Synthroid Levothyroxine: Side effects, Interactions, and Overdose

Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control after starting, changing, or discontinuing SYNTHROID see DRUG INTERACTIONS. Assess the adequacy of therapy by periodic assessment of laboratory tests and clinical evaluation.

• Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium.
• Administration of activated charcoal is a common practice in many drug overdoses and is an agent that can prevent absorption of several drugs from the gastro-intestinal system.
• This is not a complete list of side effects and others may occur.
• While hemodialysis has a limited role, antithyroid drugs and activated charcoal are ineffective.
• Note that this list is not all-inclusive and includes only common medications that may interact with Synthroid.
• Follow your doctor’s dosing instructions and try to take the medicine at the same time each day.

Dosing And Administration

Dangerous side effects or death can occur from the misuse of this medicine, especially if you are taking any other weight-loss medications or appetite suppressants. You may not be able to use levothyroxine if you have certain medical conditions. Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder or any heart problems such as a recent heart attack. The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues.

• For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms.
• Synthroid works best if you take it on an empty stomach, 30 to 60 minutes before breakfast.
• Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3 (rT3).
• The patient currently has ‘normal’ vital signs (GCS of 15) and is feeling tired but is otherwise asymptomatic.
• Oral levothyroxine sodium is a synthetic T4 hormone that exerts the same physiologic effect as endogenous T4, thereby maintaining normal T4 levels when a deficiency is present.

The counter effects of those concomitant drugs like propranolol and sertraline are always to be considered as a cause in a patient with thyronorm overdose for being asymptomatic. Certain foods and medications can interfere with the absorption of levothyroxine. The most common medications are aluminum- and magnesium-containing antacids, calcium carbonate, iron, cholestyramine, sucralfate, and sevelamer. To reduce the risk of impaired absorption, it’s recommended to take levothyroxine at least 4 hours before taking any of the medications listed above. Many other medicines can be affected by your thyroid hormone levels.

Synthroid During Pregnancy and Breastfeeding

Serum digitalis glycoside levels may decrease when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides. Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients. Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results. Stop biotin and biotin-containing supplements for at least 2 days before assessing TSH and/or T4 levels see DRUG INTERACTIONS.

Unintentional exposures in excess of 5 mg (5000 mcg) of thyroxine may benefit from administration of activated charcoal. Most unintentional exposures can be treated with no decontamination, prudent follow-up, and observation at home, especially if the calculated dose is below 4 mg (4000 mcg). 7 Virtual or telephonic follow-up should be conducted up to 10 days after exposure.

Thyroxine overdose

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your thyroid hormone levels and also make levothyroxine less effective. Because of the increased prevalence of cardiovascular disease among the elderly, initiate SYNTHROID at less than the full replacement dose see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS.

• Taking more than your recommended dose will not make this medicine more effective, and may cause serious side effects.
• Levothyroxine is a medication that is generally taken for life to maintain normal thyroid function.
• Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range see Recommended Dosage And Titration.

NP Thyroid

Take levothyroxine tablets and capsules on an empty stomach, at least 30 to 60 minutes before breakfast with a full glass of water. Tell your doctor if you are pregnant or plan to become pregnant. Having hypothyroidism during pregnancy may increase the risk of premature birth or other complications. The benefit of treating hypothyroidism may outweigh any risks to the baby. Synthroid (levothyroxine) treats hypothyroidism (low thyroid hormone) and different types of …

Levothyroxine is a prescription medication that is used to treat hypothyroidism (underactive thyroid gland). Levothyroxine works by mimicking the activity of the natural hormone that is normally generated by the thyroid gland. Levothyroxine is a medication that is generally taken for life to synthroid concentrations maintain normal thyroid function. Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine. No adverse effects on the breastfed infant have been reported and there is no information on the effects of levothyroxine on milk production. Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply.

Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of SYNTHROID may be evidence of inadequate absorption, poor compliance, drug interactions, or a combination of these factors. She had a verbal argument with her husband following which she took that medication. She was initially taken to a nearby health center but was immediately referred to our center without any primary management. She was on levothyroxine 50 mcg for hypothyroidism and sertraline 50mg along with propranolol 20 mg for Adjustment disorder. Medicines that interact with Synthroid may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Synthroid.

During the hospital stay, he developed sinus tachycardia, which was controlled with propranolol. He received stress-dose steroids; hemodialysis was performed a day earlier, and cholestyramine was administered. Thyroid hormone levels started to improve by day seven and finally normalized in 20 days, after which the home dose of levothyroxine was resumed. The human body has several mechanisms to compensate for levothyroxine toxicity, including the conversion of excess levothyroxine to inactive reverse triiodothyronine, increased binding to thyroid-binding globulin, and hepatic metabolism. This case shows that it is possible to have no symptoms even with an overdose of up to 9 mg a day of levothyroxine.