Gastrointestinal calcium–ibandronate complex

The gastrointestinal calcium–ibandronate complex is a chemical entity formed in the digestive tract when the bisphosphonate drug ibandronate is ingested alongside calcium-containing substances. This complexation occurs via chelation, where the negatively charged phosphonate groups of the ibandronate molecule bind to divalent calcium ions (Ca2+) present in food, milk, or supplements (FDA, 2011). The resulting complex is highly insoluble and possesses poor membrane permeability, which effectively prevents the absorption of the drug into the systemic circulation (StatPearls, 2023). Consequently, the formation of this complex leads to a significant reduction in the oral bioavailability of ibandronate, potentially rendering the treatment for osteoporosis ineffective. To avoid this interaction, clinical guidelines mandate that ibandronate be taken at least 60 minutes before any food or drink other than plain water. While the complex itself is not a biological target, its formation is a major pharmacokinetic hurdle in the pharmacological management of bone density disorders (PubChem, 2024).

Other names

Calcium-ibandronate chelateIbandronate-calcium complexIbandronate-calcium interaction product

Formation of an insoluble and non-absorbable chelate in the gastrointestinal tract through the binding of ibandronate's phosphonate groups to divalent calcium ions.