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Drugs reference index «Synthroid»

Synthroid


Synthroid

Generic Name: levothyroxine (Oral route)

lee-voe-thye-ROX-een

Intramuscular routePowder for Solution

Drugs with thyroid hormone activity, alone or together with other therapeutic agents, have been used for the treatment of obesity. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

Intravenous routePowder for Solution

Drugs with thyroid hormone activity, alone or together with other therapeutic agents, have been used for the treatment of obesity. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

Oral routeTablet

Thyroid hormones, including levothyroxine, either alone or with other therapeutic agents, should not be used for the treatment of obesity or weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

Thyroid hormones, including levothyroxine, should not be used either alone or with other therapeutic agents for the treatment of obesity or weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects .

Commonly used brand name(s):

In the U.S.

  • Levothroid
  • Levoxyl
  • Synthroid
  • Unithroid

Available Dosage Forms:

  • Tablet

Therapeutic Class: Thyroid Supplement

Uses For Synthroid

Levothyroxine is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Levothyroxine is also used to help decrease the size of enlarged thyroid glands (known as goiter) and to treat thyroid cancer.

This medicine is available only with your doctor's prescription.

Importance of Diet

Certain foods may affect how levothyroxine works in the body. Dosage adjustment may be needed when you have consumed any of the following:

  • Cotton seed meal.
  • Dietary fiber.
  • Soybean flour (infant formula).
  • Walnuts.

Before Using Synthroid

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of levothyroxine in children.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of levothyroxine in the elderly. However, elderly patients are more likely to have age-related heart and blood vessel problems, which may require caution in patients receiving levothyroxine.

Pregnancy

Pregnancy CategoryExplanation
All TrimestersAAdequate studies in pregnant women have not shown an increased risk of fetal abnormalities.

Breast Feeding

Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.

Interactions with Medicines

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acenocoumarol
  • Aluminum Carbonate, Basic
  • Aluminum Hydroxide
  • Aluminum Phosphate
  • Anisindione
  • Calcium Carbonate
  • Cholestyramine
  • Chromium
  • Colesevelam
  • Conjugated Estrogens
  • Dicumarol
  • Dihydroxyaluminum Aminoacetate
  • Dihydroxyaluminum Sodium Carbonate
  • Eltrombopag
  • Esterified Estrogens
  • Estradiol
  • Estriol
  • Estrone
  • Estropipate
  • Imatinib
  • Iron
  • Kelp
  • Lanthanum Carbonate
  • Lopinavir
  • Magaldrate
  • Magnesium Carbonate
  • Magnesium Hydroxide
  • Magnesium Oxide
  • Magnesium Trisilicate
  • Phenindione
  • Phenprocoumon
  • Phenytoin
  • Rifampin
  • Rifapentine
  • Ritonavir
  • Sevelamer
  • Simvastatin
  • Sodium Polystyrene Sulfonate
  • Soybean
  • Warfarin

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Using this medicine with any of the following may cause an increased risk of certain side effects but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.

  • Enteral Nutrition

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Adrenal insufficiency, untreated or
  • Heart attack or
  • Thyrotoxicosis (overactive thyroid), untreated—This medicine should NOT be used in patients with these conditions.
  • Anemia or
  • Clotting disorders or
  • Diabetes mellitus or
  • Heart disease, history of or
  • Osteoporosis or
  • Pituitary gland problems or
  • Other adrenal gland problems—Use with caution. Dosage adjustment may be needed.
  • Nontoxic diffuse goiter, history of or
  • Nodular thyroid disease, history of—Use with caution. Careful monitoring of thyroid function and clinical condition is needed to prevent hyperthyroidism.

Proper Use of levothyroxine

This section provides information on the proper use of a number of products that contain levothyroxine. It may not be specific to Synthroid. Please read with care.

This medicine usually needs to be taken for the rest of your life. Do not stop taking this medicine or change your doses without first checking with your doctor. It may take several weeks before you start to notice an improvement in your symptoms.

It is best to take this medicine on an empty stomach. Take it with a full glass of water at least 30 minutes to 1 hour before eating breakfast.

This medicine should be taken at least 4 hours before or 4 hours after other medicines that may interfere with absorption (e.g., antacids, iron and calcium supplements, orlistat).

For infants and children who cannot swallow the tablet form, the tablet can be crushed and mixed with a small amount of water (5 to 10 milliliters [mL] or 1 to 2 teaspoonfuls). You may use a spoon or dropper to give the mixture.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablet):
    • For the treatment of hypothyroidism:
      • Older adults—The dose is based on body weight and must be determined by your doctor. The usual dose is less than 1 microgram (mcg) per kilogram (kg) per day.
      • Adults and teenagers—The dose is based on body weight and must be determined by your doctor. The usual dose is 1.7 micrograms (mcg) per kilogram (kg) per day.
      • Children 0 to 3 months of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 10 to 15 mcg per kg per day.
      • Children 3 to 6 months of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 8 to 10 mcg per kg per day.
      • Children 6 to 12 months of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 6 to 8 mcg per kg per day.
      • Children 1 to 5 years of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 5 to 6 mcg per kg per day.
      • Children 6 to 12 years of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 4 to 5 mcg per kg per day.
      • Children over 12 years of age—The dose is based on body weight and must be determined by your doctor. The usual dose is 2 to 3 mcg per kg per day.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Precautions While Using Synthroid

It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Blood and urine tests will be needed to check for unwanted effects.

Levothyroxine should not be used for the treatment of obesity or for the purpose of losing weight. This medicine is ineffective for weight reduction and when taken in larger amount, it may cause more serious medical conditions.

Hypothyroidism can sometimes cause infertility in men and women. Levothyroxine should not be used for the treatment of infertility unless it is caused by hypothyroidism.

For patients with diabetes, it is very important that you keep track of your blood or urine sugar levels as instructed by your doctor. Check with your doctor immediately if you notice any changes in your sugar levels.

If you think you have become pregnant while using the medicine, tell your doctor right away. You may need a larger dose of levothyroxine while you are pregnant.

Using this medicine for a long period of time in women may cause bone loss, which could lead to osteoporosis. Talk with your doctor if you have questions or concerns about this.

Call your doctor right away if you start to have rapid or irregular heartbeat, chest pain, shortness of breath, leg cramps, headache, nervousness, irritability, sleeplessness, tremors, change in appetite, weight gain or loss, vomiting, diarrhea, excessive sweating, heat intolerance, fever, changes in menstrual periods, hives or skin rash, or any other unusual medical condition.

Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before having surgery or medical tests.

A temporary loss of hair may occur during the first few months of levothyroxine therapy. Ask your doctor about this if you have any concerns.

Synthroid Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Less common
  • Blurred or double vision
  • change in appetite
  • chest pain or discomfort
  • decreased bone mineral density
  • decreased urine output
  • diarrhea
  • difficult or labored breathing
  • difficulty in moving
  • difficulty in swallowing
  • dilated neck veins
  • dizziness
  • extreme fatigue
  • eye pain
  • fainting
  • fast, slow, irregular, pounding, or racing heartbeat or pulse
  • feeling of discomfort
  • fever
  • heat intolerance
  • hives or welts
  • increased blood pressure
  • increased pulse
  • inflammation of joints
  • irregular breathing
  • irritability
  • lack or slowing of normal growth in children
  • large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • limp pain in hip or knee
  • liver function abnormalities
  • menstrual changes
  • muscle aches, pain, or stiffness
  • nausea
  • nervousness
  • no blood pressure or pulse
  • pain in joints
  • pain or discomfort in arms, jaw, back, or neck
  • severe headache
  • shortness of breath
  • skin itching, rash, or redness
  • sleeplessness
  • stopping of heart
  • sweating
  • swelling of the face, throat, or tongue
  • swelling of the fingers, feet, or lower legs
  • swollen lymph glands
  • tightness in chest
  • tremors
  • troubled breathing
  • unconsciousness
  • vomiting
  • weight gain
  • weight loss
  • wheezing
Rare
  • Seizures

Get emergency help immediately if any of the following symptoms of overdose occur:

Symptoms of Overdose
  • Change in consciousness
  • cold clammy skin
  • confusion
  • disorientation
  • fast, weak pulse
  • lightheadedness
  • loss of consciousness
  • sudden headache
  • sudden loss of coordination
  • sudden slurring of speech

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common
  • Abdominal cramps
  • crying
  • depersonalization
  • dysphoria
  • emotionally rapidly changing moods
  • euphoria
  • excessive sweating
  • fear
  • feeling of warmth
  • hair loss
  • headache
  • increased appetite
  • mental depression
  • muscle weakness
  • nervousness
  • paranoia
  • quick to react or overreact
  • redness of the face, neck, arms, and occasionally, upper chest
  • restlessness
  • trouble getting pregnant
  • trouble sitting still
  • trouble sleeping
  • unable to sleep
  • unusual tiredness or weakness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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  • Synthroid Prescribing Information (FDA)
  • Synthroid MedFacts Consumer Leaflet (Wolters Kluwer)
  • Synthroid Detailed Consumer Information (PDR)
  • Synthroid Consumer Overview
  • Levothyroxine Detailed Consumer Information (PDR)
  • Levothyroxine Prescribing Information (FDA)
  • Levoxyl Prescribing Information (FDA)
  • Levoxyl Consumer Overview
  • Tirosint Prescribing Information (FDA)