Optimization of placebos for double-blind clinical trials. Experience with a phytopharmaceutical.

The maintenance of double-blind conditions in placebo-controlled trials depends on the quality of the placebo preparation. The placebo should match the active substance-containing preparation as closely as possible, but it must not contain any substances that might themselves be pharmacologically active. Active substances characterized by a particular colour, taste, smell or other easily perceptible properties constitute a challenge to researchers.

Transport and metabolic pathway of thymocartin (TP4) in excised bovine nasal mucosa.

Thymocartin (TP4, Arg-Lys-Asp-Val) is the 32-35 fragment of the naturally occurring thymic factor (thymopoietin). Here studies on the nasal transport and metabolism of TP4 were performed. Freshly excised bovine nasal mucosa was taken as a model membrane.

[Pharmaokinetics of beta-escin after administration of various Aesculus extract containing formulations].

With a specific radioimmunoassay the pharmacokinetics and relative bioavailability of escin was measured after administration of different formulations containing Aesculus-extract. Of special interest was the relative bioavailability of escin after administration of a newly developed film-coated tablet with sustained release in comparison to a reference formulation. In a cross-over steady-state study in 24 volunteers bioequivalence of test and reference preparation could be demonstrated.

Enzymatic cleavage of thymopoietin oligopeptides by pancreatic and intestinal brush-border enzymes.

The intestinal enzymatic degradation of the immunomodulating peptides thymotrinan (TP3), thymocartin (TP4), and thymopentin (TP5), three oligopeptides derived from the naturally occurring thymus hormone thymopoietin, was investigated to evaluate their potential for peroral drug delivery. In the presence of brush-border membrane vesicles, crude pancreas extract and everted rings from duodenum, jejunum, ileum, and colon, all peptides were shown to be degraded both by pancreatic enzymes and brush-border aminopeptidases. Degradation clearances (Cldeg) of TP3, TP4, and TP5 were calculated for a quantitative comparison of peptide stability.

[The solubility kinetics of enteric-resistant tablets using riboflavin test tablets. 6. Pharmaceutic-technologic and analytic studies on gastric juice-resistant dosage forms].

To examine the dissolution kinetics of enteric coatings in vivo a test system with riboflavine was developed. This system allows to realize the beginning of disintegration in the small gut because riboflavine is excreted in urine already within 1 h after ingestion, and to locate the area of dissolution of the tablet in vivo, because riboflavine absorption is reduced in the great gut and colon. Thus the test system allows to examine and improve coating compositions in vivo and to demonstrate changes of drug dissolution in vivo conditioned by storage of enteric coated pharmaceuticals.

[Resistance and disintegration behavior of gastric juice-resistant drug products. 3. Pharmaceutical-technological and analytical studies of gastric juice-resistant commercial preparations].

Enteric coated commercial dosage forms often do not correspond with acid resistance and disintegration requirements of the Ph. Eur. About 15-20% of 181 tested samples disintegrate during acid resistance test or do not disintegrate in buffer solution pH = 6.