ZOMETA 4mg

Indications

• Electrolyte replacement
• Management of dehydration
• Support in intravenous fluid therapy

Dosage

Children: Refer to the BNF for Children for appropriate dosing based on age and clinical condition.

Adults: Refer to the BNF for specific dosing recommendations based on clinical condition and formulation.

Mechanism of action

Trisodium compounds typically function as electrolytes that help maintain osmotic balance and proper hydration in cells. Sodium ions play a critical role in nerve impulse transmission and muscle contraction, as well as in regulating blood pressure and fluid balance within the body.

Pharmacodynamics

Trisodium compounds affect the body by influencing the electrolyte composition of body fluids. Sodium ions are essential for the depolarization of nerve membranes and the contraction of muscle fibers. They also participate in the regulation of blood volume and blood pressure through their effects on renal function and fluid retention.

Pharmacokinetics

Trisodium compounds are generally absorbed readily from the gastrointestinal tract when ingested. They are distributed throughout the body fluids and tissues, playing a role in maintaining extracellular fluid volume. The kidneys are primarily responsible for the excretion of excess sodium, regulating its concentration in the body to prevent hypernatremia or hyponatremia.

Pregnancy

There is limited data on the safety of trisodium in pregnancy. Caution is advised.

Breast-feeding

Trisodium is not known to be excreted in human milk. Caution is advised.

Storage

Store in a cool, dry place. Protect from light.

Mechanism of action

Bisphosphonates are taken into the bone where they bind to hydroxyapatite. Bone resorption by osteoclasts causes local acidification, releasing the bisphosphonate, which is taken into the osteoclast by fluid-phase endocytosis. Endocytic vesicles become acidified, releasing bisphosphonates into the cytosol of osteoclasts where they act. Osteoclasts mediate resorption of bone. When osteoclasts bind to bone they form podosomes, ring structures of F-actin. Etidronic acid also inhibits V-ATPases in the osteoclast, though the exact subunits are unknown, preventing F-actin from forming podosomes. Disruption of the podosomes causes osteoclasts to detach from bones, preventing bone resorption. Nitrogen containing bisphosphonates such as zoledronate are known to induce apoptosis of hematopoietic tumor cells by inhibiting the components of the mevalonate pathway farnesyl diphosphate synthase, farnesyl diphosphate, and geranylgeranyl diphosphate. These components are essential for post-translational prenylation of GTP-binding proteins like Rap1. The lack of prenylation of these proteins interferes with their function, and in the case of Rap1, leads to apoptosis. zoledronate also activated caspases which further contribute to apoptosis.

Pharmacodynamics

Zoledronic acid is a third generation, nitrogen containing bisphosphonate that inhibits osteoclast function and prevents bone resorption. The therapeutic window is wide as patients are unlikely to suffer severe effects from overdoses and the duration of action is long. Patients should be counselled regarding the risk of electrolyte deficiencies, renal impairment, osteonecrosis of the jaw, atypical femoral fractures, bronchoconstriction, hepatic impairment, hypocalcemia, and embryo-fetal toxicity.