Biomedical subjects
D R Uges
Publications and source records attributed to D R Uges.
Clozapine-induced agranulocytosis: a case report. Immunopathophysiological considerations.
A 46-year-old woman is described with a clozapine-induced agranulocytosis. She was treated with a broad-spectrum antibiotic and supportive care was provided with granulocyte colony-stimulating factor (G-CSF). Immune-mediated mechanisms of clozapine-induced agranulocytosis and the role of haematopoietic growth factors are discussed.
Neurotoxicity caused by valacyclovir in a patient on hemodialysis.
The authors report toxicity caused by valacyclovir in a patient on hemodialysis. After initial recuperation resulting from treatment with hemodialysis, the patient experienced a relapse of neurologic symptoms, again necessitating hemodialysis. Although acyclovir and its analogues are generally safe drugs, they should be used with caution in patients with end-stage renal disease. Therapeutic drug monitoring may be indicated.
Pharmacokinetics of piperacillin and tazobactam in critically ill patients with renal failure, treated with continuous veno-venous hemofiltration (CVVH).
OBJECTIVE: Kinetics of piperacillin (pip), in combination with the beta-lactamase inhibitor tazobactam (taz) have been studied in volunteers and patients in relatively stable conditions. The fixed drug preparation appeared to have ideal pharmacokinetic properties if renal function was normal or slightly impaired, but no data are available for critically ill patients in anuric renal failure. This study should provide such data. PATIENTS, DESIGN: We studied the pharmacokinetics in nine patients with multiple organ failure, including anuric renal failure, treated with continuous veno-venous hemofiltration (CVVH). Patients received a standard schedule of 4 g pip and 0.5 g taz administered over 0.5 h intravenously, 8 hourly. During 2 consecutive days, the serum levels of both compounds were determined, and total clearance (CIT) was calculated from serum concentrations. RESULTS: All nine patients completed day 1, and 8 completed day 2 of the protocol. On day 1, single-dose kinetics showed considerable spread, but pip/taz serum levels followed the pattern as expected, with a pip/taz concentration ratio of 20:1. On day 2, however, taz serum concentrations showed a relative increase as compared to pip, resulting in a change in the serum pip/taz concentration ratio to 10:1 on day 2. The CIT of pip was 2.52 +/- 1.38 l/h (t 1/2: 5.9 +/- 2.9 h), and CIT of taz 4.44 +/- 2.28 l/h (t 1/2: 8.1 +/- 3.7 h). The CIT and t 1/2 of pip and taz correlated highly significantly with clearance by CVVH. Despite a higher CIT, taz has a longer half-life, because of a higher volume of distribution. CONCLUSION: In CVVH dependent patients, pip/taz fixed drug preparations can be used initially, but the pip dosage should be increased relative to that of taz (or interval-adjusted) to prevent cumulation of taz, as compared to the active antimicrobial agent pip.
Randomized comparison of etoposide pharmacokinetics after oral etoposide phosphate and oral etoposide.
Etoposide phosphate is a water-soluble prodrug of etoposide. The plasma pharmacokinetics of etoposide following oral administration of etoposide phosphate or oral etoposide were compared. Seventeen patients with solid tumours were enrolled to receive oral etoposide phosphate 125 mg m(-2) on days 1-5 every 3 weeks, with escalation to 175 mg m(-2) from course 3 when possible. Patients were randomized to receive oral etoposide phosphate or oral etoposide on day 1 of course 1 and the alternative compound on day 1 of course 2. Fifteen patients received two or more courses and were evaluable for pharmacokinetic comparisons. The median AUC(inf) (area under the concentration vs time curve from zero to infinity) of etoposide was 77.7 mg l(-1) h after etoposide phosphate (95% CI 61.3-100.5) and 62.0 mg l(-1) h after oral etoposide (95% CI 52.2-76.9). The difference in favour of etoposide phosphate was borderline significant: median 9.9 mg l(-1) h (95% CI 0.1-32.8 mg l(-1) h; P = 0.05). However, the inter-patient variability of etoposide AUC(inf) was not improved (coefficients of variation 42.3% and 48.4%). Etoposide phosphate was undetectable in plasma after oral administration. Toxicities of oral etoposide phosphate were not different from those known for etoposide. In conclusion, oral etoposide phosphate does not offer a clinically relevant benefit over oral etoposide.
Mechanism of hyperthermic potentiation of cisplatin action in cisplatin-sensitive and -resistant tumour cells.
In this study, the mechanism(s) by which heat increases cis-diamminedichloroplatinum (cisplatin, cDDP) sensitivity in cDDP-sensitive and -resistant cell lines of murine as well as human origin were investigated. Heating cells at 43 degrees C during cDDP exposure was found to increase drug accumulation significantly in the cDDP-resistant cell lines but had little effect on drug accumulation in the cDDP-sensitive cell lines. DNA adduct formation, however, was significantly increased in all cell lines studied. Furthermore, ongoing formation of platinum (Pt)-DNA adducts after the end of cDDP treatment was enhanced and/or adduct removal was decreased in heated cells, resulting in relatively more DNA damage remaining at 24 h after the end of cDDP exposure. Correlation plots with survival revealed weak correlations with cellular Pt accumulation (r2 = 0.59) and initial Pt-DNA adduct formation (r2 = 0.64). Strong correlations, however, were found with Pt-DNA adducts at 6 h (r2 = 0.97) and 24 h (r2 = 0.89) after the incubation with the drug. In conclusion, the mechanism by which heat sensitizes cells for cDDP action seems to be the sum of multiple factors, which comprise heat effects on accumulation, adduct formation and adduct processing. This mechanism did not seem to differ between cDDP-sensitive and -resistant cells, emphasizing the potential of hyperthermia to reduce cDDP resistance.
Conversion of the prodrug etoposide phosphate to etoposide in gastric juice and bile.
Etoposide phosphate is a water-soluble prodrug of etoposide. It was expected that this prodrug could be used to overcome the solubility limitations and erratic bioavailability of oral etoposide. To investigate the possibility of prodrug conversion to etoposide within the gastrointestinal lumen, etoposide phosphate was dissolved in water and incubated with human gastric juice or human bile in vitro. Samples were collected during 150 min and analysed for etoposide concentration with high-performance liquid chromatography. Conversion of prodrug to etoposide during incubation with gastric juice was negligible. There was significant conversion during incubation with bile at pH 7-8. The percentage of prodrug converted to etoposide at pH 8 after 60 min was 78 +/- 18% (mean +/- S.D.) for a 0.1 mg ml-1 prodrug solution and 36 +/- 26% for 0.5 mg ml-1. At pH 7, after 60 min 22% of prodrug was converted to etoposide when incubated at 0.1 mg ml-1 and 10% at 0.5 mg ml-1. No conversion was found after inactivation of alkaline phosphate (AP) by overnight heating of bile at 65 degrees C or by the addition of disodium edetate to the bile. In conclusion, because of AP in bile, variable conversion of etoposide phosphate to etoposide can be expected within the intestinal lumen after oral administration. This could have important pharmacokinetic consequences.
Validity and reliability of self-reported exposure to environmental tobacco smoke in work offices.
Environmental tobacco smoke (ETS) is an occupational carcinogen. Large companies often examine ETS exposure by employee surveys. However, reliable and valid self-report measures have been lacking. This study compared validity and reliability of various self-report measures. One hundred and seven nonsmokers from 11 Dutch worksites were interviewed. Three self-report measures were correlated with nicotine concentrations collected with area monitors in nonsmokers' offices. Nicotine concentrations averaged 12.7 micrograms/m. The item "How much tobacco smoke, on average, is there during a day in your work office?" correlated highest with nicotine concentrations (r = 0.65; P < 0.001) and produced the lowest standard error of measurement. It was concluded that this simple self-report item may be a valid measure to assess the reach and effectiveness of worksite smoking policies.
Hyperthermic isolated limb perfusion with cisplatin in four patients with sarcomas of soft tissue and bone.
The value of hyperthermic isolated limb perfusion (HILP) with cisplatin in the management of locally advanced soft tissue sarcomas or metastatic bone sarcoma was studied. Four patients were treated with HILP under mild hyperthermia (39-40 degrees C) with 20-30 mg cisplatin/l perfused limb volume. Toxicity in the perfused limbs was moderate, and the erythema and oedema that occurred resolved spontaneously within 7-14 days as did the slight motor and sensory neuropathy over a longer period of time. Clinically, a reduction of pain was observed in all patients. Two weeks after perfusion, tumour biopsies were taken to evaluate tumour response. Two patients showed a pathological complete response, one patient showed >90% necrosis and one patient showed no response. Currently patients are treated with tumour necrosis factor and melphalan as perfusion agents. The above-mentioned results make the combination of tumour necrosis factor with cisplatin in the isolated limb perfusion setting an interesting option.
Differential expression of DNA topoisomerase II alpha and -beta in P-gp and MRP-negative VM26, mAMSA and mitoxantrone-resistant sublines of the human SCLC cell line GLC4.
Sublines of the human small-cell lung carcinoma (SCLC) cell line GLC4 with acquired resistance to teniposide, amsacrine and mitoxantrone (GLC4/VM20x, GLC4/AM3x and GLC4/MIT60x, respectively) were derived to study the contribution of DNA topoisomerase II alpha and -beta (TopoII alpha and -beta) to resistance for TopoII-targeting drugs. The cell lines did not overexpress P-glycoprotein or the multidrug resistance-associated protein but were cross-resistant to other TopoII drugs. GLC4/VM20x showed a major decrease in TopoII alpha protein (54%; for all assays presented in this paper the GLC4 level was defined to be 100%) without reduction in TopoII beta protein; GLC4/AM3x showed only a major decrease in TopoII beta protein (to 18%) and not in TopoII alpha. In GLC4/MIT60x, the TopoII alpha and -beta protein levels were both decreased (TopoII alpha to 31%; TopoII beta protein was undetectable). The decrease in TopoII alpha protein in GLC4/VM20x and GLC4/MIT60x, was mediated by decreased TopoII alpha mRNA levels. Loss of TopoII alpha gene copies contributed to the mRNA decrease in these cell lines. Only in the GLC4/MIT60x cell line was an accumulation defect observed for the drug against which the cell line was made resistant. In conclusion, TopoII alpha and -beta levels were decreased differentially in the resistant cell lines, suggesting that resistance to these drugs may be mediated by a decrease in a specific isozyme.
Hyperthermic isolated regional perfusion with cisplatin in the local treatment of spontaneous canine osteosarcoma: assessment of short-term effects.
To increase the effect of cisplatin on locoregional osteosarcoma, the short-term effect of hyperthermic isolated regional perfusion (HIRP) with cisplatin (30 mg/L extremity volume) was studied in 28 dogs with spontaneous osteogenic sarcoma, using clinical, radiological, and histological parameters. Thirty days postoperatively, mortality was 14.3%. Total platinum levels at the start of perfusion were 28.2 +/- 14.3 mg/L. A significant improvement (P < 0.001) in clinical score was observed in the overall group at 6 and 12 weeks after perfusion. The radiological parameter showed a stationary X-ray 2 weeks after perfusion and an improved X-ray 6 weeks after perfusion. Overall histological scores showed a moderate effect according to the Huvos classification. No additional therapeutic effect, according to the three parameters, could be demonstrated by increasing the perfusate temperature by 1 degrees C. HIRP with cisplatin is feasible in the local treatment of spontaneous osteosarcoma in dogs with acceptable locoregional toxicity. However, the histological results were modest, with none of the dogs showing a complete response 6 weeks after perfusion. Therefore, the search for the ideal perfusion agent with substantial contribution to the limb-sparing treatment in human osteosarcoma continues.
Vincristine disposition in children with acute lymphoblastic leukemia.
Vincristine (VCR) has been widely used to treat childhood malignancies for over thirty years, but its plasma disposition has not yet been well-defined. Therefore, we conducted a pharmacokinetic study of VCR in 17 children with acute lymphoblastic leukemia (ALL) receiving the first dose of VCR. A new high-performance liquid chromatographic assay was used for the measurement of VCR in plasma. A two-compartment pharmacokinetic model was fit to the data by nonlinear least-squares regression. Estimated pharmacokinetic parameters were highly variable; mean (S.D.) volume of distribution at steady-state was 360 (176) L.m-2; total body clearance was 431 (238) ml.min-1.m-2, and elimination half-life was 823 (390) min. These results were compared to data from eight adults with lung cancer. Mean volume of distribution in adults and children were similar, but VCR clearance was significantly larger in children (P = 0.01), resulting in a significantly longer elimination half-life in the adults (P < 0.01). We conclude that administration of a standard dosage of VCR to children with ALL results in a highly variable systemic drug exposure, which may have implications for the oncolytic effect and/or toxicity in individual patients. Comparison of data from children and adults suggests that VCR elimination rate is a function of age; this could account for more severe neurotoxicity in older patients. However, it cannot be excluded that differences between the children and adults may be due to other variables than age. Future studies should focus on the possible influence of multidrug resistance modulating agents on VCR pharmacokinetics and on pharmacokinetic-pharmacodynamic relationships in individual patients.
Continuous infusion of ceftazidime in febrile neutropenic patients with acute myeloid leukemia.
Twelve febrile patients with severe neutropenia, who had undergone aggressive chemotherapy for acute myeloid leukemia, were treated empirically with a continuous infusion of ceftazidime 100 mg/kg/day after a 500 mg loading dose, in order to study the pharmacokinetics of ceftazidime after continuous infusion and to examine the clinical applicability of continuous infusion in this patient population. Three patients had a slight decrease in renal function. All patients attained a steady-state ceftazidime serum level of > 20 micrograms/ml within 180 to 240 min, which was considered effective against most pathogens in neutropenic patients. The median volume of distribution for the patient group was 29.1 l, the elimination half-life was 2.5 h and the clearance of ceftazidime was 7.7 l/h. A subnormal kidney function influenced half-lives and clearance (but not volume of distribution), as expected. When precautions were taken to avoid known interactions between ceftazidime and other compounds to be infused simultaneously, continuous infusion of ceftazidime was applicable for treatment of neutropenic patients without major side effects.
Cellular basis for differential sensitivity to cisplatin in human germ cell tumour and colon carcinoma cell lines.
Cisplatin (CDDP) resistance mechanisms were studied in a model of three germ cell tumour and three colon carcinoma cell lines representing intrinsically CDDP-sensitive and -resistant tumours respectively. The CDDP sensitivity of the cell lines mimicked the clinical situation. The glutathione levels of the cell lines correlated with CDDP concentrations inhibiting cell survival by 50% (IC50); total cellular sulphydryl content (TSH) was unexpectedly inversely correlated with IC50. IC50 correlated neither with glutathione S-transferase (GST) nor with GST pi expression, topoisomerase I or II activity. Immediately after 4 h incubation with CDDP, platinum (Pt) accumulation and Pt bound to DNA were not correlated, but after another 24 h drug-free culture, Pt binding to DNA in germ cell tumour but not in colon carcinoma cell lines correlated with IC50. With the exception of in vitro sensitivity and TSH, none of the parameters studied discriminated between the two groups of cell lines. Correction of CDDP sensitivity parameters for phenotypical differences did not influence statistical correlations. Analysis of variance revealed a correlation between IC50 and the combination of glutathione, GST activity and Pt bound to DNA. But at other CDDP cytotoxicity levels sensitivity was also correlated with Pt accumulation, topoisomerase II activity and TSH in various combinations. This model of intrinsic CDDP resistance showed that multiple parameters ought to be studied to explain CDDP resistance, but did not elucidate the cause of the unique sensitivity of germ cell carcinoma, although the unexpected values of TSH deserve further attention.
Phase II and pharmacokinetic study of lobaplatin in patients with relapsed ovarian cancer.
In phase I studies, lobaplatin showed activity in ovarian cancer patients pretreated with platinum. A phase II trial with lobaplatin was performed in patients with refractory or relapsed ovarian cancer to define activity and pharmacokinetics. Twenty-two patients were treated with lobaplatin administered as an intravenous bolus every 4 weeks. Dependent on creatinine clearance (CRCL) patients received 30 or 50 mg m-2 lobaplatin as the starting dose. Twenty-two patients received 78 courses (median 3, range 1-6). In eight patients total platinum (TPt) in plasma and urine, free platinum (FPt) in plasma ultrafiltrate (both measured by atomic absorption spectrometry) and lobaplatin in plasma ultrafiltrate measured (by high-performance liquid chromatography) were measured. Toxicity was confined to mild nausea and vomiting, mild leucocytopenia (WHO grade 3 in 18% of the courses), and renal function-related thrombocytopenia (WHO grade 3/4 in 53% of the courses). A correlation was found between CRCL and reduction in platelet count (r = -0.77; P < 0.01). No renal toxicity was encountered. Five of 21 evaluable patients (24%) achieved a response (four complete remissions and one partial remission). Remissions occurred mainly in patients who relapsed more than 6 months after primary treatment. The median survival from start of lobaplatin treatment was 8 months. The mean areas under the curve (AUCs) were 4.2 +/- 0.5, 3.0 +/- 0.6, and 3.2 +/- 1.1 h mgl-1 for TPt, FPt and lobaplatin respectively. The free platinum fraction (FPt/TPt) was initially very high, indicating low protein binding. FPt was essentially present as intact lobaplatin. Four hours after infusion 54 +/- 5% and 24 h after infusion 74 +/- 3% of the lobaplatin dose was excreted in the urine. In conclusion, lobaplatin is a platinum compound with anti-tumour activity in patients with relapsed ovarian cancer, especially in those who have platinum-sensitive tumours. The main toxicity of lobaplatin is thrombocytopenia and its dose should be corrected according to renal function.
Continuous carboplatin infusion during 6 weeks' radiotherapy in locally inoperable non-small-cell lung cancer: a phase I and pharmacokinetic study.
A phase I study was performed in 21 patients with previously untreated, locally inoperable, non-small-cell lung cancer (NSCLC) with ambulatory continuous carboplatin infusion together with continuous thoracic irradiation over 6 weeks. A dose range for carboplatin of 15 mg m-2 day-1 during the last 21 days (first level), during the last 31 days (second level), or during 6 weeks of the radiation period (third level) and thereafter 20 or 25 mg m-2 day-1 during 6 weeks of radiation (fourth and fifth level) was used. The total radiation dose was 60 Gy given as 2 Gy day-1 for 5 days week-1. The first three patients received radiotherapy without carboplatin. WHO grade III/IV leucopenia and thrombocytopenia occurred in the last two dose levels in two out of six and one out of six patients with 20 mg m-2 day-1 respectively, and in all three patients with 25 mg m-2 day-1 (dose-limiting toxicity). One local infection around the port and a subclavian vein thrombosis occurred. Radiation toxicity of the lung and oesophagus did not seem to be influenced by carboplatin treatment. Out of 21 patients one had a complete response (CR), ten partial response (PR), six stable disease (SD) and four progressive disease (PD). Total (TPt) and ultrafilterable plasma platinum (UPt) were measured in the last three dose levels with atomic absorption spectrophotometry with Zeeman correction. The mean (s.d.) level for TPt for 6 weeks at 15, 20 and 25 mg m-2 day-1 was 0.76 (0.15), 0.78 (0.19) and 0.90 (0.22) mg l-1 for UPt 0.10 (0.03), 0.12 (0.02) and 0.20 (0.03) mg l-1 respectively. TPt concentration levelled off after 3 weeks. The mean (s.d.) CLTB for UPt was 281 +/- 21 ml min-1 and correlated with glomerular filtration rate (r = 0.61, P = 0.03). As estimated with the sigmoid Emax model defined by the Hill equation the percentage reduction in platelets correlated with the area under the curve for UPt (r = 0.77). The maximum tolerable dose of carboplatin with concomitant continuous 60 Gy radiotherapy is 25 mg m-2 day-1; the recommended dose for phase II or III studies is 20 mg m-2 day-1 day for 6 weeks.
Pharmacokinetics of vincristine in children and adolescents with acute lymphocytic leukemia.
We studied the pharmacokinetics of vincristine in children with acute lymphocytic leukemia by means of a specific high-performance liquid chromatographic assay with ultraviolet and electrochemical detection and a limited sampling strategy. Our objectives were to characterize the disposition of vincristine in pediatric patients, to determine clinical, demographic, or biochemical variables related to variability in vincristine pharmacokinetic parameters, and to assess the relationship between pharmacokinetic parameters and vincristine neurotoxicity. Plasma samples were collected at 5 and 30 minutes, and 1, 3, and 24 hours after a rapid intravenous injection during 3 minutes. Vincristine-induced neurotoxicity was retrospectively evaluated by chart review. Pharmacokinetic studies were completed for 64 doses in 54 children between 2 months and 18 years of age (median, 4.3 years), including 2-month-old monozygous twin girls. Vincristine clearance, estimated by Bayesian methods, was highly variable, with a mean (SD) clearance of 19.9 (14.9) ml/min per kilogram or 482 (342) ml/min per square meter. Mean clearance for all subjects was faster than in published studies of adults, which may be related in part to the greater specificity of the assay used in our study, as well as to age-related differences in drug disposition. Vincristine-associated neurotoxicity was frequent but mild and was not predicted by vincristine systemic exposure; however, neurotoxicity may have been underestimated. Clearance in one patient who received concomitant treatment with pentobarbital exceeded the 75th percentile for all patients, and four of five patients receiving concomitant histamine2 antagonists had clearances below the 25th percentile for all subjects, suggesting that drugs that induce or inhibit hepatic cytochrome P-450 enzymes may affect vincristine disposition. Further studies are needed to identify the factors responsible for interpatient variability in vincristine disposition and to develop improved dosing guidelines.
Effect of ultrafilterable platinum concentration on cisplatin and carboplatin cytotoxicity in human tumor and bone marrow cells in vitro.
The importance of the ultrafilterable platinum (fPt) fraction of cisplatin (CDDP) and carboplatin (CBDCA) for cytotoxicity and myelotoxicity was studied in vitro. By incubating CDDP or CBDCA with fetal calf serum (FCS) various fractions of fPt were prepared and determined by atomic absorption spectroscopy. A relation of % fPt fraction and incubation time (h) of 87e-0.1123t (r = -0.99) and 101e-0.0087t (r = -0.99) were determined for CDDP and CBDCA, respectively. Cytotoxicity in the human small cell lung carcinoma cell line GLC4 and fPt fraction were closely related for CDDP (r = 0.99) and for CBDCA r = 0.97). However, at a similar fPt fraction the concentrations inhibiting cell survival by 50% (IC50) of CBDCA exceeded that of CDDP by a factor of 10-18 with 4 h exposure and a factor of 5 with continuous exposure. Tested in the range of peak concentrations in plasma of patients and at a clinically relevant fPt fraction of 10%, CDDP was not toxic for human bone marrow cells in the CFU-GM assay, whereas it was toxic at fPt fractions of 50% and 90%. However, CBDCA was myelotoxic at a (clinically relevant) fPt fraction of 50%, and also at 75% and 90%. The use of different fPt fractions, produced by the incubation method described in this study, permits the study of platinum drugs in vitro while approximating in vivo conditions might be used to evaluate myelotoxicity of new platinum drugs prospectively. For CDDP and CBDCA the fraction fPt determines cytotoxicity on tumor cells, and their different fPt fraction in patients account at least partly for their difference in myelotoxicity.