Sodium Iodide I 131 Diagnostic
(Sodium Iodide I 131)Sodium Iodide I 131 Diagnostic Prescribing Information
Sodium Iodide I 131 Capsules Diagnostic is indicated for use in adults for:
- Assessment of thyroid function using radioactive iodine (RAI) uptake test
- Imaging the thyroid (scintigraphy)
Capsules: Each capsule contains 3.70 MBq (100 microCi) at time of calibration. Half of each capsule is white, while the other half is either pink, yellow, orange, grey or green according to the manufactured lot. The capsule will yield 2.03, 1.11, 0.61, or 0.33 MBq (55, 30, 16.5, or 9 microCi) according to the color-coded decay calendar which assigns a color and capsule activity for each week of the year. https://www.draximage.com/products/us/draximage-i-131-diagnostic-capsules/
Table 2 below displays the (5) weeks activity of the capsule starting from the calibration day.
Week | Activity (MBq) | Activity (microCi) |
| 1 | 3.70 | 100.0 |
| 2 | 2.03 | 54.9 |
| 3 | 1.11 | 30.0 |
| 4 | 0.61 | 16.5 |
| 5 | 0.33 | 8.9 |
Sodium Iodide I 131 Capsules Diagnostic is contraindicated in pregnancy [see
- Fetal Toxicity – I 131 can cause severe and irreversible hypothyroidism in the neonate. Verify absence of pregnancy before administering the product.
- Radiation Risk – I 131 contributes to patients’s long-term cumulative radiation exposure, which is associated with an increased risk of cancer. Ensure safe handling to minimize radiation exposure.
Sodium Iodide I 131 Capsules Diagnostic is contraindicated in pregnancy because sodium iodide I 131 crosses the placenta and can cause severe and irreversible hypothyroidism in the neonate. Multiple reports in the literature describe neonatal hypothryroidism following in utero exposure to sodium iodide I 131. Some of these cases were severe and irreversible. Verify pregnancy status of females of reproductive potential prior to administering Sodium Iodide I 131 Capsules Diagnostic [see
Sodium Iodide I 131 Capsules Diagnostic contributes to a patient’s overall long-term cumulative radiation exposure, which is associated with an increased risk of cancer. Follow safe administration instructions to minimize radiation exposure to the patient and healthcare providers [see
The recent intake of stable iodine in any form, or the use of thyroid or anti-thyroid drugs will affect the uptake of sodium iodide I 131. Question the patient carefully regarding their exposure to these drugs or procedures involving radiographic contrast media [see
Hypersensitivity reactions including anaphylaxis may occur in patients who receive sodium iodide I 131. Although iodine is not considered an allergen, hypersensitivity reactions may occur in relation with excipients or chemical component of the capsule, such as sodium thiosulfate. Obtain and document an allergy history, particularly a sulfite allergy. Emergency resuscitation equipment and personnel should be immediately available [see
- Lactation: Discontinue breastfeeding.
- Renal Impairment: Increases radiation exposure.
Sodium Iodide I 131 Capsules Diagnostic is contraindicated in pregnancy because fetal exposure can lead to neonatal hypothyroidism, which in some cases is severe and irreversible. Data from the published literature describe reports of neonatal thyroid abnormalities after fetal exposure, including agenesis of the thyroid and hypothyroidism (see
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies are 2-4% and 15-20%, respectively.
A fetus exposed to sodium iodide I 131 can develop neonatal hypothyroidism. Delay in diagnosis of neonatal hypothyroidism after exposure to sodium iodide I 131 in utero can result in severe sequelae such as decreased mental capacity and delayed skeletal maturation. Monitor thyroid function in any infant born after in utero exposure to sodium iodide I 131.
Literature reports of maternal exposures to sodium iodide I 131 at doses of 330-8300 MBq during 4-26 weeks estimated gestational age. There were various adverse pregnancy outcomes; the most common was hypothyroidism in infants and children.
Advise women to discontinue breastfeeding after administration of Sodium Iodide I 131 Capsules Diagnostic. Infant exposure to sodium iodide I 131 via breast milk is expected and may lead to hypothyroidism in the infant because sodium iodide I 131 in breast milk may reach concentrations equal to or greater than concentrations in maternal plasma (see
Published studies show that sodium iodide I 131 is transferred into breast milk and is taken up by the thyroid of the breastfed infant.
Sodium Iodide I 131 is contraindicated in pregnancy because it causes fetal hypothyroidism [see
Obtain a pregnancy test in females of reproductive potential and verify the absence of pregnancy before administering Sodium Iodide I 131 Capsules Diagnostic [see
Safety and efficacy in pediatric patients have not been established. Published reports suggest that the thyroid gland of pediatric patients is more sensitive to the adverse effects of sodium iodide I 131 (e.g., increased risk of radiation absorption).
Clinical experience has not identified differences in safety or effectiveness in geriatric patients compared to younger patients. However, elderly patients are more likely to have decreased renal function and radiation exposure is greater in patients with impaired renal function [see
Radiation exposure following Sodium Iodide I 131 Capsules Diagnostic is greater in patients with impaired renal function compared to patients with normal renal function [see
The following adverse reaction has been described elsewhere in the labeling:
- Hypersensitivity Reactions [see Warnings and Precautions (])
5 WARNINGS AND PRECAUTIONS- Fetal Toxicity – I 131 can cause severe and irreversible hypothyroidism in the neonate. Verify absence of pregnancy before administering the product.
- Radiation Risk – I 131 contributes to patients’s long-term cumulative radiation exposure, which is associated with an increased risk of cancer. Ensure safe handling to minimize radiation exposure.
5.1 Fetal ToxicitySodium Iodide I 131 Capsules Diagnostic is contraindicated in pregnancy because sodium iodide I 131 crosses the placenta and can cause severe and irreversible hypothyroidism in the neonate. Multiple reports in the literature describe neonatal hypothryroidism following in utero exposure to sodium iodide I 131. Some of these cases were severe and irreversible. Verify pregnancy status of females of reproductive potential prior to administering Sodium Iodide I 131 Capsules Diagnostic [see
Use in Specific Populations].5.2 Radiation ExposureSodium Iodide I 131 Capsules Diagnostic contributes to a patient’s overall long-term cumulative radiation exposure, which is associated with an increased risk of cancer. Follow safe administration instructions to minimize radiation exposure to the patient and healthcare providers [see
Dosage and Administration].5.3 Risk of Radioactive Uptake Measurement and Imaging MisinterpretationThe recent intake of stable iodine in any form, or the use of thyroid or anti-thyroid drugs will affect the uptake of sodium iodide I 131. Question the patient carefully regarding their exposure to these drugs or procedures involving radiographic contrast media [see
Drug Interactions].5.4 Hypersensitivity ReactionsHypersensitivity reactions including anaphylaxis may occur in patients who receive sodium iodide I 131. Although iodine is not considered an allergen, hypersensitivity reactions may occur in relation with excipients or chemical component of the capsule, such as sodium thiosulfate. Obtain and document an allergy history, particularly a sulfite allergy. Emergency resuscitation equipment and personnel should be immediately available [see
Adverse Reactions].
The following adverse reactions have been identified during post-approval use from Sodium Iodide I 131 Capsules Diagnostic. Because these reactions are voluntarily reported from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Adverse reactions associated with the administration of Sodium Iodide I 131 Capsules Diagnostic are:
- Gastrointestinal disorders: vomiting, nausea, and diarrhea
- General disorders and administration site conditions: local thyroid swelling
- Immune system disorders: hypersensitivity reactions
- Skin and subcutaneous tissue disorders: itching, rash, hives, and erythema
Certain drugs and iodine-containing foods interfere with the accumulation of radioiodide by the thyroid. Review the patients history, current medications, and recent diagnostic tests prior to the administration of Sodium Iodide I-131 Capsules Diagnostic. Advise patients to maintain a low-iodine diet two weeks prior to radioiodine administration and continue for several days during the uptake or imaging process and to discontinue the following products before they undergo the procedure as shown in Table 3:
Products | Recommended duration of withdrawal |
| Thionamide medications (e.g., propylthiouracil, methimazole carbimazole) | 3 days |
| Multivitamins containing iodide | 10 days |
Natural or synthetic thyroid hormones triiodothyronine thyroxine | 2 weeks 4 weeks |
| Iodine containing foods: iodinized salt, dairy products, egg yolks, seafood, turkey, and liver | 2 weeks |
| Kelp, agar, carrageenan, Lugol solution | 3 weeks |
| Saturated solution of potassium iodide | 3 weeks |
| Topical iodine (e.g., surgical skin preparation) | 3 weeks |
Radiographic contrast agents Water soluble Lipophilic | 2 months 6 months |
| Amiodarone | 6 months |
Iodine is actively transported by the sodium-iodide symporter (NIS) protein, in thyroid follicular cells. Iodide is concentrated in follicular cells up to 50 times higher than in the plasma. Iodide is metabolically oxidized by thyroid peroxidase to iodinium (I+) which in turn iodinates tyrosine residues of thyroglobulin (tri or tetra-iodinated tyrosine). The gamma emission of Iodine I 131 is imaged or counted.