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W Fürst

Publications and source records attributed to W Fürst.

At least 73 records · Page 4Linked to original sources
PubMed1984

[Pharmaceutic and biopharmaceutic evaluation of acetylaminonitropropoxybenzene (Falimint). A Biotransformation of the active agent].

2-Acetamino-4-nitropropoxybenzene is metabolized almost completely. Till now in urine of man seven components have been detected. The main way of metabolism is the oxidation of the propoxy group to a carboxyl group. Also the deacetylated compound of this acid has been found to a certain extent. A further metabolite is supposed to be oxidized in the side chain in another way. In a higher extent dealkylation to 2-acetamino-4-nitrophenol takes place which is eliminated probably in conjugation with glucuronic acid. Free 2-acetamino-4-nitrophenol and 2-amino-4-nitrophenol respectively are only detectable in traces. Deacetylation of 2-amino-4-nitropropoxybenzene takes place only in a very small extent. Till now metabolites with reduced nitro group haven't been found.

Acetanilides↗
PubMed1983

[Pharmaceutical and biopharmaceutical evaluation of acetylaminonitropropoxybenzolum (Falimint). 3: Polarographic analysis and determination of active agents].

According to its aromatic nitro group acetylaminonitropropoxybenzene (Falimint) can be determined polarographically. The typical behavior of the nitro group becomes evident by the elektrochemical reduction. The investigation has shown two phases of reduction with pH-depended half-wave-potential shifts, so that a two-step mechanism is conceivable. Using direct current polarography the substance is determined in a concentration range from 1 to 100 micrograms/ml. Low elektroaktive background signals within the potential range the four-electron reduction step are the basis for the determination of the active agent in saliva, urine and blood plasma without any extracting procedures. It is possible to identify the substance by means of oscilloand square-wave-polarography. The resulting polarogrammes are typically for the p-nitrophenyl structure. Further a new quantitativ polarographic method, named sample-DC-polarography on the stationary mercury electrode is discussed for the determination of Falimint in blood plasma without any steps of separation and cleaning in the concentration range of 0,1-3,0 micrograms/ml.

Acetanilides↗
PubMed1982

[Feasibility of the in vitro evaluation of bioavailability. 3: Method of operation of a newly-developed absorption model and results obtained with it].

In connection with the function of a newly constructed absorption model the problem of interpretation of values obtained by models in regard of bioavailability is discussed. Wrong interpretations can be obtained if nonanalogous values are compared. An interpretation is proposed to calculate a value which is analogous to the relative bioavailability (calculated bioavailability). The efficiency of the absorption model and of the interpretation method is demonstrated by three examples of preparations of phenytoin, digoxin and chloramphenicol. We compared these results with the bioavailability of these preparations and we found a good correspondence.

Absorption↗
PubMed1981

[Contributions to the liberation of drugs from suspension ointments. Part 12: On the suitability of some synthetic hydrophobic membranes for liberation studies (author's transl)].

The release rates determined for various salicylic acid and prednisolone ointments on using different membranes in the in vitro model according to Horsch and Kögel [20] were compared with one another in regard to possible membrane-specific differences in liberation kinetics and in validity. The results obtained with salicylic acid ointments by the lipophil collodion-lipid membranes and silicone membranes developed by Fürst and coworkers [14] were comparable with those yielded by the hydrophilic cellulose membrane: release rates of comparable order of magnitude; same order of ranking of the bases used; plots of the cumulated percentages of release against the root of time providing no evidence of differences in kinetics. In contrast, the permeability of a further hydrophobic membranes (silicone, polyester) was markedly lower. As to the prednisolone ointments, the collodion-lipid membranes yielded comparable release rates and orders of ranking when the drug was incorporated into hydrophilic bases, whereas the silicone membrane was considerably inferior in permeability.

Kinetics↗
PubMed1980

[Drug permeation through synthetic lipid membranes. Part 10: The effects of diffusion layers on the permeation process (author's transl)].

Two different processes take their courses during the permeation of substances through lipid membranes. The substance must pass across the diffusion layers on the membranes and also across the lipid barrier proper. The effects of these two processes on the permeation vary with the kind of the membrane and of the substance as well as with the diffusion layer thickness which is determined by the intensity of movement. Correlations have been established which permit to calculate diffusion layers, membrane permeation coefficients, and also diffusion coefficients in the diffusion layers. Thus have been provided the prerequisites for the comparison of results obtained on using different model parameters.

Diffusion↗
PubMed1980

[Drug permeation through synthetic lipid membranes. Part 13: The effects of tensides on the permeation of ionized drugs (author's transl)].

The permeation of substances present in the ionized form is most markedly affected by tensides containing ions of opposite sign. These tensides produce a considerable increase in permeation. The effect of micelle formation will become evident only if the transport of the free drug through the membrane is more rapid than the release of the drug from the micelles. If the concentrations of nonionic tensides are less than the critical micelle concentration, a permeation increase occurs which is presumably caused by a reduction of the surface tension of the membrane.

Buformin↗