Thermal stability studies of 5‐fluorouracil using diffuse reflectance infrared spectroscopy

5‐Fluorouracil is one of the oldest chemotherapy drugs and it has been in use for decades. It is an active medicine against several types of cancer and effectively blocks the replication of DNA viruses. The present study assessed the potential of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to determine the thermal stability of 5‐fluorouracil. Infrared spectra of the drug before and after exposure to thermal radiation at different temperatures were collected in diffuse reflectance mode using a Fourier transform infrared (FTIR) spectrophotometer. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analysis were carried out simultaneously to confirm and support the results of infrared spectroscopy. The DRIFT spectra reveal that the drug shows good thermal stability up to 275 °C and undergoes complete thermal breakdown at about 285 °C. The results of DSC and XRD analysis also give the same information, which support the implementation of diffuse reflectance infrared spectroscopy for the determination of thermal stability of 5‐fluorouracil. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and purification of [2‐13C]‐5‐fluorouracil

[2‐¹³C]‐5‐Fluoropyrimidine‐2,4(1H,3H)‐dione ([2‐¹³C]‐5‐fluorouracil or [2‐¹³C]‐5‐FU) is a potential diagnostic agent for measuring 5‐FU‐induced toxicity in cancer patients. It was prepared and purified with isotopic and chemical purity of>99% on a multigram scale in a two‐step synthesis from [¹³C]‐urea. Preparative separation of [2‐¹³C]‐FU and [2‐¹³C]‐uracil was carried out by automated medium pressure silica gel column chromatography. The method is applicable to a broader range of 5‐FU isotopic analogs derived from labeled uracil. Copyright © 2011 John Wiley & Sons, Ltd.     

姜黄丸水分含量测定近红外定量模型的建立

目的: 运用近红外光谱(NIR)技术对姜黄丸水分进行快速测定。方法: 采集不同批次姜黄丸样品的近红外光谱图,结合OPUS软件进行预处理,在7 552.3~6 707.5 cm^-1,6 699.8~5 538.8 cm^-1,5 515.7~4 204.3 cm^-1谱段内,选择8个主成分,采用偏最小二乘法(PLS)建立姜黄丸水分近红外定量模型。结果: 所建模型相关系数(R²)为0.998 6,交互验证均方根偏差(RMSECV)为0.233,仪器精密度及样品重复性良好,所建模型可以准确测出姜黄丸水分含量。结论: 该方法具有快速、准确、简便的特点,可以用于大批量姜黄丸水分含量的快速在线检测。     

Effect of acute hepatic failure on the hepatic first‐pass effect of 5‐fluorouracil in rats

Objectives In cancer chemotherapy for hepatocellular carcinoma, 5‐fluorouracil is widely used and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and reduce systemic toxicity. 5‐Fluorouracil is eliminated primarily by the liver and so the hepatic first‐pass effect after intrahepatic arterial administration of 5‐fluorouracil may be lower in patients with hepatic failure, and systemic toxicity may not be reduced. In this study, we have investigated the effect of acute hepatic failure on the first‐pass effect of 5‐fluorouracil in rats. Methods Experimental acute hepatic failure was induced by treatment with carbon tetrachloride (CCl₄). 5‐Fluorouracil was infused for 15 min into the hepatic artery or the saphenous vein of rats at a dose of 1.25 mg/kg. Key findings Hepatic availability in 50% CCl₄‐treated (severe hepatic failure) rats was higher than in controls. Conclusions The hepatic first‐pass effect after intrahepatic arterial administration of 5‐fluorouracil was lower in severe hepatic failure. Therefore, the reducing effect of the systemic toxicity after intrahepatic arterial administration may be lower in severe hepatic failure.     

Radiolabeling and in vitro evaluation of a new 5‐fluorouracil derivative with cell culture studies

The clinical impact and accessibility of ^99mTc tracers for cancer diagnosis would be greatly enhanced by the availability of a new, simple, and easy labeling process and radiopharmaceuticals. 5‐Fluorouracil is an antitumor drug, which has played an important role for the treatment of breast carcinoma. In the present study, a new derivative of 5‐Fluorouracil was synthesized as (1‐[{1′‐(1′′‐deoxy‐2′′,3′′:4′′,5′′‐di‐O‐isopropylidene‐β‐D‐fructopyranose‐1′′‐yl)‐1′H‐1′,2′, 3′‐triazol‐4′‐yl}methyl]‐5‐fluorouracil) ( E ) and radiolabeled with ^99mTc. It was analyzed by radio thin layer chromatography for quality control and stability. The radiolabeled complex was subjected to in vitro cell‐binding studies to determine healthy and cancer cell affinity using HaCaT and MCF‐7 cells, respectively. In addition, in vitro cytotoxicity studies of compound E were performed with HaCaT and MCF‐5 cells. The radiochemical purity of the [^99mTc]Tc E was found to be higher than 90% at room temperature up to 6 hours. The radiolabeled complex showed higher specific binding to MCF‐7 cells than HaCaT cells. IC₅₀ values of E were found 31.5 ± 3.4 μM and 20.7 ± 2.77 μM for MCF‐7 and HaCaT cells, respectively. The results demonstrated the potential of a new radiolabeled E with ^99mTc has selective for breast cancer cells.     

Influence of vasomodulators and tumor transplantation on the disposition of 5‐fluorouracil after application to the liver surface in rats

This study investigated the effect of epinephrine (a vasoconstrictor) and hydralazine (a vasodilator) on the hepatic disposition of 5‐fluorouracil (5‐FU) after application to the surface of the liver in rats. Normal livers were compared with a Walker 256 carcinoma cell tumor model. A cylindrical diffusion cell was attached to the liver surface. 5‐Fluorouracil was added into the diffusion cell in combination with vasomodulators or after pretreatment with epinephrine. After selected treatment times, the 5‐FU concentrations were assayed at three sites in the excised livers. The 5‐FU concentration in the region under the cell attachment site (site 1) was significantly higher after concomitant application of 5‐FU and epinephrine, compared with 5‐FU alone, and increased in an epinephrine dose‐dependent manner. On the other hand, preferential distribution of 5‐FU at site 1 was not seen when applied in combination with hydralazine. After 10 min of epinephrine pretreatment, the concentration of 5‐FU at site 1 was approximately two times higher than that for the control. Furthermore, the 5‐FU concentration at site 1 of the tumor model was greatly increased compared with the normal liver. These results suggest that application of epinephrine to the liver surface might enhance the accumulation of 5‐FU at the desired target site.     

近红外光谱法快速分析注射用盐酸头孢甲肟及其水分的含量

目的建立近红外通用性模型,对注射用盐酸头孢甲肟及其水分进行无损、快速定量分析。方法以不同企业生产的注射用盐酸头孢甲肟为分析对象,用光纤测定近红外漫反射光谱,并通过聚类分析方法确定校正集和预测集,考察不同预处理方法、谱段的影响,选择建立最佳的注射用盐酸头孢甲肟及其水分的定量模型。结果注射用盐酸头孢甲肟定量分析模型由36个校正集样品建立校正模型,17个样品用于外部验证,验证集相关系数为96.33%,校正集均方差为1.19%,验证集均方差为1.66%。注射用盐酸头孢甲肟水分定量分析模型由34个样品校正集样品建立校正模型,19个样品用于外部验证,验证集相关系数为96.39%,校正集均方差为0.22%,验证集均方差为0.26%。结论 2个模型结合可以对注射用盐酸头孢甲肟含量和水分进行快速测定,方法简便,结果准确可靠,适合大量重复性样品的分析测定。     

5‐Fluorouracil combined with apigenin enhances anticancer activity through mitochondrial membrane potential (ΔΨm)‐mediated apoptosis in hepatocellular carcinoma

The development of chemoresistance may reduce the efficacy of chemotherapeutic drugs for treating hepatocellular carcinoma (HCC). In the present study, the effects of apigenin on intensifying the chemosensitivity of HCC cells and an HCC xenograft model in response to 5‐fluorouracil (5‐FU) were investigated. Sub‐toxic concentrations of apigenin (4 μmol/L) significantly enhanced the cytotoxicity of 5‐FU (100 μg/mL) in HCC cells. In vivo, combined treatment with apigenin (20 mg/kg, five times/week for 3 weeks) and 5‐FU (20 mg/kg for 5 consecutive days) significantly inhibited the growth of HCC xenograft tumours. Annexin V–propidium iodide dual staining assays, terminal deoxyribonucleotidyl transferase‐mediated dUTP–digoxigenin nick end‐labelling assays and western blotting analysis were used to confirm the synergistic effects of apigenin and 5‐FU on HCC apoptosis. Coincubation of HCC cells with apigenin and 5‐FU increased levels of reactive oxygen species (ROS), which was followed by a decrease in the mitochondrial membrane potential (ΔΨm). In addition, combined triggered the mitochondrial apoptotic pathway, as indicated by decreased Bcl‐2 expression and loss of ΔΨm, with significant activation of caspase 3 and poly(ADP‐ribose) polymerase. The present study is the first to demonstrate that apigenin may potentiate the cytotoxicity of 5‐FU in HCC via inhibition of ROS‐mediated drug resistance and concurrent activation of the mitochondrial pathways of apoptosis.     

近红外光谱法快速测定呋喃妥因肠溶片的含量

目的利用近红外漫反射光谱分析技术和化学计量学方法对呋喃妥因肠溶片进行无损、快速定量分析.方法以在全国范围内不同企业生产的呋喃妥因肠溶片为分析对象,用光纤探头测定近红外漫反射光谱,通过偏最小二乘法(PLS)建立数学模型,考察了不同建模谱段和图谱预处理方法的选择对模型预测能力的影响.结果所建模型具有较好的预测能力,验证集样品的 NIR预测值与参考值间的相关系数(R2)为95.25%,平均预测偏差为1.72,预测均方差(RMSEP)为2.15.结论该方法快速、简便、结果准确,可用于药品现场快速分析.     

Probiotic Bifidobacterium bifidum G9‐1 attenuates 5‐fluorouracil‐induced intestinal mucositis in mice via suppression of dysbiosis‐related secondary inflammatory responses

Bifidobacterium, a major component of the intestinal microbiota, has been clinically used for the treatment of diarrhoea and constipation. 5‐Fluorouracil (5‐FU), widely used for cancer chemotherapy, is known to frequently induce intestinal mucositis accompanied by severe diarrhoea. The present study examined the effect of Bifidobacterium bifidum G9‐1 (BBG9‐1) on 5‐FU‐induced intestinal mucositis in mice. Intestinal mucositis was induced by repeated administration of 5‐FU for 6 days. BBG9‐1 was administered orally once daily for 9 days, beginning 3 days before the onset of 5‐FU treatment. Repeated administration of 5‐FU caused severe intestinal mucositis, characterised by shortening of villi and destruction of crypts, accompanied by increases in intestinal myeloperoxidase activity and inflammatory cytokine expression, body weight loss, and diarrhoea on day 6. Daily administration of BBG9‐1 significantly reduced the severity of intestinal mucositis and inflammatory responses and tended to attenuate clinical symptoms. In contrast, BBG9‐1 failed to prevent apoptosis induction on day 1 after the first 5‐FU administration. The structure of the intestinal microbiota, as analysed by weighted UniFrac distance, was largely altered by 5‐FU treatment, but this change was mitigated by daily administration of BBG9‐1. Moreover, 5‐FU treatment decreased the abundance of Firmicutes and increased the abundance of Bacteroidetes, but these responses were also significantly inhibited by daily administration of BBG9‐1. These results suggest that BBG9‐1 has an ameliorative effect against 5‐FU‐induced intestinal mucositis through the attenuation of inflammatory responses via improve dysbiosis. BBG9‐1 could be useful for the prevention of intestinal mucositis during cancer chemotherapy.     

Synthesis,In Vitro Cytotoxicity and Radiosensitizing Activity of Novel 3‐[(2,4‐Dinitrophenylamino)Alkyl] Derivatives of 5‐Fluorouracil

Previously, it was reported that 3[3‐(2,4‐dinitrophenylamino)‐propyl]‐5‐fluorouracil 8c unlike its components 5‐fluorouracil (5‐FU) 6 and 2,4‐dinitroaniline 2 in HT‐29 cells under aerobic conditions had no cytotoxicity but showed radiosensitizing activity. In this study several analogues of 8c differing in the number of linking methylene groups were prepared and tested for in vitro cytotoxicity and radiosensitizing activity under both aerobic and hypoxic conditions. Tethered compound 8a was prepared in one pot by the reaction of 5‐FU 6 with paraformaldehyde and 2,4‐dinitroaniline 2 in the presence of the concentrated hydrochloric acid, and compounds 8b–f were prepared by the reaction of N‐(bromoalkyl) ‐ 2,4‐dinitrobenzeneamines 5b–f with 1‐(t‐butoxycarbonyl)‐5‐fluorouracil 7 followed by hydrolysis of the protecting group. The cytotoxicity of the tested compounds were measured by 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT), and propidium iodide (PI)‐digitonin assays and values of sensitization enhancement ratio (SER) as a measure of the radiosensitizing activity were measured from radiation survival curves in the absence and presence of each sensitizer for 37% survival respectively. Results showed that tethered compounds 8a–f induced time‐ and concentration‐dependent cytotoxicity under hypoxia but had no significant effect under aerobic conditions. These compounds also showed selective and concentration‐dependent radiocytotoxicity under hypoxic conditions.     

Role of peptide YY in 5‐fluorouracil‐induced reduction of dietary intake

5‐fluorouracil (5‐FU) is part of the standard care for cancer treatment but is associated with high incidences of appetite loss and reduced food intake, which may contribute to chemotherapy‐induced cachexia (weakness and wasting of tissue). The role of gastrointestinal satiety hormones in chemotherapy‐induced appetite loss has not been intensively investigated. Peptide YY (PYY) and glucagon‐like peptide (GLP)‐1 are important signals of gastrointestinal satiety, so this study examined the roles of these gut hormones in 5‐FU‐induced reduction of dietary intake. Mice were given 5‐FU (50 mg/kg, intraperitoneal [i.p.]) every day for 4 consecutive days. Gene expression levels of proglucagon (Pro‐Gcg), a precursor of GLP‐1, and PYY in the colon were examined by real‐time RT‐PCR. Serum levels of GLP‐1 and PYY were measured by enzyme‐linked immunosorbent assay. Some mice were pretreated with the GLP‐1 receptor antagonist exendin9–39 (1 mg/kg) or the neuropeptide Y type 2 (NPY2) receptor antagonist BIIE0246 (2 mg/kg) via the i.p. route 30 minutes before 5‐FU administration. Mice receiving 5‐FU exhibited a significant reduction in food intake that was correlated with body weight loss. These mice also showed significantly enhanced expression levels of mRNAs encoding pro‐GLP‐1 and PYY in the transverse and distal colon as well as elevated serum concentrations of GLP‐1 and PYY compared to vehicle‐treated controls. The 5‐FU‐induced reduction in food intake was attenuated by BIIE0246 but not by exendin9–39. These data suggest that administration of a NPY2 receptor antagonist may be effective for attenuating the anorexia caused by 5‐FU chemotherapy.     

硫酸羟氯喹颗粒水分近红外光谱在线定量模型的建立

目的 为实时检测硫酸羟氯喹颗粒在流化床干燥过程中的水分含量变化,建立颗粒水分的在线近红外光谱定量模型.方法 物料颗粒在流化床的干燥过程中,实时取样并用水分测定仪测量颗粒水分,采用多元散射校正(multiplicative signal correction,MSC)、一阶导数和Karl Norris平滑的光谱预处理方法...     

Early‐Onset 5‐Fluorouracil Toxicity in a Patient Negative for Dihydropyrimidine Dehydrogenase Mutations: The Clinical Course of Reversal with Uridine Triacetate

An antimetabolite pyridine analog, 5‐fluorouracil (5‐FU), is used to treat solid tumors. Early toxicities may occur at standard doses of 5‐FU due to dihydropyrimidine dehydrogenase (DPD) deficiency. Uridine triacetate, approved by the Food and Drug Administration in 2015, is an oral prodrug of uridine, a pharmacologic antidote for 5‐FU toxicity. To our knowledge, this is the first case report that documents the clinical course of a patient treated with uridine triacetate to reverse early‐onset 5‐FU toxicity negative for DPD mutations. We describe the case of a 73‐year‐old man with anal cancer treated with standard‐of‐care chemotherapy and radiation. Two days after completion of his initial 5‐FU infusion, the patient developed severe mucositis and extreme fatigue, followed by a rapid decline in his blood cell counts and fevers. The patient was initiated on uridine triacetate 86 hours after completion of his 5‐FU infusion. Over a 10‐day hospital length of stay, the patient's absolute neutrophil count recovered to within normal limits, and his mucositis significantly improved. At follow‐up visits, the patient denied any residual symptoms of 5‐FU toxicity. We describe the patient's clinical course from hospital presentation to 31 days after initiation of uridine triacetate.     

Inter‐laboratory validation of the modified murine local lymph node assay based on 5‐bromo‐2′‐deoxyuridine incorporation

The murine local lymph node assay (LLNA) is a well‐established alternative to the guinea pig maximization test (GPMT) or Buehler test (BT) for the assessment of the skin sensitizing ability of a drug, cosmetic material, pesticide or industrial chemical. Instead of radioisotope using in this method, Takeyoshi M. et al. ( 2001 ) has developed a modified LLNA based on the 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation (LLNA:BrdU‐ELISA). The LLNA:BrdU‐ELISA is practically identical to the LLNA methodology excluding the use of BrdU, for which a single intraperitoneal injection of BrdU is made on day 4, and colorimetric detection of cell turnover. We conducted the validation study to evaluate the reliability and relevance of LLNA:BrdU‐ELISA. The experiment involved 7 laboratories, wherein 10 chemicals were examined under blinded conditions. In this study, 3 chemicals were examined in all laboratories and the remaining 7 were examined in 3 laboratories. The data were expressed as the BrdU incorporation using an ELISA method for each group, and the stimulation index (SI) for each chemical‐treated group was determined as the increase in the BrdU incorporation relative to the concurrent vehicle control group. An SI of 2 was set as the cut‐off value for exhibiting skin sensitization activity. The results obtained in the experiments conducted for all 10 chemicals were sufficiently consistent with small variations in their SI values. The sensitivity, specificity, and accuracy of LLNA:BrdU‐ELISA against those of GPMT/BT were 7/7 (100%), 3/3 (100%), and 10/10 (100%), respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Identification of five substituted phenethylamine derivatives 5‐MAPDB, 5‐AEDB,MDMA methylene homolog, 6‐Br‐MDMA,and 5‐APB‐NBOMe

This paper reports analytical properties of five substituted phenethylamine derivatives seized from a clandestine laboratory. These five derivatives include 5‐(2‐methylaminopropyl)‐2,3‐dihydrobenzofuran (5‐MAPDB, 1 ), 5‐(2‐aminoethyl)‐2,3‐dihydrobenzofuran (5‐AEDB, 2 ), N ,2‐dimethyl‐3‐(3,4‐methylenedioxyphenyl)propan‐1‐amine (MDMA methylene homolog, 3 ), 6‐bromo‐3,4‐methylenedioxymethamphetamine (6‐Br‐MDMA, 4 ), and 1‐(benzofuran‐5‐yl)‐N ‐(2‐methoxybenzyl)propan‐2‐amine (5‐APB‐NBOMe, 5 ). These compounds were identified by liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS), gas chromatography‐mass spectrometry (GC‐MS), and nuclear magnetic resonance spectroscopy (NMR). No analytical properties about compounds 1‐4 have appeared until now, making this the first report on these compounds. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of dimethylnitrosamine‐induced liver dysfunction on the pharmacokinetics of 5‐fluorouracil after administration of S‐1, an antitumour drug,to rats

Objectives The anti‐tumour agent S‐1 comprises tegafur (a prodrug of 5‐fluorouracil; 5‐FU), gimeracil (2‐chloro‐2,4‐dihydroxypyridine (CDHP); a competitive inhibitor of 5‐FU metabolism) and oteracil potassium. The effect of hepatic dysfunction induced by dimethylnitrosamine (DMN) on the pharmacokinetics of 5‐FU after administration of S‐1 to rats was investigated. Methods S‐1 (5 mg/kg) was administered intravenously and orally to rats with DMN‐induced liver dysfunction. Plasma concentrations of S‐1 components and 5‐FU were measured by HPLC and LC/MS‐MS. Blood tests and in‐vitro enzymatic investigations were also conducted. Key findings DMN treatment induced hepatic dysfunction and decreased the conversion of tegafur to 5‐FU in the liver without altering renal function or dihydropyrimidine dehydrogenase activity. Following intravenous administration of S‐1, the blood concentration‐time profiles of CDHP were similar between control rats and rats with hepatic dysfunction, but the half‐life of tegafur was significantly prolonged. The maximum plasma concentration (C_max) of 5‐FU was significantly reduced and the area under the blood concentration‐time curve (AUC) was reduced by 22%. Following oral administration, the C_max of tegafur, 5‐FU and CDHP were significantly decreased and half‐lives significantly increased. Hepatic dysfunction had a less pronounced effect on the AUC of 5‐FU (13.6% reduction). Conclusions The pharmacokinetic profiles of tegafur, 5‐FU and CDHP were altered by changes in the elimination rate of tegafur induced by a decrease in the conversion of tegafur to 5‐FU. However, hepatic dysfunction had less of an effect on the AUC of 5‐FU, which correlates with anti‐tumour effect, after the oral administration of S‐1.     

Combinational treatment of 5‐fluorouracil and casticin induces apoptosis in mouse leukemia WEHI‐3 cells in vitro

Leukemia is one of the major diseases causing cancer‐related deaths in the young population, and its cure rate is unsatisfying with side effects on patients. Fluorouracil (5‐FU) is currently used as an anticancer drug for leukemia patients. Casticin, a natural polymethoxyflavone, exerts anticancer activity against many human cancer cell lines in vitro, but no other reports show 5‐FU combined with casticin increased the mouse leukemia cell apoptosis in vitro. Herein, the antileukemia activity of 5‐FU combined with casticin in WEHI‐3 mouse leukemia cells was investigated in vitro. Treatment of two‐drug combination had a higher decrease in cell viability and a higher increase in apoptotic cell death, the level of DNA condensation, and the length of comet tail than that of 5‐FU or casticin treatment alone in WEHI‐3 cells. In addition, the two‐drug combination has a greater production rate of reactive oxygen species but a lower level of Ca²⁺ release and mitochondrial membrane potential (ΔΨ_m) than that of 5‐FU alone. Combined drugs also induced higher caspase‐3 and caspase‐8 activities than that of casticin alone and higher caspase‐9 activity than that of 5‐FU or casticin alone at 48 hours treatment. Furthermore, 5‐FU combined with casticin has a higher expression of Cu/Zn superoxide dismutase (SOD [Cu/Zn]) and lower catalase than that of 5‐FU or casticin treatment alone. The combined treatment has higher levels of Bax, Endo G, and cytochrome C of proapoptotic proteins than that of casticin alone and induced lower levels of B‐cell lymphoma 2 (BCL‐2) and BCL‐X of antiapoptotic proteins than that of 5‐FU or casticin only. Furthermore, the combined treatment had a higher expression of cleaved poly (ADP‐ribose) polymerase (PARP) than that of casticin only. Based on these findings, we may suggest that 5‐FU combined with casticin treatment increased apoptotic cell death in WEHI‐3 mouse leukemia cells that may undergo mitochondria and caspases signaling pathways in vitro.     

Preparation and characterization of 5‐fluorouracil‐loaded poly(ϵ‐caprolactone) microspheres for drug administration

Microspheres of 5‐fluorouracil‐loaded poly(?‐caprolactone) (PCL) were prepared by spray‐drying procedure. The degradation characteristics and 5‐fluorouracil release in vitro as well as in vivo were investigated. The average molecular weight, weight loss, crystallinity, and morphology of microspheres were determined using GPC, DSC, and SEM, at different times during the in vitro degradation process. The size distribution of the microspheres indicated that most of the particles were smaller than 3 µm. A 30% weight loss as well as an increase of crystallinity were observed on day 330 of incubation. The percentage of entrapment efficiency of 5‐FU was 49% (44 µg of drug/mg of microspheres). The in vitro total release of 5‐FU took place in 8 days. Determination of plasma 5‐FU concentration in vivo using s.c. injection of 5‐FU‐loaded microspheres in Wistar rats by HPLC with analysis of data using a non‐compartmental model showed drug in plasma 18 days after administration with a maximum drug concentration of 1.5 µg/ml at 96 h. Pharmacokineticallly, a significant increase of AUC and MRT of 5‐FU with regard to the administration of the drug in solution. Scanning electron microscopy and histological studies indicated that the microspheres were surrounded by connective tissue and inflammatory processes were not evident. As a result of these characteristics, the 5‐FU‐loaded PCL microspheres could be used for drug delivery. Drug Dev Res 63:41–53, 2004. © 2004 Wiley‐Liss, Inc.