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
• 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.
CNS: insomnia, irritability, nervousness, headache
CV: angina pectoris, hypotension, hypertension, increased cardiac output, tachycardia, arrhythmias, cardiovascular collapse
GI: vomiting, diarrhea, cramps
GU: menstrual irregularities
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
• 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.
• 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.
Pharmacologic: thyroid preparations
- Promote gluconeogenesis,
- Increase utilization and mobilization of glycogen stores,
- Stimulate protein synthesis,
- Promote cell growth and differentiation,
- Aid in the development of the brain and CNS.
|Levothyroxine PO||unknown||1–3 wk||1–3 wk|
|Liothyronine PO||unknown||24–72 hr||72 hr|
Adverse Reactions/Side EffectsUsually only seen when excessive doses cause iatrogenic hyperthyroidism
Central nervous system
- angina pectoris
- abdominal cramps
- menstrual irregularities
- weight loss
- heat intolerance
- accelerated bone maturation in children
Drug-Drug interactionBile acid sequestrants ↓ absorption of orally administered thyroid preparations.Alters the effectiveness of warfarin (INR will increase with thyroid hormone supplementation).May ↑ requirement for insulin or oral hypoglycemic agents in diabetics.Concurrent estrogen therapy may ↑ thyroid replacement requirements.↑ cardiovascular effects with adrenergics (sympathomimetics).
LiotrixContains T4 and T3 in a ratio of 4:1
- Assess apical pulse and BP prior to and periodically during therapy. Assess for tachyarrhythmias and chest pain.
- Children: Monitor height, weight, and psychomotor development.
- Lab Test Considerations: Monitor thyroid function studies prior to and during therapy.
Overdose is manifested as hyperthyroidism (tachycardia, chest pain, nervousness, insomnia, diaphoresis, tremors, weight loss). Usual treatment is to withhold dose for 2–6 days. Acute overdose is treated by induction of emesis or gastric lavage, followed by activated charcoal. Sympathetic overstimulation may be controlled by antiadrenergic drugs (beta blockers), such as propranolol. Oxygen and supportive measures to control symptoms such as fever are also used.
- Monitor blood and urine glucose in diabetic patients. Insulin or oral hypoglycemic dose may need to be increased.
Potential Nursing DiagnosesDeficient knowledge, related to medication regimen (Patient/Family Teaching)
- Administer as a single dose, preferably before breakfast to prevent insomnia.
- Initial dose is low, especially in geriatric and cardiac patients. Dose is increased gradually, based on thyroid function tests. Side effects occur more rapidly with products containing liothyronine because of its rapid onset of effect.
- For patients with difficulty swallowing, tablets can be crushed and placed in 5–10 mL of water and administered immediately via dropper or spoon; do not store suspension.
- Instruct patient to take medication as directed at the same time each day. Take missed doses as soon as remembered unless almost time for next dose. If more than 2–3 doses are missed, notify health care professional. Do not discontinue without consulting health care professional.
- Explain to patient that medication does not cure hypothyroidism; it provides a thyroid hormone supplement. Therapy is lifelong.
- Advise patient to notify health care professional if headache, nervousness, diarrhea, excessive sweating, heat intolerance, chest pain, increased pulse rate, palpitations, weight loss >2 lb/wk, or any unusual symptoms occur.
- Caution patient to avoid taking other medications concurrently with thyroid preparations unless instructed by health care professional.
- Instruct patient to inform health care professionals of thyroid therapy.
- Emphasize importance of follow-up exams to monitor effectiveness of therapy. Thyroid function tests are performed at least yearly.
- Pediatric: Discuss with parents the need for routine follow-up studies to ensure correct development. Inform patient that partial hair loss may be experienced by children on thyroid therapy. This is usually temporary.
- Resolution of symptoms of hypothyroidism and normalization of hormone levels.