Drug interactions
Propylthiouracil + Sodium iodide i-131
Severity: Major
Propylthiouracil and Sodium iodide i-131: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Antithyroid drugs reduce thyroid uptake of radioiodine, so the therapeutic radiation dose delivered to the gland may be inadequate. Treatment failure or the need for repeat dosing may result.
What this interaction means in plain words
Propylthiouracil and Sodium iodide i-131 can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Propylthiouracil inhibits thyroid peroxidase and hormone synthesis, which lowers thyroidal radioiodine uptake and retention.
What to do
Stop propylthiouracil several days before I-131 administration, typically 3 to 4 days per labeling, and do not give them together. Restart afterward according to the treating specialist's plan and monitor thyroid function.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Propylthiouracil
Frequently asked questions
Can I take Propylthiouracil with Sodium iodide i-131?
MediHelp rates the interaction as major. Propylthiouracil and Sodium iodide i-131 can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Antithyroid drugs reduce thyroid uptake of radioiodine, so the therapeutic radiation dose delivered to the gland may be inadequate. Treatment failure or the need for repeat dosing may result.
How serious is the interaction between Propylthiouracil and Sodium iodide i-131?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Stop propylthiouracil several days before I-131 administration, typically 3 to 4 days per labeling, and do not give them together. Restart afterward according to the treating specialist's plan and monitor thyroid function.
What other medicines interact with Propylthiouracil?
MediHelp also lists interactions of Propylthiouracil with, for example, Carbamazepine, Clozapine, Methimazole. The full list is on the Propylthiouracil page.
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