What is the pharmacodynamics of levothyroxine?
12.2 Pharmacodynamics 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.
Is there a drug interaction between levothyroxine?
A number of drugs have been shown to impair the absorption of levothyroxine; these drugs include calcium carbonate, aluminum- containing antacids, sucralfate, iron supplements, cholestyramine, sevelamer, and, possibly, ciprofloxacin, raloxifene, and orlistat.
What is the mechanism of action for levothyroxine?
Mechanism of action T4 and T3 bind to thyroid receptor proteins in the cell nucleus and cause metabolic effects through the control of DNA transcription and protein synthesis. Like its naturally secreted counterpart, levothyroxine is a chiral compound in the L-form.
How does thyroid hormone interact on its receptor?
Thyroid hormone receptors regulate gene expression by binding to hormone response elements (HREs) in DNA either as monomers, heterodimers with other nuclear receptors, or homodimers. Dimerizing with different nuclear receptors leads to the regulation of different genes.
How does levothyroxine work in the treatment of hypothyroidism?
Levothyroxine is a synthetic version of a hormone called thyroxine. It replaces thyroxine if your thyroid gland cannot produce it and prevents the symptoms of hypothyroidism. Levothyroxine starts working straight away, but it may be several weeks before your symptoms start to improve.
How is levothyroxine absorbed?
Oral levothyroxine sodium is absorbed in the small intestine, mainly in the jejunum and the ileum being lower the absorption rate at duodenal level. The time interval between the ingestion of oral thyroxine and its appearance in the plasma renders unlike a gastric absorption of the hormone.
What medicines interfere with thyroid medicine?
Specifically, antacids, calcium, cholesterol drugs, and iron supplements can each interfere with the way the thyroid hormone is absorbed. So, you should take these particular drugs four hours before or after taking your thyroid medication, according to the U.S. National Library of Medicine.
Is levothyroxine metabolized by cytochrome P450?
Levothyroxine has a wide drug–drug interaction spectrum, including inhibition of cytochrome P450 (CYP) 3A4 and UGT enzymes (UDP-glucuronosyltransferases), and it has been reported to increase the exposure of numerous drugs, including other tyrosine kinase inhibitors (15).
What type of receptors are thyroid hormone receptors?
Thyroid hormone receptors (TRs) are nuclear receptors which control transcription, and thereby have effects in all cells within the body. TRs are an important regulator in many basic physiological processes including development, growth, metabolism, and cardiac function.
What are receptors of hormones?
A hormone receptor is a receptor molecule that binds to a specific hormone. Hormone receptors are a wide family of proteins made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a variety of other receptors for various ligands, such as fatty acids and prostaglandins.
How does levothyroxine affect TSH?
Non-adherence to levothyroxine is generally associated with an elevated TSH. However, if missed doses are not reported by the patient, levothyroxine dose increases can lead to a low TSH if therapy is later adhered to.
What are the adverse effects of levothyroxine?
LEVOXYL®Adverse Reactions (levothyroxine sodium)
- General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating.
- Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia.
- Musculoskeletal: tremors, muscle weakness and cramps.
What affects the absorption of levothyroxine?
Food, dietary fibre and espresso coffee interfere with the absorption of levothyroxine. Malabsorptive disorders reported to affect the absorption of levothyroxine include coeliac disease, inflammatory bowel disease, lactose intolerance as well as Helicobacter pylori (H. pylori) infection and atrophic gastritis.
What is the interaction between levothyroxine and calcium?
Calcium supplements — or antacids containing calcium — can interfere with the absorption of thyroid hormone replacement medications, such as synthetic thyroid hormones levothyroxine (Synthroid, Unithroid, others) and liothyronine (Cytomel), as well as thyroid extract supplements.
What are contraindications for levothyroxine?
CONTRAINDICATIONS. Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction.
What effects levothyroxine absorption?
The absorption of levothyroxine in the gut is decreased when taking the hormone at the same time as calcium, iron and some foods and other drugs. Because of this, patients are usually instructed to take levothyroxine on an empty stomach 30-60 minutes before food intake to avoid erratic absorption of the hormone.
How is levothyroxine metabolized?
Levothyroxine is mainly absorbed in the small intestine, more specifically through the duodenum, jejunum and ileum. Very little is absorbed in the stomach. Consequently, patients with shorter small intestines (bowel resection) have reduced absorption and require higher levothyroxine doses.
What CYP metabolizes levothyroxine?
What are the two types of hormone receptors?
The main two types of transmembrane receptor hormone receptor are the G-protein-coupled receptors and the enzyme-linked receptors.
What are types of receptors?
There are two types of receptors: internal receptors and cell-surface receptors.
What is the pharmacologic mechanism of action of levothyroxine?
Levothyroxine – Clinical Pharmacology Mechanism of Action. Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA.
How does levothyroxine interact with anticoagulants?
Levothyroxine sodium increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the Levothyroxine sodium dose is increased. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments.
Does levothyroxine interact with simvastatin or simeprevir?
The excretion of Simeprevir can be decreased when combined with Levothyroxine. The metabolism of Simvastatin can be decreased when combined with Levothyroxine. The excretion of Sincalide can be decreased when combined with Levothyroxine. The serum concentration of Sirolimus can be decreased when it is combined with Levothyroxine.
Does levothyroxine interact with lypressin?
Levothyroxine may increase the vasoconstricting activities of Lypressin. Magaldrate can cause a decrease in the absorption of Levothyroxine resulting in a reduced serum concentration and potentially a decrease in efficacy.