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Hypothyroidism

Levothyroxine sodium (Levoxyl ® Synthroid®)
Synthetic levothyroxine T4

  • Replacement or supplemental therapy in the treatment of hypothyroidism except the treatment of transient hypothyroidism in the recovery phase of subacute thyroiditis.

      For Nonpregnant Healthy Women
      1.7 mcg/kg/day PO once daily.
      Clinical and laboratory evaluations should be performed at 6 to 8 week intervals (2 to 3    weeks in severely hypothyroid patients), and the dosage adjusted by 12.5 to 25 mcg increments until the serum TSH concentration is normalized and signs and symptoms resolve.

      For Pregnant Healthy Women Some Authorities Recommend an Initial Dose [2-4]
      150 mcg PO once per day OR  day or 2 mcg/kg per day.
      Clinical and laboratory evaluations should be performed at 4 week intervals until the TSH is stable. The dosage adjustment according to the following algorithm has been suggested: 

      For TSH (mU/ml) Increase levothryoxine dosage by
      4 to 10 41 +/- 24 mcg / day
      greater than 10  but less than or equal to 20 65 +/- 19 mcg / day
      greater than 20 105 +/- 32 mcg /day

      For Nonpregnant or Pregnant Women with a history of cardiovascular disease
       12.5 to 50 mcg once daily
      Adjustments of 12.5 to 25 mcg every 3 to 6 weeks until TSH is normalized.
       

  • Myxedema coma:

      300- 500 micrograms IV once. The initial dose is followed by daily intravenous doses of 75 to 100 mcg until the patient is stable and oral administration is feasible. Normal T4 levels are usually achieved in 24 hours.
       

  • Pituitary TSH suppression in the treatment or prevention of various types of euthyroid goiters including thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.

       As an adjunct to surgery and radioiodine therapy in the treatment of well differentiated (papillary and follicular) thyroid cancer.
      Levothyroxine sodium dose of greater than 2 mcg/kg/day. Generally, TSH is suppressed to <0.1 mU/L. However, in patients with high-risk tumors, the target level for TSH suppression may be <0.01 mU/L.

      In the treatment of benign nodules and nontoxic multinodular goiter.
      "
      TSH is generally suppressed to a higher target (e.g., 0.1—0.5 mU/L for nodules and 0.5—1.0 mU/L for multinodular goiter) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis "

 

Contraindicated in uncorrected adrenal insufficiency, untreated subclinical or overt thyrotoxicosis, and acute MI.

Levoxyl ® is supplied as:
(0.025, 0.05, 0.075, 0.088, 0.1, 0.112, 0.125, 0.137, 0.15, 0.175, 0.2, and 0.3 mg tablets ).

Synthroid® is supplied as:
(0.025, 0.05, 0.075, 0.088, 0.1, 0.112, 0.125, 0.137, 0.15, 0.175, 0.2, and 0.3 mg tablets Powder for intravenous injection: 6 and 10 ml vials containing 0.2 mg or 0.5mg of levothyroxine per vial.



 


Approximate Equivalent Strengths of Various Thyroid Preparations
 

Drug → Thyroid Tablets, USP
(Armour® Thyroid)
Liotrix Tablets, USP
(Thyrolar™)
Liothronine Tablets, USP
(Cytomel®)
Levothyroxine Tablets, USP
(Unithroid® , Levoxyl® , Levothroid® , Synthroid® )
Approx. Dose Equivalent 1/4 grain
(15 mg)
1/4   25 mcg (.025 mg)
Approx. Dose Equivalent 1/2 grain
(30 mg)
1/2 12.5 mcg 50 mcg (.05 mg)
Approx. Dose Equivalent 1 grain
(60 mg)
1 25 mcg 100 mcg ( .1 mg)
Approx. Dose Equivalent 1 1/2 grains (90 mg) 1 1/2 37.5 mcg 150 mcg (.15 mg)
Approx. Dose Equivalent 2 grains
 (120 mg)
2 50 mcg 200 mcg (.2 mg)
Approx. Dose Equivalent 3grains
(180 mg)
3 75 mcg 300 mcg (.3 mg)


United States Pharmacopoeia — Drug Information 2000, 20th Edition, Drug Information for the Health Care Professional; Vol. 1, pp. 2980-2986. World Color Book Services, Versailles, KY.


Hyperthyroidism

Thyroid Storm
Order set


Propylthiouracil (PTU)

Antithyroid drug. Suppresses thyroid hormone production by interfering with the organification of iodine. Inhibits peripheral conversion of thyroxine (T4) to triiodothyronine (T3).

PTU is preferred for pregnant women because methimazole has been associated with congenital aplasia cutis, a condition characterized by localized areas of absent ,"punched out", areas of  skin on the scalp. The lesions usually heal spontaneously.

  • Treatment of hyperthyroidism [5].
        Starting dose 150 mg orally every 8 hours. Dose may vary (50 to 200 mg every 8 hours)
        according to patient symptomatology.

        Free T4 is tested every two weeks and the dosage is adjusted to keep the FT4 in upper
        third of normal range. Reduce the dosage by 1/2 after FT4 begins to improve. The TSH will
        remain suppressed for weeks or months. Thyroid tests usually normalize within 3 to 8
        weeks.
        Consider obtaining a baseline leukocyte count and prothrombin time.
     

A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid.

Agranulocytosis is potentially the most serious adverse reaction. Symptoms include fever, sore throat, and malaise. Other adverse reactions include but are not limited to , aplastic anemia, metallic taste in mouth, arthralgia, myalgia, nausea, hepatitis, jaundice, lupus-like syndrome, vasculitis, hypothrombinemia, neuropathies,headache, vertigo, interstitial pneumonitis, insulin autoimmune syndrome (hypoglycemia).

Discontinue drug if agranulocytosis, aplastic anemia, hepatitis, fever, or exfoliative dermatitis occur.

(50 mg tablets)

May produce fetal goiter and hypothyroidism.
 




Methimazole (MMI) (Tapazole)
Antithyroid drug. Suppresses thyroid hormone production by interfering with the organification of iodine.

 

  • Treatment of hyperthyroidism [5].
        Starting dose 20 mg orally every 12  hours. Dose may vary (10 to 60 mg a day) according
        to patient symptomatology.
     
  • Free T4 is tested every two weeks and the dosage is adjusted to keep the FT4 in upper
        third of normal range. Reduce the dosage by 1/2 after FT4 begins to improve. The TSH will
        remain suppressed for weeks or months. Thyroid tests usually normalize within 3 to 8
        weeks.
        Consider obtain baseline leukocyte count and prothrombin time.

    A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid.

Agranulocytosis is potentially the most serious adverse reaction. Symptoms include fever, sore throat, and malaise. Other adverse reactions include but are not limited to , aplastic anemia, metallic taste in mouth, arthralgia, myalgia, nausea, hepatitis, jaundice, lupus-like syndrome, vasculitis, hypothrombinemia, neuropathies,headache, vertigo, interstitial pneumonitis, insulin autoimmune syndrome (hypoglycemia).

Discontinue drug if agranulocytosis, aplastic anemia, hepatitis, fever, or exfoliative dermatitis occur.

(5, 10 mg tablets)

-May produce fetal goiter and hypothyroidism.
Methimazole has been associated with congenital aplasia cutis, a condition characterized by localized areas of absent ,"punched out", areas of  skin on the scalp. The lesions usually heal spontaneously.
 


Propranolol (Inderal®)
Beta blocker

  • For the relief of the adrenergic symptoms of hyperthyroidism such as tremor, palpitations, heat intolerance, and nervousness.

    20 to 40 mg every 6 to 8 hours. Adjust dose to keep heart rate at 70 to 90 beats per minute. Beta blockade can be tapered after the free T4 has returned to normal range (~ 3 weeks) [5].

Avoid abrupt cessation of drug. Contraindicated in asthma, AV block, and overt heart failure.
(10, 20,40,60, 80  mg tablets)



REFERENCES

1.ACOG practice bulletin. Thyroid disease in pregnancy. Number 37, August 2002. American College of Obstetrics and Gynecology. Int J Gynaecol Obstet. 2002;79(2):171-80. PMID: 12481755
2. Hollowell JG, Staehling NW, Flanders WD, et al. Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab. 2002;87:489-499.PMID: 11836274
3. Montoro MN.Management of hypothyroidism during pregnancy.Clin Obstet Gynecol. 1997;40(1):65-80. pp 77 PMID:9103950
4. Kaplan MM Monitoring thyroxine treatment during pregnancy.Thyroid. 1992 ;2(2):147-52. PMID:1525583
5. Mestman JH. Hyperthyroidism in pregnancy.Clin Obstet Gynecol. 1997 Mar;40(1):45-64. PMID:9103949

   

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