SODIUM PHOSPHATE P 32

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SODIUM PHOSPHATE P 32 (SODIUM PHOSPHATE P 32).

How it works

Sodium phosphate P 32 is a radioactive isotope that emits beta particles, causing ionization and subsequent cell death, particularly in rapidly dividing cells. It is incorporated into DNA and RNA, concentrating in tissues with high metabolic activity such as bone marrow and neoplastic cells.

What the body does with it

Metabolism	Sodium phosphate P 32 is not metabolized; it decays with a half-life of 14.3 days via beta emission to sulfur-32.
Excretion	Renal: ~40% within 24 hours via glomerular filtration; Fecal: ~60% over 1-2 weeks as unabsorbed or secreted into bile. Total elimination approaches 100% after 2 weeks.
Half-life	Terminal elimination half-life: 14.3 days (range 13-16 days). Clinically relevant for bone marrow suppression monitoring; cumulative effect over multiple doses.
Protein binding	Primarily bound to albumin and alpha-2-macroglobulin; binding ~10-15%. Low binding due to rapid incorporation into bone mineral.
Volume of Distribution	Vd: 10-15 L/kg, reflecting extensive uptake into bone and reticuloendothelial system. Rapidly distributes to bone (especially red marrow) with slow release.
Bioavailability	Oral: 23-35% (variable due to gastric pH and food). IV: 100%. Subcutaneous: 80-90% (not commonly used).
Onset of Action	Oral: 2-4 weeks for pain palliation in skeletal metastases; IV: 1-2 weeks for hematologic effects. Direct radiation effect begins within days but symptomatic response delayed.
Duration of Action	Pain relief: 2-6 months (median 4 months). Hematologic depression: 4-8 weeks, may persist up to 3-4 months. Repeated doses not recommended within 6 months due to myelotoxicity.

Classification & Brands

Dosing & administration

Intravenous administration: 1.5 mCi (55.5 MBq) per 70 kg body weight, single dose. For polycythemia vera, oral dose: 3-5 mCi (111-185 MBq) as a single dose. Frequency is one-time or as needed based on response.

Dosage form	SOLUTION
Renal impairment	No specific guidelines; primarily excreted via decay, not renal clearance. Use with caution in severe renal impairment (GFR <30 mL/min) due to potential accumulation of phosphate.
Liver impairment	Not applicable; not metabolized by liver. Use standard dosing regardless of hepatic function.
Pediatric use	Not well established. In cases of leukemia or polycythemia, dose calculated as 0.1-0.2 mCi/kg (3.7-7.4 MBq/kg) IV or oral, not to exceed adult dose. Must be individualized.
Geriatric use	No specific dose adjustment. Monitor for myelosuppression due to reduced bone marrow reserve. Consider lower end of dosing range (e.g., 1.2-1.5 mCi IV).

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for SODIUM PHOSPHATE P 32 (SODIUM PHOSPHATE P 32).

Breastfeeding	Contraindicated during breastfeeding. Radiopharmaceuticals may accumulate in breast milk. No M/P ratio available; advice: discontinue breastfeeding for at least 4 weeks or permanently after administration.
Teratogenic Risk	Sodium phosphate P 32 is a radioactive agent emitting beta particles. Pregnancy category X. Contraindicated in pregnancy due to risk of fetal radiation exposure, causing teratogenesis, growth retardation, and carcinogenesis across all trimesters. Use only if life-threatening condition where no alternative exists.

Warnings & precautions

■ FDA Black Box Warning

Contains radioactive material. Must be handled and administered only by authorized personnel in designated facilities. Risk of leukemia, particularly in patients with polycythemia vera, and potential for genetic mutations. Not for use in benign conditions.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to sodium phosphate P 32, pre-existing severe myelosuppression, pregnancy, lactation, benign hematologic conditions (except polycythemia vera), and patients under 18 years of age (relative contraindication).

Clinical Precautions

Precautions

Myelosuppression, particularly leukopenia and thrombocytopenia. Increased risk of leukemia and other malignancies. Requires monitoring of blood counts. Avoid in pregnancy and lactation. Use caution in patients with impaired renal function.

Clinical Tips & Counseling

Drug interactions

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SODIUM PHOSPHATE P 32

Clinical safety rating: caution

Comprehensive clinical and safety monograph for SODIUM PHOSPHATE P 32 (SODIUM PHOSPHATE P 32).

How it works

What the body does with it

Metabolism	Sodium phosphate P 32 is not metabolized; it decays with a half-life of 14.3 days via beta emission to sulfur-32.
Excretion	Renal: ~40% within 24 hours via glomerular filtration; Fecal: ~60% over 1-2 weeks as unabsorbed or secreted into bile. Total elimination approaches 100% after 2 weeks.
Half-life	Terminal elimination half-life: 14.3 days (range 13-16 days). Clinically relevant for bone marrow suppression monitoring; cumulative effect over multiple doses.
Protein binding	Primarily bound to albumin and alpha-2-macroglobulin; binding ~10-15%. Low binding due to rapid incorporation into bone mineral.
Volume of Distribution	Vd: 10-15 L/kg, reflecting extensive uptake into bone and reticuloendothelial system. Rapidly distributes to bone (especially red marrow) with slow release.
Bioavailability	Oral: 23-35% (variable due to gastric pH and food). IV: 100%. Subcutaneous: 80-90% (not commonly used).
Onset of Action	Oral: 2-4 weeks for pain palliation in skeletal metastases; IV: 1-2 weeks for hematologic effects. Direct radiation effect begins within days but symptomatic response delayed.
Duration of Action	Pain relief: 2-6 months (median 4 months). Hematologic depression: 4-8 weeks, may persist up to 3-4 months. Repeated doses not recommended within 6 months due to myelotoxicity.

Classification & Brands

Dosing & administration

Dosage form	SOLUTION
Renal impairment	No specific guidelines; primarily excreted via decay, not renal clearance. Use with caution in severe renal impairment (GFR <30 mL/min) due to potential accumulation of phosphate.
Liver impairment	Not applicable; not metabolized by liver. Use standard dosing regardless of hepatic function.
Pediatric use	Not well established. In cases of leukemia or polycythemia, dose calculated as 0.1-0.2 mCi/kg (3.7-7.4 MBq/kg) IV or oral, not to exceed adult dose. Must be individualized.
Geriatric use	No specific dose adjustment. Monitor for myelosuppression due to reduced bone marrow reserve. Consider lower end of dosing range (e.g., 1.2-1.5 mCi IV).

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for SODIUM PHOSPHATE P 32 (SODIUM PHOSPHATE P 32).

Breastfeeding	Contraindicated during breastfeeding. Radiopharmaceuticals may accumulate in breast milk. No M/P ratio available; advice: discontinue breastfeeding for at least 4 weeks or permanently after administration.
Teratogenic Risk	Sodium phosphate P 32 is a radioactive agent emitting beta particles. Pregnancy category X. Contraindicated in pregnancy due to risk of fetal radiation exposure, causing teratogenesis, growth retardation, and carcinogenesis across all trimesters. Use only if life-threatening condition where no alternative exists.