Tirosint

Generic name: Levothyroxine Capsules
Drug class: Thyroid drugs

Medically reviewed by A Ras MD.

What is Tirosint?

Tirosint is a prescription medicine that contains a hormone called levothyroxine which is normally produced by the thyroid gland. Tirosint is used to treat adults and children 6 years of age or older:

to replace or give extra levothyroxine in people whose thyroid does not produce enough of this hormone.
who need surgery and radioiodine therapy to manage a type of thyroid cancer called thyroid-dependent well-differentiated thyroid cancer.

Tirosint should not be used to treat people who are recovering from swelling of the thyroid gland (thyroiditis) and whose bodies do not produce enough levothyroxine for a short time.

Tirosint is unsuitable for children less than 6 years of age or who may be unable to swallow an intact capsule.

Description

TIROSINT (levothyroxine sodium) capsules for oral use contain synthetic L-3,3′,5,5′-tetraiodothyronine sodium salt [levothyroxine (T 4) sodium]. Synthetic T4 is chemically identical to that produced in the human thyroid gland. Levothyroxine (T4) sodium has an empirical formula of C 15H 10I 4NNaO 4 ∙ x H 2O (where x = 5), molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown:

TIROSINT (levothyroxine sodium) capsules are amber-colored, round/biconvex capsules containing a viscous amber-colored liquid.

The inactive ingredients in TIROSINT are gelatin, glycerin and water.

Mechanism of Action

Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins.

The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues.

What is the most important information I should know about Tirosint?

Do not use Tirosint to treat weight problems or weight loss.
Do not take more Tirosint than your doctor prescribes for you to take. Over dosage or taking too much Tirosint may cause life-threatening side effects or death.

Who should not take Tirosint?

Do not take Tirosint:

if your adrenal glands are not working well and you have not been treated for this problem.

What should I tell my healthcare provider before taking Tirosint?

Before you take Tirosint, tell your doctor about all of your medical conditions, including if you:

have or had heart problems.
have or had thyroid nodules.
have kidney or pituitary gland problems.
have any food or drug allergies.
have a low red blood cell count (anemia).
have diabetes.
have weak bones (osteoporosis).
have or had a history of blood clotting problems.
have recently received radiation therapy with iodine (such as I-131).
are pregnant or plan to become pregnant. Tirosint may harm your unborn baby. Your doctor may need to change your Tirosint dose while you are pregnant.
are breastfeeding. Tirosint can pass into your milk. Talk to your doctor about the best way to feed your baby if you take Tirosint.

Tell your doctor about all the medicines you take including prescription and over-the-counter medicines, vitamins, and herbal supplements. Tirosint may affect the way other medicines work, and other medicines may affect how Tirosint works. You can ask your doctor or pharmacist for a list of medicines that interact with Tirosint.

How should I take Tirosint?

Take Tirosint exactly as your doctor tells you to take it.
Your doctor will tell you how much Tirosint to take each day.
Swallow Tirosint capsules whole. Do not cut, crush, or chew Tirosint capsules before swallowing. If you or your child cannot swallow Tirosint capsules whole, tell your doctor. You may need a different medicine.
Your doctor may change your dose, if needed.
Take your dose of Tirosint 1 time each day, 30 minutes to 1 hour before breakfast, on an empty stomach.
Certain medicines can interfere with how Tirosint is absorbed by your body. Take Tirosint:
- at least 4 hours before or after you take medicines that contain calcium carbonate or iron (ferrous sulfate).
- at least 4 hours before you take medicines that contain bile acid sequestrants or ion exchange resins.
Know the medicines that you take. Ask your doctor or pharmacist for a list of these medicines, if you are not sure.
Certain foods including soybean flour, cotton seed meal, walnuts, and dietary fiber can affect your treatment and dose of Tirosint. Talk to your doctor if you eat or drink these foods.
Do not remove Tirosint capsules from the original blister package until you are ready to take them.
Your doctor should do certain blood tests while you are taking Tirosint and may change your daily dose of Tirosint as needed. You should not stop taking Tirosint or change your dose unless your doctor tells you to.
It may take weeks before you notice your symptoms getting better. Keep using this medicine even if you feel well.
If you take too much Tirosint or overdose, call your doctor or poison control center at 1-800-222-1222, or go to the nearest hospital emergency room right away.

What are the possible side effects of Tirosint?

Tirosint may cause serious side effects, including:

heart problems. You may experience an increased heart rate, chest pain and irregular heartbeat. Your risk of developing heart problems may be greater if you are elderly, have heart problems, or if you take too much Tirosint. Your doctor may reduce your dose or stop treatment with Tirosint for a while if you develop heart problems.
worsening diabetic control. If you are diabetic, it may be harder to control your blood sugar levels causing hyperglycemia while taking Tirosint. Check your blood sugar levels closely after starting, changing, or stopping treatment with Tirosint. Your doctor may have to change your diabetes treatment plan.
weak or brittle bones. Your risk of developing weak or brittle bones may be greater if you are post-menopausal or you take too much Tirosint.

The most common side effects of Tirosint include:

irregular heartbeat
chest pain
shortness of breath
leg cramps
headache
nervousness
hives or skin rash
irritability
sleep problems (insomnia)
tremors
muscle weakness
change in appetite
weight loss
vomiting
diarrhea
sweating a lot
heat intolerance
fever
changes in menstrual period

Other side effects may include:

partial hair loss during the first months of treatment with Tirosint. This usually lasts a short period of time (temporary).

These are not all the possible side effects of Tirosint. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

You may also report side effects to IBSA Pharma Inc. at 1-800-587-3513 or www.fda.gov/medwatch.

General information about the safe and effective use of Tirosint

Medicines are sometimes prescribed for purposes other than those listed in a Patient Information leaflet. Do not use Tirosint for a condition for which it was not prescribed. Do not give Tirosint to other people, even if they have the same symptoms that you have. It may harm them. You can ask your pharmacist or doctor for information about Tirosint that is written for health professionals.