Moisture measurement: a new method for monitoring freeze-drying cycles.

Quality of the final product largely depends on the freeze-drying process. In turn this largely depends on an adequate control of the amount of residual moisture after freeze-drying. Measuring this amount in the chamber of the freeze-dryer to determine the end point of sublimation and the end point of secondary drying provides a reliable control with regard to the methods traditionally used (for example rapid increase in product temperature). The purpose of this study is to evaluate the benefits and disadvantages of the different methods recommended for the monitoring of a freeze-drying cycle. Two systems for the measurement of the moisture in the freeze dryer are evaluated here: the Pirani vacuum gauge, and the moisture sensor. The moisture sensor appears to be the most sensitive and reliable way of determining both the end of sublimation and the end of secondary drying of the full load batch when placed on a freeze-dryer. The immediate benefit for the industry is to allow to scale-up without the risks of under or over estimating the freeze-drying cycle.

Radioprotective activity of ethylcellulose microspheres containing WR 2721, after oral administration.

Ethylcellulose microspheres containing WR 2721 were prepared by the emulsion-solvent evaporation technique. No significant loss or degradation of this phosphorothioate was noted during preparation. Oral administration of these microspheres to mice gave an important lowering of WR 2721 toxicity and an enhancement of its radioprotective activity with a D.R.F. of about 1.7-1.8 over 2-3 h. This action is explained by the protection of WR 2721 from acid hydrolysis and degradation in the gastro-intestinal tract. The adsorption of a fraction of WR 2721 onto the surface of microspheres constitutes an inconvenience. This study confirms the interest of such carriers for providing important sustained radioprotection after oral administration.