radium-223 radium-223 radium-223 (223ra, ra-223) is an isotope of radium with an 11.4-day half-life. it was discovered in 1905 by t. godlewski, a polish chemist from kraków, and was historically known as actinium x (acx). radium-223 dichloride is an alpha particle-emitting radiotherapy drug that mimics calcium and forms complexes with hydroxyapatite at areas of increased bone turnover. the principal use of radium-223, as a radiopharmaceutical to treat metastatic cancers in bone, takes advantage of its chemical similarity to calcium, and the short range of the alpha radiation it emits. radium-223, 223rageneralsymbol223ranamesradium-223, 223ra, ra-223,actinium x, acxprotons (z)88neutrons (n)135nuclide datahalf-life (t1/2)11.43±0.05 disotope mass223.0185007(22) daparent isotopes227th223frdecay products219rndecay modesdecay modedecay energy (mev)α5.979isotopes of radium complete table of nuclides origin and preparation although radium-223 is naturally formed in trace amounts by the decay of uranium-235, it is generally made artificially, by exposing natural radium-226 to neutrons to produce radium-227, which decays with a 42-minute half-life to actinium-227. actinium-227 (half-life 21.8 years) in turn decays via thorium-227 (half-life 18.7 days) to radium-223. this decay path makes it convenient to prepare radium-223 by "milking" it from an actinium-227 containing generator or "cow", similar to the moly cows widely used to prepare the medically important isotope technetium-99m. 223ra itself decays to 219rn (half-life 3.96 s), a short-lived gaseous radon isotope, by emitting an alpha particle of 5.979 mev. medical use radium-223 chlorideclinical datatrade namesxofigoahfs/drugs.commicromedex detailed consumer informationlicense data eu ema: by inn us dailymed: xofigo routes ofadministrationintravenousatc codev10xx03 (who) legal statuslegal status au: s4 (prescription only) us: ℞-only identifiers iupac name radium-223 chloride cas number444811-40-9 npubchem cid6335825chemspidernoneuniirj00kv3vtgkeggd10398chebichebi:74895chemical and physical dataformula223racl2molar mass296.91 g/mol ny (what is this?) (verify) the pharmaceutical product and medical use of radium-223 against skeletal metastases was invented by roy h. larsen, gjermund henriksen and øyvind s. bruland and has been developed by the former norwegian company algeta asa, in a partnership with bayer, under the trade name xofigo (formerly alpharadin), and is distributed as a solution containing radium-223 chloride (1100 kbq/ml), sodium chloride, and other ingredients for intravenous injection. algeta asa was later acquired by bayer who is now the sole owner of xofigo. the recommended regimen is six treatments of 55 kbq/kg (1.5 μci/kg), repeated at 4-week intervals. mechanism of action