[Improvement of the absorption of the active substance 2'-hydroxy-5'-methyllaurophenoxamine (FLM 5011) with prodrugs and preparations]

Methods to improve the absorption of problem drugs are presented for the strongly lipophilic, poorly water-soluble, potential lipoxygenase inhibitor FLM 5011 (1). The water-solubility is improved by using prodrugs or by solubilizing. The characterization of solubility has been characterized with an suitable in vitro model system. The bioavailability of 1 in rabbits after oral administration is markedly increased using 1-prodrugs studied. The good correlation between the ABC measured in vitro and the AUC estimated in vivo demonstrates that it is possible to predict the bioavailability at the rabbit of highly lipophilic drugs such as 1 using the flow through model system.

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.

[Triperidin (Norakin): separation, stability and structure of stereoisomers]

The antiparkinsonian triperiden (1; as hydrochloride Norakin) is a mixture of the stereoisomers 1a and 1b. Their identification and separation by chromatographic methods or fractional crystallisation of the tartrates is described. By means of IR- und 13C-NMR spectral data structures of 1a and 1b are proposed. Under proton catalysis 1b racemizes to 1a. In acidic solution (heating in 0.1 mol.1-1 HCl or storage in gastric juice at 37 degrees C) hydrolysis of 1 takes place and four isomeric products were observed (Z1-Z4), which arise by cleavage of the cyclopropyl moiety. The main product Z2 was identified as the 2"-hydroxy derivative. The solid drug is stable at least for 5 years.