PHOSPHOCOL P32
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHOSPHOCOL P32 (PHOSPHOCOL P32).
Phosphocol P32 (chromic phosphate P32) is a radioactive colloid that emits beta particles. It is administered intracavitary to treat malignant effusions. The beta radiation causes local fibrosis and destruction of tumor cells lining serous cavities, reducing fluid accumulation.
| Metabolism | Not metabolized; decays via beta emission to stable phosphorus-32 with a half-life of 14.3 days. |
| Excretion | Primarily renal: approximately 70% excreted in urine within 24 hours after intravenous administration. Fecal excretion is minimal (<5%) as sodium phosphate is completely absorbed and incorporated into metabolic pathways. |
| Half-life | The physical half-life of phosphorus-32 is 14.3 days. The biological half-life in the body is approximately 9 days, resulting in an effective half-life of about 5.6 days due to combined decay and elimination. |
| Protein binding | Negligible (<5%); sodium phosphate is not notably bound to plasma proteins as it is an inorganic ion. |
| Volume of Distribution | Approximately 0.35 L/kg (0.3-0.4 L/kg) in adults, reflecting distribution mainly into extracellular fluid and uptake by bone and proliferating tissues (e.g., bone marrow, liver, spleen). |
| Bioavailability | Intravenous: 100% (complete bioavailability). Oral: Not applicable due to lack of oral formulation. Intracavitary: Absorption is limited; locally administered phosphate is retained in the cavity with systemic absorption minimal. |
| Onset of Action | Intravenous: Therapeutic effects (palliation of pain in bone metastases) may begin within 1-2 weeks. Intracavitary injection: Local radiation effect occurs within days to weeks. |
| Duration of Action | Clinical effect duration is limited by the radioactive decay and incorporation into tissues; therapeutic action typically lasts 4-6 weeks. Repeat administration may be considered after 3 months. |
Intraperitoneal: 10-20 mCi (370-740 MBq) as a single dose for malignant effusions; Intravenous: 5 mCi (185 MBq) for polycythemia vera, may repeat at 12-week intervals.
| Dosage form | INJECTABLE |
| Renal impairment | No specific guidelines; use with caution in severe impairment (GFR <30 mL/min) due to potential accumulation. |
| Liver impairment | No specific guidelines; caution in severe hepatic impairment (Child-Pugh class C) due to altered clearance. |
| Pediatric use | Not established; limited data in children. Use only if potential benefit outweighs risk. |
| Geriatric use | No specific adjustments; monitor for myelotoxicity more frequently due to age-related reduced bone marrow reserve. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PHOSPHOCOL P32 (PHOSPHOCOL P32).
| Breastfeeding | Contraindicated. Radioactivity may be excreted into breast milk. M/P ratio not established. Discontinue nursing before administration; advise against resumption for at least 2 weeks. |
| Teratogenic Risk | Category X. Phosphorus-32 emits beta radiation, which can cause fetal harm. Contraindicated in pregnancy. Risk of congenital anomalies and carcinogenesis throughout gestation. |
| Fetal Monitoring |
■ FDA Black Box Warning
Radiopharmaceutical: risk of radiation exposure to patient and medical personnel. Use only by qualified personnel. Do not use for intrapleural or intraperitoneal injection in patients with known loculation of fluid or with evidence of tumor penetrating the bowel wall. Not for intravenous, intramuscular, or subcutaneous use.
| Serious Effects |
Pregnancy, lactation, known loculation of effusion fluid, evidence of bowel perforation or fistula, active bleeding, concurrent chemotherapy or radiation therapy that may exacerbate myelosuppression, and previous radiation therapy to the cavity site.
| Precautions | Radiation safety precautions required. Risk of extravasation leading to local tissue necrosis. Use with caution in patients with severe anemia, leukopenia, or thrombocytopenia. Monitor for signs of bowel perforation or fistula formation. Pregnancy and lactation: contraindicated. Ensure proper patient shielding. |
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| Verify negative pregnancy test before use. Monitor complete blood counts and signs of radiation toxicity weekly. Fetal radiation exposure monitoring if inadvertently administered. |
| Fertility Effects | May cause gonadal radiation damage leading to temporary or permanent infertility, particularly with higher cumulative doses. Ovarian or testicular function may be impaired. |