indication

For the treatment of moderate or severe hypercalcemia associated with malignancy

pharmacology

Pamidronate is in a class of drugs called bisphosphonates. Pamidronate reduces breakdown of the bones. Pamidronate is used in the treatment of Paget's disease of bone; to reduce high levels of calcium in the blood associated with malignancy (cancer); and to reduce the breakdown of bone due to metastases of breast cancer or multiple myeloma.

mechanism of action

The mechanism of action of pamidronate is inhibition of bone resorption. Pamidronate adsorbs to calcium phosphate (hydroxyapatite) crystals in bone and may directly block dissolution of this mineral component of bone. In vitro studies also suggest that inhibition of osteoclast activity contributes to inhibition of bone resorption. Pamidronate also targets farnesyl pyrophosphate (FPP) synthase. Nitrogen-containing bisphosphonates (such as pamidronate, alendronate, risedronate, ibandronate and zoledronate) appear to act as analogues of isoprenoid diphosphate lipids, thereby inhibiting FPP synthase, an enzyme in the mevalonate pathway. Inhibition of this enzyme in osteoclasts prevents the biosynthesis of isoprenoid lipids (FPP and GGPP) that are essential for the post-translational farnesylation and geranylgeranylation of small GTPase signalling proteins. This activity inhibits osteoclast activity and reduces bone resorption and turnover. In postmenopausal women, it reduces the elevated rate of bone turnover, leading to, on average, a net gain in bone mass.

toxicity

Side effects include an allergic reaction, kidney problems, seizures, low levels of calcium, magnesium, or phosphorus in the blood

biotransformation

Pamidronate is not metabolized and is exclusively eliminated by renal excretion

absorption

Plasma concentration rises rapidly upon IV administration.

half life

The mean ± SD elimination half-life is 28 ± 7 hours

route of elimination

Pamidronate is not metabolized and is exclusively eliminated by renal excretion.