Thyconvi: Uses, Side Effects and Dosage

Serious warnings and precautions box

What THYCONVI is used for:

• To treat hypothyroidism. This condition happens when the thyroid gland does not produce enough of the hormone thyroxine.
• To suppress Thyroid-stimulating hormone (TSH) in the treatment of certain types of thyroid cancer. It acts to lower or block TSH. For these patients, THYCONVI is given in combination with surgery and radioactive iodine therapy.

How THYCONVI works:

THYCONVI contains levothyroxine sodium, which is the man-made form of thyroxine. Thyroxine is the hormone produced by a normally functioning thyroid gland.

In hypothyroidism, the thyroid gland does not produce enough thyroxine. This causes levels of thyroid hormones in the blood to drop and leads to changes in metabolism and the proper function of many organs. THYCONVI helps to replace or supplement thyroxine in the body.

Thyroid hormone replacement is usually taken for life.

The ingredients in THYCONVI are:

Medicinal ingredients: Levothyroxine sodium

Non-medicinal ingredients: Citric acid monohydrate, glycerol, purified water, sodium hydroxide, sodium methyl parahydroxybenzoate

THYCONVI comes in the following dosage form:

Oral solution; 20 mcg / mL levothyroxine sodium

Do not use THYCONVI if:

• you are allergic to thyroid hormones or any other ingredients in THYCONVI;
• you have thyrotoxicosis. This is also known as an overactive thyroid gland;

• you have recently had:

  • a heart attack,
  • acute myocarditis (inflammation/swelling of the heart muscle), or
  • acute pancarditis (general inflammation/swelling of the heart);
• you have uncorrected or untreated adrenal insufficiency. This is a condition where your adrenal glands do not make enough of the hormone cortisol;
• you are pregnant and also using medicines to treat an overactive thyroid.

To help avoid side effects and ensure proper use, talk to your healthcare professional before you take THYCONVI. Talk about any health conditions or problems you may have, including if you:

• are pregnant or plan to become pregnant while taking THYCONVI. This is because your dose will likely need to be increased;
• have any heart problems, whether or not you have received treatment for them. This includes a history of heart attack, heart disease or hardening of the arteries;

• have other medical problems, whether or not you have received treatment for them, including:

  • high blood pressure,
  • osteoporosis,
  • blood clotting disorders,
  • a history of thyroid, adrenal and/or pituitary gland problems;
• have signs or symptoms of psychotic disorders;
• are switching from a different brand of levothyroxine;
• are a woman on long-term levothyroxine sodium therapy. This is because you may experience decrease in bone density;
• develop myxedema coma, a medical emergency, which is a type of severe hypothyroidism;
• have malabsorption syndromes (inability to absorb nutrients, vitamins, and minerals from the intestinal tract into the bloodstream), since THYCONVI absorption will be decreased;
• have thyroid gland autonomy. This is a condition where the thyroid gland works on its own without signals from other parts of the body.

Other warnings you should know about:

Diabetes: If you are receiving treatment for diabetes, the dose of your diabetes medication may need to be changed after starting THYCONVI. Monitor sugar levels in your blood and urine as directed by your healthcare professional. Report any changes to your healthcare professional right away.

Surgery: Tell your healthcare professional about any surgery (including dental surgery) you are planning. Before the surgery, tell your dentist or surgeon that you are taking THYCONVI.

Breastfeeding: Small amounts of thyroid hormones will pass into your breast milk. Regardless, you can continue to take THYCONVI while you are breastfeeding. In fact, you should not stop your treatment, as normal levels of thyroid hormones will help maintain milk production.

Blood tests: You will need to have regular blood tests while you are receiving THYCONVI. These will be done to make sure that you are receiving the correct dose. As well, the results of these tests will help your doctor to know how your treatment is affecting your blood.

If you are pregnant, you will have blood tests done about every 4 weeks for the first half of your pregnancy. These tests will then be done at least once per week between weeks 26 and 32 of your pregnancy. Based on the results of these blood tests, your dose of THYCONVI may be changed.

Taking a biotin supplement may affect blood tests done to check thyroid hormone levels (called thyroid function tests). Tell your healthcare professional if you are taking biotin. It may lead to false test results. Your healthcare professional may ask you to stop taking biotin for at least 2 days before you have a thyroid function test.

Driving and using machines: THYCONVI may affect your ability to drive and use machines. Before engaging in tasks that require special attention, wait until you know how THYCONVI affects you.

Glycerol: THYCONVI contains glycerol, which may cause gastrointestinal irritation including vomiting, diarrhea and headache. This is most likely to affect babies who are newborn to about 3 months of age. Your healthcare professional will monitor you closely for signs and symptoms of gastrointestinal irritation.

Premature babies with very low birth weight: Blood pressure may be monitored regularly when levothyroxine treatment is started. This is because levothyroxine can cause a fast drop in blood pressure (known as circulatory collapse).

Tell your healthcare professional about all the medicines you take, including any drugs, vitamins, minerals, natural supplements or alternative medicines.

The following may interact with THYCONVI:

• Nutritional supplements such as:

  • biotin (vitamin B7, vitamin H; including for hair and nail)
  • calcium carbonate
  • ferrous sulfate
  • vitamin B3 (niacin / nicotinic acid)

• Medicines used to treat heart problems including high blood pressure such as:

  • digitalis glycosides (e.g. digoxin)
  • beta blockers like propranolol, atenolol, and metoprolol
  • blood thinners like warfarin and heparin
  • amiodarone
  • nitroprusside
  • diuretics like furosemide
• Medicines to treat diabetes including insulin, tolbutamide and other medicines to lower blood sugar levels

• Medicines used to treat digestion problems such as:

  • antacids that contain aluminium and magnesium (e.g. aluminium and magnesium hydroxides, simethicone)
  • proton pump inhibitors
  • metoclopramide
  • sucralfate

• Medicines used to lower high cholesterol such as:

  • colestipol
  • cholestyramine
  • lovastatin

• Medicines to lower levels of phosphorus in the blood such as:

  • polystyrene sulfonate
  • sevelamer
  • lanthanum carbonate

• Medicines used to treat mental health problems and seizures such as:

  • antidepressants like sertraline, maprotiline, amitriptyline, St. John’s Wort
  • lithium
  • perphenazine
  • carbamazepine
  • phenytoin
  • diazepam
  • methadone, heroin
  • phenobarbital
  • aminoglutethimide
  • hydantoins

• Medicines used to treat some cancers such as:

  • tyrosine kinase inhibitors like imatinib and sunitinib
  • tamoxifen
  • 5-flurouracil
  • Mitotane
  • Mercaptopurine
  • Octreotide
  • Interferon alpha (IFN-a)
  • Interleukin-2
• Medicines used for weight loss including orlistat and other diet medicines.

• Medicines used to treat inflammatory conditions such as:

  • glucocorticoids (including the corticosteroids dexamethasone and prednisone)
  • non-steroidal anti-inflammatory drugs (NSAIDs) like fenamates, phenylbutazone, and salicylates
• Iodide, which is used for imaging like x-rays and CT scans
• Medicines for asthma or other breathing problems
• Medicines for colds, sinus problems, hay fever or other allergies (including nose drops or sprays)
• A medicine to treat Parkinson’s disease and restless leg syndrome called dopamine

• Medicines to treat bacterial, viral or fungal infections such as:

  • a medicine to treat HIV and AIDS called ritonavir
  • medicines to treat tuberculosis such as para-aminosalicylate, ethionamide
  • ciprofloxacin
  • sulfonamides
  • rifampin
  • resorcinol

• Hormones such as

  • estrogens that are taken by mouth including birth control pills
  • growth hormones such as somatotropin
  • muscle building hormones including anabolic steroids

• Other medicines used to treat thyroid problems such as:

  • methimazole or carbimazole
  • propylthiouracil (PTU)

Some medicines or supplements may interfere with any blood tests done to determine thyroid hormone levels (thyroid function tests). It is important to inform your healthcare professional of all medicines or supplements you are taking before and at the time of blood tests.

Eating certain foods such as soybean flour, soybean infant formula, cotton seed, walnuts, orange juice fortified with calcium and dietary fiber may decrease absorption of levothyroxine. You may require a change in the dose.

How to take THYCONVI:

• Exactly as your healthcare professional tells you.
• Take your dose once per day at the same time every day.

• Take your dose on an empty stomach, 30 minutes to 1 hour before breakfast.

• Food and drink can affect how your body absorbs THYCONVI®. For this reason, if you do take your dose with food or drink, be sure to take it this way each time. You must be consistent with how you take your dose.
• If you are using other medicines, your healthcare professional may recommend that you take THYCONVI 4 hours before or 4 hours after these other medicines.
• Once you have started THYCONVI, it may take several weeks before you notice an improvement in symptoms.
• Take THYCONVI by mouth. Only use the oral dosing syringe provided by the pharmacy to measure and give your dose. Do not use a household teaspoon or tablespoon. The oral dosing syringe is used to measure your dose to the correct marking. For example, if your dose is 50 mcg, the corresponding volume is 2.5 mL.
• Pay attention when measuring a small dose or a dose for a child.
• Always measure the exact dose of THYCONVI that your healthcare professional has indicated.

Usual dose:

The usual dose of THYCONVI is different for everyone. Your healthcare professional will decide on the dose that is right for you. Your dose will depend on:

• your age,
• your weight,
• the type of thyroid condition you have,
• how well your heart and blood vessels are working,
• any other illnesses that you have (including if you are pregnant),
• other medications you are taking,
• how long you have had symptoms of thyroid problems, and
• how severe your symptoms are.

You are likely to start treatment at a lower dose. Your dose may be increased a little at a time to prevent side effects.

A child’s dose will change as they grow and get older.

Do not change the amount of THYCONVI you take or how often you take it, unless your healthcare professional tells you to.

Do not stop taking THYCONVI without first talking to your healthcare professional.

Overdose:

You may not experience symptoms of an overdose until several days after taking too much THYCONVI.

Signs and symptoms of overdose may include weight loss, increased appetite, heart palpitations (fast or irregular beating of the heart), nervousness, diarrhea, abdominal cramps, sweating, fast heartbeat, fever, changes in period bleeding, convulsions and seizures (fits). Coma and death are also possible.

Missed dose:

If you miss a dose of THYCONVI, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your next scheduled dose. Go back to the regular dosing schedule. Do not take two doses at the same time. If you miss more than two doses, contact your healthcare professional.

Possible side effects from using THYCONVI:

These are not all the possible side effects you may have when taking THYCONVI. If you experience any side effects not listed here, tell your healthcare professional.

• fever, flushing and excessive sweating
• restlessness, nervousness, anxiety, rapid changes in emotion
• trouble sleeping
• temporary hair loss
• diarrhea, vomiting, nausea, stomach cramps
• changes in menstrual cycle, trouble having a child (impaired fertility)
• fatigue
• headache
• muscle weakness, tremors
• reduced adult height due to early closure of growth plates in bones
• change in appetite, weight gain or loss

THYCONVI can cause abnormal test results. Your healthcare professional will decide when to perform blood tests and other diagnostic tests and will interpret the results.

Serious side effects and what to do about them

If you have a troublesome symptom or side effect that is not listed here or becomes bad enough to interfere with your daily activities, tell your healthcare professional.

Reporting side effects

Storage:

Store THYCONVI at room temperature (15 to 25°C) in the original package. Protect THYCONVI from light.

After first opening of the bottle, use within 8 weeks.

Any leftover solution in the bottle must be properly disposed of according to your local guidelines. Ask your healthcare professional how best to do this.

Do not take THYCONVI after the expiry date shown on the label.

Keep out of reach and sight of children.

If you want more information about THYCONVI:

• Talk to your healthcare professional
• Find the full product monograph that is prepared for healthcare professionals and includes the Patient Medication Information by visiting the Health Canada Drug Product Database website (https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-product-database.html); the manufacturer’s website www.thyconvi.com; or by calling 1-888-439-0013.

Date of Authorization: 2026-08-26