Review on novel oral iron formulations with enhanced bioavailability for the treatment of iron deficiency

Iron deficiency (ID), if it remains untreated, leads to severe conditions of anemia, and based on the WHO data, ID is the primary cause of anemia worldwide, specifically in women. Iron deficiency without anemia can be treated with oral iron salts, but despite the availability of plenty of conventional iron products on the market, the problem persists. This is due to poor patient compliance resulting from poor iron bioavailability because of its carrier-mediated absorption by the DMT1 carrier protein, mainly in duodenal enterocytes, and associated GI side effects due to unabsorbed iron in the GI region. GI side effects are less with EC and SR iron products due to the release of a small amount of iron at a time but are not beneficial due to poor bioavailability caused by the short gastric emptying time, as iron released beyond the duodenum, remains unabsorbed in a significant fraction. Novel iron formulations like spherical lipid-coated particles, microspheres, nanoparticles, SLNs, liposomes, and sucrosomial iron are researched and developed to reduce GI side effects because of encapsulated iron and to improve bioavailability based on higher solubility related to small size and higher permeability due to the lipoidal outer surface, bypassing carrier-mediated absorption. However, gastroretentive iron tablets, capsules, and pellets dosage forms that release iron slowly for a prolonged period at the absorption site, which improves its bioavailability with lower GI side effects, seem to be a better approach based on ease in their manufacturing on a large scale and other issues like cost, market size, etc. over liposomal nanoproducts and can be focused on for future development. This review study focuses on the delivery of iron using innovative oral iron formulations designed to enhance bioavailability with reduced side effects. It delves into the problems associated with conventional and sustained-release iron products. The authors have compiled patented and non-patented literature and relevant clinical trials of oral iron products to perform a gap analysis, providing valuable insights for researchers working on the development of iron formulations.