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Iodotope Dosage

Generic name: Sodium Iodide, I-131
Dosage form: capsules, USP

Medically reviewed on August 7, 2017.

Hyperthyroidism: The total amount of sodium iodide I 131 needed to achieve a clinical remission without destruction of the entire thyroid gland has been found to vary widely; the usual dose range is 148 to 370 megabecquerels (4 to 10 millicuries). Toxic nodular goiter and other special situations will require the use of larger doses.

Carcinoma of the thyroid: Dosage must be determined individually. The usual dose for ablation of normal thyroid tissue is 1850 megabecquerels (50 millicuries), with subsequent therapeutic doses usually 3700 to 5550 megabecquerels (100 to 150 millicuries).

The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration.

Radiation Dosimetry

Following oral administration of sodium iodide I 131, about 40 percent of the activity has an effective half-life of 0.34 days and 60 percent has an effective half-life of 7.61 days. On this basis the estimated absorbed radiation doses to an average adult (70 kg) from an oral dose of 370 MBq (10 mCi) of sodium iodide I 131 are shown in Table 4.

Absorbed Radiation Doses
Tissue mGy/370 MBq rads/10 mCi
Thyroid 350,000 35,000.0
Testes 92 9.2
Ovaries 93 9.3
Whole-body 160 16.0

Method of Calculation: A Schema for Absorbed-Dose Calculations for Biologically Distributed Radionuclides, MIRD Pamphlet No. 1. J Nucl Med Suppl 1:7, 1968

Further information

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