Doctoral Defense Anna Justen
We are pleased to announce that Mrs. Anna Justen has successfully completed her disputation in the doctoral program. The members of the chair of Solids Process Engineering congratulate Mrs. Justen on this great academic achievement!
Her PhD thesis was titled: „Enhancing Drug Dissolution by Solid Crystalline Suspensions: Mechanistic Studies and Process Development“
Solid dispersions are a promising approach to enhance drug dissolution of poorly water-soluble drugs in solid dosage forms. Thereby a poorly water-soluble drug is embedded in a highly water-soluble carrier material. Especially solid crystalline dispersions have the advantage of a remarkably fast drug dissolution combined with a long shelf life due to the stable, crystalline form. Sugar alcohols such as xylitol and mannitol proved advantageous due to their inert character and hence high compatibility with various drugs as well as high water-solubility. Understanding the mechanism of enhanced drug dissolution facilitated by the presence of a carrier material such as xylitol is of high importance for pharmaceutical formulation development. The research presented in this study investigates the mechanisms driving enhanced drug dissolution in solid crystalline formulations containing the carrier material xylitol and poorly water-soluble model drugs. Various parameters including drug load, hydrodynamics, and particle size were systematically investigated, resulting in the proposal of a mechanism describing enhanced drug dissolution.
To prepare such dosage forms, several challenges have to be faced. Generally, small particles in the submicron and micron range are desired for increased drug dissolution rate. One part of this study outlines the development of a versatile spray dryer capable of producing uniform submicron and micron drug particles.
An efficient separation technique of such submicron and micron particles is electrostatic precipitation. Therefore, one further focus of this study was the development of a melt electrostatic precipitator capable of precipitating drug particles with high specific resistivity over prolonged precipitation times. Utilizing a continuous wall film as a collection electrode prevented the formation of highly resistive particle layers. Despite challenges such as thermophoresis or the built-up of a thermal boundary layer, fundamental insights into electrostatic precipitation with a heated collecting electrode were gained.
Overall, in this study a deeper understanding of the dissolution enhancing factors in solid crystalline dispersions was gained. Furthermore, an approach to manufacturing these solid dosage forms by designing a suitable spray dryer and an electrostatic precipitator with advantageous features was presented.