Biomedical subjects

K M Feld

Publications and source records attributed to K M Feld.

3 recordsLinked to original sources

PubMed1982

Influence of benzalkonium chloride on the dissolution rate behavior of several solid-phase preparations of cholesterol in bile acid solutions.

Cholesterol dissolution rate accelerators, such as benzalkonium chloride, function by reducing the interfacial barrier that exists between the negatively-charged bile acid micelle and the negatively-charged cholesterol surface. It has been proposed that this reaction is accomplished by the binding of the positively-charged accelerator to the negatively-charged micelle. An earlier report showed that different solid preparations of cholesterol give different dissolution rates under the same conditions and these differences can be primarily accounted for by variations in the interfacial transport constant (P). By using the rotating disk dissolution apparatus and the Levich theory it has been possible to study the dissolution behavior of different cholesterol solid phases as a function of the benzalkonium chloride concentration. It was shown that the ratios of P values for the different phases are relatively constant over the range of the accelerator concentrations. This suggests that the accelerators act primarily on the micelle to enhance dissolution rate.

Benzalkonium Compounds↗

PubMed1981

Dissolution rate behavior of solid cholesterol preparations in bile acid solutions.

Recent work in these laboratories showed that different preparations of cholesterol monohydrate and anhydrous cholesterol had different dissolution rates under the same conditions. A method was developed by which both the thermodynamic contribution (Cs) and the interfacial kinetic contribution (P) to dissolution could be determined from experimental data. The rotating-disk dissolution method was used with the Levich theory to assess the data. Dissolution rates were determined in solutions partially saturated with cholesterol. Dynamic solubilities were determined by plotting dissolution rates (J/A) versus bulk concentration (Cb) and extrapolating to zero J/A. By using a best-fit analysis, it was possible to determine solubility as well as the interfacial transport constant independently. When this method was used to study differences in dissolution behavior of different solid preparations of cholesterol the differences could be accounted for primarily by variations in the interfacial transport constant rather than by solubility variations.

Benzoates↗

PubMed1981

Variability in dissolution rates of cholesterol pellets in bile acid solutions.

Large variations in dissolution rate behavior of cholesterol monohydrate pellets may result from small changes in experimental procedures. For example, when cholesterol monohydrate pellets were stored overnight prior to a dissolution run, the initial dissolution rates varied by more than a factor of 2. It is well known that cholesterol monohydrate is converted to anhydrous cholesterol; cholesterol may be unstable toward light. heat, and other radiation in the presence of air, leading to its decomposition. To determine the cause of the variable dissolution rates, experiments were conducted with pellets "aged" under various conditions. The data shown that the probable cause of the variations is the pellet surface conversion of the monohydrate to anhydrous cholesterol, which may take place during pellet storage. The combined effects of temperature and humidity seem to be important. A uniform experimental procedure is needed if investigators hope to reproduce results within their own laboratories as well as reproduce the findings of others.

Bile Acids and Salts↗