Population Pharmacokinetics and Pharmacodynamics of Ciprofloxacin Prophylaxis in Pediatric Acute Lymphoblastic Leukemia Patients.

BACKGROUND: Ciprofloxacin is used as antimicrobial prophylaxis in pediatric acute lymphoblastic leukemia (ALL) to decrease infections with gram-negative bacteria. However, there are no clear guidelines concerning prophylactic dose. AIMS: To determine the pharmacokinetics and pharmacodynamics (PKPD) of ciprofloxacin prophylaxis in a pediatric ALL population. The effect of patient characteristics and antileukemic treatment on ciprofloxacin exposure, the area under the concentration time curve over minimal inhibitory concentration (AUC24/MIC) ratios, and emergence of resistance were studied. METHODS: A total of 615 samples from 129 children (0-18 years) with ALL were collected in a multicenter prospective study. A population pharmacokinetic model was developed. Microbiological cultures were collected prior to and during prophylaxis. An AUC24/MIC of ≥125 was defined as target ratio. RESULTS: A 1-compartment model with zero-order absorption and allometric scaling best described the data. No significant (P < .01) covariates remained after backward elimination and no effect of asparaginase or azoles were found. Ciprofloxacin AUC24 was 16.9 mg*h/L in the prednisone prophase versus 29.3 mg*h/L with concomitant chemotherapy. Overall, 100%, 81%, and 18% of patients at, respectively, MIC of 0.063, 0.125, and 0.25 mg/L achieved AUC24/MIC ≥ 125. In 13% of the patients, resistant bacteria were found during prophylactic treatment. CONCLUSION: Ciprofloxacin exposure shows an almost 2-fold change throughout the treatment of pediatric ALL. Depending on the appropriateness of 125 as target ratio, therapeutic drug monitoring or dose adjustments might be indicated for less susceptible bacteria starting from ≥ 0.125 mg/L to prevent the emergence of resistance and reach required targets for efficacy.

The role of the MTHFR 677C>T polymorphism in methotrexate-induced liver toxicity: a meta-analysis in patients with cancer.

Methotrexate (MTX), one of the important pillars in the treatment of different forms of cancer, is associated with the development of hepatotoxicity. The 677C>T variant (rs1801133) in the methylenetetrahydrofolate reductase (MTHFR) gene might affect the development of hepatotoxicity. Results in literature are, however, contradictive. The aim of this study was to evaluate the role of the MTHFR 677C>T polymorphism in MTX-induced hepatotoxicity by analyzing a Dutch cohort of pediatric patients treated with high doses of MTX and subsequently performing a meta-analysis. Ninety-eight patients receiving 542 courses of high-dose MTX were genotyped for the MTHFR 677C>T variant. Hepatotoxicity was evaluated retrospectively according to common terminology criteria for adverse events-National Cancer Institute criteria. The influence of MTHFR 677C>T on hepatotoxicity was examined using a generalized estimating equation (GEE) analysis. A fixed-effect meta-analysis based on this and previous studies investigating the association between the MTHFR 677C>T polymorphism and uniformly coded hepatotoxicity was performed. The GEE analysis showed an increased risk of developing hepatotoxicity for T versus C allele (odds ratio (OR) 1.8; 95% confidence interval (CI) 1.0-3.2, P=0.04). This finding was not supported by the meta-analysis including seven studies and 1044 patients; the OR for the 677T versus C allele was 1.1 (95% CI 0.84-1.5, P=0.25). Heterogeneity between studies was observed, possibly related to differences in MTX dose and leucovorin rescue. In conclusion, in patients with cancer, the MTHFR 677T allele has only a minor role in the development of MTX-induced hepatotoxicity. Observed heterogeneity between studies warrants further study into (tailored) leucovorin rescue.

Effect of azole antifungal therapy on vincristine toxicity in childhood acute lymphoblastic leukaemia.

BACKGROUND: Vincristine is one of the cornerstones of the treatment of children with acute lymphoblastic leukaemia (ALL). Constipation, and peripheral and central neurotoxicities are the most common side effects. A comparative study exploring vincristine toxicity in individual patients receiving vincristine with and without azoles, however, is lacking. METHODS: In total, 20 paediatric patients with de novo ALL were included. In each patient, vincristine toxicity in the period with and without azole co-medication was retrospectively graded according to the US National Cancer Institute toxicity scale. Statistical analysis was performed using the Wilcoxon signed rank test and McNemar's test. RESULTS: Patients receiving vincristine in combination with azole treatment experienced significantly more constipation and peripheral neurotoxicity (P = 0.001 and P < 0.001, respectively). Vincristine-induced CNS toxicity was only seen in patients (30%) receiving vincristine in combination with azole treatment. CONCLUSIONS: Vincristine toxicity is significantly enhanced when combined with azole treatment and can even be life threatening. Therefore, we advise avoidance of the combination of azole and vincristine treatments in patients with ALL.

Polymorphisms and mutations of human TMPRSS6 in iron deficiency anemia.

Male subjects with iron deficiency from the general population were examined for polymorphisms or sporadic mutations in TMPRSS6 to identify genetic risk factors for iron deficiency anemia. Three uncommon non-synonymous polymorphisms were identified, G228D, R446W, and V795I (allele frequencies 0.0074, 0.023 and 0.0074 respectively), of which the R446W polymorphism appeared to be overrepresented in the anemic population. In addition, three children with iron refractory iron deficiency anemia, and one sibling with iron responsive iron deficiency anemia were also examined for polymorphisms or sporadic mutations in TMPRSS6. Two children (family 1) were compound heterozygotes for a L674F mutation and a previously described splicing defect predicted to cause skipping of exon 13 (IVS13+1 G>A). One child from the second family was homozygous for a deletion (497T) causing a frameshift (L166X+36) and premature termination. The sibling and mother from the second family were compound heterozygotes for the L166X mutation and the uncommon R446W polymorphism. Although in vitro expression studies demonstrated that the R446W isoform was biologically similar to wildtype Tmprss6, clinical data indicate that the R446W produces a milder disease when carried in trans with severe mutation in Tmprss6. The four children carrying mutations in TMPRSS6 all exhibited inappropriately high urinary hepcidin levels for the degree of iron deficiency.

Vero cytotoxin binding to polymorphonuclear leukocytes among households with children with hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation of patients with HUS. This study investigated whether VT bound to PMNL could be detected in persons in households with patients with HUS. Serum antibodies against E. coli O157 and, when available, fecal samples from patients with HUS and household members were studied for the presence of VTEC infection. The circulating PMNL of 82% of the household members were positive for VT, whereas stool and/or serum examination showed only 21% positivity. Thus, current methods underestimate the number of infected persons in households with patients with HUS.

[Hemolytic uremic syndrome in children]. / Het hemolytisch-uremisch syndroom op de kinderleeftijd.

In Europe, haemolytic uraemic syndrome (HUS) is the most frequent cause of acute renal insufficiency during childhood. In the Netherlands about 20 children per year are seriously affected. Following a prodromal phase of mostly bloody diarrhoea, the main symptoms become evident, namely, haemolytic anaemia, thrombocytopenia and renal failure. The syndrome is caused by a verocytotoxin producing Escherichia coli, which damages the endothelium of the arterioles and glomeruli in the kidney. In humans, the most important cause of infection is the consumption of infected food-stuffs. After transport through the intestinal epithelium, the toxin becomes attached to the neutrophils, which transport it through the circulatory system, mainly to the kidneys where it has a toxic effect. Why the endothelial cells in these organs are the main targets for this toxin is as yet unknown. A symptomatic treatment is given to the 10% of infected patients who develop HUS. Increasing knowledge about the pathogenesis has resulted in new forms of treatment that will be studied during the next few years.

Detection of apoptosis in kidney biopsies of patients with D+ hemolytic uremic syndrome.

In this study we have investigated the presence of apoptotic cells in renal biopsy material of seven patients with hemolytic uremic syndrome (HUS) by using an improved and stringent terminal deoxynucleotidyl nick-end labeling (TUNEL) technique. Renal biopsy material was taken in the second or third week after onset of the disease. Renal biopsy material of patients with minimal lesions nephrotic syndrome or thin basement syndrome were used as control. It has been reported that nonapoptotic cells can be labeled nonspecifically due to proteinase K pretreatment or a delay in fixation when only TUNEL technique is used. In post mortem material this delay in fixation is seen. Moreover, it has been described that mainly nonapoptotic cells that shows signs of active gene transcription can be labeled in this nonspecific way. For this reason we used the TUNEL technique in combination with a label for RNA synthesis and splicing factor (SC-35). Indeed, we found nonspecific labeling of nonapoptotic nuclei in biopsy material of HUS patients, but not in control biopsy material. By using co-labeling with RNA synthesis factor SC-35, we were able to identify true apoptotic cells. There was a significant increase (p < 0.05) in the presence of apoptotic cells in biopsy material of HUS patients compared with material of controls. About 80 % of apoptotic cells were detected in tubuli and only 20 % in glomeruli of the renal biopsies of HUS patients. Furthermore, most apoptotic cells were detected in those patients that had received peritoneal dialysis suggesting that there is a relationship between severity of the disease and amount of apoptotic cells. The finding of apoptotic cells suggest that apoptosis plays a role in HUS.

Autosomal recessive inheritance of von Willebrand factor-cleaving protease deficiency.

A child with chronic relapsing thrombotic thrombocytopenic purpura (TTP/HUS) had recurrent thrombocytopenia, microangiopathic hemolytic anemia with fragmented erythrocytes, microthrombi in the lung vessels, and renal dysfunction. Assay of von Willebrand factor (vWF)-cleaving protease showed a complete protease deficiency in the patient and subnormal activities in the mother and in two asymptomatic siblings. No inhibitor of vWF-cleaving protease was detected in the patient's plasma. Periodic transfusions of fresh-frozen plasma prevented further acute episodes of TTP/HUS. Specific diagnosis of the constitutional deficiency of vWF-cleaving protease helps to provide successful prophylactic therapy.

Binding and transfer of verocytotoxin by polymorphonuclear leukocytes in hemolytic uremic syndrome.

The hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children. The role of a verocytotoxin (VT)-producing Escherichia coli has been strongly implicated in the epidemic form of HUS. Although direct toxicity of VT on glomerular endothelial cells has been demonstrated, it remained still unclear how the VT is transported from the intestine to the target organs. In this study we demonstrate that VT, when incubated in whole blood, binds rapidly and completely to human polymorphonuclear leukocytes (PMNs) and not to other components of blood. Binding studies with (125)I-VT-1 showed a single class of binding sites on freshly isolated, nonstimulated human PMNs. The K(d) of VT-binding to PMNs was 10(-8) mol/L, 100-fold less than that of the VT-receptor globotriaosylceramide. On incubation of VT-preloaded PMNs with human glomerular microvascular endothelial cells (GMVECs), transfer of VT-1 to the endothelial cells occurred. Incubation of nonstimulated GMVECs with VT-preloaded PMNs, but not with PMNs or VT-1 alone, caused inhibition of protein synthesis and cell death. Our data are in concert with a role of PMNs in the transfer of VT from the intestine to the kidney endothelium. This transfer occurs by selective binding to a specific receptor on PMNs and subsequent passing of the ligand VT to the VT-receptor on GMVECs, which causes cell damage. This new mechanism further underpins the important role of PMNs in HUS.