Use of an in vitro absorption model system for predicting sustained release of verapamil.

It is shown that it is possible to characterize sustained release formulations in vitro using not only dissolution data but also an absorption model system. The mean dissolution time (MDT) has been shown to be a suitable parameter for evaluating sustained release formulations in vitro. t1/2 and mean residence time (MRT) have been shown to be convenient pharmacokinetic parameters for characterizing sustained release formulations. For comparing in vitro and in vivo results the quotients MDT normal/MDT retard and MRT normal/MRT retard do seem to be useful.

[Evaluation of retard drug forms with special reference to their therapeutic aspects]. / Effektivitätsbetrachtungen bei Retardarzneimitteln unter besonderer Berücksichtigung therapeutischer Aspekte.

The useful development and application of controlled-release dosage forms is an important possibility to improve the pharmacotherapy of many diseases. However, according to the present social conditions of reproduction the introduction of a new drug has to be directed not only to a high therapeutic benefit but also to an increased social efficiency i.e., to an improvement of cost-benefit-relation. In the present study, therefore, the effect of using controlled-release dosage forms on the development of social efficiency is discussed. Basing on a comprehensive estimation of the therapeutic efficiency (therapeutic advantages and disadvantages) of controlled-release dosage forms the criteria of cost and benefit being of importance for a complex evaluation of efficiency are described.

[Improvement of the solubility behavior of problem drugs. 9. In vitro absorption studies using melting solidification products of iomeglamic acid]. / Beiträge zur Verbesserung des Auflösungsverhaltens von Problemarzneistoffen. 9. Mitteilung: In-vitro-Resorptionsuntersuchungen mit lomeglamsäure-Schmelzerstarrungsprodukten.

By means of the absorption apparatus according to Fürst and Neubert the solid dispersions of the iomeglamic acid were studied with regard to their in vitro absorption properties. All products showed better half lives of transport in relation to the pure compound. This was in correlation to the solubility parameters.

[The control of drug release of heavy-soluble, weak basic drugs in matrix tablets using the example of medazepam]. / Zur Steuerung der Arzneistofffreigabe schwerlöslicher, schwach basischer Arzneistoffe aus Matrixtabletten am Beispiel von Medazepam.

According to ideas about the diffusion layer in the process of dissolving solids the release of medazepam as a model substance for heavy-soluble, weak alkaline substances is modified by incorporation of solid acids of different solubility and dissociation rate into the matrix. The determination of the solubility and a "virtual" pH-value within the matrix tablets leads to the evaluation of the liberation. A relatively continuous release of medazepam following different pH-values in the medium was obtained by microencapsulation of the citrus acid incorporated. Using the ideas of the diffusion layer to explain the conditions within the matrix it becomes possible to control and influence the drug release from the matrix tablet.

[Preparations of matrix tablets from a polyacrylate base]. / Darstellung von Matrixtabletten auf der Basis von Polyacrylaten.

The authors report with the example of the model drug, caffeine, on the preparation and investigation of matrix tablets on the basis of acrylates. The release values obtained were analysed by the equations of Higuchi and also Noyes-Whitney. It was demonstrated, that the polymer composition and the drug content in the tablets have an influence on the release of the drug.

[Improvement of the solubility of problem drugs. 1. Production of iomeglamic acid fused and solidified products]. / Beiträge zur Verbesserung des Auflösungsverhaltens von Problemarzneistoffen. 1. Mitteilung: Herstellung eines lomeglamsäure-Schmelzerstarrungsproduktes.

The insoluble X-ray diagnostic iomeglamic acid could be converted to a more soluble modification by melting and solidifying it in liquid nitrogen. The amorphous state is proved by X-ray diffraction and differential thermal analysis. During storage, recristallisation of the product appears. By means of the proved amorphous state, it seems possible to determine the amount of the amorphous state, which makes the drug more soluble from solid dispersions.