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Biomedical subjects

P Canal

Publications and source records attributed to P Canal.

11 recordsLinked to original sources
PubMed1992

Confluence-dependent resistance in human colon cancer cells: role of reduced drug accumulation and low intrinsic chemosensitivity of resting cells.

In vitro sensitivity of HT29 human colon cancer cells to doxorubicin (DXR), vincristine (VCR), etoposide (VP16), cisplatin (CDDP), melphalan (L-PAM) and 5-fluorouracil (5FU) was markedly reduced when cell-culture density increased. For some drugs, confluence-dependent resistance (CDR) was partly due to decreased intracellular drug accumulation; the ratio of mean intracellular drug content of non confluent to confluent cells (NC/C) was 2.5 for DXR, 4.1 for VCR and 7.4 for VP16. Altered drug penetration with confluence could be related to decrease of plasma membrane fluidity as measured by the fluorescence polarization method. Reduction of drug intracellular accumulation was nil or weak for L-PAM (NC/C = 1.0), CDDP (NC/C = 1.2) and 5 FU (NC/C = 1.8). Even if drug concentration was adjusted in culture medium to produce similar intracellular drug content in confluent and non confluent cells, higher intrinsic resistance of confluent cells was still evidenced for DXR and VP16 but not for VCR, the only agent without direct interaction with DNA. DXR- and VP16-induced DNA breakage was also less important in confluent than in non-confluent cells. CDR appeared closely related to an increased proportion of non-cycling cells at confluence, as demonstrated by flow cytometry, expression of nuclear antigen recognized by Ki67 MAb and expression of topoisomerase II. CDR is probably a major factor in the poor sensitivity of colorectal adenocarcinomas to chemotherapy.

Antineoplastic Agents↗
PubMed1992

Human pharmacokinetics of N-L-leucyl-doxorubicin, a new anthracycline derivative, and its correlation with clinical toxicities.

A pharmacokinetic study of N-L-leucyl-doxorubicin, a new derivative of doxorubicin, has been undertaken during a phase I trial in 19 patients with advanced cancer after intravenous bolus administration at doses ranging from 30 to 240 mg/m2. The pharmacokinetics of N-L-leucyl-doxorubicin was linear with a total body clearance of 41.3 +/- 25.7 L/hr/m2. N-L-leucyl-doxorubicin was extensively metabolized into doxorubicin, which appeared in plasma immediately after N-L-leucyl-doxorubicin infusion. The mean molar doxorubicin/N-L-leucyl-doxorubicin area under the curve (AUC) ratio was 0.49 +/- 0.22 and was independent of the administered dose. A relationship has been established between the doxorubicin AUC (r = 0.74; p less than 0.001) and the surviving factor in white blood cell counts. Other toxic side effects (thrombocytopenia or stomatitis) did not correlate with any pharmacokinetic parameter. These findings suggest that the degree of metabolization of N-L-leucyl-doxorubicin into doxorubicin may be responsible for the toxicity, that is, N-L-leucyl-doxorubicin may simply represent a pro-drug for doxorubicin.

Dose-Response Relationship, Drug↗
PubMed1992

Cardiotoxicity of high-dose continuous infusion fluorouracil: a prospective clinical study.

PURPOSE: A prospective clinical study was performed to determine the incidence of high-dose continuous intravenous infusion fluorouracil (5FU-CIV) cardiotoxicity. PATIENTS AND METHODS: Three hundred sixty-seven patients who were given first-cycle high-dose 5FU-CIV were monitored for cardiac function by clinical examination, ECG, and laboratory tests. 5FU-CIV was administered during a 96- or 120-hour period at doses that ranged from 600 to 1,000 mg/m2/d. Associated drugs included cisplatin (56%), mitomycin (12.5%), folinic acid (leucovorin) (7%), and others (14%). Thirty-nine patients (10.5%) received 5FU as a single agent. RESULTS: 5FU-induced cardiac events occurred in 28 patients (7.6%; 95% confidence interval, 4.9% to 10.3%). Nine of them had a history of cardiac disease. Primary tumors included head and neck (n = 13), gastrointestinal (n = 6), breast (n = 3), and others (n = 6). The mean onset time of cardiac symptoms was 3 days (range, 2 to 5). Inaugural symptoms included angina pectoris (n = 18), hypotension (n = 6), hypertension (n = 5), malaise (n = 4), dyspnea (n = 2), arrhythmia (n = 1), or sudden death (n = 1). At 5FU discontinuation, six patients' cardiac symptoms returned to baseline, but 21 patients experienced unstable angina (n = 8), hypotension/cardiovascular collapse (n = 11), pulmonary edema (n = 1), or sudden death (n = 4). The lethality rate was 2.2% (five sudden deaths plus three irreversible collapses). ECG showed repolarization changes (ST segment deviation; T-wave inversion) in 65% and/or diffuse microvoltage in 22% of the patients who presented with cardiac events. Echocardiography showed partial or global hypokinesia in nine of the 16 patients who were examined, and one case of prolonged akinesia. Cardiac enzymes rarely showed an increase (n = 2). In severe but reversible cases, clinical, ECG, and echographic parameters returned to baseline status within 48 hours after the drug discontinuation. A fluorine 19 nuclear magnetic resonance (19F NMR) analysis of urine was performed on 14 patients; six had cardiac symptoms and eight did not. Fluoroacetate (FAC), a known cardiotoxic compound, was detected in all cases. CONCLUSION: In our study, the incidence of high-dose 5FU-CVI cardiotoxicity was 7.6%. The hypothesis of a toxic cardiomyopathic process requires further confirmation.

Adult↗
PubMed1991

Pharmacokinetic modeling of plasma and cerebrospinal fluid methotrexate after high-dose intravenous infusion in children.

A pharmacokinetic study was performed in plasma and cerebrospinal fluid (CSF) of patients suffering from brain tumors to describe the disposition of methotrexate. An open three-compartment model was developed to fit together the data obtained in plasma and CSF. The pharmacokinetic parameters obtained by the model agreed with those obtained with classical analysis and the fitting correctly depicted the plasma and CSF concentration decays. According to the results, such a model could be applied to other anticancer drugs.

Adolescent↗
PubMed1991

Phase I/II pharmacokinetic study of mitoxantrone by continuous venous infusion in patients with solid tumours and lymphoproliferative diseases.

Phase I and pharmacokinetic studies were performed in order to evaluate the maximum tolerated dose and the efficiency of 120 h continuous venous infusion (CVI) of mitoxantrone. 25 patients suffering from either metastatic solid tumour or refractory lymphoproliferative disease were included in the study. The starting dose was 2 mg/m2 per day and was increased by a 0.2 mg/m2 per day step dose. The main toxicity observed was leukopenia which became limiting in more than 50% of the patients receiving 2.4 mg/m2 per day (12 mg/m2 over a 120 h period); this dose was defined as the maximal tolerated dose in these pretreated patients. One partial response and three stable diseases were observed. A plasma plateau concentration of mitoxantrone (2.13 [S.D. 0.54] micrograms/1 at 2 mg/m2 per day, 2.56 [1.32] micrograms/1 at 2.2 per day and 3.46 [1.32] micrograms/l at 2.4 mg/m2 per day) was reached within 24-48 h. It was linearly related to the administered dose. The mean plasma clearance of mitoxantrone was 27.8 [14.2] l/h/m2 and the volume of distribution of the beta phase averaged 2327 [2125] l/m2. An inverse relationship was established between the mitoxantrone clearance and the degree of hematologic toxicity. This 120 h CVI mitoxantrone schedule was safe and could be repeated every 3 weeks in an outpatient setting. The relationship between mitoxantrone clearance and the drug related haematotoxicity could be used for an individual dose adjustment.

Adolescent↗
PubMed1991

Radiosensitivity of jejunal mucosa after whole abdomen irradiation and CDDP pretreatment.

Pretreatment of mice with a single radiation dose of 11.5 Gy or with fractionated irradiation (2 x 6.5 or 7.5 Gy, with an interval time of 12 hr) led to a relative decrease in the radiosensitivity of jejunal crypt cells when a second single dose of radiation was delivered 2 months later. When the same irradiation pretreatment was combined with CDDP (6 mg/kg, i.p.) injected 12 hr after single radiation or between two equal doses of radiation, similar crypt cells resistance was obtained. The combination of CDDP with irradiation did not modify the radiosensitivity of jejunal crypts in comparison with irradiation alone, even when the total radiation dose was delivered in 2 split doses. This induced radioresistance was demonstrated to be a reflection of late injury on intestinal tissue, presumably due to hypoxia resulting from vascular damage. It seems that the administration of CDDP did not change the possible hypoxia suspected in crypt cells of mice pretreated with single radiation dose. However, mouse lethality increased significantly when CDDP was combined with irradiation.

Animals↗
PubMed1991

Concomitant evaluation of efficiency, acute and delayed toxicities of combined treatment of radiation and CDDP on an in vivo model.

The efficiency, acute and delayed toxicities of different radio-chemotherapeutic combinations were assessed on an in vivo model (Krebs II ascitic carcinoma grafted to female Swiss mice). Mice were given whole abdomen irradiation (WAI) 2.5 to 10 Gy as a single dose (WAI). CDDP was given intraperitoneally at 0.5 to 4 mg/kg dose level, 12 hr before or after WAI. There was a relationship between dose of CDDP and increase of life span (ILS) of mice. However, WAI did not increase the life span. When a single dose of 2 mg/kg CDDP was given prior to a 2.5 Gy WAI, the ILS reached 47%. By contrast, it was only 37% when treatment sequence was reversed. When the WAI dose level was increased to 5 Gy, the ILS was not increased. The jejunal crypt cell number, determined 3 days after the last treatment, was not modified, regardless of the treatment sequence. There was no delayed renal toxicity. The study on the Krebs II ascites model confirms the tumor cell therapeutic potentiation without exacerbation of normal tissue damage.

Animals↗