[Drug-induced osteomalacia]

In our country, calcium- or phosphate-deficient rickets/osteomalacia due to malnutrition are scarcely reported. However, osteomalacia induced by drugs, such as anti-epileptics, etidronate and saccharated ferric oxide (SFO) is occasionally reported. When SFO is repeatedly injected to patients with iron-deficient anemia for a prolonged period, a tiny amount of SFO is excreted into renal tubules, where it exerts toxic effects on renal phosphate reabsorption and 1alpha-hydroxylase activity, leading to hypophosphatemic osteomalacia. Furthermore, Fe accumulates on the calcification front, resulting in impairment of bone formation. Although the SFO-induced osteomalacia is reversible, SFO should be used according to instructions of the package inserts, since it is a very effective parental agent for patients with iron-deficient anemia.