a master’s thesis at the College of Pharmacy at the University of Basrah discussed (Application of quality by design and quantitative numerical analysis to develop an inflatable gastric drug retention system for the treatment of Metoprolol Tartrate) 
The researcher Mustafa Musa Khalaf Namouk’s thesis included the use of the full factorial design by Design-Expert™️
To study the effect of independent variables (HPMC and Carbopol)
 As a result of the factorial design, 16 different formulas were prepared (by the solvent casting method). The preparations were prepared with different quantities of polymers and in different proportions. The dependent variables were the swelling index and drug release in the laboratory, and the improved formula F14 was chosen.
Due to the high swelling index and appropriate drug release behavior, 86.24% of metoprolol was released within 12 hours.
The aim of the study was to develop and evaluate a novel scalable gastric drug retention system based on metoprolol distension.