Drug interactions
Levothyroxine + Protriptyline
Severity: Moderate
Levothyroxine and Protriptyline: 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
Thyroid hormone can increase sensitivity to catecholamines, and tricyclic antidepressants potentiate adrenergic effects. Together they may increase the risk of tachycardia, arrhythmias and CNS stimulation, particularly when thyroid replacement is excessive.
What this interaction means in plain words
Levothyroxine and Protriptyline 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.
Why it happens
Additive pharmacodynamic effect: thyroid hormone increases adrenergic receptor sensitivity while tricyclics block catecholamine reuptake and have antimuscarinic and proarrhythmic effects.
What to do
Monitor heart rate, rhythm and mental status, especially when starting or increasing levothyroxine. Keep thyroid replacement at the lowest effective dose and consider an ECG in patients with cardiac disease.
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 Levothyroxine
Frequently asked questions
Can I take Levothyroxine with Protriptyline?
MediHelp rates the interaction as moderate. Levothyroxine and Protriptyline 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. Thyroid hormone can increase sensitivity to catecholamines, and tricyclic antidepressants potentiate adrenergic effects. Together they may increase the risk of tachycardia, arrhythmias and CNS stimulation, particularly when thyroid replacement is excessive.
How serious is the interaction between Levothyroxine and Protriptyline?
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 heart rate, rhythm and mental status, especially when starting or increasing levothyroxine. Keep thyroid replacement at the lowest effective dose and consider an ECG in patients with cardiac disease.
What other medicines interact with Levothyroxine?
MediHelp also lists interactions of Levothyroxine with, for example, Cholestyramine, Sodium iodide i-131, Tiratricol. The full list is on the Levothyroxine page.
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