Simultaneous control of flotation and release kinetics from clay- containing pellets designed for oral delivery of some trace elements

A gastroretentive floating dosage form, composed of a multiple-unit pellet system containing significant amounts of a clay powder used as a source of trace elements including iron and zinc has been developed, with its formulation based on the use of conventional polymeric and mineral excipients. Clays are frequently used in many countries by pregnant women for diverse reasons related to their condition; however, gastrointestinal absorption of these trace elements is often poor and incomplete, and is at least partially due to the localization of the transporters concerned in the upper part of the gastrointestinal tract. The pellets described herein were designed to be retained by flotation in the stomach cavity for a few hours, with simultaneous control of the release of the trace elements in order to optimize their gastro-intestinal absorption. This was achieved by embedding the clay particles in hydroxypropyl methylcellulose. Buoyancy was optimized by including sodium bicarbonate, generating carbon dioxide upon contact with the acidic gastric fluids. Finally, a gas-entrapped methacrylate coating membrane improved flotation. It was determined that the buoyancy time for the coated pellets could thus be extended by up to 5 h and that the ions released from coated and even non-coated pellets could be time-controlled. Moreover, the total amount of ions released from the clay was increased when the formulations were added, in comparison to raw clay as follows: Fe2 + (95 versus 40%), Fe3 + (70 versus 30%), Zn2 + (60 versus 40%).