of total free fluorodeoxynucleotides formed from FUra was reduced by two-thirds following MTX pretreatment, suggesting that the action of MTX in preventing the stable incorporation of FUra into DNA was to reduce the availability of FdUTP.     

Severe 5-fluorouracil toxicity associated with a marked alteration of pharmacokinetics of 5-fluorouracil and its catabolite 5-fluoro-5,6-dihydrouracil: a case report

OBJECTIVE: To describe the altered pharmacokinetics of 5-fluorouracil (5-FU) and its major catabolite 5-fluoro-5,6-dihydrouracil (5-FDHU) in a 52-year-old woman affected by a severe 5-FU toxicity. METHODS: Toxicities were rated according to World Health Organization. 5-FU and 5-FDHU plasma concentrations and dihydropyrimidine dehydrogenase (DPD) activity of peripheral blood mononuclear cells (PBMC) were measured by HPLC analysis. RESULTS: After a single cycle of 5-FU therapy the patient developed grade 4 diarrhea and stomatitis, grade 3 vomiting, neutropenia, and dermatitis. Compared to a control population, 5-FU AUC, elimination half-life, and C(max) were markedly increased (24.75 vs. 9.25 +/- 0.63 h microg/ml, >5 vs. 0.36 +/- 0.05 h, and 58.54 vs. 37.2 +/- 4.03 microg/ml, respectively) whereas systemic clearance was decreased (12 vs. 51.29 +/- 2.97 l/h/m2); also 5-FDHU AUC (3.3 vs. 12.35 +/- 0.7 h microg/ml) and C(max) (3.4 vs. 4.56 +/- 0.15 microg/ml), which was reached with delay, were reduced. Surprisingly, the PBMC DPD activity (110.8 pmol/min/mg protein) and urinary uracil (68.32 micromol/g urinary creatinine) were within normal range. CONCLUSIONS: Our results show the altered 5-FU and 5-FDHU pharmacokinetics in a severe 5-FU toxicity case due to an impairment of the hepatic DPD activity and suggest the necessity of a pharmacological evaluation of 5-FU treated patients.     

静脉滴注大剂量甲氨蝶呤致亚急性神经中毒

1例20岁男性患者因骨肉瘤给予2个周期大剂量甲氨蝶呤化疗(8 g/m2)。第2次化疗后第7天,患者突然出现言语不畅、左手麻木、恶心、乏力,后逐渐进展为失语、双上肢强直、双下肢麻木。实验室检查:白细胞计数12.5×109/L,红细胞计数3.6×1012/L,血红蛋白111 g/L,血小板计数101×109/L。头部CT扫描未见异常。给予吸氧。约3 h后症状好转。第2天下午患者在无诱因情况下又出现相似症状。颅脑磁共振成像、弥散加权成像、脑电图、心脏多普勒超声、颈动脉超声检查均正常。静脉滴注马来酸桂哌齐特和胞磷胆碱,2 d后症状消失。     

大剂量甲氨蝶呤化疗致儿童药物超敏反应的临床护理

目的 总结2例大剂量甲氨蝶呤化疗致儿童药物超敏反应的临床护理措施。方法 主要护理措施包括病情观察、皮肤护理、口腔护理、症状管理及心理护理。结果 2例患儿均未发生严重并发症,康复出院。结论 大剂量甲氨蝶呤引起的药物超敏反应不常见,一旦发生,护士在协助治疗的同时,应加强对病情的观察和对皮肤、口腔的护理,做好症状管理及心理护理,为患儿减轻痛苦,促进其康复。     

Modulation of 5-fluorouracil host toxicity by 5-(benzyloxybenzyl)barbituric acid acyclonucleoside, a uridine phosphorylase inhibitor, and 2',3',5'-tri-O-acetyluridine, a prodrug of uridine

Administration of 200 mg/kg of 5-fluorouracil (FUra) to mice bearing human colon carcinoma DLD-1 xenografts resulted in 100% mortality. Oral administration of 2000 mg/kg of 2',3',5'-tri-O-acetyluridine (TAU), a prodrug of uridine, in combination with 120 mg/kg of 5-(benzyloxybenzyl)barbituric acid acyclonucleoside (BBBA), the most potent known inhibitor of uridine phosphorylase (UrdPase, EC 2.4.2. 3), 2 hr after the administration of the same dose of FUra completely protected the mice (100% survival) from the toxicity of FUra. This combination also reduced tumor weight by 67% compared with 46% achieved by the maximum tolerated dose (50 mg/kg) of FUra alone. Similarly, administration of BBBA plus TAU 1 hr before or 4 hr after the administration of FUra reduced the tumor weight by 53 and 37%, respectively. However, these schedules were less effective in protecting the host from the toxicity of FUra than when the treatment was carried out at 2 hr after FUra administration. TAU alone did not protect from FUra host toxicity. The efficiency of the BBBA plus TAU combination in rescuing from FUra host toxicities is attributed to the exceptional effectiveness of this combination in raising and maintaining higher plasma uridine concentrations than those achieved by TAU alone or by equimolar doses of uridine (Ashour et al., Biochem Pharmacol 51: 1601-1612, 1996). The present results suggest that the BBBA plus TAU combination can provide a better substitute for the massive doses of uridine required to achieve the high levels of uridine necessary to rescue or protect from FUra host toxicities without the toxic side-effects associated with such doses of uridine. The combination of TAU plus BBBA may also allow the escalation of FUra doses for better chemotherapeutic efficacy. Alternatively, the combination may be used as a rescue regimen in the occasional cases where cancer patients receive a lethal overdose of FUra.     

Modulation of 5-fluorouracil by 5-ethyl-2'-deoxyuridine on cell lines expressing different dihydropyrimidine dehydrogenase activities

The purpose of the present study was to clarify the significance of the inhibition of dihydropyrimidine dehydrogenase (DPD) in the modulation of 5-fluorouracil (5-FU) action by 5-ethyl-2'-deoxyuridine (EUdR). Four human cell lines, which differed in their susceptibility to 5-FU and in their DPD activity, were selected as biological objects. Several other enzymes of pyrimidine metabolism, i.e. thymidylate synthase (TS), thymidine kinase (TK) and pyrimidine nucleoside phosphorylase (PNP), which might be involved in the 5-FU action were also studied to elucidate their potential role in the modulation of 5-FU cytotoxicity. Two out of the four cell lines, i.e. COLO1 and SW620, showed low (57 and 28 pmol/min/mg protein) and the other two cell lines, i.e. CAL51 and CAL33, showed high (235 and 184 pmol/min/mg protein) DPD activity, respectively. In our study, contrary to our expectation, no correlation between the DPD and TS activity of the cell lines and their 5-FU sensitivity could be observed. EUdR alone was cytotoxic only on CAL33 cells in a concentration below 1 mM (IC50=194 microM) which might be due to the high TK activity (857 pmol/min/mg protein) measured in this cell line, favoring the formation of the phosphorylated nucleotides EdUMP and EdUTP indispensable for the inhibition of TS and DNA polymerase, respectively. Surprisingly, although EUdR by metabolizing to EUra was able to reduce the high activity of DPD in CAL33 and CAL51 cells by 47 and 55%, respectively, no potentiation of the 5-FU action occurred on these cell lines. On the contrary, enhancement of the 5-FU cytotoxicity was demonstrated on COLO1 and SW620 cells with low DPD activity. Our findings suggest that the 5-FU modulatory action of EUdR may be directed on other molecular targets than DPD as well, i.e. the augmentation of TS inhibition by EdUMP as demonstrated on SW620 cells might be one of these mechanisms.     

Relationship between plasma concentrations of 5-fluorouracil and 5-fluoro-5,6-dihydrouracil and toxicity of 5-fluorouracil infusions in cancer patients

This study investigated the relationship among the pharmacokinetics of 5-fluorouracil (5-FU) and 5-fluoro-5,6-dihydrouracil (5-FDHU); the activity of dihydropyrimidine dehydrogenase (DPD) in peripheral blood mononuclear cells; and treatment-related toxicity in 26 patients with surgically resected colorectal cancer treated with short daily infusions of 5-FU adjuvant chemotherapy, each cycle consisting of 5 consecutive days every 4 weeks. After the first chemotherapeutic cycle, severe stomatitis and diarrhea occurred in 5 patients and were related to the variations in the systemic disposition of the drug rather than to DPD activity. These patients showed a significant decrease in 5-FU clearance, and an increase in the 5-FU/5-FDHU area under the time-concentration curve (AUC) ratio, as compared with patients who experienced mild toxicities, whereas a low DPD activity was observed in only 2 patients. In conclusion, the results of this study demonstrate that the alterations in 5-FU and 5-FDHU pharmacokinetics are related to severe toxicities in patients treated with short intravenous infusion of 5-FU.     

5-氟尿嘧啶神经酰胺脂质体急性毒性的昼夜节律研究

目的研究5-氟尿嘧啶(5-FU)半乳糖神经酰胺(GalCer)脂质体急性毒性是否存在昼夜节律.方法分别于4、10、16、22时,采用静脉注射(iv),观察小鼠给予包封有5-FU的GalCer脂质体后所产生的毒性反应和死亡情况,计算半数致死量(LD50).结果iv 5-FU GalCer脂质体LD50分别为171.0、252.5、270.1和202.7 mg@kg-1;其95%可信区间分别为152.8～190.3、226.8～281.1、222.0～327.5和173.1～236.5 mg@kg-1.结论5-FU GalCer脂质体夜间的急性毒性大于白天,存在着明显的昼夜节律现象.     

Clinical experience with 5-fluorouracil (5-FU) and high-dose folinic acid in solid tumors

This paper reports experience with high-dose folinic acid (HDFA) and 5-fluorouracil (5-FU) in the treatment of 130 patients with various types of tumor. While the objective results obtained from gastrointestinal malignancies (response rate = 15%) are no better than those usually gained by 5-FU alone, impressive results were achieved in patients with advanced and mainly pretreated breast cancer (response rate = 44%). Haematological toxicity was generally mild, while oral mucositis, diarrhoea and conjunctivitis were major side effects. Our data suggest that HDFA and 5-FU seem a very promising combination and warrant further investigation.     

Pharmacokinetics of high-dose methotrexate treatment in children

Summary The pharmacokinetics of intravenous high-dose methotrexate were studied in two groups of children being treated for malignant diseases, mostly acute lymphatic leukemia. The peak serum level of methotrexate of 2.32·10^–5 mol/l was found in children given 500 mg methotrexate/m² by a 24 h infusion, and another group given 2790 mg/m² during a 6 h infusion had serum levels as high as 2.16·10^–4 mol/l. The decay of serum concentration of methotrexate after completion of the infusion followed a diphasic curve, with an initial serum half-life of 4.8 h, followed by a second half-life of 34.4 h at distribution equilibrium. The apparent volume of distribution was 56.8 litres/m². Significant levels of methotrexate were found in cerebrospinal fluid, but penetration into cerebrospinal fluid was slow. Urinary excretion of methotrexate was considerable. Four to five days after commencement of the infusion, urinary concentrations of methotrexate still exceeded the serum levels.     

大剂量甲氨蝶呤治疗儿童白血病毒副作用临床研究

目的：研究大剂量甲氨蝶呤（HDMTX）加四氢叶酸钙（CF）解救的方案治疗儿童白血病的临床毒副作用。方法：16例急性淋巴细胞白血病进行了40例次的HDMTX-GF的治疗，对用药前后患儿的临床表现，血尿常规、心电图、心肌酶谱、肝肾功能等和患儿的一般反应，皮肝粘膜损害、心脏毒性、肝肾损害、神经毒性、骨髓抑制等进行对照研究。结果；骨髓抑制发生率72.5%，持续时间3-13d；肝功能损害37.5%，但均较轻；恶心、呕吐30.0%；皮疹的5.0%；心电图异常和心肌酶谱异常为12.5%和17.5%；2例因严重不良反应死亡。结论：大剂量甲氨蝶呤加四氢叶酸钙治疗儿童白血病时，毒副作用较为常见，大多可耐受；个别可出现严重毒副作用，故应注意患儿个体差异，有条件的单位应监测血药浓度，防止出现严重的毒副作用，并根据血药浓度进行适当的四氢叶酸钙解救，避免过度解救而影响疗效。     

5-氟尿嘧啶联合甲氨蝶呤治疗恶性滋养细胞肿瘤的临床疗效

目的 探讨5-氟尿嘧啶(5-Fu)联合甲氨蝶呤治疗恶性滋养细胞肿瘤的临床疗效。方法 以入院病例号为编号,根据随机数字表法,将80名确诊为恶性滋养细胞肿瘤的患者随机分成两组,每组40例。对照组给予5-Fu化疗;观察组给予5-Fu联合甲氨蝶呤治疗。观察两组患者治疗后血人绒毛膜促性腺激素(HCG)变化、临床症状缓解情况、疗效及不良反应等指标变化情况,探讨其临床治疗价值。结果 治疗后,观察组临床有效率为97.5%,明显高于对照组的85.0%,两组比较差异有统计学意义(P<0.05)。治疗后,观察组血HCG最高滴定值<10³ mIU/mL患者数为8例,明显高于对照组的4例,两组比较差异有统计学意义(P<0.05);观察组血HCG最高滴定值>10⁵ mIU/mL患者数为6例,明显低于对照组的18例,两组比较差异有统计学意义(P<0.05)。两组患者不同程度出现白细胞减少、恶心、呕吐、口腔溃疡等不良反应,但组间差异无统计学意义。结论 5-Fu联合甲氨蝶呤治疗恶性滋养细胞肿瘤疗效确切且安全可靠,值得临床推广应用。