Iobenguane
Encyclopedia
Iobenguane, also known as metaiodobenzylguanidine or mIBG, or MIBG (tradename Adreview) is a radiopharmaceutical, used in a scintigraphy
method called MIBG scan. Iobenguane is a radiolabeled
molecule similar to noradrenaline.
The radioisotope of iodine
used for the label can be iodine-123
(for imaging purposes only) or iodine-131
(which must be used when tissue
destruction is desired, but is sometimes used for imaging also).
It localizes to adrenergic tissue and thus can be used to identify the location of tumor
s such as phaeochromocytomas and neuroblastoma
s. With I-131 it can also be used to eradicate tumor cells that take up and metabolize norepinephrine.
is indicated for nuclear medicine scintigraphy with iobenguane/mIBG. This competitively inhibits radioiodine uptake, preventing excessive radioiodine levels in the thyroid and minimizing the risk of thyroid ablation ( in the case of I-131). The minimal risk of thryoid carcinogenesis is also reduced as a result.
The FDA-approved dosing of potassium iodide for this purpose are as follows: infants less than 1 month old, 16mg; children 1 month to 3 years, 32 mg; children 3 years to 18 years, 65mg; adults 130mg. However, some sources recommend alternative dosing regimens.
Not all sources are in agreement on the necessary duration of thyroid blockade, although agreement appears to have been reached about the necessity of blockade for both scintigraphic and therapeutic applications of iobenguane. Commercially available iobenguane is labeled with iodine-123
, and product labeling recommends administration of potassium iodide 1 hour prior to administration of the radiopharmaceutical for all age groups , while the European Associated of Nuclear Medicine recommends (for iobenguane labeled with either I-131 or I-123,) that potassium iodide administration begin one day prior to radiopharmaceutical administration, and continue until the day following the injection, with the exception of new-borns, who do not require potassium iodide doses following radiopharmaceutical injection.
Product labeling for diagnostic iodine-131 iobenguane recommends potassium iodide administration one day before injection and continuing 5 to 7 days following. Iodine-131 iobenguane used for therapeutic purposes requires a different pre-medication duration, beginning 24-48 hours prior to iobenguane injection and continuing 10-15 days following injection.
Scintigraphy
Scintigraphy is a form of diagnostic test used in nuclear medicine, wherein radioisotopes are taken internally, and the emitted radiation is captured by external detectors to form two-dimensional images...
method called MIBG scan. Iobenguane is a radiolabeled
Isotopic labeling
Isotopic labeling is a technique for tracking the passage of a sample of substance through a system. The substance is 'labeled' by including unusual isotopes in its chemical composition...
molecule similar to noradrenaline.
The radioisotope of iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
used for the label can be iodine-123
Iodine-123
Iodine-123 is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography . The isotope's half-life is 13.22 hours; the decay by electron capture to tellurium-123 emits gamma radiation with predominant energies of 159 keV and 127 keV...
(for imaging purposes only) or iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...
(which must be used when tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
destruction is desired, but is sometimes used for imaging also).
It localizes to adrenergic tissue and thus can be used to identify the location of tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s such as phaeochromocytomas and neuroblastoma
Neuroblastoma
Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an annual incidence of about 650 cases per year in the US , and 100 cases per year in the UK . Close to 50 percent of neuroblastoma cases occur in children younger than two years old...
s. With I-131 it can also be used to eradicate tumor cells that take up and metabolize norepinephrine.
Thyroid precautions and use with potassium iodide
Thyroid blockade with (nonradioactive) potassium iodidePotassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
is indicated for nuclear medicine scintigraphy with iobenguane/mIBG. This competitively inhibits radioiodine uptake, preventing excessive radioiodine levels in the thyroid and minimizing the risk of thyroid ablation ( in the case of I-131). The minimal risk of thryoid carcinogenesis is also reduced as a result.
The FDA-approved dosing of potassium iodide for this purpose are as follows: infants less than 1 month old, 16mg; children 1 month to 3 years, 32 mg; children 3 years to 18 years, 65mg; adults 130mg. However, some sources recommend alternative dosing regimens.
Not all sources are in agreement on the necessary duration of thyroid blockade, although agreement appears to have been reached about the necessity of blockade for both scintigraphic and therapeutic applications of iobenguane. Commercially available iobenguane is labeled with iodine-123
Iodine-123
Iodine-123 is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography . The isotope's half-life is 13.22 hours; the decay by electron capture to tellurium-123 emits gamma radiation with predominant energies of 159 keV and 127 keV...
, and product labeling recommends administration of potassium iodide 1 hour prior to administration of the radiopharmaceutical for all age groups , while the European Associated of Nuclear Medicine recommends (for iobenguane labeled with either I-131 or I-123,) that potassium iodide administration begin one day prior to radiopharmaceutical administration, and continue until the day following the injection, with the exception of new-borns, who do not require potassium iodide doses following radiopharmaceutical injection.
Product labeling for diagnostic iodine-131 iobenguane recommends potassium iodide administration one day before injection and continuing 5 to 7 days following. Iodine-131 iobenguane used for therapeutic purposes requires a different pre-medication duration, beginning 24-48 hours prior to iobenguane injection and continuing 10-15 days following injection.
External links
- Iodine 131-metaiodobenzylguanidine at the NCI Drug Dictionary