[en] Using infrared spectroscopy, we studied the character of intermolecular interactions in the samples blood plasma of oncological patients with bone metastases in the treatment of their modern β-emitter ¹⁵³Sm-oxabifor. The therapeutic dose of the ¹⁵³Sm-oxabifor was 1.0 mCi/kg of the patient's body weight. Analysis of the IR-spectra showed that already after the first course of palliative radionuclide therapy there is a tendency to balance the products of free radical nature and antioxidants, which indicates the effectiveness of the treatment. Molecular changes in the blood plasma of cancer patients with bone metastases registered using infrared spectroscopy are specific during palliative therapy. (author)