Levothyroxine: Uses, Dosage, Side Effects

Common brand names of levothyroxine in the US include Synthroid, Levoxyl, Unithroid, and Tirosint. Upon first prescribing levothyroxine, medication adjustment should occur every 6 to 8 weeks until the patient reaches a steady state. A clinician should then order TSH and free T4 levels immediately. If the free T4 comes back elevated, the clinician should decrease the dose of levothyroxine to prevent cardiac complications and other symptoms of hyperthyroidism. Finally, clinicians should refer the patient to an endocrinologist if hypothyroidism is due to central causes. In all the scenarios mentioned above, pharmacists should ensure proper dosing and report to the clinician if there is any potential drug-drug interaction or if supplies may dictate a change to a different formulation.

Drug Interactions for Synthroid

You should call if you have any questions about poisoning or poison prevention. The patient will not develop significant life-threatening toxicity from this co-ingestion. Synthroid is a prescription medicine used to treat hypothyroidism (low thyroid hormone). Levothyroxine is given when your thyroid does not produce enough of this hormone on its own.

What to Expect at the Emergency Room

One way to confirm the presence of LT-4 tablets in the gastric cavity is endoscopy, easily conducted in many hospitals and emergency rooms. LT-4 tablets are dissolved by the gastric juice, but there are no data about the rate of dissolution of a large number of tablets of LT-4. Most probably LT-4 would not be entirely dissolved by the gastric juice and may not be absorbed in the duodenum (normally about 10-15%) but would be absorbed in the jejuno-ileum (normally about 53% of absorption of LT4). Thyroid hormone increases metabolic clearance of glucocorticoids. Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency.

Before Calling Emergency

Discuss the utility of thyroid function tests in this patient. Levothroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma … Your child’s dose needs may change if the child gains or loses weight. Synthroid works best if you take it on an empty stomach, 30 to 60 minutes before breakfast. Follow your doctor’s dosing instructions and try to take the medicine at the same time each day. Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use levothyroxine only for the indication prescribed.

Drug Summary

Thyroid hormone pills used to treat hypothyroid dogs typically contains a much higher dose of thyroid hormone and if mistakenly taken by humans can lead to thyroxine poisoning. Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones synthroid tums exist in reverse equilibrium with small amounts of free hormone. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins see DRUG INTERACTIONS.

Addition of SYNTHROID therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control, especially when thyroid therapy is started, changed, or discontinued see WARNINGS AND PRECAUTIONS. For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range. For adult patients with primary hypothyroidism, titrate until the patient is clinically euthyroid and the serum TSH returns to normal see Recommended Dosage And Titration. Psychiatric illness often accompany drug overdose or poisoning.

• Acute massive doses of L-thyroxine typically have a mild clinical course that can be controlled by activated charcoal, or possibly cholestyramine, propranolol, dexamethasone, and supporting measures, with close medical evaluation.
• Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements.
• We report a case of asymptomatic levothyroxine over dosage (2.5mg) in a chronic hypothyroid patient who also was concomitantly taking propranolol and sertraline for adjustment disorder.

Side Effects for Synthroid

The recommended starting daily dosage of SYNTHROID in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1. 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. Dosage titration is based on serum TSH or free-T4 see Important Considerations For Dosing. For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of SYNTHROID dosage adequacy and should not be used to monitor therapy.

• Currently available studies have not demonstrated increased risk to the fetus in pregnant women taking levothyroxine.
• 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.
• Tell your doctor about all your current medicines and any medicine you start or stop using.
• Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine.

Unithroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma … Levoxyl treats hypothyroidism (low thyroid hormone) and treats or prevents goiter. Tirosint is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma … This is not a complete list of side effects and others may occur. Levothyroxine is also used in adults along with surgery and radioactive iodine therapy to treat a certain type of thyroid cancer. Glucocorticoids (Dexamethasone 4 mg orally) decrease the conversion of LT4 to T3, the active hormone.

T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybeans. In addition, many drugs and foods affect T4 absorption see DRUG INTERACTIONS. Psychiatric patients with hypothyroidism may intentionally consume levothyroxine tablets with suicidal notion. Thyroid hormones can increase the body’s metabolism and promote weight loss.

If so, advise them to stop biotin supplementation at least 2 days before assessing TSH and/or T4 levels see DOSAGE AND ADMINISTRATION and DRUG INTERACTIONS. Note that this list is not all-inclusive and includes only common medications that may interact with Synthroid. You should refer to the prescribing information for Synthroid for a complete list of interactions. Consult the regional poison control center or local medical toxicologist (certified through the American Board of Medical Toxicology or the American Board of Emergency Medicine) for additional information and patient care recommendations. Admit all symptomatic patients and place them on cardiac monitoring. Symptomatic patients require correction of dehydration and control of hyperthermia.