Chapter 31pharm

Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

CHAPTER 31CHAPTER 31

Thyroid and Antithyroid DrugsThyroid and Antithyroid Drugs

22Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Thyroid GlandThyroid Gland

Secretes three hormones essential for proper Secretes three hormones essential for proper regulation of metabolismregulation of metabolism Thyroxine (TThyroxine (T44))

Triiodothyronine (TTriiodothyronine (T33))

CalcitoninCalcitonin Located near the parathyroid gland, which is Located near the parathyroid gland, which is

responsible for maintaining adequate levels responsible for maintaining adequate levels of calcium in the extracellular fluidof calcium in the extracellular fluid


Hypothyroidism: Hypothyroidism: Deficiency in Thyroid HormonesDeficiency in Thyroid Hormones

Primary: abnormality in the thyroid gland itselfPrimary: abnormality in the thyroid gland itself Secondary: results when the pituitary gland is Secondary: results when the pituitary gland is

dysfunctional and does not secrete TSHdysfunctional and does not secrete TSH Tertiary: results when the hypothalamus Tertiary: results when the hypothalamus

gland does not secrete TRH, which stimulates gland does not secrete TRH, which stimulates the release of TSHthe release of TSH


HypothyroidismHypothyroidism

CretinismCretinism Hyposecretion of thyroid hormone during youthHyposecretion of thyroid hormone during youth Low metabolic rate, retarded growth and sexual Low metabolic rate, retarded growth and sexual

development, possible mental retardationdevelopment, possible mental retardation


Hypothyroidism (cont’d)Hypothyroidism (cont’d)

MyxedemaMyxedema Hyposecretion of thyroid hormone during Hyposecretion of thyroid hormone during

adulthoodadulthood Decreased metabolic rate, loss of mental and Decreased metabolic rate, loss of mental and

physical stamina, weight gain, loss of hair, firm physical stamina, weight gain, loss of hair, firm edema, yellow dullness of the skinedema, yellow dullness of the skin



GoiterGoiter Enlargement of the thyroid glandEnlargement of the thyroid gland Results from overstimulation by elevated levels of Results from overstimulation by elevated levels of

TSHTSH TSH is elevated because there is little or no TSH is elevated because there is little or no

thyroid hormone in circulationthyroid hormone in circulation



Common symptomsCommon symptoms Thickened skinThickened skin Hair lossHair loss ConstipationConstipation LethargyLethargy AnorexiaAnorexia


Thyroid PreparationsThyroid Preparations

levothyroxine (Synthroid, Levothyroid)levothyroxine (Synthroid, Levothyroid) Synthetic thyroid hormone TSynthetic thyroid hormone T44

liothyronine (Cytomel)liothyronine (Cytomel) Synthetic thyroid hormone TSynthetic thyroid hormone T33

liotrix (Thyrolar)liotrix (Thyrolar) Synthetic thyroid hormone TSynthetic thyroid hormone T33 and T and T44 combined combined

thyroidthyroid Desiccated (dried) animal thyroid glandDesiccated (dried) animal thyroid gland


Mechanism of ActionMechanism of Action

Thyroid preparations are given to replace Thyroid preparations are given to replace what the thyroid gland cannot produce to what the thyroid gland cannot produce to achieve normal thyroid levels (euthyroid)achieve normal thyroid levels (euthyroid)

Thyroid drugs work the same way as thyroid Thyroid drugs work the same way as thyroid hormoneshormones


IndicationsIndications

To treat all three forms of hypothyroidismTo treat all three forms of hypothyroidism Levothyroxine is the preferred drug because its Levothyroxine is the preferred drug because its

hormonal content is standardized; therefore, its hormonal content is standardized; therefore, its effect is predictableeffect is predictable

““Euthyroid”Euthyroid”


Indications (cont’d)Indications (cont’d)

Also used for thyroid replacement in patients Also used for thyroid replacement in patients whose thyroid glands have been surgically whose thyroid glands have been surgically removed or destroyed by radioactive iodine in removed or destroyed by radioactive iodine in the treatment of thyroid cancer or the treatment of thyroid cancer or hyperthyroidismhyperthyroidism


Adverse EffectsAdverse Effects

Cardiac dysrhythmia is the most significant Cardiac dysrhythmia is the most significant adverse effectadverse effect

May also cause:May also cause: Tachycardia, palpitations, angina, hypertension, Tachycardia, palpitations, angina, hypertension,

insomnia, tremors, headache, anxiety, nausea, insomnia, tremors, headache, anxiety, nausea, diarrhea, menstrual irregularities, weight loss, diarrhea, menstrual irregularities, weight loss, appetite changes, sweating, heat intolerance, appetite changes, sweating, heat intolerance, othersothers


Hyperthyroidism: Hyperthyroidism: Excessive Thyroid HormonesExcessive Thyroid Hormones

Caused by several diseasesCaused by several diseases Graves’ diseaseGraves’ disease Multinodular diseaseMultinodular disease Plummer’s disease (rare)Plummer’s disease (rare)

• Also called toxic nodular diseaseAlso called toxic nodular disease

Thyroid storm (induced by stress or infection)Thyroid storm (induced by stress or infection)• Severe and potentially life-threateningSevere and potentially life-threatening


HyperthyroidismHyperthyroidism

Affects multiple body systems, resulting in an Affects multiple body systems, resulting in an overall increase in metabolismoverall increase in metabolism DiarrheaDiarrhea FlushingFlushing Increased appetiteIncreased appetite Muscle weaknessMuscle weakness Sleep disordersSleep disorders Altered menstrual flowAltered menstrual flow

FatigueFatigue PalpitationsPalpitations NervousnessNervousness Heat intoleranceHeat intolerance Irritability Irritability


Treatment of HyperthyroidismTreatment of Hyperthyroidism

Radioactive iodine (IRadioactive iodine (I131131) works by destroying ) works by destroying the thyroid glandthe thyroid gland

Surgery to remove all or part of the thyroid Surgery to remove all or part of the thyroid glandgland Lifelong thyroid hormone replacement will be Lifelong thyroid hormone replacement will be

neededneeded


Treatment of Hyperthyroidism Treatment of Hyperthyroidism (cont’d)(cont’d)

Antithyroid drugs: thioamide derivativesAntithyroid drugs: thioamide derivatives methimazole (Tapazole)methimazole (Tapazole) propylthiouracil (PTU)propylthiouracil (PTU)


Antithyroid DrugsAntithyroid Drugs

Used to palliate hyperthyroidism and to Used to palliate hyperthyroidism and to prevent the surge in thyroid hormones that prevent the surge in thyroid hormones that occurs after surgical treatment or during occurs after surgical treatment or during radioactive iodine treatment for radioactive iodine treatment for hyperthyroidismhyperthyroidism

May cause liver and bone marrow toxicityMay cause liver and bone marrow toxicity


Nursing ImplicationsNursing Implications

Assess for drug allergies, contraindications, Assess for drug allergies, contraindications, potential drug interactionspotential drug interactions

Obtain baseline vital signs, weightObtain baseline vital signs, weight Cautious use advised for those with cardiac Cautious use advised for those with cardiac

disease, hypertension, and pregnant womendisease, hypertension, and pregnant women


Nursing Implications (cont’d)Nursing Implications (cont’d)

During pregnancy, treatment for During pregnancy, treatment for hypothyroidism should continuehypothyroidism should continue

Fetal growth may be retarded if maternal Fetal growth may be retarded if maternal hypothyroidism is untreated during pregnancyhypothyroidism is untreated during pregnancy Adjust dosage every 4 weeks to keep TSH at the Adjust dosage every 4 weeks to keep TSH at the

lower end of the normal rangelower end of the normal range



Teach patient to take thyroid drugs once daily Teach patient to take thyroid drugs once daily in the morning to decrease the likelihood of in the morning to decrease the likelihood of insomnia if taken later in the dayinsomnia if taken later in the day

Teach patient to take the medications at the Teach patient to take the medications at the same time every day and not to switch same time every day and not to switch brands without physician approvalbrands without physician approval



Teach patients to report any unusual Teach patients to report any unusual symptoms, chest pain, or heart palpitationssymptoms, chest pain, or heart palpitations

Teach patients not to take over-the-counter Teach patients not to take over-the-counter medications without physician approvalmedications without physician approval

Teach patients that therapeutic effects may Teach patients that therapeutic effects may take several months to occurtake several months to occur



Teach patients the importance of alerting Teach patients the importance of alerting health care providers of thyroid medication health care providers of thyroid medication useuse May enhance activity of anticoagulantsMay enhance activity of anticoagulants Diabetic patients may need increased dosages of Diabetic patients may need increased dosages of

hypoglycemic medshypoglycemic meds May decrease serum digoxin levelsMay decrease serum digoxin levels



Antithyroid medications Antithyroid medications Better tolerated when given with foodBetter tolerated when given with food Give at the same time each day to maintain Give at the same time each day to maintain

consistent blood levelsconsistent blood levels Never stop these medications abruptlyNever stop these medications abruptly Avoid eating foods high in iodine (seafood, soy Avoid eating foods high in iodine (seafood, soy

sauce, tofu, and iodized salt)sauce, tofu, and iodized salt)



Monitor for therapeutic responseMonitor for therapeutic response Monitor for adverse effectsMonitor for adverse effects

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Chapter 31pharm