Search PubMed⌕ Search

Biomedical subjects

R C Donehower

Publications and source records attributed to R C Donehower.

125 records · Page 7Linked to original sources
PubMed1986

Pharmacology and toxicity of high-dose cytarabine by 72-hour continuous infusion.

Most studies using high-dose cytarabine (ara-c) for the therapy of acute leukemia have employed intermittent short infusions. In this study, we have evaluated the pharmacology and toxicity of high-dose ara-c by 72-hour continuous infusion. Plasma ara-c concentrations varied from 3.6 microM at the starting dose of 4 g/m2/72 hours to 22.6 microM at 18 g. Plasma clearance appeared to decrease progressively at doses greater than 10 g, suggesting that the route of elimination was saturable. CSF ara-c concentrations ranged from 1.2 microM at 4 g to 4.1 microM at 18 g; the ratio of CSF to plasma ara-c decreased progressively from 0.33 at 4 g to 0.18 at 18 g. The toxic effects were significant and included myelosuppression, nausea, and vomiting in all patients. No single dose-limiting toxicity was identified. Further dose escalation was precluded by combined organ system effects, which included hepatic, pulmonary, renal, and gastrointestinal toxic effects. Attempts to incorporate a 72-hour infusion of ara-c into a combination chemotherapy regimen should proceed cautiously with a starting dose of 6 g/m2/72 hours.

Acute Disease↗
PubMed1985

Tastes associated with parenteral chemotherapy for breast cancer.

We employed a structured interview to retrospectively study tastes and vomiting associated with the parenteral components of cyclophosphamide, methotrexate, and 5-FU in 45 patients with stage II-IV breast cancer. Sixteen patients (36%) reported tastes which generally occurred in each cycle within 30 minutes of parenteral drug administration, lasted less than or equal to 1 hour, and were bitter. Five patients recalled that tastes seemed to produce vomiting. Tasting was significantly associated with postchemotherapy (P less than 0.01) but not anticipatory vomiting. Employing logistic regression techniques, tasting did not significantly improve prediction of anticipatory vomiting by postchemotherapy vomiting. Tastes may be produced by the action of plasma or salivary cyclophosphamide, methotrexate, and 5-FU on taste buds. While tastes might cause some vomiting, they are not necessary for it. Because this was a retrospective study with a small sample, these findings require confirmation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Phase I study of N-methylformamide in patients with advanced cancer.

N-Methylformamide (N-MF) belongs to a class of polar-planar compounds which induce cellular differentiation. Preclinical antitumor activity was demonstrated against human mammary, colon, and lung tumor xenografts and L1210 and P388 murine leukemias. This phase I study used a single bolus infusion of N-MF given weekly X 3 doses every 6 weeks. Thirty-five patients were treated with N-MF at doses which ranged from 125 to 3125 mg/m2/week. The dose-limiting toxic effects included nausea and vomiting, anorexia, malaise, and liver function abnormalities. No myelosuppression was seen. The recommended dose for phase II trials of N-MF with this schedule is to initiate therapy at 2000 mg/m2 weekly X 3 and escalate to 2500 mg/m2 if the initial dose was well tolerated.

Adult↗
PubMed1984

Hepatic toxicity of low doses of mithramycin in hypercalcemia.

The medical records of patients receiving mithramycin for the treatment of hypercalcemia at The Johns Hopkins Oncology Center were reviewed. Of 67 evaluable patients, 11 (16%) developed hepatic toxicity when graded using standard criteria. The pattern of laboratory abnormalities noted suggested mild hepatocellular damage that was reversible within 2 weeks. Review of these patients did not identify factors which predispose to hepatic toxicity, although failure to do so may reflect the limited number of toxic patients evaluated. Mild, reversible hepatic dysfunction appears to be a more common sequela of mithramycin administration than has previously been recognized.

Chemical and Drug Induced Liver Injury↗
PubMed1984

Direct relationship of marrow cell growth and 1-beta-D-arabinofuranosylcytosine metabolism.

To define the relationship between perturbed cell growth and intracellular metabolism of 1-beta-D-arabinofuranosylcytosine (ara-C) in sensitive human cells, growth kinetic, and biochemical pharmacological determinants were examined in normal human bone marrow populations in vitro in normal serum and in the presence of drug-induced humoral stimulatory activity (HSA). Cells cultured in HSA demonstrated both increased proliferation and greater ara-C-related inhibition of DNA synthesis than did cells maintained in normal serum, as measured by [3H]thymidine incorporation into DNA and [3H]thymidine granulocyte precursor labeling index. Parallel measurements of [3H]ara-C incorporation into DNA demonstrated similar behavior in HSA-perturbed cells. When these cultured cells were exposed to 1 and 10 microM ara-C, intracellular formation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate over 3 hr and retention of this active form during 1 subsequent hr in drug-free medium were both increased in HSA-stimulated cells relative to cells cultured in normal serum. These studies demonstrate coupling of induced cell growth kinetics with enhanced intracellular metabolism of the S-phase-specific antimetabolite ara-C in normal human marrow cells. The close direct relationship between growth kinetic perturbation and augmentation of intracellular ara-C activation in this normal hematopoietic model provides a basis for comparison with leukemic cell populations, in which uncoupling of growth kinetics and pharmacokinetics may signify divergence from normal drug-sensitive cell behavior and, thus, resistance to ara-C cytotoxicity.

Bone Marrow↗
PubMed1982

Evaluation of weekly escalating doses of dichloromethotrexate in patients with hepatocellular carcinoma and other solid tumors.

Twenty-one patients with solid tumors were treated with weekly 6-h intravenous infusions of dichloromethotrexate (DCM), with escalating doses every other week. Frequently observed toxicities included leukopenia, thrombocytopenia, and mucositis. Nausea, vomiting, diarrhea, and elevation of hepatic enzymes and bilirubin occurred less often. The toxicity of DCM was dose-dependent; the maximum tolerated dosage excalation plan was 400 mg/m2 x 2 weeks, 800 mg/m2 x 2 weeks, and then 1,200 mg/m2 weekly. Plasma concentrations of DCM were measured during 61 infusions and apparent half-lives determined. The plasma elimination of DCM appears to be similar to that of methotrexate. Three objective tumor responses seen in the seven hepatocellular carcinoma patients treated warrant further investigation.

Adolescent↗
PubMed1982

Phase I-phase II trial of N-phosphonacetyl-L-aspartic acid given by intravenous infusion and 5-fluorouracil given by bolus injection.

A phase I clinical trial of N-phosphonacetyl-L-aspartic acid (PALA) and 5-fluorouracil (FUra) was performed on 30 patients. PALA was given as a 15-minute iv infusion once daily for 5 days, and FUra was given as a bolus injection on days 2, 3, 4, and 5. Cycles of treatment were repeated every 3 weeks. Dose-limiting toxicity was manifested by stomatitis and diarrhea. Skin rash was observed also but was not dose limiting. No consistent hematopoietic or renal toxicity was observed. Seventeen patients with disseminated metastatic melanoma and measurable disease were evaluated for response. One partial response was seen; however, the response was associated with significant toxicity, and the treatment could not be repeated. Stable disease was observed in 3 patients with melanoma, 1 patient with colon carcinoma, and 1 patient with ovarian carcinoma. Our findings suggest that the clinical activity of PALA and FUra given according to the above schedule for melanoma is less than 25% (P less than 0.05). Pharmacokinetic studies of FUra revealed no consistent effect of PALA pretreatment on FUra disappearance in plasma. The mean FUra elimination half-line in plasma was 7.11 +/- 0.84 minutes (SEM), which is no different from that reported for FUra alone. The recommended doses on this schedule for phase II studies are 1,000 mg PALA/m2/day iv daily for 5 days and 200 mg FUra/m2/day iv on days 2, 3, 4, and 5.

Adult↗
PubMed1980

Metabolic conversion of methotrexate in man.

Metabolism of methotrexate (MTX) to closely related analogues has been increasingly recognized in recent years. 7-Hydroxymethotrexate, 2,4-diamino-N10-methylpteroic acid, and methotrexate poly-gamma-glutamates have been established as products of metabolic conversion in man. The significance of the formation of these metabolites has not been firmly established. Certain of these compounds may play a role in the development of the renal failure syndrome associated with high-dose infusions, contribute to the chronic toxicity of MTX administration, and cross-react to a significant degree in radioimmunoassay methods for measurement of MTX concentrations.

Antibody Specificity↗
PubMed1979

Presence of 2,4-diamino-N10-methylpteroic acid after high-dose methotrexate.

Assay of plasma methotrexate has been established as important to its safe use. We have investigated the specificity of 2 assay procedures for methotrexate: the competitive dihydrofolate reductase binding assay (CRBA) and the radioimmunoassay (RIA). The RIA of plasma methotrexate resulted in consistently higher values than the CRBA, with greater differences at later measurement times. A compound that strongly cross-reacts in the RIA, but not the CRBA, has been identified in plasma and urine of patients on high-dose methotrexate therapy, and appears to be the carboxypeptidase cleavage product (2,4-diamino-N10-methylpteroic acid) on the basis of chromatographic and ultraviolet spectral properties. Although this compound is present as a minor contaminant in commercial methotrexate preparations, quantitative assessment of urinary excretion suggests that in man a major portion of the compound is derived from methotrexate metabolism.

Biological Assay↗
PubMedDate not supplied

Pharmacokinetics and pharmacodynamics of topotecan in patients with advanced cancer.

Topotecan, a semisynthetic water-soluble analog of camptothecin, is the first topoisomerase I-directed drug to enter clinical trial in the United States in over 20 yr. In this study, 30-min infusions of topotecan were administered daily for 5 days every 3 weeks at doses ranging from 0.5 to 2.5 mg/m2. Topotecan is reversibly hydrolyzed in a pH-dependent reaction in aqueous solutions to the ring-open hydroxy acid. The disposition of the closed ring lactone has been studied in 26 patients, and the disposition of both lactone and hydroxy acid has been studied in 12 patients. The clearance rate for topotecan lactone was 1220 ml/min/m2, with a range of 300-4760 ml/min/m2. The clearance rate for total topotecan (lactone and hydroxy acid) was 493 ml/min/m2, with a range of 163-815 ml/min/m2. A model for the disposition of lactone and hydroxy acid incorporating both reversible hydrolysis and elimination was developed. We have shown that topotecan is partially hydrolyzed prior to administration in parenteral solutions, and that clearance of the parent compound proceeds in vivo by conversion to hydroxy acid and elimination. Renal clearance accounted for 30 +/- 18% of drug elimination in patients. The relationship between topotecan dose and myelotoxicity is well fit by a sigmoidal Emax model, as is the relationship between total topotecan area under the concentration-time curve and myelotoxicity. The disposition of topotecan was also studied in mice. The clearance rate for total topotecan in mice was 330 ml/min/m2 after administration of topotecan lactone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗