Best answer: What does levothyroxine do to INR?

Levothyroxine has a long half-life, and it generally takes weeks for the patient to become euthyroid, thus increasing the chance that an increased INR would be detected. Moreover, elderly patients are often dosed conservatively, which could have prolonged the process even more.

Does levothyroxine affect INR?

Background: Drug interaction references report that initiation of levothyroxine potentiates the effects of warfarin, and recommend more frequent International Normalized Ratio (INR) monitoring, but the mechanism is not well understood.

Does levothyroxine interfere with warfarin?

warfarin levothyroxine

Increasing your thyroid hormone levels can sensitize you to the effects of warfarin, which may increase your risk of bleeding. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications.

Does hypothyroidism decrease INR?

To help ensure safe and effective therapy, frequent monitoring of the INR is required. Hypothyroidism decreases the effect of warfarin likely by reducing the catabolism of vitamin K dependent clotting factors. This effect is documented to have marked clinical significance (Table).

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Is levothyroxine a blood thinner?

No, it’s not a blood thinner, an antidepressant or a cholesterol-lowering drug—it’s Synthroid, a medication used to treat underactive thyroid (hypothyroidism).

What drugs interfere with levothyroxine?

A number of drugs have been shown to impair the absorption of levothyroxine; these drugs include calcium carbonate, aluminum- containing antacids, sucralfate, iron supplements, cholestyramine, sevelamer, and, possibly, ciprofloxacin, raloxifene, and orlistat.

Can blood thinners affect thyroid?

Patients taking warfarin and thyroid hormones concurrently need to be advised that any change in their thyroid may result in alteration in their anticoagulant response. This change would include any change in their thyroid therapy, including discontinuation or changes in doses.

Can warfarin cause hypothyroidism?

The authors found that the effects of liver disease, hyperthyroidism and hypothyroidism on the response to warfarin are well documented in the literature. The liver is the principal site of synthesis of plasma proteins and clotting factors.

What are the side effects of levothyroxine?

Common side effects may include:

  • muscle weakness;
  • headache, leg cramps;
  • nervousness, trouble sleeping;
  • diarrhea; or.
  • skin rash, partial hair loss.


What are the side effects of warfarin?

What are the side effects of warfarin?

  • Severe bleeding, including heavier than normal menstrual bleeding.
  • Red or brown urine.
  • Black or bloody stool.
  • Severe headache or stomach pain.
  • Joint pain, discomfort or swelling, especially after an injury.
  • Vomiting of blood or material that looks like coffee grounds.
  • Coughing up blood.

How does hyperthyroidism affect INR?

Hyperthyroidism causes an increased sensitivity to the anticoagulant effects of warfarin. This may lead to a supratherapeutic INR and possibly bleeding if warfarin dosages are not adjusted cautiously.


What drugs can affect the thyroid?

Which drugs can cause thyroid dysfunction and should this be treated?

  • Amiodarone. Amiodarone can cause transient alterations of thyroid function tests, as well as overt hypothyroidism or hyperthyroidism. …
  • Lithium. …
  • Interferons (IFN) …
  • Tyrosine Kinase Inhibitors (TKIs) …
  • Alemtuzumab. …
  • Iodine-containing medications and agents.

Which clotting factors does warfarin affect?

Warfarin is a vitamin K antagonist and inhibits synthesis of vitamin K–dependent clotting factors (II, VII, IX, X) and proteins C and S.

Can you survive without thyroid medication?

The short answer is yes. People can live full, long lives without a thyroid (or with an underactive thyroid) if they take medication to replace the absence of thyroid hormones in their body.

How do you know when your thyroid medicine needs adjusting?

General joint and muscle pains are common when hypothyroidism is not sufficiently treated, and your dosage of thyroid hormone needs to be increased. Joint and muscle weakness and pain, especially in the arms and legs, can be evidence that you need an increased dose of antithyroid drugs for your hyperthyroidism.

What are the long term side effects of levothyroxine?

If the levothyroxine dose is too high, serious side effects can occur, mainly affecting the heart, and include (DailyMed, 2019):

  • Irregular heartbeat (arrhythmia)
  • High blood pressure.
  • Heart failure.
  • Chest pain (angina)
  • Heart attack (myocardial infarction)
  • Cardiac arrest (heart stops working)


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