Etidronic acid (HEDP)

Etidronic acid is a first-generation, non-nitrogenous bisphosphonate drug primarily used to regulate bone metabolism and treat resorptive bone diseases such as Paget's disease, osteoporosis, and heterotopic ossification [2, 5, 6]. It functions by binding with high affinity to hydroxyapatite crystals in the bone matrix, particularly at sites of active remodeling [5, 9]. Once localized to the bone, it is internalized by osteoclasts during the resorption process [5, 9]. Inside the osteoclast, etidronic acid is metabolized into a cytotoxic, non-hydrolyzable analog of adenosine triphosphate (ATP), which disrupts cellular energy metabolism and induces osteoclast apoptosis [1, 9]. This reduction in osteoclast activity effectively slows bone turnover and increases bone mineral density [6, 9]. Clinically, it is also used to manage hypercalcemia of malignancy and as a chelating agent in various industrial and cosmetic applications [2, 4, 6]. Its absorption is significantly reduced by the concurrent administration of calcium, magnesium, or aluminum-containing antacids and supplements [5, 8]. Unlike newer nitrogen-containing bisphosphonates, prolonged continuous use of etidronic acid can inhibit bone mineralization, potentially leading to osteomalacia [2, 6].

Other names

Etidronate1-Hydroxyethylidene-1,1-diphosphonic acidHEDPHEDPADidronel

Etidronic acid binds to hydroxyapatite in the bone matrix and is internalized by osteoclasts, where it is metabolized into a non-hydrolyzable ATP analog that induces apoptosis by inhibiting mitochondrial enzymes [1, 9].