Levothyroxine
(Synthroid, Levothroid, Levoxine) |
Category:
Description:
Indications:
-
Hypothyroidism
(including cretinism, myxedema, non-toxic goiter)
-
Pituitary
TSH suppression (thyroid nodules, Hashimoto’s disease, multinodular
goiter, thyroid cancer)
-
Thyrotoxicosis
(with antithyroid drugs)
Contraindications:
-
Adrenal
insufficiency, MI
-
Thryrotoxicosis,
hypersensitivity
Precautions:
Adverse
Reactions (Side Effects):
-
CNS:
headache, insomnia, nervousness, tremors
-
CV:
angina pectoris, cardiac arrest, cardiac dysrhythmias, palpitations,
tachycardia
-
GI:
diarrhea, gastric
intolerance, vomiting
-
GU:
menstrual irregularities
-
MISC:
fever, heat intolerance, sweating, weight loss, allergic skin
reactions (rare)
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Dosage:
Administered
orally, intramuscularly, intravenously
Adult:
-
Hypothyroidism:
-
PO
50mcg daily to start, increase by 25-50mcg daily at intervals of
2-4 weeks, usual dose 100-200mcg daily as a single dose;
-
use
= < 25 mcg/day in patients with long-standing hypothyroidism if
cardovascular impairment present;
-
IM/IV
50% of oral dose
-
Myxedema:
-
IV
200-500mcg 1 time, then 100-300mcg the next day as needed;
-
resume
oral therapy as soon as clinical situation stabilized
-
TSH
suppression:
Child
-
0-6
months: PO 8-10 mcg/kg or 25-50mcg daily
-
6-12
months: PO 6-8 mcg/kg or 50-75mcg daily
-
1-5
years: PO 5-6 mcg/kg or 75-100mcg daily
-
6-12
years: PO 4-5 mcg/kg or 100-150mcg daily
-
IM/IV
75% of oral dose
Drug
interactions:
-
Bile
sequestrants: reduced serum thyroid hormone concentrations
-
Carbamazepine,
phenytoin, rifampin: increased elimination of thryroid hormones;
possible increased requirement for thryroid hormone in hypothyroid
patients
-
Oral
anticoagulants: thryoid hormones increase catabolism of vitamin
K-dependent clotting factors; an increase or decrease in clinical
thyroid status will increase or decrease the hypoprothrombinemic
response to oral anticoagulants
-
Theophylline:
reduced serum theophylline concentrations with initiation of thyroid
therapy
Special
considerations:
-
Transient,
partial hair loss may be experienced by children in the 1st few months of therapy
-
Take
as a single daily dose, preferably before breakfast
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The information contained here is an
abbreviated summary. For more detailed and complete information, consult the
manufacturer's product information sheets or standard textbooks
Source: Operational Medicine 2001, Health
Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau
of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington,
D.C., 20372-5300
This information is provided by The Brookside Associates. The Brookside
Associates, LLC. is a private organization, not affiliated with any governmental
agency. The opinions presented here are those of the author and do not
necessarily represent the opinions of the Brookside Associates or the Department
of Defense. The presence of any advertising on these pages does not constitute
an endorsement of that product or service by either the US Department of Defense
or the Brookside Associates. All material presented here is unclassified.
C. 2009, 2014, All Rights Reserved
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