Etidronate Disodium
**Etidronate disodium** is a first-generation **bisphosphonate** primarily utilized in veterinary medicine to manage severe **hypercalcemia of malignancy**. * Acts as a potent inhibitor of normal and abnormal bone resorption. * While historically significant, its clinical use has largely been superseded by newer, more potent nitrogenous bisphosphonates (e.g., pamidronate, zoledronate) which offer less frequent dosing and a superior safety profile. * **Clinical Pearl**: Prolonged use of first-generation bisphosphonates like etidronate can lead to impaired bone mineralization, a risk significantly reduced with newer generations.
Mechanism: Etidronate is a non-nitrogenous bisphosphonate that acts as a non-hydrolyzable analog of **pyrophosphate**. * Binds strongly to **hydroxyapatite crystals** in the bone matrix. * During bone resorption, the drug is taken up by **osteoclasts**. * Intracellularly, it is incorporated into non-hydrolyzable, cytotoxic ATP analogs → inhibits ATP-dependent intracellular enzymes → induces **osteoclast apoptosis**. * Decreased osteoclast activity → reduced bone resorption → lowered serum calcium levels. * Additionally increases serum phosphate, presumably by enhancing renal tubular reabsorption.
Dosing by species
- For severe hypercalcemia associated with neoplastic disease · 5-20 mg/kg/day PO · PO · q24h
- For severe hypercalcemia associated with neoplastic disease · 5-15 mg/kg daily to twice daily PO · PO · q12-24h · for moderate to severe hypercalcemia
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Severe renal function impairment (serum creatinine >5 mg/dL)
Adverse effects
- Diarrhea
- Nausea (with higher oral doses)
- Bone pain/tenderness
- Increases in serum creatinine
- 'Frozen bone' syndrome in dogs (weakened bones and fractures due to inhibited bone remodeling)
Drug interactions
- Antacids, dairy products, mineral supplements (iron, magnesium, calcium, aluminum) · Absorption of oral etidronate may be inhibited; separate etidronate doses from these substances by at least two hours.
Monitoring
- Serum calcium
- Serum protein
Overdose
Overdoses may result in **hypocalcemia** (ECG changes may occur), **bleeding problems** (secondary to rapid chelation of calcium), and **proximal renal tubule damage**. * **Treatment**: Use standard gut emptying protocols after oral ingestion when warranted. * IV calcium administration (e.g., calcium gluconate) may be used to reverse hypocalcemia. * Intensive monitoring is suggested.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.