Impact of cumulative fluid balance on the pharmacokinetics of extended infusion meropenem in critically ill patients with sepsis.

BACKGROUND: Meropenem dosing for septic critically patients is difficult due to pathophysiological changes associated with sepsis as well as supportive symptomatic therapies. A prospective single-center study assessed whether fluid retention alters meropenem pharmacokinetics and the achievement of the pharmacokinetic/pharmacodynamic (PK/PD) targets for efficacy. METHODS: Twenty-five septic ICU patients (19 m, 6f) aged 32-86 years with the mean APACHE II score of 20.2 (range 11-33), suffering mainly from perioperative intra-abdominal or respiratory infections and septic shock (n = 18), were investigated over three days after the start of extended 3-h i.v. infusions of meropenem q8h. Urinary creatinine clearance (CLcr) and cumulative fluid balance (CFB) were measured daily. Plasma meropenem was measured, and Bayesian estimates of PK parameters were calculated. RESULTS: Eleven patients (9 with peritonitis) were classified as fluid overload (FO) based on a positive day 1 CFB of more than 10% body weight. Compared to NoFO patients (n = 14, 11 with pneumonia), the FO patients had a lower meropenem clearance (CLme 8.5 ± 3.2 vs 11.5 ± 3.5 L/h), higher volume of distribution (V1 14.9 ± 3.5 vs 13.5 ± 4.1 L) and longer half-life (t1/2 1.4 ± 0.63 vs 0.92 ± 0.54 h) (p < 0.05). Over three days, the CFB of the FO patients decreased (11.7 ± 3.3 vs 6.7 ± 4.3 L, p < 0.05) and the PK parameters reached the values comparable with NoFO patients (CLme 12.4 ± 3.8 vs 11.5 ± 2.0 L/h, V1 13.7 ± 2.0 vs 14.0 ± 5.1 L, t1/2 0.81 ± 0.23 vs 0.87 ± 0.40 h). The CLcr and Cockroft-Gault CLcr were stable in time and comparable. The correlation with CLme was weak to moderate (CLcr, day 3 CGCLcr) or absent (day 1 and 2 CGCLcr). Dosing with 2 g meropenem q8h ensured adequate concentrations to treat infections with sensitive pathogens (MIC 2 mg/L). The proportion of pre-dose concentrations exceeding the MIC 8 mg/L and the fraction time with a target-exceeding concentration were higher in the FO group (day 1-3 f Cmin > MIC: 67 vs 27%, p < 0.001; day 1%f T > MIC: 79 ± 17 vs 58 ± 17, p < 0.05). CONCLUSIONS: These findings emphasize the importance of TDM and a cautious approach to augmented maintenance dosing of meropenem to patients with FO infected with less susceptible pathogens, if guided by population covariate relationships between CLme and creatinine clearance.

Plasmafiltration as an effective method in the removal of circulating pegylated liposomal doxorubicin (PLD) and the reduction of mucocutaneous toxicity during the treatment of advanced platinum-resistant ovarian cancer.

PURPOSE: The present study evaluates the safety and efficacy of double-plasma filtration (PF) to remove the exceeding pegylated liposomal doxorubicin (PLD) in circulation, thus reducing mucocutaneous toxicity. METHODS: A total of 16 patients with platinum-resistant ovarian cancer were treated with 50 mg/m2 PLD applied in 1-h IV infusion every 28 days. PF was scheduled at 44-46 h post-infusion. The concentration of plasma PLD and non-liposomal doxorubicin (NLD) was monitored with high-performance liquid chromatography at 116 h post-infusion. A non-linear method for mixed-effects was used in the population pharmacokinetic model. The dose fraction of PLD eliminated by the patient prior to PF was compared with the fraction removed by PF. PLD-related toxicity was recorded according to CTCAE v4.0 criteria and compared to historical data. Anticancer effects were evaluated according to RECIST 1.1 criteria. RESULTS: The patients received a median of 3 (2-6) chemotherapy cycles. A total of 53 cycles with PF were evaluated, which removed 31% (10) of the dose; on the other hand, the fraction eliminated prior to PF was of 34% (7). Exposure to NLD reached only 10% of exposure to the parent PLD. PLD-related toxicity was low, finding only one case of grade 3 hand-foot syndrome (6.7%) and grade 1 mucositis (6.7%). Other adverse effects were also mild (grade 1-2). PF-related adverse effects were low (7%). Median progression-free survival (PFS) and overall survival (OS) was of 3.6 (1.5-8.1) and 7.5 (1.7-26.7) months, respectively. Furthermore, 33% of the patients achieved stable disease (SD), whereas that 67% progressed. CONCLUSION: PF can be considered as safe and effective for the extracorporeal removal of PLD, resulting in a lower incidence of mucocutaneous toxicity.

Covariate determinants of effective dosing regimens for time-dependent beta-lactam antibiotics for critically ill patients.

AIMS: Critically ill patients undergoing aggressive fluid resuscitation and treated empirically with hydrosoluble time-dependent beta-lactam antibiotics are at risk for sub-therapeutic plasma concentrations. The aim of this study was to assess the impact of two covariates - creatinine clearance (Clcr) and cumulative fluid balance (CFB) on pharmacokinetics/pharmacodynamics (PK/PD) target attainment within a week of treatment with meropenem (ME) or piperacillin/tazobactam (PIP/TZB). METHODS: In this prospective observational pharmacokinetic (PK) study, 18 critically ill patients admitted to a surgical Intensive Care Unit (ICU) were enrolled. The primary PK/PD target was free antibiotic concentrations above MIC at 100% of the dosing interval (100%fT>MIC) to obtain maximum bactericidal activity. Drug concentration was measured using liquid chromatography-tandem mass spectrometry. RESULTS: The treatment of both 8 septic patients with IV extended ME dosing 2 g/3 h q8 h and 10 polytraumatized patients with IV intermittent PIP/TZB dosing 4.0/0.5 g q8 h was monitored. 8/18 patients (44%) manifested augmented renal clearence (ARC) where Clcr ≥130 mL/min/1.73 m2. Maximum changes were reported on days 2-3: the median positive CFB followed by the large median volume of distribution: Vdme=70.3 L (41.9-101.5), Vdpip = 46.8 L (39.7-60.0). 100%fTme>MIC was achieved in all patients on ME (aged ≥60 years), and only in two patients (non-ARC, aged ≥65 years) out of 10 on PIP/TZB. A mixed model analysis revealed positive relationship of CFBpip with Vdpip (P=0.021). CONCLUSION: Assuming that the positive correlation between CFB and Vd exists for piperacillin in the setting of the pathological state, then CFB should predict Vdpip across subjects at each and every time point.

Plasmafiltration as a possible contributor to kinetic targeting of pegylated liposomal doxorubicin (PLD) in order to prevent organ toxicity and immunosuppression.

PURPOSE: To examine the removal of pegylated liposomal doxorubicin (PLD) during plasmafiltration (PF) and determine whether the drug could be withheld prior to its organ distribution responsible for mucocutaneous toxicity. METHODS: Six patients suffering from platinum-resistant ovarian cancer were treated with a 1-h IV infusion 50 mg/m(2) of PLD/cycle-for three cycles q4w. Over 44 (46)-47(49) h postinfusion, five patients (14 cycles in total) underwent PF using a cascade PF method consisted of plasma separation by centrifugation and plasma treatment using filtration based one volume of plasma treatment, i.e., 3.18 L (±0.6 L) and plasma flow 1.0 L/h (0.91-1.48 L/h). Doxorubicin concentration in blood was monitored by a high-performance liquid chromatography method for 116 h postinfusion. Pharmacokinetic parameters determined from plasma concentration included volume of distribution, total body clearance, half-life of elimination, and area under the plasma concentration versus time. The amount of doxorubicin in the body eliminated by the patient and via extracorporeal treatment was evaluated. Toxicity was tested using CTCAE v4.0. RESULTS: The efficacy of PF and early responses to PLD/PF combination strategy were as follows: over 44(46) h postinfusion considered necessary for target distribution of PLD to tumor, patients eliminated 46 % (35-56 %) of the dose administered. Over 44(46)-47(49) h postinfusion, a single one-volume plasma filtration removed 40 % (22-45 %) (Mi5) of the remaining doxorubicin amount in the body. Total fraction eliminated attained 81 % (75-86 %). The most common treatment-related adverse events (grade 1-2) such as nausea (4/14 cycles-28 %) and vomiting (3/14 cycles-21 %) appeared during 44 h postinfusion. Hematological toxicity-anemia (5/14 cycles-35 %) was reported after cycle II termination. Symptoms of PPE-like syndrome (grade 1-2) appeared in one patient concomitantly with thrombophlebitis and malignant effusion. In this study, only one adverse reaction (1/14-7 %) as short-term malaise and nausea was reported by the investigator as probably related to PF. CONCLUSION: A single one-volume PF does remove a clinically important amount of doxorubicin in a kinetic targeting approach. There were no serious signs of drug toxicity and/or PF-related adverse events. Kinetically guided therapy with pegylated liposomal doxorubicin combined with PF may be a useful tool to the higher efficacy and tolerability of therapy with PLD.

A pilot study on pharmacokinetic/pharmacodynamic target attainment in critically ill patients receiving piperacillin/tazobactam.

BACKGROUND: In critically ill patients, multi-trauma and intensive therapy can influence the pharmacokinetics (PK) and pharmacodynamics (PD) of antibiotics with time-dependent bacterial killing. Consequently, PK/PD targets (%fT>MIC) - crucial for antimicrobial effects -may not be attained. METHODS: Two patients admitted to the surgical ICU of the University Hospital in Hradec Králove for multiple-trauma were given piperacillin/tazobactam by 1-hour IV infusion 4/0.5 g every 8h. PK variables: total and renal clearance (CLtot, CLR), volume of distribution (Vd), and elimination half-life (T1/2) were calculated, followed by glomerular filtration rate (MDRD) and cumulative fluid balance (CFB-total fluid volume based on 24-h registered fluid intake minus output). The PK/PD target attainment (100%fT>MIC) was defined as free (f) piperacillin plasma concentrations that remain, during the entire dosing interval (T), above the minimum inhibitory concentration (100%fT>MIC) within days 4-8 (when CFB culminates and disappears). Piperacillin concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and corrected for unbound fraction (22%). RESULTS: CFB culminated over days 2-5 reaching 15-30 L and was associated with a large Vd (29-42 L). While MDRD in patient 1 was low (0.3-0.4 mL s⁻¹ 1.7 m⁻²), that of patient 2 was increasing (> 3.1 mL s⁻¹ 1.7 m⁻²), which was associated with augmented CLR. In patient 2, the fT reached only 62, 52, and 44% on days 4, 6, and 8, respectively. In patient 1, the %fT was much higher, attaining values four to fivefold greater than that targeted. CONCLUSIONS: Critically ill patients are at risk of drug under- or overdosing without dose up-titration with regard to covariate effects and individual drug pharmacokinetics.

[Current view of vancomycin in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections]. / Soucasný náhled na vankomycin v lécbe infekcí staflokokem rezistentním na methicillin (MRSA).

The review article interprets recommendations for treating methicillin-resistant Staphylococcus aureus (MRSA) infections with vancomycin. These stem from a 2009 consensus followed by numerous preclinical and clinical studies carried out until now. They are based on defining the predictors of the bactericidal activity of vancomycin that are different from those in beta-lactam and aminoglycoside antibiotics. The predictors are AUC0-24/MIC >400 and Cₘᵢₙ. Practice requires recommendations on how to achieve maximum effectiveness and safety of vancomycin administered by intermittent vs. continuous infusion by setting target concentrations under dynamically changing conditions. Changes in the kinetics and dynamics of the antibiotic due to pathological covariates (SIRS, sepsis) and treatment should be detected as soon as possible by therapeutic monitoring aimed at individual adjustment of dosage.

Kinetically guided neoadjuvant chemoradiotherapy based on 5-Fluorouracil in patients with locally advanced rectal cancer.

BACKGROUND AND PURPOSE: This study estimated patients' early response following neoadjuvant chemoradiotherapy (CHRT) of locally advanced rectal cancer based on 5-fluorouracil (5-FU). The target was to achieve pathological complete response (pCR; residual disease-free stage) and toxicities of grade ≤2, using individual dosing predicted according to the steady-state plasma concentration (C ss) and pharmacokinetic parameters of 5-FU: the area under the time-concentration curve at steady state (AUC) and clearance (CL). PATIENTS AND METHODS: This open-label prospective study enrolled 33 adult patients treated with 5-FU administered as a continuous intravenous infusion over 4-5 weeks, as follows: in Group 1a (N = 6), the patients received a standard dose of 300 mg/m(2)/24 h. In Group 1b (N = 7), the patients were treated with an escalated dose of 400-1,000 mg/m(2)/24 h. In Group 2 (N = 20), the patients were given dosing kinetically guided in order to reach the target range of 5-FU C ss 50-100 µg/L. Tolerability was tested according to Common Terminology Criteria for Adverse Events v3.0 (CTCAE). Radiotherapy was delivered with 10-15 MV photon beams at 1.8 Gy/fraction up to 50.4 Gy in 28 daily fractions for 5 days a week. Surgery followed 4-6 weeks after the completion of CHRT and clinical restaging. The pCR and residual tumour stage were evaluated using preoperative tumour downstaging in magnetic resonance, postoperative histopathological staging and tumour regression rate (residual disease). RESULTS AND CONCLUSION: The cumulative AUC of 5-FU (total exposure to the drug) correlated with cumulative 5-FU dose (r = 0.61; p < 0.001) and residual disease (r s = -0.53; p < 0.005). A higher target pCR rate was reached in patients individually treated (Group 2) who finished the whole 5-week CHRT. The individual daily dose needed to reach the target C ss should be >350 mg/m(2) (up to 600 mg/m(2)) provided that 5-FU metabolic ratio is within the range of 2.5-6 and the cumulative AUC5wks is within 50-100 mg·h/L.

A rat model of early sepsis: relationships between gentamicin pharmacokinetics and systemic and renal effects of bacterial lipopolysaccharide combined with interleukin-2.

A rat model of early sepsis induced by lipopolysaccharide (LPS) combined with interleukin-2 (IL-2) was developed. The primary aim was to assess the pharmacokinetics of gentamicin and sepsis-induced pathophysiological changes. Moreover, the effects on the glomerular filtration rate and tubular function were studied in septic and control rats. First, an intravenous (i.v.) bolus of LPSIL-2 (1 mg/kg-Pseudomonas aeruginosa, 15 µg/kg IL-2) or saline (controls, C) was administred. The Wistar rats were treated 30 min after LPSIL-2 with gentamicin as a 3 mg/kg i.v. bolus followed 10 min later by an i.v. 170-min infusion (GE, 0.09 mg/kg·min(-1)). The monitoring of vital functions, biochemistry and GE concentrations was performed. Creatinine clearance was 2-3 times lower and fractional urea excretion was 3-4 times less in septic rats as compared to controls(p<0.05), although urine flow was comparable. Capillary leakage caused a 55% elevation in the volume of distribution (V(c)) in the LPSIL+GE group vs. C+GE (p<0.05). The renal CL(ge) was less (2.2±0.59 vs. 3.8±0.53 mL/min·kg(-1), p<0.05), while the total CL(ge) was comparable (5.9±1.5 vs. 6.7±1.1 mL/min·kg(-1); p=0.30). In the LPSIL+GE group relative to C+GE, the half-life (t(1/2)) was 79% higher (p<0.05) and GE concentrations detected at the end of the study in the plasma and kidney were elevated 2.5-fold (p=0.09) and 2.2-fold (p<0.05), respectively. The model reproduced several consequences of early sepsis like in patients such as capillary leak, a decreased glomerular filtration rate (GFR) and the changes in pharmacokinetics of GE (increased values of V(c) and t(1/2) and a drop in renal CL(ge) proportional to that of CL(cr)). Nonrenal routes which, for the most part, compensate the reduced renal CL(ge) in septic rats deserve further study.

Cancer drug-resistance and a look at specific proteins: Rho GDP-dissociation inhibitor 2, Y-box binding protein 1, and HSP70/90 organizing protein in proteomics clinical application.

Resistance to anti-cancer drugs is a well recognized problem and very often it is responsible for failure of the cancer treatment. In this study, the proteome alterations associated with the development of acquired resistance to cyclin-depedent kinases inhibitor bohemine, a promising anti-cancer drug, were analyzed with the primary aim of identifying potential targets of resistance within the cell that could pave a way to selective elimination of specific resistant cell types. A model of parental susceptible CEM T-lymphoblastic leukemia cells and its resistant counterpart CEM-BOH was used and advanced 2-D liquid chromatography was applied to fractionate cellular proteins. Differentially expressed identified proteins were further verified using immunoblotting and immunohistochemistry. Our study has revealed that Rho GDP-dissociation inhibitor 2, Y-box binding protein 1, and the HSP70/90 organizing protein have a critical role to play in resistance to cyclin-depedent kinases inhibitor. The results indicated not only that quantitative protein changes play an important role in drug-resistance, but also that there are various other parameters such as truncation, post-translational modification(s), and subcellular localization of selected proteins. Furthermore, these proteins were validated for their roles in drug resistance using different cell lines resistant to diverse representatives of anti-cancer drugs such as vincristine and daunorubicin.

The third Central and Eastern European Proteomic conference.

The third Central and Eastern European Proteomic Conference was held at Hotel Benzcur, Budapest, Hungary, from the 6-9 October 2009. The meeting was the third in a series of proteomic conferences to be held in this region of Europe, with the key aim of strengthening the links with scientists from Central and Eastern Europe, as well as international groups worldwide. It was attended by more than 150 delegates from various countries and many proteomic topics, including biomarker discovery, post-translational modifications, clinical proteomics, as well as new proteomic technologies, which may facilitate future progress, were discussed over the 3 days.

Proteome mining of human follicular fluid reveals a crucial role of complement cascade and key biological pathways in women undergoing in vitro fertilization.

In vitro fertilization (IVF) is fraught with problems and currently proteomics approaches are being tried out to examine the microenvironment of the follicle in order to assess biological and immunological parameters that may affect its development. Additionally, better understanding of reproductive process may help increase IVF birth rate per embryo transfer and at the same time avoid spontaneous miscarriages or life threatening conditions such as ovarian hyperstimulation syndrome. The primary aim of this study was to search for specific differences in protein composition of human follicular fluid (HFF) and plasma in order to identify proteins that accumulate or are absent in HFF. Depletion of abundant proteins combined with multidimensional protein fractionation allowed the study of middle- and lower-abundance proteins. Paired comparison study examining HFF with plasma/serum from women undergoing successful IVF revealed important differences in the protein composition which may improve our knowledge of the follicular microenvironment and its biological role. This study showed involvement of innate immune function of complement cascade in HFF. Complement inhibition and the presence of C-terminal fragment of perlecan suggested possible links to angiogenesis which is a vital process in folliculogenesis and placental development. Differences in proteins associated with blood coagulation were also found in the follicular milieu. Several specific proteins were observed, many of which have not yet been associated with follicle/oocyte maturation. These proteins together with their regulatory pathways may play a vital role in the reproductive process.

High-dose methotrexate in children with acute lymphoblastic leukemia: 7-hydroxymethotrexate systemic exposure and urinary concentrations at the steady state correlate well with those of methotrexate.

The present study evaluated the pharmacokinetics of methotrexate (MTX, CAS 59-05-2) and 7-hydroxymethotrexate (7-OHMTX, CAS 5939-37-7) in children with acute lymphoblastic leukemia (ALL) with particular interest devoted to the renal excretion at the steady-state and to the relationships between total (CL) and renal clearances (CL(R)) of both compounds. Ten children (seven girls) aged 8.5 years (2.9-16) years with standard or medium-risk ALL received four 24-h i.v. infusions of high-dose MTX (HDMTX, 5 g/m2) with leucovorin (CAS 58-05-9) rescue according to the ALL-BFM-95 protocol. MTX and 7-OHMTX were assayed in plasma and urine by high-performance liquid chromatography. At the steady-state, the clearance (CL) of MTX (6.28 +/- 2.79 l h(-1)) was correlated with its CL(R) (r(s) = 0.79, p < 0.0001) which accounted for 61% (SD 26%) of the former. There were weak correlations between pretreatment values of creatinine clearance calculated using Schwartz's formula and the drug's CL (r(s) = 0.30, p < 0.05) or CLR (r(s) = 0.41, p < 0.02). In contrast, the CL(R) accounted for only 26% (SD 15%) of the metabolite's CL which was estimated assuming 10% conversion of MTX to 7-OHMTX. The CL values of both compounds were highly correlated (r(s) = 0.86, p < 0.0001). The CL(R) of the parent compound was on the average 9-fold higher (range: 3.5- to 17-fold) and was strongly correlated with the CL(R) of the metabolite (r(s) = 0.87, p < 0.0001). The ratio 7-OHMTX/MTX of urinary concentrations was between 2.4 and 9.8% with the mean value of 4.1%. This study suggests that during the 24-h i.v. infusions of HDMTX to children with ALL, the exposure of patients to 7-OHMTX can be reasonably well predicted from the knowledge of MTX concentrations. The steady-state renal CLs, total CLs as well as urinary concentrations of the parent compound and metabolite are highly correlated and the correlation of plasma concentrations is moderate. Therefore, it is unlikely that simultaneous evaluation of 7-OHMTX and MTX steady-state concentrations could improve the predictive performance of the latter towards the response or the risk of complications, although future larger studies should verify this conclusion.

Tolerability and outcomes of kinetically guided therapy with gentamicin in critically ill neonates during the first week of life: an open-label, prospective study.

BACKGROUND: Aminoglycosides are bactericidal antibiotics used worldwide for the treatment of serious infections in critically ill patients, including neonates. Critically ill neonates constitute a unique challenge in dosing owing to the pathologic alterations that accompany severe illness and the rapidly changing conditions of these patients. OBJECTIVES: The main objective of this study was to analyze the kinetically guided dosage adjustment of gentamicin in neonates critically ill during the first week of life based on plasma concentrations after the first dose and to identify the impact of covariates (eg, fluid intake, body fluid retention) with respect to gestational age (GA). Tolerability of therapy was also assessed. METHODS: This 10-day, open-label, prospective study included neonates critically ill during the first week of life admitted to the neonatal intensive care unit of a children's hospital between January 2006 and July 2009. Hearing and renal assessments were conducted over a 24-month follow-up period. The patients were treated with gentamicin for suspected sepsis, proven sepsis, or pneumonia as an early sign of sepsis. The first and second doses of gentamicin 4 mg/kg were adjusted according to birth weight and GA: group 1 (GA < 34 weeks), 48-hour interdose intervals; group 2 (GA 34-38 weeks), 36 hours; and group 3 (GA > 38 weeks), 24 or 48 hours. Individual pharmacokinetic parameters were estimated after the first dose (given in 30-minute intravenous infusions) using 4 concentrations. Individual pharmacokinetic parameters were estimated by fitting the parameters of a 2-compartment model into 4 concentrations. The last 2 blood samples were taken 30 minutes before the fourth infusion (C(trough,3)) and 1 hour after its start (C(max,4)). Dosing was individualized to reach target ranges for the C(trough,3) (0.5-2.0 mg/L) and C(max,4) (6-10 mg/L) values. If needed, initial dosing was changed after the second dose by adjusting (reducing or increasing) the third and subsequent doses, or by adjusting (prolonging or shortening) the interdose intervals. C(trough,3) and C(max,4) were assessed to determine differences between predicted and assayed values. Fluid retention was registered as the difference between fluid intake and urine output at different intervals related to the first dose per kilogram of birth weight, and from the start of the first infusion (0 hour) to the day of the fourth infusion. The C(max)/minimum inhibitory concentration (MIC) ratio was determined for assessment of optimal response. Tolerability was evaluated during the 24-month follow-up period using renal sonography to screen for nephrocalcinosis and transient evoked otoacoustic emission recordings to evaluate hearing abnormalities. RESULTS: A total of 84 neonates (all white; 53 males, 31 females; birth weight range, 0.8-4.56 kg; GA range, 24-42 weeks) were enrolled in 3 groups: group 1, GA < 34 weeks, n = 27; group 2, GA 34-38 weeks, n = 22; and group 3, GA > 38 weeks, n = 35. The C(max) value detected 1 hour after the start of the first infusion (C(max,1)) reached the target range of 6-10 mg/L in 66 of the 84 neonates (79%). After the initial dose, C(max,1) was variable (%CV, 29%); the failure rate to reach 6 mg/L was 13%. V(d) decreased with GA (r = -0.30, P < 0.01) and achieved mean (SD) rates of 0.51 (0.10), 0.48 (0.13), and 0.40 (0.15) L/kg in groups 1, 2, and 3, respectively. Neither C(max) nor V(d) was correlated with fluid intake relative to the first infusion. Mean gentamicin clearance measured after dose 1 (0.47 [0.23], 0.66 [0.26], and 0.76 [0.32] mL/min/kg) increased with GA (r = 0.45, P < 0.001). The interdose interval was prolonged after the second and subsequent infusions in 8 of 84 neonates (10%) or by decreasing the third dose and subsequent doses in 51 neonates (61%). The target C(max,4) and C(trough,3) values occurred in 63% (22 of 35) and 83% (29 of 35) of full-term patients (GA >38 weeks), respectively. In preterm neonates, the target range for C(max,4) was reached in 11 of 27 patients (41%) in group 1 and 11 of 22 patients (50%) in group 2; for C(trough,3), the target range was reached in 25 patients (93%) in group 1 and in 16 (73%) in group 2. C(trough,3) >2 mg/L was detected in 1 full-term neonate, and gentamicin was withdrawn. Suspected fluid retention within the time period of 0 hour to the day of the fourth infusion was well correlated with actual body weight (r = 0.58, P < 0.001), but it was negatively correlated with C(max,4) (r = -0.25, P = 0.02). Thirteen of the 84 neonates (15%) had confirmed sepsis. C(max)/MIC was >12 except for 2 resistant staphylococcal infections (C(max)/MIC = 0.4); amikacin and vancomycin were substituted for gentamicin in these cases. Clinical signs and laboratory data indicative of suspected sepsis disappeared in 5 to 10 days in 68 of 71 neonates. In 1 neonate, gentamicin was withdrawn after dose 4 because of a high C(trough,3) value. In the 3 remaining neonates, C-reactive protein was decreased >10 days without changing therapy. Two neonates died, 1 of severe hypoxic-ischemic encephalopathy as a consequence of perinatal asphyxia and another of stage IV intraventricular hemorrhage. Transient renal dysfunction attributable to gentamicin was detected in 1 case. No signs of late toxicity (nephrocalcinosis) were found during the second year of follow-up. Two neonates were diagnosed with unilateral hearing loss, a secondary phenomenon of hypoxic-ischemic encephalopathy thought to be related to the severe perinatal asphyxia. CONCLUSIONS: The initial dose of gentamicin 4 mg/kg for these critically ill premature and mature neonates with sepsis during the first week of life was high enough to reach bactericidal C(max,1) within 6-10 mg/L. C(max,1) <6 mg/L occurred in 13% of neonates. The interdose interval modified according to the recommendation resulted in C(trough) values within the target range of 0.5-2.0 mg/L in all but 2 neonates. The kinetically guided maintenance dosing of gentamicin based on plasma concentrations after the first dose should be optimized, taking into account actual body weight. (EudraCT number: 2005-002723-13).

Modelling the genesis and treatment of cancer: the potential role of physiologically based pharmacodynamics.

Physiologically based modelling of pharmacodynamics/toxicodynamics requires an a priori knowledge on the underlying mechanisms causing toxicity or causing the disease. In the context of cancer, the objective of the expert meeting was to discuss the molecular understanding of the disease, modelling approaches used so far to describe the process, preclinical models of cancer treatment and to evaluate modelling approaches developed based on improved knowledge. Molecular events in cancerogenesis can be detected using 'omics' technology, a tool applied in experimental carcinogenesis, but also for diagnostics and prognosis. The molecular understanding forms the basis for new drugs, for example targeting protein kinases specifically expressed in cancer. At present, empirical preclinical models of tumour growth are in great use as the development of physiological models is cost and resource intensive. Although a major challenge in PKPD modelling in oncology patients is the complexity of the system, based in part on preclinical models, successful models have been constructed describing the mechanism of action and providing a tool to establish levels of biomarker associated with efficacy and assisting in defining biologically effective dose range selection for first dose in man. To follow the concentration in the tumour compartment enables to link kinetics and dynamics. In order to obtain a reliable model of tumour growth dynamics and drug effects, specific aspects of the modelling of the concentration-effect relationship in cancer treatment that need to be accounted for include: the physiological/circadian rhythms of the cell cycle; the treatment with combinations and the need to optimally choose appropriate combinations of the multiple agents to study; and the schedule dependence of the response in the clinical situation.

Up-regulation of renal Mdr1 and Mrp2 transporters during amiodarone pretreatment in rats.

Although amiodarone (AMD) is known to produce drug-drug interactions through inhibition of transporter-mediated excretion of drugs, its impact on these mechanisms during chronic treatment has not been described yet. Therefore, the aim of this study was to investigate the influence of AMD pretreatment on the main multidrug transporting proteins, Mdr1 and Mrp2, in the liver and kidney. The expression of the transporters and pharmacokinetics of their substrates, rhodamine-123 (Rho123) and endogenous conjugated bilirubin (CB), were evaluated in rats after either AMD oral pretreatments (4-14 days) or single intravenous bolus. AMD pretreatment of all durations up-regulated renal Mdr1 and Mrp2 protein expression to 155-190% and 152-223% of the control values, respectively. In agreement, we observed a corresponding increase in renal clearance of both substrates. Hepatic expression was increased only for Mdr1 to 234-270% of controls, which was associated with increased biliary elimination of amiodarone without change in Rho123 biliary clearance. Interestingly, hepatic expression of another Mdr transporter, Mdr2, was progressively decreased by amiodarone administration. Acute administration of AMD reduced Rho123 biliary clearance by 64%. Our results indicate that repeated administration of AMD to rats is associated with significant increase in hepatic and renal expression of Mdr1 and Mrp2 transporters, which may contribute to variability in pharmacokinetics of AMD and simultaneously applied drugs.

Alteration of methotrexate biliary and renal elimination during extrahepatic and intrahepatic cholestasis in rats.

Methotrexate (MTX), an important anticancer and immunosuppressive agent, has been suggested for the treatment of primary biliary cirrhosis. However, the drug's pharmacodynamics and toxicity is dependent on its concentrations in plasma which in turn are directly related to MTX's elimination in the liver and kidney. Therefore, the aim of this study was to evaluate changes in MTX biliary and renal excretion during either intrahepatic or obstructive cholestasis in rats. The steady state pharmacokinetic parameters of MTX were evaluated in rats one (BDO1) or seven (BDO7) days after bile duct obstruction (BDO) or 18 h after administration of lipopolysaccharide (LPS). In comparison to the respective control groups, biliary and total clearances of MTX were decreased to 12% and 49% in the BDO1 group, to 5% and 56% in the BDO7 animals, and to 42% and 43% in the LPS group, respectively. Renal clearance of MTX was unchanged in BDO groups, but decreased to 23% of controls in the LPS animals. The serum biochemistry and expression of main hepatic MTX transporters (Mrp2, Mrp3, Mrp4, Bcrp, Oatp1a1, Oatp1a4 and Oatp1b2) confirmed the pathological cholestatic changes in the liver and partly elucidated the cause of changes in MTX pharmacokinetic parameters. In conclusion, this study is the first describing marked alteration of MTX hepatic and renal elimination induced by cholestasis in rats. Moreover, the reported changes in MTX pharmacokinetics and respective transporter expression suggest important mechanistic differences between the two widely used cholestatic models.

Meropenem pharmacokinetics in the newborn.

We studied meropenem in 23 pre-term (gestational age, 29 to 36 weeks) and 15 full-term (gestational age, 37 to 42 weeks) neonates. Meropenem doses of 10, 20, and 40 mg/kg were administered as single doses (30-min intravenous infusion) on a random basis. Blood was obtained for determining the meropenem concentration nine times. Each child required other antimicrobials for proven/suspected bacterial infections. Samples were assayed by high-performance liquid chromatography analysis. Population pharmacokinetic parameter values were obtained by employing the BigNPAG program. Model building was performed by the likelihood ratio test. The final model included estimated creatinine clearance (CLcr) (Schwartz formula) and weight (Wt) in the calculation of clearance (meropenem clearance = 0.00112 x CLcr + 0.0925 x Wt + 0.156 liter/hr). The overall fit of the model to the data was good (observed = 1.037 x predicted - 0.096; r2 = 0.977). Given the distributions of estimated creatinine clearance and weight between pre-term and full-term neonates, meropenem clearance was substantially higher in the full-term group. A Monte Carlo simulation was performed using the creatinine clearance and weight distributions for pre-term and full-term populations separately, examining 20- and 40-mg/kg doses, 8- and 12-h dosing intervals, and 0.5-h and 4-h infusion times. The 8-h interval produced robust target attainments (both populations). If more resistant organisms were to be treated (MIC of 4 to 8 mg/liter), the 40-mg/kg dose and a prolonged infusion was favored. Treating clinicians need to balance dose choices for optimizing target attainment against potential toxicity. These findings require validation in clinical circumstances.

Challenges in cancer research and multifaceted approaches for cancer biomarker quest.

Recent advances in cancer biology have subsequently led to the development of new molecularly targeted anti-cancer agents that can effectively hit cancer-related proteins and pathways. Despite better insight into genomic aberrations and diversity of cancer phenotypes, it is apparent that proteomics too deserves attention in cancer research. Currently, a wide range of proteomic technologies are being used in quest for new cancer biomarkers with effective use. These, together with newer technologies such as multiplex assays could significantly contribute to the discovery and development of selective and specific cancer biomarkers with diagnostic or prognostic values for monitoring the disease state. This review attempts to illustrate recent advances in the field of cancer biomarkers and multifaceted approaches undertaken in combating cancer.

Amiodarone modulates pharmacokinetics of low-dose methotrexate in rats.

Clinical studies of low-dose methotrexate (LDMTX) pharmacokinetics document increased plasma concentrations of MTX after co-administration of the drug with amiodarone or macrolide antibiotics. As drug-drug interactions may increase the toxicity of LDMTX, a rat model was used to follow renal and biliary elimination of MTX during its constant-rate i.v. infusion and concomitant single bolus i.v. injections of amiodarone or azithromycin. The mean steady-state plasma concentration of 1.7+/-0.1 micromol/l was reached and the total clearance achieved 17.7+/-1.0 ml/min/kg. Administration of amiodarone decreased the biliary clearance of MTX to 73% of the control values (p<0.05). Correspondingly, the total clearance decreased to 72% and plasma MTX concentrations were augmented to 2.5+/-0.4 micromol/l (p<0.05). Amiodarone-treated rats exhibited a 3.3-fold decrease in the renal clearance (p<0.05) of conjugated bilirubin, which was associated with its increased plasma concentration. In contrast, azithromycin did not alter any of the MTX pharmacokinetic parameters. In conclusion, this is the first report describing the impairment of MTX hepatic elimination during co-administration with amiodarone. This study also provides new insight into acute amiodarone-induced hyperbilirubinaemia, where increased bilirubin production and decreased renal clearance may contribute to this effect. Importantly, azithromycin seems to be a safe co-medication during LDMTX therapy.