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Biomedical subjects

P J Waaler

Publications and source records attributed to P J Waaler.

3 recordsLinked to original sources
PubMed2001

Accelerated stability studies of morphine injections in plastic ampoules.

Although oxygen sensitive, morphine injections are produced in plastic ampoules. In this study, the shelf life of sodium metabisulphite stabilised morphine injections in plastic ampoules was evaluated by accelerated studies at temperatures ranging from 50 to 80 degrees C. A derived model based on the rate equation and the Arrhenius equation was used for extrapolation. Determination of morphine and oxidation products was done by reversed phase ion pair HPLC. The concentration of morphine remained constant during the stability studies. The oxidation of morphine was partly compensated for by diffusion of water through the ampoules. A lag phase was observed for the formation of pseudomorphine. The shelf life is limited to 15 months by diffusion of water through the ampoules.

Chromatography, High Pressure Liquid↗
PubMed1992

Optimization of a matrix tablet formulation using a mixture design.

The simplex centroid design was applied to the optimization of a modified release tablet formulation. A base granulation was made with the active ingredient naftidrofuryl. The variables investigated included fractions of the excipients microcrystalline cellulose, lactose and dicalcium phosphate dihydrate. The release rate, crushing strength, friability and weight variation were determined as response parameters. Mathematical models were fitted to the data obtained by the lattice method, described by Scheffé and by means of multiple linear regression. Regression analysis indicated a relatively good fit of the models. On the basis of the regression models, contour plots were constructed. An increase in the amount of dicalcium phosphate caused lower release rate and increased weight variation. An increase in the content of lactose showed lower strength and increased friability, whereas an increase in the amount of microcrystalline cellulose had the opposite effect.

Chemistry, Pharmaceutical↗