In a collaborative project funded by Innosuisse and Enzian Pharmaceutics, scientists at Enzian Pharmaceutics and the University of Zurich (UZH) have reached an important milestone in the development of a new gastroretentive dosage form. Such dosage forms temporarily reside in the stomach, and deliver drugs into the stomach and the blood for prolonged time. Two recent studies on dogs and pigs published in the International Journal of Pharmaceutics confirm the new dosage form's prolonged gastric residence in such large animals [1,2].
The development of gastroretentive dosage forms has been the object of intense research for decades. These dosage forms enable drug release into the stomach for prolonged time, better control of drug absorption rate, and drug concentration in blood. This in turn enables improved efficacy, safety, and convenience of many prevailing drug therapies.
The most promising concept for gastric retention developed to date is the expandable dosage form. Such dosage forms are smaller than the diameter of the esophagus to facilitate ingestion. But in the stomach they expand to a size greater than the diameter of the pylorus, thus precluding their immediate passage into the small intestine. To date, however, short gastric residence times and safety considerations have limited their use.
To overcome these limitations, scientists at Enzian Pharmaceutics have developed expandable fibrous dosage forms. The fibrous forms comprise a cross-ply structure of water-absorbing fibers coated with a fiber-strengthening, enteric coating. Upon immersing in a dissolution fluid, these dosage forms absorb water and form an expanded viscoelastic mass with adequate mechanical strength for prolonged gastric residence.
The dosage forms were tested in dogs and pigs at the Diagnostic Imaging Research Unit (DIRU) of the Vetsuisse Faculty at UZH. The DIRU has built up an expertise for clinical applied research and provides services for a wide range of animal studies.
In this collaboration it was shown that with appropriate thickness of the fiber-strengthening coating the dosage forms resided in the stomach of dogs for 31 hours and then dissolved and safely excreted. Moreover, in pigs it was shown that the gastric residence time could be controlled by varying the thickness of the coating.
Thus, the expandable fibrous dosage forms can be optimally designed for prolonged, safe gastric residence. The team is now testing the concentration of various types of drugs in the blood of animals after administering the new dosage forms, and comparing it to that of state-of-the art tablets and capsules.
 Aron H. Blaesi, Dolf Kümmerlen, Henning Richter, Nannaji Saka, Mechanical strength and gastric residence time of expandable fibrous dosage forms, Int. J. Pharm. 613, (2022), 120792. DOI: 10.1016/j.ijpharm.2021.120792
 Aron H. Blaesi, Thomas Echtermann, Henning Richter, Nannaji Saka, The effect of a semi-permeable, strengthening fiber coating on the expansion, mechanical properties, and residence time of gastroretentive fibrous dosage forms, Int. J. Pharm. 642, (2023), 122378. DOI: 10.1016/j.ijpharm.2022.122378