Pamidronate (Aredia®) and Zoledronate (Zometa®)

Pamidronate and zoledronate are closely related medications and intravenous cousins of alendronate (Fosamax®) and risedronate (Actonel®). If pamidronate or zoledronate is recommended, it probably means you are intolerant of Fosamax or Actonel because of stomach or esophagus problems, or an inability to swallow pills.  Like Fosamax and Actonel, pamidronate and zoledronate help reduce risk of fracture in those with osteoporosis or other states associated with a high risk of fracture. They also are used to treat Paget’s disease and to help prevent tumors from spreading to bones.

These agents bind tightly to bone, where they inhibit the action of bone cells (osteoclasts). Osteoclasts remove mineral and bone protein from bones, making them thinner and structurally weaker. As a result, bones are more easily broken from minor trauma, such as a fall on a loose rug or ice. By reducing the activity of osteoclasts, pamidronate and zoledronate allow bone-building cells to replace some of what the osteoclasts removed, which strengthens bones and reduces the risk of fracture.

For osteoporosis, the standard dose is 30 mg every three months of pamidronate. The standard dose for zoledronate is 2 mg every six months or 4 mg every 12 months. Lower doses may be used if you have kidney problems or at your doctor’s discretion. For Paget’s disease, the dose may be higher and more frequent.

Because pamidronate and zoledronate are intravenous, they do not irritate the stomach and esophagus. Some people rarely experience pain in the limbs (from bone or muscle) while on these medications. Low blood calcium (hypocalcemia) rarely occurs, with an increased risk with lower calcium and vitamin D intake.

With high doses used in cancer treatment and very rarely in doses used to treat osteoporosis, cases have been reported of the jawbone not being able to heal after major dental procedures, such as root canals and oral surgery. As a precaution, all patients starting pamidronate or zoledronate are advised to see their dentist to confirm that no significant dental procedures are planned. Such procedures should be avoided, if possible, for at least three months after your last infusion.

Pamidronate and zoledronate help improve bone density gradually, about 5 percent to 10 percent in the spine and 3 percent to 5 percent in the hip over three years to five years. After three years, both drugs tend to maintain rather than increase bone density.

The risk of spine fractures is reduced within six months of starting these medicines. Risk reduction of hip, wrist or other nonspine fracture takes longer.

Both drugs bind tightly to bone and retention of medication on bone is expected after several years of use. Therefore, some protection against fractures may persist after stopping the drug, especially if it has been used for several years.

In Paget’s disease, disease activity, such as the blood level of alkaline phosphatase, gradually lessen within a few months. Bone pain associated with Paget’s disease subsides in three months to six months.

Your doctor may check your kidney function and blood calcium, plus test your bone metabolism. Repeat bone mineral density testing is conducted two years after starting pamidronate or zoledronate to check bone density improvement.

It is very important for people on pamidronate or zoledronate to get adequate amounts of calcium and vitamin D through their diet or supplements. Inadequate amounts may block the benefit of these medications.

Tell your doctor immediately about any significant dental procedures (root canals, wisdom teeth extraction). Simple cavities, fillings and filling replacements are not a concern with these medications.