Biomedical subjects

Jochem Alsenz

Publications and source records attributed to Jochem Alsenz.

5 recordsLinked to original sources

PubMed2005

P-glycoprotein and surfactants: effect on intestinal talinolol absorption.

BACKGROUND AND OBJECTIVE: Surfactants used in pharmaceutical formulations can modulate drug absorption by multiple mechanisms including inhibition of intestinal P-glycoprotein (P-gp). Our objective was to analyze the effect of 2 surfactants with different affinity for P-gp in vitro on the intestinal absorption and bioavailability of the P-gp substrate talinolol in humans. METHODS: In vitro, the influence of surfactants on talinolol permeability was studied in Caco-2 cells. In vivo, an open-label 3-way crossover study with 9 healthy male volunteers was performed. Subjects were intubated with a 1-lumen nasogastrointestinal tube. The study solution, containing either talinolol (50 mg), talinolol and D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) (0.04%), or talinolol and Poloxamer 188 (0.8%), was administered through the tube. RESULTS: TPGS, but not Poloxamer 188, inhibited the P-gp-mediated talinolol transport in Caco-2 cells. In healthy volunteers TPGS increased the area under the plasma concentration-time curve with extrapolation to infinity (AUC 0-infinity ) of talinolol by 39% (90% confidence interval, 1.10-1.75) and the maximum plasma concentration (C max) by 100% (90% confidence interval, 1.39-2.88). Poloxamer 188 did not significantly alter the AUC 0-infinity or C max of talinolol. CONCLUSIONS: This in vivo intraduodenal perfusion study showed that low concentrations of TPGS, close to the concentrations that showed P-gp inhibition in vitro, significantly increased the bioavailability of talinolol. The study design excluded modulation of solubility by TPGS and unspecific surfactant-related effects. The latter was supported by the absence of modulation of the talinolol pharmacokinetics by Poloxamer 188, which does not modulate P-gp. Therefore we consider intestinal P-gp inhibition by TPGS as the major underlying mechanism for the increase in talinolol bioavailability.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Drug-excipient compatibility testing using a high-throughput approach and statistical design.

The aim of our research was to develop a miniaturized high throughput drug-excipient compatibility test. Experiments were planned and evaluated using statistical experimental design. Binary mixtures of a drug, acetylsalicylic acid, or fluoxetine hydrochloride, and of excipients commonly used in solid dosage forms were prepared at a ratio of approximately 1:100 in 96-well microtiter plates. Samples were exposed to different temperature (40 degrees C/ 50 degrees C) and humidity (10%/75%) for different time (1 week/4 weeks), and chemical drug degradation was analyzed using a fast gradient high pressure liquid chromatography (HPLC). Categorical statistical design was applied to identify the effects and interactions of time, temperature, humidity, and excipient on drug degradation. Acetylsalicylic acid was least stable in the presence of magnesium stearate, dibasic calcium phosphate, or sodium starch glycolate. Fluoxetine hydrochloride exhibited a marked degradation only with lactose. Factor-interaction plots revealed that the relative humidity had the strongest effect on the drug excipient blends tested. In conclusion, the developed technique enables fast drug-excipient compatibility testing and identification of interactions. Since only 0.1 mg of drug is needed per data point, fast rational preselection of the pharmaceutical additives can be performed early in solid dosage form development.

Aspirin↗

PubMed2004

The critical concentration of C1-esterase inhibitor (C1-INH) in human serum preventing auto-activation of the first component of complement (C1).

C1-esterase inhibitor (C1-INH) was depleted from normal human serum (NHS) at 4 degrees C by affinity chromatography with a monoclonal anti-C1-INH antibody (mAb 13 E1) coupled to CNBr-activated Sepharose 4B. The C1-INH-depleted serum (C1-INH-depl-HS) had normal levels of C1, C4, and CH 50 and C1-INH concentration was less than 10% of normal (15 microg/ml in C1-INH-depl-HS compared to 230 microg/ml in NHS). C1-auto-activation in C1-INH-depl-HS was followed by measuring C4-consumption in a haemolytic assay and by detection of activated C1s in a C1s-ELISA. After a lag phase of 10-20 min, C1-auto-activation in C1-INH depl-HS occurred and reached its maximum after 40 min at 37 degrees C. In contrast, neutralization of C1-INH activity in NHS by addition of monoclonal antibodies directed against its C1s-binding site, resulted in an immediate, spontaneous C1-activation without a lag-phase and reached its maximum already after 20 min (mAb 140) and 25 min (mAb 88G2). Addition of highly purified C1-INH or NHS as source of C1-INH to C1-INH-depleted serum to a final concentration of 55 microg/ml (22% of normal C1-INH concentration in HS) was sufficient to control spontaneous C1-activation.

Animals↗

PubMed2003

The role of surfactants in the reversal of active transport mediated by multidrug resistance proteins.

A variety of seven nonionic, one amphoteric and, one anionic surfactant that are applied or investigated as surfactants in drug formulation, were analyzed for their capacity to modulate carrier-mediated transport by efflux pumps. Two cell lines, murine monocytic leukemia cells overexpressing P-glycoprotein (P-gp) and Madin-Darby canine kidney cells stably overexpresssing human multidrug resistance-associated protein 2 (MRP2), were used as test systems. The modulation of P-gp and of MRP2 function was studied by the reversal of rhodamine 123 and of methylfluorescein-glutathione conjugate transport, respectively. Mechanisms that were not transporter related and could lead to misinterpretations were identified, such as probe quenching, probe encapsulation by micelles, and membrane damage. P-gp-mediated rhodamine 123 transport was inhibited by five nonionic surfactants in a concentration-dependent manner and in the order TPGS > Pluronic PE8100 > Cremophor EL > Pluronic PE6100 approximately Tween 80. In contrast, none of the surfactants showed a significant inhibition of MRP2-mediated efflux in Madin-Darby canine kidney/MRP2 cells. In conclusion, the results indicate that surfactants demonstrate a transporter-specific interaction, rather than unspecific membrane permeabilization. The present analysis offers insight in the possible mechanisms of surfactant interactions with biological membranes and could help to identify specific drug formulations.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Development of a 7-day, 96-well Caco-2 permeability assay with high-throughput direct UV compound analysis.

PURPOSE: The aim was to replace the traditional 21-day Caco-2 permeability protocol by a more high-throughput assay. METHODS: Caco-2 cells were seeded at high density in 96-well plates in novel cell culture boxes. After 7 days, drug permeability studies were performed. Samples were analyzed by a new UV detection method. RESULTS: With increased cell seeding density. functional Caco-2 monolayers with polarized efflux transporters were established after 7 days in 96-well polycarbonate filter plates in standard medium. For faster feeding and to eliminate medium replacement in each individual well, plates were completely submerged in medium in novel cell culture boxes, and only medium outside the plate was exchanged. For high-throughput sample analysis, a novel UV-transparent transport buffer was established that allowed direct quantification of permeated drug from its UV absorption. In vitro permeability studies analyzing 22 passively absorbed drugs in the new model correlated well with reported human permeability values (r2 = 0.8725). CONCLUSIONS: The new 7-day. 96-well Caco-2 permeability model tight to UV analysis offers considerable time, cost, and resource savings compared to the traditional model. It has a potential for automation and makes it possible to determine the permeability of passively diffusing compounds and to classify them according to the BCS in a truly medium- to high-throughput mode.

Algorithms↗