Evaluation of drug prescribing patterns and therapeutic drug monitoring practice using electronic medical records.

Therapeutic drug monitoring (TDM) is performed for drugs with narrow therapeutic indices. At Seoul National University Hospital (SNUH) and Seoul National University Bundang Hospital (SNUBH), TDM services are provided for various drugs such as antibiotics and antiepileptics. This study aimed to identify prescription patterns over time using electronic medical records and analyze their relationship with TDM practice. Data were collected from a clinical data warehouse from 2007 to 2020, and the number of patients, total number of drug administration days, serum level tests, and TDM were calculated. The ratio was calculated as the number of serum level tests or TDM to the total number of drug administration days. The study included 136,427 and 162,927 patients from SNUH and SNUBH who were prescribed 11 specified drugs. Each drug showed different prescription patterns over time, and the serum level test and TDM also changed with prescription pattern changes. Serum level test or TDM of antibiotics was frequently used compared to antiepileptics. As some drugs' usage and test for drugs have decreased newly developed drugs are replacing old drugs. It is recommended that TDM services include these new drugs as well for an effective and safe therapy.

Assessment of induced CYP3A activity in pregnant women using 4ß-hydroxycholesterol: Cholesterol ratio as an appropriate metabolic marker.

AIMS: This study was aimed at evaluating changes in CYP3A activity following and during pregnancy by analyzing metabolic markers for CYP3A activity, which can help avoid unnecessary drug exposure and invasive sampling. METHODS: Forty-eight pregnant women and 25 non-pregnant women were enrolled in this study. Plasma and urine samples were collected from the pregnant women during each trimester and from the non-pregnant women for evaluation of metabolic markers for CYP3A activity. Metabolic markers for CYP3A activity were measured using GC-MS. RESULTS: An increased 4ß-hydroxycholesterol/cholesterol ratio, consistent with high CYP3A activity, was observed in pregnant women compared with that in non-pregnant women; however, no differences were observed among trimesters. No significant differences were observed in urinary markers. CONCLUSIONS: We observed an increase in the activity of CYP3A following but not during pregnancy when measured using the 4ß-hydroxycholesterol/cholesterol ratio. In addition, based on our results, we suggest that the plasma 4ß-hydroxycholesterol/cholesterol ratio be used to measure CYP3A activity in pregnant women.

Assessment of Hepatic Cytochrome P450 3A Activity Using Metabolic Markers in Patients with Renal Impairment.

BACKGROUND: The renal function of individuals is one of the reasons for the variations in therapeutic response to various drugs. Patients with renal impairment are often exposed to drug toxicity, even with drugs that are usually eliminated by hepatic metabolism. Previous study has reported an increased plasma concentration of indoxyl sulfate and decreased plasma concentration of 4ß-hydroxy (OH)-cholesterol in stable kidney transplant recipients, implicating indoxyl sulfate as a cytochrome P450 (CYP) inhibiting factor. In this study, we aimed to evaluate the impact of renal impairment severity-dependent accumulation of indoxyl sulfate on hepatic CYP3A activity using metabolic markers. METHODS: Sixty-six subjects were enrolled in this study; based on estimated glomerular filtration rate (eGFR), they were classified as having mild, moderate, or severe renal impairment. The plasma concentration of indoxyl sulfate was quantified using liquid chromatography-mass spectrometry (LC-MS). Urinary and plasma markers (6ß-OH-cortisol/cortisol, 6ß-OH-cortisone/cortisone, 4ß-OH-cholesterol) for hepatic CYP3A activity were quantified using gas chromatography-mass spectrometry (GC-MS). The total plasma concentration of cholesterol was measured using the enzymatic colorimetric assay to calculate the 4ß-OH-cholesterol/cholesterol ratio. The correlation between variables was assessed using Pearson's correlation test. RESULTS: There was a significant negative correlation between MDRD eGFR and indoxyl sulfate levels. The levels of urinary 6ß-OH-cortisol/cortisol and 6ß-OH-cortisone/cortisone as well as plasma 4ß-OH-cholesterol and 4ß-OH-cholesterol/cholesterol were not correlated with MDRD eGFR and the plasma concentration of indoxyl sulfate. CONCLUSION: Hepatic CYP3A activity may not be affected by renal impairment-induced accumulation of plasma indoxyl sulfate.

Assessment of Appropriateness of an Initial Dosing Regimen of Vancomycin and Development of a New Dosing Nomogram.

Vancomycin is a glycopeptide antibiotic used to treat Gram-positive infections including methicillin-resistant Staphylococcus aureus (MRSA). The objectives of this study were to evaluate the appropriateness of the initial dosing regimen of vancomycin, identify factors to be considered in regimen selection and develop a new dosing nomogram. Therapeutic drug monitoring (TDM) data of vancomycin obtained from Seoul National University Hospital from 2011 to 2013 were included in this analysis. The vancomycin trough concentrations at steady-state were estimated using Abbott's PKS software program and then categorized into three levels: subtherapeutic, therapeutic and toxic. The newly developed nomograms were evaluated by analysing the percentage of patients with target vancomycin trough concentration using the data of 2,570 patients of the first TDM cases. Therapeutic level was achieved only in approximately one-fifth of the cases, while 56.0% and 23.8% of the TDMs were considered subtherapeutic and toxic, respectively. As body-weight and creatinine clearance (CrCL) increased, the proportion of patients with a subtherapeutic level increased. Using the newly developed nomogram increased the proportion of patients who achieved therapeutic levels from 23.1% to 45.0% or 13.8% to 36.2% (target, 10-15 and 15-20 mg/L, respectively). These results suggest that the vancomycin concentrations fail to reach the therapeutic level or exceed the safe upper margin of the therapeutic level depending on age, body-weight and CrCL. Considering these factors, the new nomograms provide a strategy to achieve target concentrations of vancomycin more rapidly than existing regimens.

A fixed-dose combination tablet of gemigliptin and metformin sustained release has comparable pharmacodynamic, pharmacokinetic, and tolerability profiles to separate tablets in healthy subjects.

BACKGROUND: In type 2 diabetes mellitus, fixed-dose combination (FDC) can provide the complementary benefits of correction of multiple pathophysiologic defects such as dysfunctions in glycemic or metabolic control while improving compliance compared with separate tablets taken together. The objective of the study reported here was to compare the pharmacodynamic (PD), pharmacokinetic (PK), and tolerability profiles of gemigliptin and extended-release metformin (metformin XR) between FDC and separate tablets. METHODS: A randomized, open-label, single-dose, two-way, two-period, crossover study was conducted in 28 healthy male volunteers. Two FDC tablets of gemigliptin/metformin 25/500 mg or separate tablets of gemigliptin (50 mg ×1) and metformin XR (500 mg ×2) were orally administered in each period. Serial blood samples were collected up to 48 hours post-dose to determine dipeptidyl peptidase 4 (DPP-4) activity using spectrophotometric assay and concentrations of gemigliptin and metformin using tandem mass spectrometry. Geometric mean ratios (GMRs) of FDC to separate tablet formulations and their 90% confidence intervals (CIs) were calculated to compare the PD and PK parameters between the two formulations. Tolerability was assessed throughout the study. RESULTS: The plasma DPP-4 activity-time curves of the FDC and the separate tablets almost overlapped, leading to a GMR (90% CI) of the FDC to separate tablets for the plasma DPP-4 activity and its maximum inhibition of 1.00 (0.97-1.04) and 0.92 (0.82-1.05), respectively. Likewise, all of the GMRs (90% CIs) of FDC to separate tablets for the area under the plasma concentration-time curve and maximum plasma concentration of gemigliptin and metformin fell entirely within the conventional bioequivalence range of 0.80-1.25. Both the FDC and separate tablets were well tolerated. CONCLUSION: The PD, PK, and tolerability profiles of gemigliptin and metformin XR in FDC and separate tablets were found to be comparable. The FDC tablet of gemigliptin and metformin sustained release can be a convenient therapeutic option in patients with type 2 diabetes mellitus requiring a combination approach.

Korean, Japanese, and Chinese populations featured similar genes encoding drug-metabolizing enzymes and transporters: a DMET Plus microarray assessment.

BACKGROUND: Interethnic differences in genetic polymorphism in genes encoding drug-metabolizing enzymes and transporters are one of the major factors that cause ethnic differences in drug response. This study aimed to investigate genetic polymorphisms in genes involved in drug metabolism, transport, and excretion among Korean, Japanese, and Chinese populations, the three major East Asian ethnic groups. METHODS: The frequencies of 1936 variants representing 225 genes encoding drug-metabolizing enzymes and transporters were determined from 786 healthy participants (448 Korean, 208 Japanese, and 130 Chinese) using the Affymetrix Drug-Metabolizing Enzymes and Transporters Plus microarray. To compare allele or genotype frequencies in the high-dimensional data among the three East Asian ethnic groups, multiple testing, principal component analysis (PCA), and regularized multinomial logit model through least absolute shrinkage and selection operator were used. RESULTS: On microarray analysis, 1071 of 1936 variants (>50% of markers) were found to be monomorphic. In a large number of genetic variants, the fixation index and Pearson's correlation coefficient of minor allele frequencies were less than 0.034 and greater than 0.95, respectively, among the three ethnic groups. PCA identified 47 genetic variants with multiple testing, but was unable to discriminate ethnic groups by the first three components. Multinomial least absolute shrinkage and selection operator analysis identified 269 genetic variants that showed different frequencies among the three ethnic groups. However, none of those variants distinguished between the three ethnic groups during subsequent PCA. CONCLUSION: Korean, Japanese, and Chinese populations are not pharmacogenetically distant from one another, at least with regard to drug disposition, metabolism, and elimination.

An assessment of the pharmacokinetics, pharmacodynamics, and tolerability of GCPGC, a novel pegylated granulocyte colony-stimulating factor (G-CSF), in healthy subjects.

INTRODUCTION: A pegylated recombinant human granulocyte colony-stimulating factor (G-CSF) is effective in reducing the severity and duration of neutropenia. This study was performed to investigate the pharmacokinetics (PK), pharmacodynamics (PD), and tolerability of GCPGC, a new formulation of pegylated G-CSF, in healthy volunteers and to compare them with those of pegfilgrastim (Neulasta®). METHODS: Twenty-five healthy Korean male volunteers randomly received a single subcutaneous (SC) GCPGC injection at a dose of 30 (n = 10), 100 (n = 10), or 300 (n = 5) µg/kg or placebo in a 4:1 ratio in a double-blind manner. Additionally, 8 subjects received a SC dose of pegfilgrastim at 100 µg/kg. Blood samples were collected up to 14 days after both therapies. The absolute neutrophil count (ANC) and CD34(+) cell counts were the PD markers. RESULTS: After GCPGC administration, 4 different pharmacokinetic phases were identified, indicating target-mediated drug disposition (TMDD) for the elimination of GCPGC, which was slowed down as the dose was increased, resulting in a higher than proportional dose-normalized exposure to GCPGC. Although GCPGC was cleared faster than pegfilgrastim, leading to a 19 % lower systemic exposure to pegylated G-CSF, the increase in ANC and CD34(+) were ~20 % greater by GCPGC at 100 µg/kg than pegfilgrastim. Thrombocytopenia, splenomegaly, and hemoperitoneum occurred in one subject in the 300 µg/kg GCPGC group, which resolved completely with appropriate care. CONCLUSIONS: GCPGC showed a non-linear TMDD. The PK-PD characteristics of GCPGC at 30-100 µg/kg were comparable to those of pegfilgrastim at 100 µg/kg. GCPGC at 30-100 µg/kg was well tolerated in healthy Korean males.

Exploration of optimal dosing regimens of haloperidol, a D2 Antagonist, via modeling and simulation analysis in a D2 receptor occupancy study.

PURPOSE: To evaluate the potential usage of D(2) receptor occupancy (D2RO) measured by positron emission tomography (PET) in antipsychotic development. METHODS: In this randomized, parallel group study, eight healthy male volunteers received oral doses of 0.5 (n = 3), 1 (n = 2), or 3 mg (n = 3) of haloperidol once daily for 7 days. PET's were scanned before haloperidol, and on days 8, 12, with serial pharmacokinetic sampling on day 7. Pharmacokinetics and binding potential to D(2) receptor in putamen and caudate nucleus over time were analyzed using NONMEM, and simulations for the profiles of D2RO over time on various regimens of haloperidol were conducted to find the optimal dosing regimens. RESULTS: One compartment model with a saturable binding compartment, and inhibitory E(max) model in the effect compartment best described the data. Plasma haloperidol concentrations at half-maximal inhibition were 0.791 and 0.650 ng/ml, in putamen and caudate nucleus. Simulation suggested haloperidol 2 mg every 12 h is near the optimal dose. CONCLUSION: This study showed that sparse D2RO measurements in steady state pharmacodynamic design after multiple dosing could reveal the possibility of treatment effect of D(2) antagonist, and could identify the potential optimal doses for later clinical studies by modeling and simulation.

Assessment of the effect of mirodenafil on the hemodynamics of healthy male Korean volunteers administered tamsulosin: a randomized, double-blind, placebo-controlled, 2-period crossover study.

BACKGROUND: Both mirodenafil, a phosphodiesterase type 5 inhibitor for the treatment of erectile dysfunction, and tamsulosin, a selective α(1A)-adrenergic receptor antagonist for the treatment of benign prostatic hyperplasia, have mild vasodilational effects. OBJECTIVE: The aim of this study was to investigate the effect of mirodenafil on the hemodynamics of healthy volunteers who were administered tamsulosin. METHODS: Healthy, Korean normotensive male volunteers were enrolled in a randomized, placebo-controlled, double-blind, 2-sequence, 2-period crossover study. Mirodenafil 100 mg or placebo was administered orally after pretreatment with tamsulosin 0.2 mg once daily for 7 days in each period, with a 1-week washout period. Blood pressure (BP) and pulse rate (PR) in supine and standing positions were measured repeatedly before and until 24 hours after the administration of mirodenafil or placebo. The mean differences from the baseline values of the maximum changes of BP and PR, which were measured at 4 and 24 hours, were analyzed by using a mixed-effects model. RESULTS: Eighteen subjects (mean [SD] age, 26.8 [3.9] years; weight, 65.5 [7.0] kg) were administered any trial medication, and 16 of them completed the study. For 4 hours/24 hours after mirodenafil administration, the mean maximal changes from baseline versus placebo in supine systolic BP, diastolic BP, and PR were -1.0 mm Hg (95% CI, -4.2 to 2.2) (P = 0.53)/-1.2 mm Hg (95% CI, -5.3 to 2.9) (P = 0.56), -2.1 mm Hg (95% CI, -4.6 to 0.4) (P = 0.10)/-1.1 mm Hg (95% CI, -3.9 to 1.6) (P = 0.39), and 7.2 beats/min (95% CI, 4.7 to 9.6) (P < 0.05)/4.8 beats/min (95% CI, 1.4 to 8.1) (P < 0.05), respectively. Those changes in a standing position were -4.0 mm Hg (95% CI, -8.9 to 0.9) (P = 0.10)/-4.3 mm Hg (95% CI, -10.0 to 1.5) (P = 0.13), -1.1 mm Hg (95% CI, -4.9 to 2.7) (P = 0.54)/-1.9 mm Hg (95% CI, -5.5 to 1.7) (P = 0.27), and 10.7 beats/min (95% CI, 4.4 to 16.9) (P < 0.05)/6.0 beats/min (95% CI, 0.7 to 11.3) (P < 0.05), respectively. A total of 33 adverse events (AEs) were reported in 9 of 18 subjects. The number of subjects with AEs (P = 0.13) and the number of AEs (P = 0.26) were not significantly different between the 2 groups. The most common AEs were vasodilational symptoms, such as nasal congestion, headache, and flushing. CONCLUSIONS: The coadministration of mirodenafil 100 mg did not induce a significant decrease in BP when associated with an increase in PR in these healthy male Korean volunteers administered tamsulosin 0.2 mg compared with placebo. (Clinical Trial Registry, http://cris.cdc.go.kr/cris/en/: KCT0000117).

Assessment of the pharmacokinetics of co-administered metformin and lobeglitazone, a thiazolidinedione antihyperglycemic agent, in healthy subjects.

OBJECTIVE: Lobeglitazone as a thiazolidinedione antihyperglycemic agent activates peroxisome proliferator-activated receptor (PPAR) γ and may be suitable as monotherapy or in combination with other antihyperglycemic agents. The primary objective of this study was to investigate potential pharmacokinetic interactions between lobeglitazone and metformin in healthy Korean subjects. METHODS: A randomized, open-label, multiple-dose, three-treatment, three-period, three-sequence, crossover study was conducted in 24 healthy Korean male volunteers. Serial blood samples were collected after lobeglitazone (0.5 mg/day) and metformin (1000 mg/day) were administered alone or concomitantly for 5 days in each period, and drug concentrations were determined by liquid chromatography-tandem mass spectrometry. CLINICAL TRAIL REGISTRATION NUMBER: NCT01005160. RESULTS: The steady-state maximum plasma concentrations (C(max, ss); mean ± standard deviation) of lobeglitazone and metformin alone were 29.38 ± 5.25 ng/mL and 1661.84 ± 471.88 ng/mL, respectively; the C(max, ss) during co-administration were 27.15 ± 5.75 ng/mL and 1779.92 ± 405.20 ng/mL, respectively. The steady-state areas under the concentration-time curves during the dose interval (AUC(τ, ss); mean ± standard deviation) of sole administration of lobeglitazone and metformin were 277.53 ± 65.25 ng*h/mL and 9650.27 ± 2089.81 ng*h/mL, respectively. When lobeglitazone and metformin were administered concomitantly, the AUC(τ, ss) were 257.29 ± 60.61 ng*h/mL and 10600.58 ± 1960.40 ng*h/mL, respectively. The geometric mean ratios (90% confidence interval) of co-medication to lobeglitazone alone were 0.92 (0.87-0.97; C(max, ss)) and 0.93 (0.87-0.99; AUC(τ, ss)), and those for co-medication to metformin monotherapy were 1.09 (0.99-1.19; C(max, ss)) and 1.11 (1.04-1.19; AUC(τ, ss)). Both monotherapies and combination therapy were well tolerated; 52 self-resolving, non-serious adverse events were reported from 17 subjects. CONCLUSION: Lobeglitazone did not significantly affect the pharmacokinetics of metformin or vice versa when both drugs were co-administered. Lobeglitazone can be co-administered with metformin without dose adjustment for either agent. Therefore further patient studies are needed to corroborate these results.

Assessment of the drug-drug interactions between fimasartan and hydrochlorothiazide in healthy volunteers.

AIM: Fimasartan is a selective angiotensin II receptor blocker. Hydrochlorothiazide (HCTZ), which is used to treat hypertension and edematous conditions, is coadministered with many antihypertensive agents. METHODS: An open-label, randomized, multiple-dosing, 2-arm, 1-sequence, 2-period study was conducted to assess the effects of fimasartan (240 mg) on HCTZ (25 mg) or vice versa in 18 and 14 healthy male volunteers, respectively. During each drug administration period, drugs were given once daily for 7 days, with a 7-day washout period between the 2 administration periods. RESULTS: The respective geometric mean ratios of fimasartan for AUC τ,ss and C max,ss with HCTZ were 1.30 [90% confidence interval (CI), 0.84-2.01] and 1.17 (90% CI, 0.93-1.47) compared with fimasartan alone. The respective geometric mean ratios of HCTZ for AUC τ,ss and C max,ss with fimasartan were 0.94 (90% CI, 0.84-1.04) and 0.88 (90% CI, 0.80-0.97) compared with HCTZ alone. Plasma renin activity indicated no significant differences between fimasartan monotherapy and coadministered treatment. CONCLUSIONS: Fimasartan administered alone or in combination with HCTZ was well tolerated at the described dosages. Coadministration of fimasartan increased the urinary excretion of HCTZ and urine volume, but these observations are unlikely to have any clinical relevance.

Assessment of the analgesic effect of remifentanil using three pain models in healthy Korean volunteers: a randomized, controlled study.

Quantitative pain assessment in human beings is useful for developing new analgesics. This study assessed the analgesic effect of remifentanil in 20 healthy Korean men using three pain models to investigate whether these models can be used in Asians. The study was a double-blind, placebo-controlled, two-way cross-over study. The subjects received intravenous remifentanil with doses starting at 0.01 µg/kg/min. and increasing by 0.01 µg/kg/min. up to 0.10 µg/kg/min. in one session; they received placebo in another session. Heat pain thresholds were assessed at dose levels of 0.02, 0.05, 0.08 and 0.10 µg/kg/min. Pressure pain threshold and tolerance and mechanical pain threshold were assessed at 0.08 µg/kg/min. Remifentanil dose-dependently increased the heat pain threshold. The differences (95% confidence interval) between remifentanil and placebo were 1.54°C (0.78, 2.31), 1.82°C (1.11, 2.54) and 2.47°C (1.55, 3.38) at 0.05, 0.08 and 0.10 µg/kg/min. remifentanil, respectively. Remifentanil conferred a significantly higher pressure pain threshold and tolerance than placebo (p = 0.0001). There was a trend of increasing mechanical pain threshold with remifentanil, although it was not statistically significant. The results suggest that heat pain and pressure pain models are valid in East Asians for assessing analgesic effects.

Comparative pharmacokinetics and tolerability of branded etanercept (25 mg) and its biosimilar (25 mg): a randomized, open-label, single-dose, two-sequence, crossover study in healthy Korean male volunteers.

BACKGROUND: The biosimilar is a recombinant dimeric tumor necrosis factor receptor (TNFR) under development for the treatment of rheumatoid arthritis. OBJECTIVE: The aim of this study was to compare the pharmacokinetics and/or tolerability of branded etanercept and its biosimilar in healthy Korean men before investigating the clinical efficacy of the biosimilar in subjects. METHODS: Etanercept (reference, 25 mg) or its biosimilar (test, 25 mg) was subcutaneously injected to the periumbilical area of healthy volunteers in a randomized, open-label, single-dose, active-controlled, two-sequence, crossover study. Plasma concentrations of TNFR in serial blood samples for 480 hours after dosing were measured by ELISA. The primary outcome, pharmacokinetic characteristics, was assessed via geometric mean ratios (GMRs) of the log-transformed pharmacokinetic parameters. The second outcome, tolerability, was evaluated using physical examinations, electrocardiograms, clinical laboratory tests, vital sign measurements, and adverse events (AEs) by unmasked investigators. RESULTS: Twenty-three men of mean age (%CV) 25.8 years (17.1%) and weight 70.5 kg (12.8%) were administered study medication. Four subjects dropped out after the first period; their data were included in the analysis. Both test and reference drugs were absorbed with a median T(max) of 72 (range, 36-144) hours and eliminated with mean (%CV) t(½) of 92.7 (20.9%) and 87.4 (16.6%) hours, respectively. The GMRs (90% CIs) of the test to reference drug for C(max), AUC(0-t), and AUC(0-∞) were 0.99 (0.83-1.17), 0.95 (0.79-1.13), and 0.95 (0.80-1.13), respectively. Eleven of 21 (52.4%) and 8 of 21 (38.1%) subjects administered the test and reference drugs reported 22 and 21 AEs, respectively. Common AEs were headache (14.3%), throat irritation (8.5%), and epistaxis (9.5%). Three serious AEs related to a traffic accident (back, neck, and musculoskeletal pain) were reported in a test drug-treated subject. CONCLUSIONS: In this select group of Korean healthy male volunteers, the reference drug and the test biosimilar met the standard criteria for assuming bioequivalence as defined by Korean regulatory authorities. Because the reference drug is a biological product, further trials for assessment of its efficacy are still required by Korean authorities. World Health Organization International Clinical Trials Registry Platform identifier: KCT0000118.

Population pharmacokinetic analysis and dosing regimen optimization of aprotinin in neonates and young infants undergoing cardiopulmonary bypass.

The objective of this study was to determine an optimal dosing regimen for maintaining the therapeutic target range of aprotinin in neonates and young infants during cardiopulmonary bypass (CPB). A total of 27 patients scheduled for open heart surgery were enrolled. Aprotinin was administered a 25 000 KIU (kallikrein inhibition unit)/kg bolus before operation, a 35 000 KIU/kg for CPB circuit priming, and a 12 500 KIU/kg/hour continuous infusion intra- and immediate postoperative period. Blood samples were obtained at 12 time points per patient. Population pharmacokinetic modeling and Monte-Carlo simulations were used to optimize the aprotinin dosing regimen. No mortality or aprotinin-related complication was encountered. A CPB adjusted 2-compartment model best fit the data. Clearance was 687 mL/hour during CPB and 350 mL/hour pre- and post-CPB, and corresponding volumes of distribution were 1577 mL and 1352 mL, respectively. The simulations conducted showed that more than twice the dose administered in this study is required to maintain the target concentration of aprotinin. The pharmacokinetics of aprotinin appears to be affected more sensitively by CPB in neonates and young infants than in adults. Therefore, dosage adjustment considering these pharmacokinetic differences and the influence of CPB is needed in neonates and young infants.