Pamidronate

Pamidronate is a nitrogen-containing bisphosphonate used to treat conditions characterized by excessive bone resorption. It is commonly prescribed for hypercalcemia of malignancy and for certain osteolytic bone metastases, and has been used in some cases of Paget disease of bone. It is typically given by intravenous infusion and is not taken orally.

The drug works by inhibiting osteoclast-mediated bone resorption. Pamidronate binds to hydroxyapatite in bone and, once taken up by osteoclasts, disrupts the mevalonate pathway, leading to reduced osteoclast activity and, over time, decreased bone turnover. This helps lower serum calcium in hypercalcemia and can stabilize bone lesions in metastatic disease.

Administration and dosing are guided by the indication and patient factors. Pamidronate is administered as an IV infusion over several hours, with regimens varying by condition. For hypercalcemia of malignancy, typical schedules involve repeating infusions every few weeks until calcium levels normalize. Dosing for osteoporosis or other bone disorders is less common and also depends on clinical judgment.

Common adverse effects include fever and flu-like symptoms after infusion, bone, joint, or muscle pain, and electrolyte disturbances such as hypocalcemia or hypophosphatemia. Nephrotoxicity is a concern, so renal function and hydration are monitored. Rare but serious risks include osteonecrosis of the jaw and osteonecrosis of the external auditory canal. Caution is advised in pregnancy and in significant kidney impairment; calcium and vitamin D should be managed to maintain normocalcemia.

Pamidronate’s use has declined somewhat with newer bisphosphonates, but it remains a therapeutic option in selected settings.