Technetium ⁹⁹ᵐTc oxidronic acid

Exact mechanism is not known. It is generally accepted that technetium ⁹⁹ᵐTc oxidronic acid localizes on the surface of hydroxyapatite crystals by a process termed chemisorption, with blood flow and/or blood concentration being most important in the delivery of the agent to sites of uptake.

During the 24 hours following injection, technetium ⁹⁹ᵐTc oxidronic acid is rapidly cleared from blood and other non-osseous tissues and accumulates in the skeleton and urine in humans. Blood levels are about 10% of the injected dose at one hour post-injection and continue to fall to about 6%, 4% and 3% at 2, 3 and 4 hours, respectively. When measured at 24 hours following its administration, skeletal retention is approximately 50% of the injected dose. Technetium ⁹⁹ᵐTc oxidronic acid exhibits its greatest affinity for areas of altered osteogenesis and actively metabolizing bone.