Synthroid Injection

In the U.S.

• Synthroid

Available Dosage Forms:

• Powder for Solution

Therapeutic Class: Thyroid Supplement

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.

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

• Changes in appetite
• changes in menstrual periods
• chest pain
• diarrhea
• fast or irregular heartbeat
• fever
• hand tremors
• headache
• irritability
• leg cramps
• nervousness
• sensitivity to heat
• shortness of breath
• sweating
• trouble sleeping
• vomiting
• weight loss

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.

You may not be able to take Synthroid if you have certain medical conditions. Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder, a thyroid disorder called thyrotoxicosis, or if you have any recent or current symptoms of a heart attack.

Synthroid should not be used to treat obesity or weight problems. Dangerous side effects or death can occur from the misuse of levothyroxine, especially if you are taking any other weight-loss medications or appetite suppressants.

Since thyroid hormone occurs naturally in the body, almost anyone can take Synthroid. However, you may not be able to take this medicine if you have certain medical conditions.

To make sure Synthroid is safe for you, tell your doctor if you have:

• a thyroid disorder called thyrotoxicosis;

• heart disease, coronary artery disease, or a history of blood clots;

• diabetes (insulin or oral diabetes medication doses may need to be changed when you start taking Synthroid);

• anemia (lack of red blood cells);

• osteoporosis, or low bone mineral density;

• problems with your pituitary gland;

• any food or drug allergies;

• an untreated or uncontrolled adrenal gland disorder; or

• if you have recently had a heart attack, or are having any symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the jaw or shoulder, nausea, sweating, general ill feeling).

Tell your doctor if you have recently received radiation therapy with iodine (such as I-131).

Levothyroxine is not expected to harm an unborn baby. If you become pregnant while taking Synthroid, do not stop taking the medicine without your doctor's advice. Having low thyroid hormone levels during pregnancy could harm both mother and baby. Your dose needs may be different during pregnancy.

Levothyroxine can pass into breast milk, but it is not expected to be harmful to a nursing baby. Tell your doctor if you are breast-feeding. Your dose needs may be different while you are nursing.

Do not give this medicine to a child without medical advice.

Take Synthroid exactly as prescribed by your doctor. Follow all directions on your prescription label. Your doctor may occasionally change your dose. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Synthroid works best if you take it on an empty stomach, one-half to one hour before breakfast. Levothyroxine absorption is increased on an empty stomach. Follow your doctor's dosing instructions and try to take the medicine at the same time each day.

If a child is using this medicine, tell your doctor if the child has any changes in weight. Levothyroxine doses are based on weight in children, and any changes may affect your child's dose.

It may take several weeks before your body starts to respond to Synthroid. Keep using this medicine even if you feel well. You may need to use levothyroxine for the rest of your life.

While using Synthroid, you may need frequent medical tests. Tell any doctor or dentist who treats you that you are using this medicine.

Store at room temperature away from moisture and heat.

Do not share Synthroid with another person, even if they have the same symptoms you have.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include headache, leg cramps, tremors, feeling nervous or irritable, chest pain, shortness of breath, and fast or pounding heartbeats.

• Only 40-60% of a dose of Synthroid is absorbed from the gastrointestinal tract. Absorption is increased by fasting and decreased by certain foods, in older age, and by some medications.
• May take up to 4 to 6 weeks for blood levels of Synthroid to stabilize with regular dosing.

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