Tirosint Drug Interactions: What You Need to Know

If you take Tirosint for hypothyroidism, you need to know that it interacts with a surprising number of common medications, supplements, and even foods. Some interactions reduce how well Tirosint works. Others can make your other medications stronger or weaker.

This guide covers the major and moderate drug interactions, supplements and OTC products to watch, food interactions, and exactly what to tell your doctor to stay safe.

How Drug Interactions With Tirosint Work

Drug interactions with Tirosint generally happen in two ways:

1. Absorption interference — Something you take binds to the Levothyroxine in Tirosint or changes your stomach acid, preventing your body from absorbing the full dose. This is the most common type of interaction.
2. Metabolism changes — Another medication speeds up or slows down how fast your body breaks down thyroid hormones, effectively changing your dose without changing what you swallow.

One advantage of Tirosint's gel capsule formulation is that its liquid center with minimal inactive ingredients may be less susceptible to some absorption issues compared to Levothyroxine tablets. However, the interactions below still apply — timing and awareness are essential.

Medications That Interact With Tirosint

Major Interactions (Separate or Monitor Closely)

These medications have well-documented interactions with Tirosint and require either dose separation (usually 4 hours) or close monitoring:

• Calcium Carbonate (Tums, Caltrate, Os-Cal) — Binds to Levothyroxine and significantly reduces absorption. Separate by at least 4 hours.
• Iron Supplements (Ferrous Sulfate, Ferrous Gluconate) — Also binds to Levothyroxine. Separate by at least 4 hours.
• Cholestyramine (Questran) and Colestipol (Colestid) — Bile acid sequestrants that bind thyroid hormones in the gut. Separate by at least 4 hours.
• Sucralfate (Carafate) — Coats the stomach lining and can trap Levothyroxine. Separate by at least 4 hours.
• Aluminum-Containing Antacids (Maalox, Mylanta) — Reduce absorption. Separate by at least 4 hours.
• Proton Pump Inhibitors — Omeprazole (Prilosec), Esomeprazole (Nexium), Lansoprazole (Prevacid), Pantoprazole (Protonix) — Reduce stomach acid, which may decrease Levothyroxine absorption. Your doctor may need to increase your Tirosint dose if you take a PPI regularly. Note: Tirosint's gel capsule may be less affected by PPIs than tablets.
• Warfarin (Coumadin) — Levothyroxine increases the blood-thinning effect of Warfarin. Your doctor should monitor your INR closely when starting or changing Tirosint doses.
• Carbamazepine (Tegretol), Phenytoin (Dilantin), Rifampin (Rifadin) — These medications speed up the metabolism of thyroid hormones, meaning your body breaks down Tirosint faster. Your doctor may need to increase your dose.

Moderate Interactions (May Need Dose Adjustment)

• Estrogen-Containing Oral Contraceptives and Hormone Replacement Therapy — Estrogen increases thyroid-binding globulin (TBG), which can lower the amount of free thyroid hormone available. Your Tirosint dose may need to be increased.
• Sertraline (Zoloft) — May decrease T4 levels. Monitor thyroid function if starting or stopping Sertraline.
• Digoxin (Lanoxin) — Thyroid hormone replacement may reduce Digoxin levels. Your doctor should monitor Digoxin levels.
• Diabetes Medications — Insulin and oral medications like Metformin may need dose adjustments when thyroid levels change. Correcting hypothyroidism can alter blood sugar control.
• Lithium (Lithobid) — Can cause hypothyroidism on its own and may interfere with thyroid function. Close monitoring required.

Supplements and OTC Products to Watch

Many common supplements interact with Tirosint:

• Calcium supplements — Including calcium-fortified vitamins. Separate by 4 hours.
• Iron-containing multivitamins — The iron content can reduce absorption. Separate by 4 hours.
• Magnesium supplements — May reduce absorption. Separate by 4 hours.
• Biotin (Vitamin B7) — Does not affect Tirosint absorption, but high-dose Biotin can interfere with thyroid lab tests, causing falsely abnormal TSH and T4 results. Stop Biotin 2-3 days before thyroid blood work.

General rule: Take Tirosint by itself, 30-60 minutes before breakfast, and save all supplements for at least 4 hours later.

Food and Drink Interactions

What you eat and drink can also affect how well Tirosint works:

• Soy products (tofu, soy milk, edamame, soybean flour) — May decrease Levothyroxine absorption. If you eat soy regularly, your doctor may need to adjust your dose.
• High-fiber foods — Excessive dietary fiber can decrease absorption. Maintain a consistent fiber intake rather than dramatically changing it.
• Walnuts — May decrease absorption. Separate from Tirosint by several hours.
• Grapefruit juice — May decrease absorption of Levothyroxine.
• Coffee — Can decrease absorption if taken at the same time. However, Tirosint's gel capsule formulation may be less affected by coffee than tablets. Still, it's best to wait at least 30 minutes after taking Tirosint before having coffee.
• Calcium-fortified foods (orange juice, cereals) — Treat these like calcium supplements and separate by 4 hours.

What to Tell Your Doctor

To help your doctor manage your Tirosint safely, always tell them about:

• All prescription medications you take — including birth control, blood thinners, seizure medications, antacids, and diabetes drugs
• All supplements and vitamins — especially calcium, iron, magnesium, and Biotin
• OTC medications — including antacids like Tums, PPIs like Prilosec, and stomach medications like Carafate
• Dietary changes — starting a high-soy diet, going high-fiber, or significantly changing eating habits
• New medications — whenever another doctor prescribes something new, mention that you take Tirosint

It's also a good idea to remind your pharmacist that you take Tirosint every time you pick up a new medication. Pharmacists are trained to catch drug interactions and can flag potential problems.

Final Thoughts

Tirosint is a safe and effective thyroid medication, but like all Levothyroxine products, it has meaningful interactions with common medications, supplements, and foods. The key takeaway: take Tirosint by itself on an empty stomach, and separate it from calcium, iron, antacids, and most supplements by at least 4 hours.

If you're taking any of the medications listed above, talk to your doctor about timing and potential dose adjustments. And if you need to fill your Tirosint prescription, Medfinder can help you find a pharmacy with it in stock.