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J Schüller

Publications and source records attributed to J Schüller.

94 records · Page 6Linked to original sources
PubMedDate not supplied

Red blood cell partitioning of the [6S]- and the [6R]-isomer of N5-formyltetrahydrofolic acid.

The in vitro interaction of the [6S]- and [6R]-stereoisomers of CHO-THFA with human RBCs was investigated in the (therapeutically comparable) concentration range from 1.0 to 12.5 micrograms/ml. Both compounds are bound to RBCs with a kRBC ranging from 0.13 to 0.75 for [6S]-CHO-THFA and from 0.06 to 0.33 for [6R]-CHO-THFA, respectively. The interaction of the [6S]-form with RBCs is about two times higher than of the [6R]-form. Incubation of CHO-THFA with RBCs over 24 h showed an accelerated disappearance from the test solution for [6R]-CHO-THFA with a mean t1/2 of 49.9 h in compare to t1/2 = 58.2 h for the [6S]-enantiomer. The results indicate that RBCs may play a major role for the pharmacokinetics and metabolism of CHO-THFA and may act as an intravasal depot especially for [6S]-CHO-THFA.

Binding Sites↗
PubMedDate not supplied

In vitro and in vivo binding of epirubicin to red blood cells and human plasma proteins.

In this study, the in vitro interaction of epirubicin (EPR), a cytostatic antibiotic, with plasma proteins (PP), namely alpha-HSA, gamma-HSG, alpha+beta-HSG and with isolated human red blood cells (RBCs) was investigated and further correlated with the in vivo pharmacokinetics and binding of EPR and two of its metabolites, 13-dihydroepirubicin and 7-deoxydoxorubicinone to RBCs. The in vitro encapsulation rate in isolated erythrocytes amounts to 52.9 +/- 2.8% and remains constant within the range of studied concentrations (2.5-20 micrograms/ml). EPR was found to bind differently to the various PP in vitro. Binding to alpha-HSA amounted up to 51.0 +/- 7.10%, to alpha+beta-HSG 79.45 +/- 2.7%, to gamma-HSG 57.1 +/- 2.8%. The in vivo-binding rate of EPR, dihydroepirubicin and deoxydoxorubicinone to RBCs after 5 min of injection was 32 +/- 6.96%, 11.6 +/- 3.1% and 10.05 +/- 3.5% respectively, their availability in serum was 42.6 +/- 11.8%, 2.4 +/- 0.4% and 1.2 +/- 0.67% respectively.

Blood Proteins↗
PubMedDate not supplied

Pharmacokinetic interaction between 4'-epidoxorubicin and the multidrug resistance reverting agent quinine.

The serum and red blood cell (RBCs) disposition of epirubicin (EPR) after intravenous bolus injection without and with coadministered quinine ( QUI) was investigated in patients undergoing a cyclic chemotherapy with EPR. QUI possesses a statistical significant influence on the EPR serum concentrations and, as a consequence, on the pharmacokinetic parameters for the initial distribution phase of EPR. Within the first 15 min after administration, EPR was distributed from the central compartment distinctly faster in compare to the control, when QUI was preadministered (t(1/2) = 6 min for the control group and t(1/2) = 3 min with QUI; -46%, p < 0.05). Yet, in the beta-phase when drug-elimination predominates, no statistical significant influence of QUI in regard to EPR serum and RBC concentrations could be observed. Half-life of elimination was 0.5 h for the control group and 8.6 h for the QUI group (-10%). The mean initial serum concentration (co) was reduced significantly by QUI from 7359 +/- 506 ng/ml to 4351 +/- 1682 ng/ml (-42%, p < 0.005). Furthermore, QUI caused a reduction of the serum bioavailability of EPR (expressed as AUC(o-24)-values) from 3404 +/- 1008 ng/ml x h to 2359 +/- 1073 ng/ml x h (-31%, p < 0.05). Vd and Vdbeta were increased at about 90% and the mean total body clearance was accelerated from 45.3 to 1487 ml/min, but due to the large standard deviations the calculated difference for these parameters was not statistically significant. In the observed time interval of 24 h, the red blood cell coefficient of distribution k(rbc) of EPR was lower if QUI was coadministered (k(rbc) = 1.25 +/- 0.12 for the control group k(rbc) = 1.15 +/- 0.13 under QUI; p < 0.04). The results point out that QUI induces an accelerated distribution of EPR from the blood into the tissue and that QUI additionally may have influence on the red-blood cell partitioning of EPR.

Antibiotics, Antineoplastic↗