Drug interactions
Levothyroxine + Selpercatinib
Severity: Moderate
Levothyroxine and Selpercatinib: moderate 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
Levothyroxine may be less effective during selpercatinib therapy, potentially leading to hypothyroid symptoms. Thyroid function may need closer follow-up, especially after thyroidectomy in medullary thyroid cancer.
What this interaction means in plain words
Levothyroxine and Selpercatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Levothyroxine belongs to Endocrine; Selpercatinib belongs to Oncology.
Why it happens
Selpercatinib may inhibit peripheral conversion of T4 to T3; the mechanism is not firmly established.
What to do
Monitor TSH and free T3/T4 regularly and adjust levothyroxine; consider adding liothyronine if hypothyroid symptoms persist.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Selpercatinib
Other interactions of Levothyroxine
Frequently asked questions
Can I take Levothyroxine with Selpercatinib?
MediHelp rates the interaction as moderate. Levothyroxine and Selpercatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Levothyroxine may be less effective during selpercatinib therapy, potentially leading to hypothyroid symptoms. Thyroid function may need closer follow-up, especially after thyroidectomy in medullary thyroid cancer.
How serious is the interaction between Levothyroxine and Selpercatinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor TSH and free T3/T4 regularly and adjust levothyroxine; consider adding liothyronine if hypothyroid symptoms persist.
What other medicines interact with Selpercatinib?
MediHelp also lists interactions of Selpercatinib with, for example, Amiodarone, Amisulpride, Amitriptyline. The full list is on the Selpercatinib page.
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