Levothyroxine with Lanthanum Carbonate Interaction Details

Brand Names Associated with Levothyroxine

Brand Names Associated with Lanthanum Carbonate

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Nov 05, 2023

Interaction Effect

Decreased levothyroxine exposure and serum thyroxine (T4) level

Interaction Summary

Concurrent use of lanthanum carbonate and levothyroxine results in decreased absorption of levothyroxine. In one study, concurrent administration of lanthanum carbonate with levothyroxine significantly reduced the exposure of levothyroxine by about 40%. Patients should be monitored for an adequate response to levothyroxine therapy and the levothyroxine dose should be adjusted appropriately. Administer levothyroxine at least 4 hours apart from lanthanum .

Severity

Moderate

Onset

Rapid

Evidence

Probable

How To Manage Interaction

Concomitant use of lanthanum carbonate and levothyroxine causes a reduction in the absorption of levothyroxine. If both medications are administered concurrently, monitor patients for an adequate response to levothyroxine therapy (T4 and TSH levels) and adjust the levothyroxine dose appropriately. Administer levothyroxine at least 4 hours apart from lanthanum .

Mechanism Of Interaction

Reduced absorption of levothyroxine by binding with lanthanum carbonate

Literature Reports

A) There was a reduction in the exposure of levothyroxine when concomitantly administered with lanthanum carbonate according to a study of 6 euthyroid healthy volunteers. Patients age 27 to 40 years, with normal serum thyroxine (T4) and thyrotropin (TSH) levels at baseline were administered levothyroxine sodium 1 mg orally at visit 1, followed by levothyroxine plus colesevelam 3.75 g or lanthanum carbonate 500 mg at 2 subsequent study visits at least 3 weeks apart. The mean increase of T4 AUC when levothyroxine was given alone was 1692 +/-183.5 mcg x min/dL, but the increase was blunted when concomitant lanthanum carbonate was administered (982.5 +/- 172.3 mcg x min/dL; 59.1% of the area of levothyroxine alone) .

Levothyroxine Overview

• Levothyroxine is used to treat hypothyroidism (condition where the thyroid gland does not produce enough thyroid hormone). It is also used with surgery and radioactive iodine therapy to treat thyroid cancer. Levothyroxine is in a class of medications called hormones. It works by replacing thyroid hormone that is normally produced by the body.

• Without thyroid hormone, your body cannot function properly, which may result in poor growth, slow speech, lack of energy, excessive tiredness, constipation, weight gain, hair loss, dry, thick skin, increased sensitivity to cold, joint and muscle pain, heavy or irregular menstrual periods, and depression. When taken correctly, levothyroxine reverses these symptoms.

Lanthanum Carbonate Overview

• Lanthanum is used to reduce blood levels of phosphate in people with kidney disease. High levels of phosphate in the blood can cause bone problems. Lanthanum is in a clsas of medications called phosphate binders. It binds phosphorus that you get from foods in your diet and prevents it from being absorbed into your blood stream.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.