The Pharmacokinetics (PK) of Voriconazole in Children BINER ORHANER B Univ. Trakya, Pediatric Hematology, Edirne, Turkey.
Background: Invasive fungal infections are a major cause of morbidity and mortality in immuncomprimised patients. The most common fungi responsible for severe infections are Aspergillus. Voriconazole is a broad spectrum second generation triazole antifungal agent. It is indicated for the treatment of invasive aspergillosis. Pediatric dosage finding and safety evaluations have not been completed. Aims: 1)The aim of this study was to review the literature about studies done on the PK of voriconazole in children. 2) The clinical results of our 5 cases with Aspergillus infection (4 pulmonary, 1 bloodstream) with voriconazole treatment were shown.
Methods:Literature was searched with the key words “voriconazole, pharmacokinetic, children, invasive fungal infection” and the studies were evaluated.
Results: Children require higher doses of voriconazole than adults to attain similar serum concentrations over time because the drug exhibits non-linear pharmacokinetics in adults, but exhibits linearity in children. A significant relationship between disease progression and drug concentration was described in adults (Antimicrob Agents Chemother 2006;50.1570). Based upon studies in children, it appears that a pediatric dosage of 11 mg/kg administered every 12 h is approximately bioequivalent to an adult dosage of 4 mg/kg given 12 h. Plasma samples for voriconazole HPLC assay from 14 subjects revealed that in children receiving dosages of ≥4 mg/kg iv bid was lower than that of adult volunteers receiving 4 and 5 mg/kg bid (Walsh TJ, et al). In another study done in 5 children with ages ranged from 2 to 10 years old voriconazole was administered at dosages varied from 3.4 mg/kgevery 12 h to 8.1 mg/kg every 8 h and plasma voriconazole concentrationswere found to be unpredictable for these paediatric patients (Arch Dis Child 2008;93:578).Therefore, using voriconazole at recommended doses for adults may lead to clinical failures in children. Also, recent observations suggest that hepatic toxicity and visual disturbance might be dose related. Five of our cases treated successfully without any major side effect with voriconozole (14 mg/kg/d) will be presented.
Conclusions: 1) Children might require higher doses of voriconazole than adults to attain similar serum concentrations over time because of its linear PKs in children. Studies about the optimum dosage of voriconoazole in children should be conducted in a large number of children.
Modification of the Infarct Size Limiting Effects of Statins by Antiplatelet Drugs BIRNBAUM Y1,2, YE Y1,2, PEREZ-POLO J.R2.
1The Division of Cardiology, 2The Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, Texas.
Background: Therapy for acute coronary syndromes includes statins and anti-platelet agents. Statins limit infarct size (IS) in animal models by activation of phosphoinositide-3-kinase (PI3K) with subsequent activation of ecto-5-nucleotidase (that generates adenosine) and Akt/endothelial nitric oxide synthase (eNOS) with downstream activation of inducible NOS (iNOS) and COX2. Inhibition of the PI3K, adenosine receptors, eNOS, iNOS and COX2 abrogates the IS-limiting effects of statins.
Methods: Rats received 3-day oral atorvastatin (ATV) or vehicle with or without dipyridamole (DIP, 6mg/kg/d), cilostazol (CIL, 20mg/kg/d), or aspirin (ASA, 5, 10 or 20mg/kg at reperfusion). Rats underwent 30-minute coronary artery occlusion and 4-hour reperfusion.
Results: ATV (10mg/kg/d) limited IS. Intravenous ASA before reperfusion attenuated this effect. DIP alone and ATV (2mg/kg/d) alone had no effect on IS; however, IS was significantly reduced in the ATV+DIP combination. Myocardial adenosine levels were higher in the ATV+DIP group than in the ATV alone, DIP alone and the control group. The protective effect was abolished with theophylline, indicating that it is mediated by adenosine receptor activation. CIL alone, and especially when combined with ATV (2 mg/kg/d) limited IS. CIL increased myocardial levels of adenosine and Akt and eNOS phosphorylation. In addition, by increasing tissue cAMP levels, CIL activated protein kinase- A that phosphorylates eNOS. CIL inhibited PTEN, thus leading to augmentation of Akt and subsequently eNOS phosphorylation.
Conclusions: Aspirin blocks the IS-limiting effects of statins, whereas both dipyridamole and cilostazol have synergistic effects with statins. It might be that the anti-platelet regimens should be modified for patients receiving statins.
Structure and Function of the Ubiquitous TRPC channels: Targets in Need of Magical Bullets. BIRNBAUMER L Laboratory.of Neurobiology, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina 27708 USA
The canonical transient receptor potential (TRPC) channels were discovered in our laboratory in 1995-96. They are homolgues of the Drosophila light-activated channels Trp and Trp-like and were cloned to test the hypothesis that in mammalian cells they might be at the root of not only Gq-activated non-selective cation currents but also store-operated Ca2+ entry (SOCE). In initially 6, now 7, TRPCs have distant homology to voltage-gated cation channels and span the membrane 6 times. Between their discovery and now, the participation of TRPCs as members of SOCE channels has been controversial and indirect. An alternative hypothesis emerged after the discovery in 2005 of STIM, a 1-pass Ca2+-sensing membrane protein located in the ER that organizes plasma membrane SOCE channels, and in 2006 of Orai, a 4-pass plasma membrane protein whose loss is responsible for a familiar form of severe combined immunodefficiency and whose expression together with STIM engenders in TRPC expressing cells very large SOCE activity. This alternative hypothesis postulates Orai as the SOCE channel activated by STIM and does not include a role for TRPCs. However, as we published in Jan 2007, Orai and TRPCs interact functionally, seen as a TRPC-dependent enhancement of SOCE upon expression of low levels of Orai . We proposed that instead of forming channels, Orai appear to be regulatory proteins that confer Ca2+-selective SOCE channel properties to the otherwise non-selective cation channels formed by TRPCs without Orai. In support, SOCE channels were shown in other laboratories to be dynamically assembled in lipid rafts from which TRPCs and Orai can be co-immunoprecipitated. A survey of the literature shows that physiologic roles for TRPCs have been proven in the central nervous system, in the cardiovascular system, in the kidney, in epithelia, endothelia and blood-borne cells, and in various muscle types. TRPCs act in these tissues either by depolarizing their membrane or through the Ca2+ they allow to enter upon association with Orai. The latter includes cell proliferation. TRPCs play roles in human diseases, including cancer. TRPCs and Orai are important targets waiting for the development of Magic Bullets that will help in better understanding their role and in ameliorating diseases involving altered TRPC and/or Orai funcitons.
Birošová L, Mikulášová M
Slovak University of Technology, Bratislava, Slovakia
Background: Mutation rate of bacteria is often affected by environmental conditions. Various stress such starvation, oxidative or radiating stress can result in increased frequency of mutations leading to antibiotic resistance. The aim of this work was to determine the mutation frequency leading to ciprofloxacin resistance induced by depleted media and hydrogen peroxide and to find molecular determinants of ciprofloxacin resistance in selected mutants.
Methods: Oxidative stress was evoked by 3h cultivation of S. typhimurium with hydrogen peroxide in 3 concentrations (0.4, 0.8, 2, 4 mM). Starvation was studied after incubation (3h) of bacteria in control Luria-Bertani medium (LB) and in nutritionally depleted media 10%LB and Nutrient broth No. 1. Resistant strains were counted on agar plates supplemented with ciprofloxacin (0.06 mg/ml) after 72 h of incubation at 37°C. The frequency of resistant mutants (resistance index RI) represents mean number of resistant cells divided by the total number of viable cells per culture. Data represent the mean of three independent experiments; each experiment was made in five parallels and statistically evaluated by Student’s t-test. Mutations in gyrA were determined using AS-PCR-RFLP method. Levels of outer membrane porin F were detected with SDS-PAGE.
Results: Short-term cultivation in 10% LB caused 430 fold increase of RI while in Nutrient broth No.1 it was only 57 fold rise. In ciprofloxacin-resistant strains generated by long-term starvation were detected decreased levels of OmpF protein. With rising dose of H2O2 was RI increasing up to 33-fold of spontaneous mutation frequency to ciprofloxacin resistance. In nutritionally depleted medium with H2O2 has mutation frequency increased more than 103-time. 80% of resistant strains had mutation in gyrA. 37% of them had mutation in codon Ser-83 and 63% in codon Asp-87.
Conclusions: 1) Starvation increases mutagenesis leading to ciprofloxacin resistance. 2) Short-term treatment of S.typhimurium in nutritionally depleted media caused higher increase of ciprofloxacin RI than long-term incubation.3) Long-term starvation is leading to decreased levels of OmpF. 4) Oxidative stress induced by H2O2 in conjunction with lack of nutrients in environment increases mutation frequency to ciprofloxacin resistance. 5) Majority of ciprofloxacin-resistant strains generated by H2O2 has mutation in gyrA gene.
This work was supported by the Slovak Grant Agency VEGA (Projects no.1/4305/07)
