Strontium chloride sr 89 [USAN]

Absorption

Following intravenous injection, strontium chloride 89 behaves like its calcium analog. It clears rapidly from the blood stream and selectively gets localized on the bone mineral, preferentially in zones of osteogenesis, where it can stay retained for about 14 days.

Toxicity

A single case of fatal septicemia following leukopenia has been reported during clinical trials. Bone marrow depression leading to thrombocytopenia (unusual bleeding or bruising; black, tarry stools; blood in urine or stools; pinpoint red spots on skin), and leukopenia (cough or hoarseness; fever or chills; lower back or side pain; painful or difficult urination)

Background

Strontium chloride (Sr-89), initially FDA-approved in 1993, is used as a paliative therapeutic option to help relieve the pain from bone metastases. Strontium chloride is mainly used in cases of metastatic castrate-resistant prostate cancer. Bone metastases is a common and severe complication presented in advanced stages of the disease. It is usually presented mainly in patients with prostatic and breast cancer, as well as in cancer of lung, bladder and thyroid. There has been some cases of apparent tumor regression which has given it a potential tumoricidal effect.

Indications

Strontium-89 Chloride Injection is indicated as a paliative for the relief of bone pain in patients with skeletal metastases. It is impotant to confirm the presence of bone metastases prior the beginning of therapy.

Pharmacokinetics

Metastatic bone lesions are zones of high bone mineral turnover. Thus, there is a constant need of calcium supply for the development of the malignancy. Strontium chloride 89 is a divalent ion, similar to calcium, therefore it is taken up by sites of active osteogenesis. This relieves bone metastatic-driven pain withouth generating important side effects and it also presents a very little radioprotection concern. Once combined with external beam radiotherapy, strontium chloride 89 can emit β particules with a maximum range in tissue of 6-8mm. This radiation is capable to reduce new bone metastases and produces an analgesic role.

Metabolism

Strontium can interact with components than normally bind to calcium, including hydroxyapatite (main component of mineralized bone), calcium-binding or calcium-transport proteins. It can form complexes with different inorganic anions like carbonate, citrate, phosphate, carboxylic acid or lactate.