Dose individualization of intravenous busulfan in pediatric patients undergoing bone marrow transplantation: impact and in vitro evaluation of infusion lag-time

OBJECTIVES

To apply therapeutic drug monitoring and dose-individualization of intravenous Busulfan to paediatric patients and evaluate the impact of syringe-pump induced Busulfan infusion lag-time after in vitro estimation.

METHODS

76 children and adolescents were administered 2 h intravenous Busulfan infusion every 6 h (16 doses). Busulfan plasma levels, withdrawn by an optimized sampling scheme and measured by a validated HPLC-PDA method, were used to estimate basic PK parameters, AUC, Cmax, kel, t1/2, applying Non-Compartmental Analysis. In vivo infusion lag-time was simulated in vitro and used to evaluate its impact on AUC estimation.

KEY FINDINGS

Mean (%CV) Busulfan AUC, Cmax, clearance and t1/2 for pediatric population were found 962.3 μm × min (33.1), 0.95 mg/L (41.4), 0.27 L/h/kg (33.3), 2.2 h (27.8), respectively. TDM applied to 76 children revealed 6 (7.9%) being above and 25 (32.9%) below therapeutic-range (AUC: 900-1350 μm × min). After dose correction, all patients were measured below toxic levels (AUC < 1500 μm × min), no patient below 900 μm × min. Incorporation of infusion lag-time revealed lower AUCs with 17.1% more patients and 23.1% more younger patients, with body weight <16 kg, being below the therapeutic-range.

CONCLUSIONS

TDM, applied successfully to 76 children, confirmed the need for Busulfan dose-individualization in paediatric patients. Infusion lag-time was proved clinically significant for younger, low body-weight patients and those close to the lower therapeutic-range limit.

Crocus sativus L. aqueous extract reduces atherogenesis, increases atherosclerotic plaque stability and improves glucose control in diabetic atherosclerotic animals

BACKGROUND AND AIMS

We aimed to evaluate a possible atheroprotective effect of saffron aqueous extract (SFE), and its potential anti-inflammatory mechanisms, in apoE knockout (ApoE^-/-) mice.

METHODS

Fifty male, ApoE^-/- mice, fed a high-fat diet (HFD) for 12 weeks, were randomized into 5 groups: (1) baseline group, euthanatized, without intervention, (2) three saffron groups, receiving HFD and 30,60,90 mg/kg/day of SFE, respectively, for four weeks, per os through gavage, after reconstitution in water for injection (WFI), (3) control group (COG), receiving daily HFD and the same volume of WFI (four weeks). After blood sampling and euthanasia, aortic roots were excised and analyzed for gene expression and/or percentage of aortic stenosis, relative content of macrophages, smooth muscle cells (SMCs), connective tissue, tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinases-2,-3,-9 (MMP-2,-3,-9) and their inhibitor (TIMP-2) and IL-6. SFE doses were determined by a pilot serum pharmacokinetic study in C57BL/6J wild-type mice.

RESULTS

SFE did not affect body weight and total cholesterol levels (p > 0.05), while high SFE dose significantly ameliorated glucose and triglycerides profiles compared to other groups (p < 0.05). SFE considerably decreased aortic stenosis in a dose-dependent manner (p < 0.05). Furthermore, increasing SFE doses proportionally reduced macrophages content and increased within plaques content of collagen, elastin, and SMCs, promoting more stable plaque phenotype compared to COG (p < 0.05). Those effects seemed to be associated with a considerable reduction (>30%) in IL-6, TNF-α, MCP-1, MMP-2,-3,-9 (p < 0.05) and MMP-2/TIMP-2 ratio.

CONCLUSIONS

SFE exerted dose-dependent anti-atherosclerotic and plaque-stabilizing effects in Apo-E^-/- mice, probably mediated by a favorable modification of inflammatory mechanisms, which requires further investigation.

Saffron (Crocus sativus) intake provides nutritional preconditioning against myocardial ischemia-reperfusion injury in Wild Type and ApoE(-/-) mice: Involvement of Nrf2 activation

BACKGROUND AND AIMS

Saffron is an antioxidant herbal derivative; however, its efficacy as a nutritional cardioprotective agent has not been fully elucidated. We investigated the cardioprotective properties of a standardized saffron aqueous extract (SFE) against ischemia/reperfusion (I/R) injury in Wild-Type (WT) and ApoE^(-/-) mice and the underlying molecular mechanisms.

METHODS AND RESULTS

WT and ApoE^(-/-) mice were subjected to 30 min I and 2 h R, with the following per os interventions for 4 weeks: 1) WT Control Group, receiving Water for Injection (WFI); 2) WT Crocus Group, receiving SFE at a dose of 60 mg/kg/day; 3) WT Crocus + Wort group, receiving SFE as described above and wortmannin at a dose of 60 μg/kg bolus 15 min before R; 4) ApoE^(-/-) Control Group, receiving WFI; 5) ApoE^(-/-) Crocus Group, receiving SFE at a dose of 60 mg/kg/day and 6) ApoE^(-/-) Crocus + Wort: receiving SFE as described above and wortmannin at a dose of 60 μg/kg bolus, 15 min before R. Ischemic area/area at risk (I/R%) ratio was measured. Blood samples and ischemic myocardial tissue were collected at the 10th min of reperfusion for assessment of troponin I, malondialdehyde (MDA), nitrotyrosine (NT), p-eNOS, eNOS, p-Akt, Akt, p-p42/p-p44, p-GSK3β, GSK3β, IL-6, Nrf2, HO-1 and MnSOD expression. The effect of SFE on Nrf2 expression was also evaluated in vitro. SFE reduced infarct size in WT (16.15 ± 3.7% vs 41.57 ± 2.48%, ***p < 0.001) and in ApoE^(-/-) mice (16.14 ± 1.47% vs 45.57 ± 1.73%, ***p < 0.001). The administration of wortmannin resulted in partial inhibition of the infarct size limitation efficacy of SFE (in both WT and Apo-E^(-/-) mice). Mice receiving SFE showed increased levels of eNOS, p-Akt, p-ERK1/2, p-44/p-42 and p-GSK3β-Ser9 and reduced expression of IL-6 and iNOS; furthermore, SFE reduced the levels of MDA and NT. SFE induced Nrf2 expression and its downstream targets, HO-1 and MnSOD in the myocardium of the treated animals, and induced Nrf2 expression in vitro in a dose-dependent manner.

CONCLUSIONS

SFE limits myocardial infarction in Wild-Type and ApoE^(-/-) mice in a multifaceted manner including activation of Akt/eNOS/ERK1/2/GSK3-β and through Nrf2 pathway, bestowing antioxidant protection against I/R.

Pharmacokinetics of doripenem in CSF of patients with non-inflamed meninges

OBJECTIVES

To investigate intact blood-brain barrier (BBB) penetration by doripenem and characterize doripenem pharmacokinetics in CSF using a pharmacokinetic model.

PATIENTS AND METHODS

Thirty-eight neurological patients with no active neurological disease or CNS infection received a single 500 mg doripenem dose before pump implantation surgery, or lumbar puncture, for intrathecal baclofen administration. In most cases single CSF and blood samples were collected per patient and analysed for doripenem with HPLC. A two-stage pharmacokinetic analysis was performed to estimate: (i) empirical Bayesian estimates (EBEs) of individual doripenem plasma pharmacokinetic parameters, using plasma doripenem concentrations and literature population priors for a two-compartment model; and (ii) doripenem CSF pharmacokinetic parameters using simulated plasma concentrations from stage (i) as a forcing function. The mean values of the structural model parameters, k(CSF) (distribution rate constant) and PC (CSF/plasma partition coefficient), and the residual variability were estimated.

RESULTS

The mean estimates of the parameters were k(CSF)= 0.105 h(-1) and PC= 0.053, corresponding to mean steady-state doripenem CSF concentrations of 0.20 mg/L and 0.40 mg/L for regimens of 3 × 500 mg daily and 3 × 1000 mg daily, respectively, and a mean equilibrium half-life of 6.6 h. The model was validated internally using a visual predictive check (VPC) and bootstrap. Simulating two dosing scenarios gave doripenem levels in the CSF above or close to the literature MIC values.

CONCLUSIONS

The present NONMEM software analysis shows that doripenem crosses intact BBB significantly and suggests that the drug should be further evaluated as a candidate to treat certain CNS infections, since drug penetration through BBB is enhanced by meningeal inflammation.

In-vitro study on the competitive binding of diflunisal and uraemic toxins to serum albumin and human plasma using a potentiometric ion-probe technique

The competitive binding of diflunisal and three well-known uraemic toxins (3-indoxyl sulfate, indole-3-acetic acid and hippuric acid) to bovine serum albumin (BSA), human serum albumin (HSA) and human plasma was studied by direct potentiometry. The method used the potentiometric drug ion-probe technique with a home-made ion sensor (electrode) selective to the drug anion. The site-oriented Scatchard model was used to describe the binding of diflunisal to BSA, HSA and human plasma, while the general competitive binding model was used to calculate the binding parameters of the three uraemic toxins to BSA. Diflunisal binding parameters, number of binding sites, ni and association constants for each class of binding site, Ki, were calculated in the absence and presence of uraemic toxins. Although diflunisal exhibits high binding affinity for site I of HSA and the three uraemic toxins bind primarily to site II, strong interaction was observed between the drug and the three toxins, which were found to affect the binding of diflunisal on its primary class of binding sites on both BSA and HSA molecules and on human plasma. These results are strong evidence that the decreased binding of diflunisal that occurs in uraemic plasma may not be solely attributed to the lower albumin concentration observed in many patients with renal failure. The uraemic toxins that accumulate in uraemic plasma may displace the drug from its specific binding sites on plasma proteins, resulting in increased free drug plasma concentration in uraemic patients.

The power law can describe the 'entire' drug release curve from HPMC-based matrix tablets: a hypothesis

The purposes of this study were to (i) re-examine the relevance of Higuchi equation and the power law using both simulated and experimental release data in conjunction with the linearized, in terms of t(1/2), percent of drug release plots, (ii) demonstrate that the power law describes the entire drug release profile of several experimental data, and (iii) point out a physically based hypothesis for the successful use of power law in describing the entire drug release profile. Simulated data generated from the equation of power law were further analyzed using linear regression analysis in accord with the Higuchi equation. The analysis revealed that data generated from the equation of power law can be misinterpreted as obeying the Higuchi equation. The use of power law in describing the entire drug release curve from HPMC-based matrix tablets is validated by direct fit of power law equation to published data of other authors. A hypothesis based on the nonclassical diffusion of the solutes in the HPMC matrices is used to interpret the successful use of the power law in describing the entire release profile.

Non-linear regression analysis with errors in both variables: estimation of co-operative binding parameters

Four different parameter estimation criteria, the geometric mean functional relationship (GMFR), the maximum likelihood (ML), the perpendicular least-squares (PLS) and the non-linear weighted least squares (WLS), were used to fit a model to the observed data when both regression variables were subject to error. Performances of these criteria were evaluated by fitting the co-operative drug-protein binding Hill model on simulated data containing errors in both variables. Six types of data were simulated with known variances. Comparison of the criteria was done by evaluating the bias, the relative standard deviation (S.D.) and the root-mean-squared error (RMSE), between estimated and true parameter values. Results show that (1) for data with correlated errors, all criteria perform poorly; in particular, the GMFR and ML criteria. For data with uncorrelated errors, all criteria perform equally well with regard to the RMSE. (2) Use of GMFR and ML lead to lower values for S.D. but higher biases compared with WLS and PLS. (3) WLS performs less well when equal dispersion is applied to the two observed variables.

A displacement approach for competitive drug-protein binding studies using the potentiometric 1-anilino-8-naphthalene-sulfonate probe technique

A displacement approach for competitive binding studies was developed. The method utilizes the potentiometric 1-anilino-8-naphthalene-sulfonate (ANS) probe technique and is applied to the binding study of several non-steroidal anti-inflammatory drugs (NSADs) to bovine serum albumin (BSA). A home-made ANS electrode was used to monitor the displaced free ANS probe from its binding sites on the protein molecule by the stepwise addition of the studied drug. To assess and compare quantitatively the displacing ability of the various drugs, the 'ANS Displacement Index' is used. The possible interference of 19 ionizable drugs (NSADs, sulfonamides, etc.) to the ANS selective electrode at pH 7.4 was studied and their potentiometric selectivity coefficients (K(pot)(ANS,D)) were determined. Correction procedures for the determination of the free ANS concentration are proposed in the case of interfering ionic drugs. A blank binding experiment in conjunction with the incorporation of K(pot)(ANS,D) values in the 'general competitive site oriented model' allows one to derive estimates for the drug binding parameters, i.e. the number of binding sites and association constants.

Modeling of supersaturated dissolution data

A recursion equation which relies on the population growth model of dissolution is used for the analysis of supersaturated dissolution data. The concentration-time data of dissolution experiments are initially transformed to fractions of dose dissolved-generations by adopting an appropriate time interval as the time step of the recursion equation. A computer program is used to derive estimates for the maximum fraction of dose dissolved and the fraction of dose remaining in solution at steady state. Good fittings were observed when this equation was applied to phenytoin and nifedipine supersaturated dissolution data obtained from literature.

Use of 1-anilino-8-napthalenesulphonate as an ion probe for the potentiometric study of the binding of sulphonamides to bovine serum albumin and plasma

The binding of sulphafurazole, sulphamethizole and sulphamethoxazole to bovine serum albumin (BSA) and human plasma has been studied in-vitro by potentiometry using an electrode selective for the ion probe 1-anilino-8-napthalenesulphonate (ANS). The method requires two separate potentiometric titrations of the binder solution with ANS in the absence and in the presence of sulphonamides. ANS displaced sulphonamides from the first-class of binding sites of both binders. The binding constants for sulphonamide-BSA interactions were higher than those for sulphonamide-human plasma. The expansion of the least linear limit of the response curve of the electrode down to 10(-7) M in the presence of BSA was also demonstrated. The reverse reaction, i.e. the displacement of the probe from the binding sites induced by the sulphonamides, was also explored. The proposed method is suitable for studying competitive binding interactions in biological specimens.