a mixture of liothyronine sodium and levothyroxine sodium in a ratio of 1:4 by weight; used for replacement therapy in hypothyroidism and for the prophylaxis and treatment of goiter and of thyroid cancer; administered orally as the sodium salt.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.



Pharmacologic class: Synthetic thyroid hormone

Therapeutic class: Thyroid hormone replacement

Pregnancy risk category A

FDA Box Warning

• Drug has been used (alone or with other agents) to treat obesity. In euthyroid patients, doses within range of daily hormonal requirements are ineffective for weight loss. Larger doses may produce serious or even life-threatening toxicity, particularly when given with sympathomimetic amines (such as those used for anorectic effects).


Increases basal metabolic rate, helps regulate cell growth and differentiation, and enhances metabolism of lipids, proteins, and carbohydrates


Tablets: 12.5 mcg levothyroxine sodium and 3.1 mcg liothyronine sodium (Thyrolar-¼); 25 mcg levothyroxine sodium and 6.25 mcg liothyronine sodium (Thyrolar-½); 50 mcg levothyroxine sodium and 12.5 mcg liothyronine sodium (Thyrolar-1); 100 mcg levothyroxine sodium and 25 mcg liothyronine sodium (Thyrolar-2); 150 mcg levothyroxine sodium and 37.5 mcg liothyronine sodium (Thyrolar-3)

Indications and dosages


Adults: All dosages individualized. Initially, one tablet Thyrolar-½ P.O., increased by one tablet Thyrolar-¼ P.O. daily until desired effect occurs. Usual maintenance dosage is one tablet Thyrolar-1 or Thyrolar-2 P.O. daily, adjusted within first 4 weeks based on laboratory results.

Congenital hypothyroidism

Children older than age 12: 18.75/75 mcg P.O. daily

Children ages 6 to 11: 12.5/50 to 18.75/75 mcg P.O. daily

Children ages 1 to 5: 9.35/37.5 to 12.5/50 mcg P.O. daily

Children ages 6 to 12 months: 6.25/25 to 9.35/37.5 mcg P.O. daily

Children up to 6 months: 3.1/12.5 to 6.25/25 mcg (Thyrolar-¼) P.O. daily

Dosage adjustment

• Severe, long-standing hypothyroidism

• Cardiovascular disease

• Psychosis or agitation

• Elderly patients


• Hypersensitivity to drug or its components

• Acute myocardial infarction

• Uncorrected thyrotoxicosis

• Uncorrected adrenal insufficiency and coexisting hypothyroidism


Use cautiously in:

• cardiovascular disease, severe renal insufficiency, diabetes mellitus, uncorrected adrenocortical disorders

• elderly patients

• pregnant or breastfeeding patients.


• Know that all dosages are highly individualized.

• Administer single daily dose in morning with or without food.

Adverse reactions

CNS: insomnia, irritability, nervousness, headache

CV: angina pectoris, hypotension, hypertension, increased cardiac output, tachycardia, arrhythmias, cardiovascular collapse

GI: vomiting, diarrhea, cramps

GU: menstrual irregularities

Metabolic: hyperthyroidism

Musculoskeletal: accelerated bone maturation (in children), decreased bone density (with long-term use in women)

Skin: alopecia (in children), diaphoresis

Other: weight loss, heat intolerance


Drug-drug. Aminoglutethimide, amiodarone, anabolic steroids, antithyroid drugs, asparaginase, barbiturates, carbamazepine, chloral hydrate, cholestyramine, clofibrate, colestipol, corticosteroids, danazol, diazepam, estrogens, ethionamide, fluorouracil, heparin (with I.V. use), insulin, lithium, methadone, mitotane, nitroprusside, oxyphenbutazone, P-aminosalicyclic acid, perphenazine, phenylbutazone, phenytoin, propranolol, salicylates (large doses), sulfonylureas, thiazides: altered thyroid function test results

Anticoagulants: increased anticoagulant action

Beta-adrenergic blockers (selected): decreased beta blocker action

Cardiac glycosides: decreased cardiac glycoside blood level

Cholestyramine, colestipol: liotrix inefficacy

Theophyllines: decreased theophylline clearance

Drug-diagnostic tests. Thyroid function tests: decreased values

Drug-food. Foods high in iron or fiber, soybeans: decreased drug absorption

Patient monitoring

• Monitor for evidence of overdose, such as signs and symptoms of hyperthyroidism (weight loss, cardiac symptoms, abdominal cramps).

• Watch closely for signs and symptoms of undertreatment.

• In patients with Addison's disease or diabetes mellitus, assess for signs that these conditions are worsening. In diabetic patients, monitor blood glucose level.

• Check vital signs and ECG routinely.

• Monitor thyroid and liver function tests.

• Assess for signs and symptoms of bleeding tendency, especially if patient's taking anticoagulants.

Patient teaching

• Inform patient or parents that drug should be taken in morning with or without food.

• Explain that patient may require lifelong therapy and will need to undergo regular blood testing.

• Advise diabetic patient (or his parents) to monitor patient's blood glucose level closely.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

• Inform parents that hair loss may occur in children during first few months of therapy but that this effect is usually transient.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


An obsolete therapeutic agent consisting of liothyronine sodium and levothyroxine sodium.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
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References in periodicals archive ?
Thyroid hormone medications, including levothyroxine (Levothroid, Levoxyl, Synthroid), liothyronine (Cytomel) and liotrix (Euthroid, Thyrolar), are given when blood tests show that you have hypothyroidism,.
$1.02 * (Cytomel) liotrix 120 mg/day $0.71 * (Thyrolar) thyroid, 120-180 $0.09 * Desiccated mg/day (120 mg) Drug Comment + levothyroxine Synthetic [T.sub.4].