Levothyroxine Liothyronine Synthetic

Levothyroxine Liothyronine Synthetic Brand Name– Thyrolar

What is Levothyroxine Liothyronine Synthetic

Levothyroxine Liothyronine Synthetic also known as Liotrix USP, is an oral synthetic thyroid hormone preparation used for replacement therapy in individuals with deficient intrinsic thyroid hormones.

Liotrix is a mixture of two synthetic thyroid hormones: T4 (tetraiodothyronine sodium or levothyroxine) and T3 (triiodothyronine or liothyronine), in a 4-to-1 ratio by weight, respectively.

The logic behind the choice of the 4:1 ratio is unclear. In the euthyroid patient, the ratio of T4:T3 in thyroglobulin is roughly 20:1; the ratio of the serum concentration of T4:T3 is about 70:1; and the ratio of the total extrathyroidal T4:T3 is about 17:1. When this drug was originally developed, it was thought that both T3 and T4 were required for adequate thyroid hormone replacement; however, it was later discovered that roughly 80% of endogenous T3 is produced extraglandularly as a metabolite of T4.

Patients receiving levothyroxine alone will become euthyroid; thus products containing T3 and T4 offer no discernible advantage over levothyroxine alone in the treatment of hypothyroidism.

Replacement of thyroid hormone using levothyroxine (T4) is alone sufficient in most individuals with hypothyroidism, and is the preferred replacement therapy for routine use in patients of all ages.

However, in select patients, such as those who continue to have symptoms despite euthyroid status after stabilization of a dose for T4 replacement, the partial substitution of T3 for T4 may be beneficial.

Like natural thyroid hormone mixtures, levothyroxine; liothyronine (synthetic), has the potential to produce post-ingestion peaks in serum T3 that may cause symptoms of thyroid excess in some patients.

Levothyroxine Liothyronine Synthetic has a standardized hormonal content that may be preferable to the use of porcine thyroid hormone products in such patients. A “Liotrix -1” strength tablet is roughly comparable in potency to a biologically standardized levothyroxine; liothyronine mixture from porcine thyroid gland (e.g., Armour Thyroid).

Levothyroxine Liothyronine Synthetic products were FDA-approved prior to 1982.

Indications

  1. cretinism
  2. hyperthyroidism diagnosis
  3. hypothyroidism
  4. myxedema

Thyroid Products Equivalent Oral Dosages; listings are estimates only:

Preparation—dosage equivalents—(T4: T3 ratio)

Levothyroxine—0.1 mg—(1:0)

Liothyronine—25 mcg—(0:1)

Liotrix-1—50—60mcg/12.5—15mcg—(4:1)

Thyroid USP—60 mg (1 grain)—(2—5:1)

For the treatment of hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. This category includes cretinism (congenital hypothyroidism), myxedema, and ordinary hypothyroidism in patients of any age (pediatrics, adults, the elderly), or state (including pregnancy); primary hypothyroidism resulting from functional deficiency, primary atrophy, partial or total absence of thyroid gland, or the effects of surgery, radiation, or drugs with or without the presence of goiter; and secondary (pituitary), or tertiary (hypothalamic) hypothyroidism

Side Effects

  1. alopecia
  2. anorexia
  3. anxiety
  4. atrial fibrillation
  5. chest pain (unspecified)
  6. diaphoresis
  7. diarrhea
  8. fever
  9. headache
  10. heart failure
  11. heat intolerance
  12. hyperthyroidism
  13. insomnia
  14. irritability
  15. menstrual irregularity
  16. nausea
  17. palpitations
  18. peripheral edema
  19. pruritus
  20. pseudotumor cerebri
  21. sinus tachycardia
  22. thyrotoxicosis
  23. tremor
  24. urticaria
  25. vomiting
  26. weight loss

Monitoring Parameters

  • blood pressure
  • heart rate
  • thyroid function tests (TFTs)
  • total T3 (triiodothyronine)

Contraindications

  • acute myocardial infarction
  • adrenal insufficiency
  • angina
  • breast-feeding
  • cardiac arrhythmias
  • cardiac disease
  • coronary artery disease
  • diabetes mellitus
  • geriatric
  • hypertension
  • hypopituitarism
  • infants
  • infertility
  • neonates
  • obesity treatment
  • osteoporosis
  • pregnancy
  • surgery
  • tartrazine dye hypersensitivity
  • thyrotoxicosis

Interactions

  • Acarbose
  • Acetaminophen; Butalbital
  • Acetaminophen; Butalbital; Caffeine
  • Acetaminophen; Butalbital; Caffeine; Codeine
  • Acetohexamide
  • Albiglutide
  • Alendronate
  • Alendronate; Cholecalciferol
  • Alogliptin
  • Alogliptin; Metformin
  • Alogliptin; Pioglitazone
  • Alpha-glucosidase Inhibitors
  • Aluminum Hydroxide
  • Aluminum Hydroxide; Magnesium Carbonate
  • Aluminum Hydroxide; Magnesium Hydroxide
  • Aluminum Hydroxide; Magnesium Hydroxide; Simethicone
  • Aluminum Hydroxide; Magnesium Trisilicate
  • Amiodarone
  • Amobarbital
  • Amoxapine
  • Amoxicillin; Clarithromycin; Lansoprazole
  • Amoxicillin; Clarithromycin; Omeprazole
  • Asparaginase Erwinia chrysanthemi
  • Aspirin, ASA; Butalbital; Caffeine
  • Aspirin, ASA; Butalbital; Caffeine; Codeine
  • Aspirin, ASA; Omeprazole
  • Atropine; Hyoscyamine; Phenobarbital; Scopolamine
  • Azelastine; Fluticasone
  • Barbiturates
  • Beclomethasone
  • Belladonna Alkaloids; Ergotamine; Phenobarbital
  • Beta-agonists
  • Beta-blockers
  • Betamethasone
  • Budesonide
  • Budesonide; Formoterol
  • Butabarbital
  • Calcium
  • Calcium Acetate
  • Calcium Carbonate
  • Calcium Carbonate; Magnesium Hydroxide
  • Calcium Carbonate; Risedronate
  • Calcium Carbonate; Simethicone
  • Calcium Chloride
  • Calcium Gluconate
  • Calcium; Vitamin D
  • Canagliflozin
  • Canagliflozin; Metformin
  • Carbamazepine
  • Chlorpropamide
  • Cholestyramine
  • Chromium
  • Ciclesonide
  • Cocaine
  • Colesevelam
  • Colestipol
  • Corticosteroids
  • Cortisone
  • Cyclosporine
  • Dapagliflozin
  • Dapagliflozin; Metformin
  • Dapagliflozin; Saxagliptin
  • Deflazacort
  • Dexamethasone
  • Dexlansoprazole
  • Didanosine, ddI
  • Digoxin
  • Dulaglutide
  • Empagliflozin
  • Empagliflozin; Linagliptin
  • Empagliflozin; Linagliptin; Metformin
  • Empagliflozin; Metformin
  • enteral feedings
  • Ertugliflozin; Metformin
  • Ertugliflozin; Sitagliptin
  • Esomeprazole
  • Esomeprazole; Naproxen
  • Estrogens
  • Ethinyl Estradiol; Norethindrone Acetate; Ferrous fumarate
  • Ethinyl Estradiol; Norethindrone; Ferrous fumarate
  • Exenatide
  • Fludrocortisone
  • Flunisolide
  • Fluoxymesterone
  • Fluticasone
  • Fluticasone; Salmeterol
  • Fluticasone; Umeclidinium; Vilanterol
  • Fluticasone; Vilanterol
  • food
  • Formoterol; Mometasone
  • Furosemide
  • Glimepiride
  • Glimepiride; Pioglitazone
  • Glimepiride; Rosiglitazone
  • Glipizide
  • Glipizide; Metformin
  • Glyburide
  • Glyburide; Metformin
  • Hetastarch; Dextrose; Electrolytes
  • Hydantoins
  • Hydrocortisone
  • Imatinib
  • Indinavir
  • Insulin Degludec; Liraglutide
  • Insulin Glargine; Lixisenatide
  • Insulins
  • Iodine; Potassium Iodide, KI
  • Iodoquinol
  • Iohexol
  • Iopamidol
  • Iopromide
  • Ioversol
  • Iron
  • Iron Salts
  • Iron Sucrose, Sucroferric Oxyhydroxide
  • Isoniazid, INH; Pyrazinamide, PZA; Rifampin
  • Isoniazid, INH; Rifampin
  • Isosulfan Blue
  • Ketamine
  • L-Asparaginase Escherichia coli
  • Lansoprazole
  • Lansoprazole; Naproxen
  • Lanthanum Carbonate
  • Linagliptin
  • Linagliptin; Metformin
  • Liraglutide
  • Lithium
  • Lixisenatide
  • Magnesium
  • Maprotiline
  • Meglitinides
  • Mephobarbital
  • Metformin
  • Metformin; Pioglitazone
  • Metformin; Repaglinide
  • Metformin; Rosiglitazone
  • Metformin; Saxagliptin
  • Metformin; Sitagliptin
  • Methimazole
  • Methohexital
  • Methylprednisolone
  • Miglitol
  • Mometasone
  • Non-Ionic Contrast Media
  • Omeprazole
  • Omeprazole; Amoxicillin; Rifabutin
  • Omeprazole; Sodium Bicarbonate
  • Orlistat
  • Pantoprazole
  • Pentobarbital
  • Phenobarbital
  • Pioglitazone
  • Polycarbophil
  • Polysaccharide-Iron Complex
  • Potassium Iodide, KI
  • Pramlintide
  • Prednisolone
  • Prednisone
  • Primidone
  • Propylthiouracil, PTU
  • Proton pump inhibitors
  • Rabeprazole
  • Raloxifene
  • Rifampin
  • Rosiglitazone
  • Saxagliptin
  • Secobarbital
  • Semaglutide
  • Sevelamer
  • Simethicone
  • Simvastatin; Sitagliptin
  • Sitagliptin
  • Sodium Ferric Gluconate Complex; ferric pyrophosphate citrate
  • Sodium Iodide
  • Sodium Polystyrene Sulfonate
  • Somatropin, rh-GH
  • Sucralfate
  • Sulfonylureas
  • Sympathomimetics
  • Teduglutide
  • Theophylline, Aminophylline
  • Thiazolidinediones
  • Thiopental
  • Tirofiban
  • Tolazamide
  • Tolbutamide
  • Tretinoin, ATRA
  • Triamcinolone
  • Tricyclic antidepressants
  • Warfarin
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