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Thyroid, Desiccated

Pronunciation

(THYE roid DES i kay tid)

Index Terms

  • Desiccated Thyroid
  • Levothyroxine and Liothyronine
  • Tetraiodothyronine and Triiodothyronine
  • Thyroid Extract
  • Thyroid USP

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Tablet, Oral:

Armour Thyroid: 15 mg, 30 mg, 60 mg, 90 mg, 120 mg

Armour Thyroid: 180 mg [scored]

Armour Thyroid: 240 mg

Armour Thyroid: 300 mg [scored]

Nature-Throid: 16.25 mg, 32.5 mg

Nature-Throid: 48.75 mg, 65 mg, 81.25 mg, 97.5 mg, 113.75 mg, 130 mg, 146.25 mg, 162.5 mg, 195 mg, 260 mg, 325 mg [scored]

NP Thyroid: 15 mg, 30 mg, 60 mg, 90 mg

Westhroid: 16.25 mg [DSC], 32.5 mg

Westhroid: 48.75 mg [DSC], 65 mg [scored]

Westhroid: 81.25 mg [DSC]

Westhroid: 97.5 mg, 113.75 mg [DSC], 130 mg, 146.25 mg [DSC], 162.5 mg [DSC], 195 mg, 260 mg [DSC], 325 mg [DSC] [scored]

Westhroid-P: 16.25 mg [DSC], 32.5 mg [DSC], 48.75 mg [DSC], 65 mg [DSC], 97.5 mg [DSC], 130 mg [DSC]

WP Thyroid: 16.25 mg, 32.5 mg

WP Thyroid: 48.75 mg, 65 mg [scored]

WP Thyroid: 81.25 mg

WP Thyroid: 97.5 mg, 113.75 mg, 130 mg [scored]

Brand Names: U.S.

  • Armour Thyroid
  • Nature-Throid
  • NP Thyroid
  • Westhroid
  • Westhroid-P [DSC]
  • WP Thyroid

Pharmacologic Category

  • Thyroid Product

Pharmacology

The primary active compound is T3 (triiodothyronine), which may be converted from T4 (thyroxine) and then circulates throughout the body to influence growth and maturation of various tissues; exact mechanism of action is unknown; however, it is believed the thyroid hormone exerts its many metabolic effects through control of DNA transcription and protein synthesis; involved in normal metabolism, growth, and development; promotes gluconeogenesis, increases utilization and mobilization of glycogen stores and stimulates protein synthesis, increases basal metabolic rate

Absorption

Thyroxine (T4): 40% to 80%; T3: 95%; desiccated thyroid contains T4, T3, and iodine (primarily bound)

Metabolism

Hepatic to triiodothyronine (active); ~80% T4 deiodinated in kidney and periphery; glucuronidation/conjugation also occurs; undergoes enterohepatic recirculation

Excretion

Urine (major route of elimination); partially feces

Onset of Action

Liothyronine (T3): ~3 hours

Time to Peak

Serum: T4: 2 to 4 hours; T3: 2 to 3 days

Half-Life Elimination

T4: Euthyroid: 6 to 7 days; Hyperthyroid: 3 to 4 days; Hypothyroid: 9 to 10 days

T3: 0.75 days (Brent, 2011)

Protein Binding

T4: >99% bound to plasma proteins including thyroxine-binding globulin, thyroxine-binding prealbumin, and albumin

Use: Labeled Indications

Replacement or supplemental therapy in hypothyroidism; pituitary TSH suppressants (thyroid nodules, thyroiditis, multinodular goiter, thyroid cancer)

Contraindications

Hypersensitivity to beef or pork or any component of the formulation; untreated thyrotoxicosis; uncorrected adrenal insufficiency

Dosing: Adult

Note: The American Association of Clinical Endocrinologists does not recommend the use of desiccated thyroid for thyroid replacement therapy for hypothyroidism (Baskin, 2002). Tablet strengths may vary by manufacturer in terms of grains or mg; dosing recommendations are based on general clinical equivalencies that 1 grain = 60 mg or 65 mg; 1/2 grain = 30 mg or 32.5 mg; and 1/4 grain = 15 mg or 16.25 mg.

Hypothyroidism: Oral: Initial: 15-30 mg; increase with 15 mg increments every 2-3 weeks; use 15 mg in patients with cardiovascular disease or long-standing myxedema. Maintenance dose: Usually 60-120 mg/day; monitor TSH and clinical symptoms.

Dosing: Geriatric

Not recommended for use in the elderly.

Dosing: Pediatric

Hypothyroidism: Oral: See table. Note: The American Thyroid Association/American Association of Clinical Endocrinologists do not recommend the use of desiccated thyroid for thyroid replacement therapy for hypothyroidism (ATA/AACE [Garber 2012]). Tablet strengths may vary by manufacturer in terms of grains or mg; dosing recommendations are based on general clinical equivalencies that 1 grain = 60 mg or 65 mg; 1/2 grain = 30 mg or 32.5 mg; and 1/4 grain = 15 mg or 16.25 mg.

Recommended Pediatric Dosage for Congenital Hypothyroidism

Age

Daily Dose

(mg)

Daily Dose/kg

(mg)

0-6 mo

15-30

4.8-6

6-12 mo

30-45

3.6-4.8

1-5 y

45-60

3-3.6

6-12 y

60-90

2.4-3

>12 y

>90

1.2-1.8

Table has been converted to the following text.

Recommended Pediatric Dosage for Congenital Hypothyroidism

• 0-6 months: 15-30 mg/day; 4.8-6 mg/kg/day

• 6-12 months: 30-45 mg/day; 3.6-4.8 mg/kg/day

• 1-5 years: 45-60 mg/day; 3-3.6 mg/kg/day

• 6-12 years: 60-90 mg/day; 2.4-3 mg/kg/day

• >12 years: >90 mg/day; 1.2-1.8 mg/kg/day

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling.

Administration

Administer on an empty stomach. Take in the morning before breakfast.

Dietary Considerations

Should be taken on an empty stomach.

Storage

Store at 15°C to 30°C (59°F to 86°F).

Drug Interactions

Bile Acid Sequestrants: May decrease the serum concentration of Thyroid Products. Management: Administer oral thyroid products at least 4 h prior to colesevelam, and at least 1 h before or 4-6 h after cholestyramine. Specific recommendations for colestipol are not available. Monitor for decreased concentrations/effects of the thyroid product. Consider therapy modification

Calcium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral calcium polystyrene sulfonate and thyroid products (eg, levothyroxine) or administer calcium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral). Consider therapy modification

Calcium Salts: May diminish the therapeutic effect of Thyroid Products. Management: Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Consider therapy modification

CarBAMazepine: May decrease the serum concentration of Thyroid Products. Monitor therapy

Ciprofloxacin (Systemic): May decrease the serum concentration of Thyroid Products. Monitor therapy

Estrogen Derivatives: May diminish the therapeutic effect of Thyroid Products. Monitor therapy

Fosphenytoin: May decrease the serum concentration of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Monitor therapy

Lanthanum: May decrease the serum concentration of Thyroid Products. Management: Administer oral thyroid products at least two hours before or after lanthanum. Consider therapy modification

Phenytoin: May decrease the serum concentration of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Monitor therapy

Piracetam: May enhance the adverse/toxic effect of Thyroid Products. Specifically, symptoms including confusion, irritability, and sleep disorder have been described during concomitant use. Monitor therapy

RifAMPin: May decrease the serum concentration of Thyroid Products. Monitor therapy

Selective Serotonin Reuptake Inhibitors: May diminish the therapeutic effect of Thyroid Products. Thyroid product dose requirements may be increased. Monitor therapy

Sodium Iodide I131: Thyroid Products may diminish the therapeutic effect of Sodium Iodide I131. Avoid combination

Sodium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral sodium polystyrene sulfonate and thyroid products (e.g., levothyroxine) or administer sodium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral). Consider therapy modification

Theophylline Derivatives: Thyroid Products may increase the metabolism of Theophylline Derivatives. Exceptions: Dyphylline. Monitor therapy

Tricyclic Antidepressants: Thyroid Products may enhance the arrhythmogenic effect of Tricyclic Antidepressants. Thyroid Products may enhance the stimulatory effect of Tricyclic Antidepressants. Monitor therapy

Vitamin K Antagonists (eg, warfarin): Thyroid Products may enhance the anticoagulant effect of Vitamin K Antagonists. Monitor therapy

Test Interactions

T4-binding globulin (TBG): Factors that alter binding in serum (ATA/AACE [Garber 2012]):

Note: T4 is ~99.97% protein bound. Factors that alter protein binding will affect serum total T4 levels; however, measurement of serum free T4 (the metabolically active moiety) has largely replaced serum total T4 for thyroid status assessment.

Conditions/states that increase TBG binding: Pregnancy, hepatitis, porphyria, neonatal state

Medications that increase TBG binding: Estrogens, 5-fluorouracil, heroin, methadone, mitotane, perphenazine, selective estrogen receptor modulators (eg, tamoxifen, raloxifene)

Conditions/states that decrease TBG binding: Hepatic failure, nephrosis, severe illness

Medications that decrease TBG binding: Androgens, anabolic steroids, glucocorticoids, L-asparaginase, nicotinic acid

Thyroxine (T4) and Triiodothyronine (T3): Serum binding inhibitors (ATA/AACE [Garber 2012]):

Medications that inhibit T4 and T3 binding: Carbamazepine, furosemide, free fatty acids, heparin, NSAIDS (variable, transient), phenytoin, salicylates

Thyroid gland hormone: Interference with production and secretion (ATA/AACE [Garber 2012]):

Medications affecting iodine uptake: Amiodarone, iodinated contrast agents, iodine, ethionamide

Medications affecting hormone production: Amiodarone, ethionamide, iodinated contrast agents, iodine, sulfonylureas, sulfonamides, thionamides (carbimazole, methimazole, propylthiouracil)

Medications affecting secretion: Amiodarone, iodinated contrast agents, iodine, lithium

Medications inducing thyroiditis: Alemtuzumab, amiodarone, antiangiogenic agents (lenalidomide, thalidomide), denileukin diftitoxin, interferon alpha, interleukins, lithium, tyrosine kinase inhibitors (sunitinib, sorafenib)

Medications potentially causing the development of Graves’: Alemtuzumab, interferon alpha, highly active antiretroviral therapy

Medications potentially ameliorating thyroiditis (if autoimmune) or Graves’: Glucocorticoids

Hypothalamic-pituitary axis and TSH: Interference with secretion (ATA/AACE [Garber 2012]):

Medications decreasing TSH secretion: Bexarotene, dopamine, dopaminergic agonists (bromocriptine, cabergoline), glucocorticoids, interleukin-6, metformin, opiates, somatostatin analogues (octreotide, lanreotide), thyroid hormone analogues

Medications increasing TSH secretion: Amphetamine, interleukin 2, metoclopramide, ritonavir, St John's wort

Medications potentially causing hypophysitis: Ipilimumab

Adverse Reactions

Adverse reactions are often indicative of excess thyroid replacement and/or hyperthyroidism.

<1% (Limited to important or life-threatening): Alopecia, cardiac arrhythmia, chest pain, dyspnea, myalgia, palpitations, tachycardia, tremor, tremor of hands

ALERT: U.S. Boxed Warning

Weight reduction:

Drugs with thyroid hormone activity, alone or with other therapeutic agents, have been used for the treatment of obesity. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.

Warnings/Precautions

Disease-related concerns:

• Adrenal insufficiency: Use with caution in patients with adrenal insufficiency; symptoms may be exaggerated or aggravated; contraindicated in patients with uncorrected adrenal insufficiency. Treatment with glucocorticoids should precede thyroid replacement therapy in patients with adrenal insufficiency (ATA/AACE [Garber 2012]).

• Cardiovascular disease: Use with caution and reduce dosage in patients with angina pectoris or other cardiovascular disease; chronic hypothyroidism predisposes patients to coronary artery disease.

• Diabetes: Use with caution in patients with diabetes mellitus and insipidus; symptoms may be exaggerated or aggravated.

• Myxedema: Use with caution in patients with myxedema; symptoms may be exaggerated or aggravated; initial dosage reduction is recommended in patients with long-standing myxedema.

Dosage form specific issues:

• Desiccated thyroid: Contains variable amounts of T3, T4, and other triiodothyronine compounds which are more likely to cause cardiac signs or symptoms due to fluctuating levels.

Other warnings/precautions:

• Infertility (unapproved use): Thyroid supplements are not recommended for the treatment of female or male infertility, unless associated with hypothyroidism.

• Weight reduction (unapproved use): [US Boxed Warning]: In euthyroid patients, thyroid supplements are ineffective and potentially toxic for weight reduction. High doses may produce serious or even life-threatening toxic effects particularly when used with some anorectic drugs.

Monitoring Parameters

T4, TSH; heart rate, blood pressure; clinical signs of hypo- and hyperthyroidism; TSH is the most reliable guide for evaluating adequacy of thyroid replacement dosage. TSH may be elevated during the first few months of thyroid replacement despite patients being clinically euthyroid. In cases where T4 remains low and TSH is within normal limits, an evaluation of “free” (unbound) T4 is needed to evaluate further increase in dosage.

Alternate recommendations: Adults: Monitor TSH 4 to 8 weeks after treatment initiation or dose changes, 6 months after adequate replacement dose determined, followed by every 12 months thereafter (or more frequently depending on clinical situation) (ATA/AACE [Garber 2012]).

Pregnancy Risk Factor

A

Pregnancy Considerations

Endogenous thyroid hormones minimally cross the placenta; the fetal thyroid becomes active around the end of the first trimester. Liothyronine has not been found to increase the risk of teratogenic or adverse effects following maternal use during pregnancy.

Uncontrolled maternal hypothyroidism may result in adverse neonatal and maternal outcomes. To prevent adverse events, normal maternal thyroid function should be maintained prior to conception and throughout pregnancy. Levothyroxine is considered the treatment of choice for the control of hypothyroidism during pregnancy.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Have patient report immediately to prescriber angina, tachycardia, arrhythmia, headache, shortness of breath, anxiety, tremors, insomnia, temperature sensitivity, sweating a lot, lack of appetite, more hungry, excessive weight gain or loss, diarrhea, vomiting, irritability, abdominal cramps, leg cramps, loss of strength and energy, or menstrual irregularities (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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