PAMIDRONATE DISODIUM

Clinical safety rating: avoid

Contraindicated (not allowed)

How it works

Bisphosphonate that inhibits osteoclast-mediated bone resorption by adsorbing to hydroxyapatite crystals and inhibiting their dissolution, and by inhibiting osteoclast activity via farnesyl pyrophosphate synthase inhibition.

What the body does with it

Metabolism	Not metabolized; excreted unchanged primarily by the kidneys.
Excretion	Primarily renal; 30-62% of unchanged drug excreted in urine within 72 hours, with the remainder bound to bone and slowly released. Biliary/fecal elimination is negligible (<1%).
Half-life	Triphasic: terminal elimination half-life (t1/2γ) is 27-28 hours, representing slow release from bone. Clinical context: prolonged suppression of bone resorption persists weeks after serum levels become undetectable.
Protein binding	Approximately 54%, mainly to albumin.
Volume of Distribution	0.2-0.3 L/kg; distributes primarily to bone (particularly osteoclast-active surfaces) and liver, with minimal soft tissue penetration.
Bioavailability	Not applicable orally (negligible absorption, <1%). IV bioavailability is 100%.
Onset of Action	IV: Reduction in serum calcium begins within 24-48 hours, maximal effect at 4-7 days. No oral formulation.
Duration of Action	Serum calcium remains normalized for 2-3 weeks after a single IV dose; bone resorption inhibition may persist up to 6 months due to skeletal retention.

Classification & Brands

Dosing & administration

90 mg intravenously over 2-24 hours every 3-4 weeks for hypercalcemia of malignancy; 60-90 mg intravenously over 2-24 hours every 2-4 weeks for osteolytic bone metastases or Paget disease.

Dosage form	INJECTABLE
Renal impairment	Contraindicated if CrCl <30 mL/min. For CrCl 30-60 mL/min: reduce dose to 60 mg or extend infusion interval. Monitor serum creatinine prior to each dose.
Liver impairment	No specific dose adjustment recommended based on Child-Pugh score; use with caution in severe hepatic impairment.
Pediatric use	Not FDA-approved for pediatric use. Limited data: 0.5-2 mg/kg intravenously over 4-24 hours for hypercalcemia, but safety and efficacy not established.
Geriatric use	No specific dose adjustment based on age alone; assess renal function closely as elderly patients are more likely to have decreased creatinine clearance. Monitor for renal toxicity and electrolyte imbalances.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Nephrotoxic drugs may increase risk of renal impairment Can cause renal impairment and hypocalcemia.

Breastfeeding	Excretion in human milk unknown; M/P ratio not established. Due to potential calcium metabolism disruption in neonate, breastfeeding is not recommended during therapy.
Teratogenic Risk	Pamidronate disodium is pregnancy category D. First trimester: potential skeletal abnormalities, low birth weight. Second and third trimesters: risk of fetal hypocalcemia, skeletal dysplasia, reduced fetal growth. Animal studies show fetal skeletal delays and maternal toxicity.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Not indicated for osteoporosis. Risk of severe renal impairment, especially with rapid infusion. Osteonecrosis of the jaw has been reported.

Side Effect Profile

Common Effects	bone metastases
Serious Effects

Absolute Contraindications

Hypersensitivity to bisphosphonates, severe renal impairment (creatinine clearance <30 mL/min), hypocalcemia (relative).

Clinical Precautions

Precautions

Renal toxicity (monitor renal function, avoid in severe renal impairment), osteonecrosis of the jaw (dental exam before therapy), hypocalcemia (ensure adequate calcium/vitamin D), severe musculoskeletal pain, atrial fibrillation (in long-term use), bronchospasm in aspirin-sensitive asthmatics.

Clinical Tips & Counseling

Drug interactions

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