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Samarium SM 153 Lexidronam

Pronouncation: (sah-MARE-ee-uhm SM 153 lex-IH-drah-nam)
Class: Radiopharmaceutical

Trade Names:
Quadramet
- Injection 1850 MBq/mL

Pharmacology

Consisting of radioactive samarium and a tetraphosphonate chelator, EDTMP. The mechanism of action of samarium in relieving the pain of bone metastases is not known.

Indications and Usage

Relief of pain in patients with osteoblastic metastatic bone lesions that enhance on radionuclide bone scan.

Unlabeled Uses

Ankylosing spondylitis; Paget disease; rheumatoid arthritis.

Contraindications

Hypersensitivity to EDTMP or similar phosphonate compounds.

Dosage and Administration

Bone Lesions
Adults

IV 1 mCi/kg, administered over a period of 1 min through a secure indwelling catheter and followed with a saline flush. Exercise caution when determining the dose in very thin or very obese patients.

General Advice

Have the patient ingest (or receive by IV administration) a minimum of 500 mL (2ߙcups) of fluids prior to injection and void as often as possible after injection to minimize radiation exposure to the bladder.
Samarium contains calcium and may be incompatible with solutions that contain molecules that can complex with and form calcium precipitates.
Do not dilute or mix with other solutions.

Storage/Stability

Thaw at room temperature before administration and use within 8 h. Store frozen at −20° to −10°C (−4° to 14°F) in a lead shielded container.

Drug Interactions

Chemotherapy

Do not give samarium concurrently with chemotherapy or external beam radiation therapy unless the benefit outweighs the risks. Do not give samarium after either of these treatments until there has been time for adequate marrow recovery.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Arrhythmias; chest pain; hypertension; hypotension; sinus bradycardia; vasodilation.

CNS

Dizziness; paresthesia; spinal cord compression; cerebrovascular accident/stroke.

Dermatologic

Purpura; rash.

GI

Abdominal pain; diarrhea; nausea; vomiting.

Hematologic

Bleeding manifestations

Ecchymosis; epistaxis; hematuria; bone marrow suppression; coagulation disorder; hemoglobin decreased; leukopenia; lymphadenopathy; thrombocytopenia; bone marrow toxicity.

Respiratory

Bronchitis; cough increased; pneumonia.

Miscellaneous

Fever; chills; unspecified infection; oral moniliasis; myasthenia; pathologic fracture.

Precautions

Monitor

Before administering samarium, give consideration to the patient's current clinical and hematologic status and bone marrow response history to treatment with myelotoxic agents. Exercise caution in treating cancer patients whose platelet counts are falling or who have other clinical or laboratory findings suggesting DIC. Monitor blood counts weekly for at least 8 wk or until recovery of adequate bone marrow function.

Pregnancy

Category C .

Lactation

Discontinue breast-feeding or discontinue the drug.

Children

Safety and efficacy in children younger than 16 yr of age have not been established.

Pain flare reactions

Some patients have reported a transient increase in bone pain shortly after injection (flare reaction). This is usually mild and self-limiting and occurs within 72 h of injection.

Bone marrow suppression

Samarium causes bone marrow suppression. Use with caution in patients with compromised bone marrow reserves.

Radioactivity

Verify dose.

ECG changes

Use caution and appropriate monitoring.

Skeletal effects

Spinal cord compression frequently occurs in patients with known metastases to the cervical, thoracic, or lumbar spine. Administration for pain relief of metastatic bone cancer does not prevent the development of spinal cord compression.

Incontinence

Take special precautions with bladder catherization in incontinent patients to minimize the risk of radioactive contamination.

Hypocalcemia

Exercise caution when administering to patients at risk for developing hypocalcemia.

Flare reactions

A transient increase in bone pain shortly after injection (flare reaction) may occur.

Overdosage

Symptoms

Bone marrow suppression.

Patient Information

Advise patients that for several hours following administration, radioactivity will be present in excreted urine. To help protect themselves and others in their environment, precautions need to be taken for 12 h following administration. Whenever possible, use a toilet rather than a urinal and flush the toilet several times after each use. Clean up spilled urine completely and wash hands thoroughly. If blood or urine gets onto clothing, wash the clothing separately or store for 1 to 2 wk to allow for decay of the samarium.
Women of childbearing age should have a negative pregnancy test before administration of samarium. If this drug is used during pregnancy or if a patient becomes pregnant after taking this drug, apprise her of the potential hazard to the fetus. Advise women of childbearing potential to avoid becoming pregnant soon after receiving samarium. Advise male and female patients to use an effective method of contraception after samarium administration.