Aldo La Manna

Description and validation of an apparatus for gel strength measurements

Abstract The increasing interest in gel-like dosage forms and in systems that undergo gelification upon contact with biological fluids (like hydrogels and hydrophilic swellable matrices) suggests the importance of gel strength measurements. For example, it has been suggested that the strength rather than the viscosity of the gel layer plays a major role in drug release from hydrophilic matrices. Nevertheless, probably due to the lack of a user-friendly and suitable apparatus, the gel strength parameter is not routinely investigated in preformulation and formulation studies of such dosage forms. In the present work, an apparatus, which had been previously designed for the characterisation of industrial polymers, was modified to make it suitable for measuring the gel strength of pharmaceutical systems and its performance was validated under differing experimental conditions. The results of gel strength measurements effected on hydroxypropylmethylcellulose solutions and on κ-carrageenan and carboxyvinyl polymer gels are reported herein.

Modification of the Dissolution Behaviour of a Water‐insoluble Drug, Naftazone, for Zero‐order Release Matrix Preparation*

Abstract— The preparation of hydrophilic matrix tablets able to release naftazone, a water‐insoluble drug, into an aqueous medium at a constant rate (zero‐order dissolution) is described. Enhancement of dissolution rate of the drug was achieved using cross‐linked carmellose sodium, β‐cyclodextrin or hydroxypropyl‐β‐cyclodextrin. Hypromellose was used as a water‐gelling polymer. Tablets could be prepared that released naftazone at a constant rate over 16 h.

Press-Coated Systems for Drug Release Control

The final aim of controlled delivery systems is to obtain drug release kinetics meeting the therapeutic need. Since a constant plasma level is adequate in many forms of therapy, a zero-order release of drug from dosage form is often desirable.

The mechanisms of disintegration of compressed particulate systems

SummaryDisintegration of compacts in the presence of a solvent is followed by measurement of the disintegration force development as a function of time. The process is described by the delamination of the compact and the rate of expansion of the detached layers using a new equation.

A New Indomethacin Lysinate Modified Release System

Considering some disadvantages shown by indomethacin osmotic devices, a new drug delivery system capable of releasing indomethacin lysinate at a constant rate has been prepared. The system mainly consists of: i a monolithic core, obtained by compression of a water insoluble polymer (CAP) mixed with the drug, an alkaline buffer agent and a polyalcohol having negative dissolution heat. ii a polymeric film insoluble in biological fluids, obtained by spray-coating the monolithic surface, acting as release controlling membrane. In order to determine the optimal delivery rate capable of maintaining indomethacin therapeutic plasma levels, dissolution tests (U.S.P. XX paddle) data were compared with in vivo (humans) plasma levels. A good correlation between in vitro and in vivo data was obtained thus demonstrating the reliability of the system. This new drug delivery system offers the following advantages: a the abrupt drug release from the core is hindered by its monolithic structure b the drug release is independent of the environmental pH value c a zero order release kinetics is maintained until 70% of drug is released d the geometric characteristics of the new drug delivery system assure a high bioavailability.