Etidronate Disodium
EHDP, Na2EHDP, sodium etidronate
Also known as: Anfozan · Bonemass · Didronate · Difosfen · Diphos · Dralen · Dronate-OS · Etidrate · Etiplus · Feminoflex · Ostedron · Osteodidronel · Osteum · Ostogene · Ostopor · Somaflex · Sviroxit · disodium etidronate · Na2EHDP
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For severe hypercalcemia associated with neoplastic disease | 5-15 mg/kg daily to twice daily PO | PO | q12-24h | — | 🌎 NA |
- For severe hypercalcemia associated with neoplastic disease: for moderate to severe hypercalcemia
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For severe hypercalcemia associated with neoplastic disease | 5-20 mg/kg/day PO | PO | q24h | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
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- While historically significant, its clinical use has largely been superseded by newer, more potent nitrogenous bisphosphonates (e.g., pamidronate, zoledronate) which offer less frequent dosing and a superior safety profile.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 of action
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.
Safety & warnings
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)
Precautions
Risk vs. benefit should be carefully considered in patients with bone fractures (delays healing), enterocolitis (higher risk of diarrhea), cardiac failure (especially with parenteral etidronate as patients may not tolerate the extra fluid load), or those with moderate renal function impairment (serum creatinines 2.5-5 mg/dL).
Warning: Do not confuse etidronate with etretinate or etomidate.
Safety during pregnancy has not been established (FDA Category C). It is unknown if the drug enters milk.
Drug interactions
Absorption of oral etidronate may be inhibited; separate etidronate doses from these substances by at least two hours.
Monitoring
- Serum calcium
- Serum protein
Pharmacokinetics
Absorption
Oral absorption is poor and dose dependent (1-20%). Food substantially reduces the amount absorbed.
Distribution
Rapidly cleared from blood and 50% of the drug absorbed goes into bone. At usual doses, it appears that etidronate does not cross the placenta.
Metabolism
Not metabolized; excreted unchanged.
Elimination
Approximately 50% of the absorbed dose is excreted unchanged by the kidneys within 24 hours; the remainder is chemisorbed to bone and then slowly eliminated.
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.
Available products
Formulations
- Tablets
Human-labeled
- Etidronate Disodium Tablets: 200 mg & 400 mg (Didronel, generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store tablets in tight containers at room temperature.
Client information
Important Administration Note: This medication must be given on an empty stomach to ensure it is absorbed properly. Food, especially dairy products, will block the drug from entering your pet's system.
- Watch for side effects: Contact your veterinarian immediately if your pet experiences loss of appetite (anorexia), vomiting, or diarrhea.
- Bone health: In rare cases, long-term use can affect bone strength. Monitor your pet for any signs of bone pain or limping.
- Do not give with antacids or mineral supplements (like calcium or iron) within 2 hours of this medication.
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.