Zoledronic acid belongs to the class of nitrogen-containing bisphosphonates and acts primarily on bone. It is an inhibitor of osteoclast-mediated bone resorption. The action of bisphosphonates on bone is based on their high affinity for mineralized bone. Intravenously administered Zoledronic acid is rapidly distributed to bone. The main molecular target of Zoledronic acid in the osteoclast is the enzyme farnesyl pyrophosphate synthase, but this does not exclude other mechanisms. Clinical studies in tumour-induced hypercalcemia demonstrated that the effect of Zoledronic acid is characterized by decreases in serum calcium and urinary calcium excretion. In addition to its inhibitory activity against bone resorption, Zoledronic acid also possesses anti-tumour activity, anti-angiogenic activity, anti-pain activity, cytostatic and pro-apoptotic activity on tumour cells and synergistic cytostatic effect with other anti-cancer drugs. There was no accumulation of the active substance in plasma after multiple doses given every 28 days. Zoledronic acid is not metabolized and is excreted unchanged via the kidney.