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K Fechner

Publications and source records attributed to K Fechner.

8 recordsLinked to original sources
PubMed1991

In-vivo release of a GnRH agonist from a slow-release poly(lactide-glycolide) copolymer preparation: comparison in rat, rabbit and guinea-pig.

Different batches of 50:50 poly((+-)-lactide-glycolide) copolymer (PLG) were used as biodegradable carriers for D-Phe6-gonadotropin-releasing hormone (GnRHa) in the form of injectable long-acting implants loaded with 10% GnRHa and tracer amounts of [125I]GnRHa. After their injection subcutaneously into rats, rabbits, and guinea-pigs, the release kinetics of the peptide were determined by counting the radioactivity remaining in the implants (i) after recovery from the rats after death or (ii) directly on the skin above the injection site of rabbits and guinea-pigs in-vivo. No significant differences in the release pattern of the peptide amongst the three species whether the release process was controlled by diffusion or by degradation of the polymeric matrix were found. It is concluded that the results of in-vivo release tests using laboratory animals are valid for man and that enzymes are not involved in the degradation of the polymeric matrix. The results may be of general importance for the use of long-term release PLG formulations of highly active drugs, especially peptides and proteins.

Animals↗
PubMed1985

[The influence of viscosity-increasing pharmaceutic aids on the liberation of the peptide gonadotropin releasing hormone (GnRH) in solution].

The in vitro liberation of the peptide hormone GnRH from polymer solutions was studied as a function of the viscosity of the polymer solutions. The liberation experiments were performed with a flow through dialysis apparatus. From solutions of dextran, carboxymethylcellulose, hydroxyethylcellulose, and polyvinylpyrrolidone the release of GnRH is prolonged whereas the release of GnRH from highly viscous solutions of methylcellulose and polyacrylic acid is not. The delivery process was found to be diffusion-controlled in solutions of dextran, carboxymethylcellulose, and hydroxyethylcellulose. In solutions of polyvinylpyrrolidone the diffusion-controlled prolongation of the GnRH release is additionally influenced by binding of the peptide to the polymer. The results imply that in these polymer solutions the diffusion coefficient of GnRH does not obey the classical relation D approximately 1/eta which is often used to predict liberation from viscous solutions. Thus, the measured macroscopic viscosity of the polymer solutions is not relevant for the diffusion-controlled prolongation of the in vitro release of GnRH. This phenomenon can be explained by the obstruction effect and the microviscosity of the polymer solutions. The described rapid and simple method can be applied for the quantitative determination of the prolonged release in polymer solutions based on diffusion-controlled processes and is useful in the comparison of the efficacy of various polymeric additives. Furthermore the method allows the quantitative proof of the decrease of diffusion in viscous low-molecular solutions and the proof of prolongations of delivery due to the binding of the investigated drug to the polymer.

Diffusion↗
PubMedDate not supplied

CT findings in tuboovarian abscess.

As there are little data in the radiologic literature regarding the CT appearance of and the associated findings of tuboovarian abscesses (TOA), we retrospectively reviewed CT from seven patients with nine TOAs. They were bilateral in two patients and unilateral in the remaining five. The most common appearance of these abscesses was that of a somewhat tubular septated cystic pelvic mass with uniform wall thickness and with loss of fat planes between the mass and the adjacent pelvic organs (usually the uterus when present). Ipsilateral ureterectasis was also seen in four of nine lesions. Although these findings are not specific for TOA, they should be considered when pelvic masses having the above configuration are seen on CT.

Abscess↗