[Studies of 5-FU concentrations associated with microangiography in colorectal cancer tissue]

In order to elucidate the effect of supplying vessels on 5-FU distribution within a tumor, the correlation between 5-FU tissue concentration and tumor microangiography was examined in 31 patients with colorectal cancer after administration of 5-FU (500 mg/day for 3 days). The 5-FU concentration at the tumor margin was significantly higher than that in the other two tissue areas (p less than 0.05). A low 5-FU concentration was noted in the central region of ulcerative cancer showing vertical invasion with vascular disarray and/or histological necrotic foci. This type of tumor also showed a low RNA index by flow cytometry. The present study indicates that the vascular change and vascular pattern of a tumor may be a major contributing factor to 5-FU transfer from the blood circulation into a tumor.

Pharmacokinetics and pharmacodynamics of locoregional 5 fluorouracil (5FU) in advanced colorectal liver metastases

By measuring peripheral drug levels in plasma, the effect of combining albumin microspheres with angiotensin II on systemic exposure to 5FU when administered by bolus injection into the hepatic artery in patients with advanced colorectal liver metastases has been assessed. The results suggest that despite hepatic arterial administration of 5FU, there was no reduction in systemic exposure when compared with that associated with intravenous injection of the same dose. Neither albumin microspheres nor angiotensin II appeared to improve the regional advantage. There have been a number of reports relating the plasma levels of cytotoxic agents with pharmacodynamic parameters. We have shown significant direct correlations between 5FU clearance and 1 week post treatment platelet and white cell counts, and an inverse relationship between the area under the 5FU plasma concentration-time curve (AUC) and 1 week post treatment platelet count and white cell count respectively.

Reevaluation of the maximum tolerated dose of continuous venous infusion of 5-fluorouracil with pharmacokinetics

5-Fluorouracil (5-FU) was administered as a continuous ambulatory venous infusion to 25 patients in a Phase I trial. The principal dose limiting toxic effect observed was mucositis. Skin rash and diarrhea occurred less frequently. Hematological toxicity was modest, and no hepatic toxicity was seen. One partial remission of 138 days duration was seen in a patient with metastatic breast carcinoma who was previously refractory to a 5-FU combination regimen. Patient tolerance of 5-FU delivered in this manner appeared highly variable. On the basis of this trial, we recommend that future studies evaluating the efficacy of long-term venous infusion of 5-FU should utilize a dosage of 450 mg/m2/day.

Polyvinyl alcohol membrane permeability characteristics of 5-fluorouracil

5-fluorouracil is a useful new treatment modality in the difficult glaucoma filtering patient. However, its use is attended by a high incidence of complications principally involving the corneal epithelium. The pharmacokinetics of this drug suggest that a sustained release delivery system might avoid many of these problems if it could produce therapeutic levels in the subconjunctival space while avoiding toxic levels in the cornea and other ocular structures. In vitro studies of release rates for polyvinyl alcohol membranes suggest that this material could form the basis of such a delivery system.

Familial deficiency of dihydropyrimidine dehydrogenase. Biochemical basis for familial pyrimidinemia and severe 5-fluorouracil-induced toxicity

Severe neurotoxicity due to 5-fluorouracil (FUra) has previously been described in a patient with familial pyrimidinemia. We now report the biochemical basis for both the pyrimidinemia and neurotoxicity in a patient we have recently studied. After administration of a "test" dose of FUra (25 mg/m2, 600 microCi[6-3H]FUra by intravenous bolus) to a patient who had previously developed neurotoxicity after FUra, a markedly prolonged elimination half-life (159 min) was observed with no evidence of FUra catabolites in plasma or cerebrospinal fluid and with 89.7% of the administered dose being excreted into the urine as unchanged FUra. Using a sensitive assay for dihydropyrimidine dehydrogenase in peripheral blood mononuclear cells, we demonstrated complete deficiency of enzyme activity in the patient and partial deficiency of enzyme activity in her father and children consistent with an autosomal recessive pattern of inheritance. Patients who are deficient in this enzyme are likely to develop severe toxicity after FUra administration.

Effect of PSK, a protein-bound polysaccharide from Coriolus versicolor, on drug-metabolizing enzymes in sarcoma-180 bearing and normal mice

The effects of PSK and Propionibacterium acnes (anaerobic Corynebacterium) on hepatic drug-metabolizing enzymes were studied using sarcoma-180 bearing and non-tumor bearing mice. PSK had no influence on aminopyrine N-demethylase and aniline hydroxylase activities, cytochrome P-450 concentration in hepatic microsomes, and the reductase activity of cytochrome c in normal mice. The content of cytochrome P-450 was not significantly reduced in S-180 bearing mice. On the other hand, P. acnes administration significantly decreased the amount of cytochromes P-450 and b5 and aminopyrine N-demethylase activity. When FT-207 (Tegafur) was administered orally to S-180 bearing mice combined with the immunoadjuvants, only P. acnes significantly reduced the 5-FU levels in the serum and some organs.

5-Fluorouracil-associated cardiotoxicity

Cardiotoxicity manifested as myocardial ischemia is not generally recognized as a side effect of 5-fluorouracil. However, there have been at least 35 cases reported since 1975. In only one of these cases was a somewhat detailed evaluation done to rule out underlying coronary disease. The case reported here of 5-FU cardiotoxicity included an extensive cardiac evaluation to rule out underlying coronary disease and to assess spasm. The literature on 5-FU cardiotoxicity is also reviewed, and its possible mechanisms are analyzed.

Interactions of methotrexate and cyclophosphamide with the pharmacokinetics of 5-fluorouracil in an animal model

The interaction of methotrexate and/or cyclophosphamide with the pharmacokinetics of 5-fluorouracil (5-FU) was studied in tumor-bearing WAG/Rij rats. Four groups were formed including treatment with single-agent 5-FU (eight rats); 5-FU plus methotrexate (11 rats); 5-FU plus cyclophosphamide (12 rats); and 5-FU, cyclophosphamide, and methotrexate (13 rats). The area-under-the-plasma-concentration/time curve, total-body clearance, elimination half-life, mean residence time, and steady-state volume of distribution were computed and compared. The mean residence time and elimination half-life of 5-FU increased when methotrexate was included in the combination. The increase was significant (P less than 0.05) for 5-FU, cyclophosphamide, and methotrexate versus 5-FU and cyclophosphamide.

Dose and flow dependence of 5-fluorouracil elimination by the isolated perfused rat liver

The influences of dose and hepatic blood flow on the elimination of 5-fluorouracil (FUra) by the isolated perfused rat liver were investigated. FUra was injected into the perfusion reservoir and then serial blood samples were collected over 2-3 h. FUra concentration was determined chromatographically. In some experiments, the conversion of [2-14C]FUra to 14CO2 was also determined. With livers perfused at 20 ml/min, the initial decrease in plasma FUra concentration was linear with time (apparent zero-order kinetics); at concentrations below about 25 microM, the decrease became exponential (apparent first-order kinetics). Semilogarithmic plots of FUra concentration/dose versus time obtained with different doses were not superposable, consistent with saturable (Michaelis-Menten) elimination. Vmax and Km were 6-11 nmol/ml/min and 33-45 microM, respectively. Hepatic clearance during first-order elimination was close to 20 ml/min. About 84% of the dose was converted to CO2, indicating that catabolic metabolism was the principal route of elimination. As hepatic blood flow increased from 10 to 30 ml/min, Vmax was unchanged but Km decreased progressively from 84 to 32 microM, and clearance increased from 12 to 29 ml/min. It was concluded that hepatic FUra elimination is highly dependent upon both dose and blood flow.

Temporary blood flow stasis with degradable starch microspheres (DSM) for liver metastases in a rat model

A reliable liver metastasis model using intraportal injections of sarcoma cells was established in syngeneic hooded Lister rats to study the blood supply of the tumours and to evaluate the role of degradable starch microspheres (DSM) in conjunction with selective hepatic arterial and portal venous chemotherapy. The tumour/normal liver (T/L) ratio after intra-arterial and intraportal injection of 113Sn microspheres was 1.04 (range: 0.38-1.15) and 0.03 (range: 0.006-0.22), respectively. After intravenous 14C-iodoantipyrine quantitative autoradiography of tumour and normal regions demonstrated a mean T/L ratio of 0.74 +/- 0.05. After hepatic artery ligation (HAL) and portal vein ligation (PVL) the values were 0.32 +/- 0.05 and 0.42 +/- 0.05, respectively. These results confirm that the vascularity of the tumours in this model is similar to human colorectal cancer metastases. Radiolabelled 14C 5-Fluorouracil (5-FU) was given intravenously, via the hepatic artery and via the portal vein (the latter two routes with and without DSM). Quantitative autoradiography of tumour regions showed that selective hepatic arterial administration with DSM resulted in a significantly increased concentration of 14C-5-FU within the tumours. These results suggest that DSM may enhance the therapeutic benefit of hepatic arterial 5-FU by increasing its uptake into tumours.

[Effects of intravenous alimentation on adjuvant chemotherapy--an experimental study on the distribution of 5-FU after injection of tegafur (2)]

The stomach, small and large intestines, heart, lungs, bone and kidneys were removed from 48 Sato lung cancer-bearing rats used in the previous experiments and given 90 mg/kg of tegafur (FT-207) by single intravenous administration and tissue 5-FU and FT-207 concentrations were measured. FT-207 concentration in the alimentary canal was somewhat lower than the blood concentration, but both were lowered in parallel. 5-FU concentration in the stomach and large intestines showed virtually identical changes in both IVH and PO groups, but IVH group tended to have higher concentration. IVH group showed higher values than PO group anytime, particularly in the large intestines. A reduction of the side effects on the digestive system via intravenous alimentation was thought due to the elimination of mechanical stimulation via a cessation of oral feeding. 5-FU concentration in the bone was highest in PO group at six hours after administration and blood concentration changes were parallel, but there was virtually no change in IVH group. Maximum values were found one hour after administration and slowly declined thereafter; at 24 hrs the values were 0.059 +/- 0.013 microgram/g, relatively high compared to the PO group at 0.041 +/- 0.022 microgram/g. In the present study under intravenous alimentation, the concentration changes were slight in spite of 5-FU maximum concentration being lower than that by oral feeding and the long-term high concentration which was maintained; this is thought to be a disadvantageous action with regard to the bone marrow. FT-207 concentration in the kidney, heart and lungs was the same as that for the blood, with a gradual reduction in IVH group. 5-FU concentration was the same for the kidneys and IVH group quickly reached to the high levels compared to PO group with only slight changes thereafter. Effects of continuous water load might be involved but not clear.

Increased uptake of 5-FU in experimental liver tumours by simultaneous infusion of norepinephrine

The effect of the simultaneous administration of norepinephrine and 5-fluorouracil (5-FU) on the uptake of radiolabelled 5-FU by liver tumours was studied in rats. Three different concentrations of 5-FU were used (15, 1.5 and 0.15 microgram/g body weight). The drugs were infused over a 30 min period via the hepatic artery, following cannulation of the gastroduodenal artery. The radioactivity in liver tumour, normal liver, lungs and intestines was estimated by liquid scintillation counting. At all concentrations tested, an increased uptake of radioactive 5-FU was found in the tumour when norepinephrine was infused. Tumour/liver ratios also increased significantly in all these cases. No significant differences were noted between norepinephrine infused and control animals in the radioactivity in normal liver, lungs and intestines. The effects noted were possibly due to changes in blood flow within the liver, but the possibility of a direct effect of norepinephrine on DNA metabolism is discussed.

Disposition and availability of 5-fluorouracil prodrug 5'-deoxy-5-fluorouridine after oral administration in rats

5'-Deoxy-5-fluorouridine (dFUR) is a prodrug of 5-fluorouracil (FU) and requires metabolic activation by enzymes that are abundant in several tumors as well as in some normal tissues. 5'-Deoxy-5-fluorouridine is presently under investigation as an orally administered anticancer drug. This study examines the absorption and disposition of orally administered dFUR and its systemic availability in female Fischer rats. Animals were given an oral dose of unlabeled dFUR solution (500 mg.kg-1) and, 5 min later, an intravenous (i.v.) tracer dose of [6-3H]dFUR over a period of 1 min. The concomitant i.v. dose was given to assess the drug clearance during absorption of the oral dose. The blood concentrations of radiolabeled and unlabeled dFUR and FU were analyzed by high-pressure liquid chromatography and liquid scintillation counting. The clearance of the i.v. tracer dose of [6-3H]dFUR was 18.5 +/- 2.5 mL.kg-1.min-1 (mean +/- SD, n = 5). The oral bioavailability, calculated using the clearance of [6-3H]dFUR and the area under the blood concentration-time curve (AUC) of unlabeled dFUR, was 63.4 +/- 16.9%. Eighty to ninety percent of the absorption was completed by 8 h. The absorption rate of dFUR, analyzed by the Loo-Riegelman method, suggests that drug absorption took place in part by saturable mechanisms. The AUC of FU after the oral dose was 15-35% higher than that after i.v. injections of dFUR at the same dose. Analysis of the FU data indicates that a fraction of the dFUR dose was metabolized to FU during the presystemic first pass.

Pharmacodynamic aspects of in vitro and in vivo chemosensitivity tests

To determine the optimal conditions for clonogenic assay, the antitumor activities of 5-fluorouracil (5-FU) in vitro and in vivo were compared from a pharmacodynamic viewpoint in a human carcinoma xenograft-nude mouse system. In the clonogenic assay, tumor cells were exposed to 5-FU continuously for 2 weeks, and the results of the assay were evaluated in terms of colony survival rates (T/C). Tumor-bearing BALB/c male nude mice were treated with 5-FU, and the results were evaluated in terms of the lowest values of relative mean tumor weights (T/C). To compute the area under the curve (AUC) after administration of 5-FU in vitro and in vivo, agar and serum levels of 5-FU were measured by bioassay. Antitumor activities in terms of T/Cs against a gastric carcinoma strain (H-111) depended highly on the AUCs in vitro and in vivo. The T/C in vitro (z) was correlated with the AUC in vitro (w), z = 58.4 x 0.99331w, and the T/C in vivo (y) was also correlated with the AUC in vivo (x), y = 52.1 x 0.88552x. On the assumption that the T/Cs of these two regression equations were equivalent (y = z), a correlation between w and x was derived. To predict the T/C at the maximum tolerated dose of 5-FU in mice, the optimal drug concentration in vitro was calculated to be 2.7 micrograms/ml, which also proved to be suitable for seven other carcinoma strains. Our experimental system was thought to be adequate for selecting the optimal drug concentration in the clonogenic assay.

Serum, urine and peritoneal fluid levels of 5-FU following intraperitoneal administration

Seven patients with advanced colon cancer, refractory to conventional chemotherapy, and malignant disease confined to the intra-abdominal space received a total of 24 consecutive courses of ip 5-Fluorouracil (5-FU). 5-FU 1000 mg was administered in 2 L of warm (37 degrees C) dialysate daily for five consecutive days every 28 days. 5-FU concentrations in serum, peritoneal fluid and urine were measured by high pressure liquid chromatography (HPLC). The mean disappearance half-life of 5-FU from the peritoneal fluid was 1.6 hours with a mean permeability area product (PA) of 22.4 ml/min. The mean peritoneal AUC was 450 +/- 165 times greater than the mean serum AUC. Ip 5-FU treatment is well tolerated, can be safely administered on an outpatient basis and produces a significant pharmacological advantage over conventional routes of administration.

Incorporation of 5-fluorouracil into RNA of normal tissues and an adenocarcinoma in protein-deprived rats

One of the main cytotoxic effects of 5-FU is its incorporation into RNA. In rats, protein deprivation increases the incorporation of labelled precursors into liver RNA. We examined the effect of protein deprivation on the incorporation of a therapeutic dose of 5-FU into the liver, small intestine, kidney and bone marrow and into an adenocarcinoma transplanted to the liver in the rat. The rats were fed either on a 25% or a 0% casein diet for one week. Some rats from both groups were given amino acids or glucose parenterally. Therapeutic 5-[3H]-FU was given in a 2 h infusion by the hepatic artery and the rats were sacrificed one h later. Incorporation into liver and intestinal RNA increased significantly with protein deprivation. The increase was largely eliminated by parenteral feeding of amino acids. No differences were found in incorporation into tumor and bone marrow RNA in protein deprivation. Incorporation into the acid soluble fraction and DNA is also reported.

5-Fluorouracil incorporation into RNA of a rat liver adenocarcinoma after hepatic artery injection together with degradable starch microspheres

The effect of degradable starch microspheres (DSM) on the cellular incorporation of 5-fluorouracil (FUra) was studied in rats with solitary liver tumours. 3H-labelled FUra [0.78 mg (6000 nmol)/kg b.wt.] was injected with saline or mixed with DSM, into the hepatic artery. Labelling of the acid soluble fraction (ASF), RNA and DNA of tumour, liver, bone marrow and small intestine was measured 60 minutes after injection. The DSM had no significant effect on the incorporation of FUra into the ASF or RNA, neither in tumour nor liver tissue. Regarding the tumour/normal tissue ratios of specific radioactivities, there was with DSM a higher tumour/liver and a higher tumour/bone marrow ratio in the ASF, indicating an increased tumour drug exposure with DSM. However, this was not accompanied by any significant increase in drug anabolism.