DOSAGE AND ADMINISTRATION
The dosage of thyroid hormones is determined by the
indication and must in every case be individualized according to patient
response and laboratory findings. Thyroid hormones are given orally. In acute,
emergency conditions, injectable levothyroxine sodium may be given
intravenously when oral administration is not feasible or desirable, as in the
treatment of myxedema coma, or during total parenteral nutrition. Intramuscular
administration is not advisable because of reported poor absorption.
Therapy is usually instituted using low doses, with
increments which depend on the cardiovascular status of the patient. The usual
starting dose is 30 mg NP Thyroid, with increments of 15 mg every 2 to 3 weeks.
A lower starting dosage, 15 mg/day, is recommended in patients with long
standing myxedema, particularly if cardiovascular impairment is suspected, in
which case extreme caution is recommended. The appearance of angina is an
indication for a reduction in dosage. Most patients require 60 to 120 mg/day.
Failure to respond to doses of 180 mg suggests lack of compliance or
malabsorption. Maintenance dosages 60 to 120 mg/day usually result in normal serum
levothyroxine (T4) and liothyronine (T3) levels. Adequate therapy usually
results in normal TSH and T4 levels after 2 to 3 weeks of therapy. Readjustment
of thyroid hormone dosage should be made within the first four weeks of
therapy, after proper clinical and laboratory evaluations, including serum
levels of T4, bound and free, and TSH. T3 may be used in preference to
levothyroxine (T4) during radio-isotope scanning procedures, since induction of
hypothyroidism in those cases is more abrupt and can be of shorter duration. It
may also be preferred when impairment of peripheral conversion of T4 and T3 is
Myxedema coma is usually precipitated in the hypothyroid
patient of long-standing by intercurrent illness or drugs such as sedatives and
anesthetics and should be considered a medical emergency. Therapy should be
directed at the correction of electrolyte disturbances and possible infection
besides the administration of thyroid hormones. Corticosteroids should be
administered routinely. T4 and T3 may be administered via a nasogastric tube
but the preferred route of administration of both hormones is intravenous.
Levothyroxine sodium (T4) is given at starting dose of 400 mcg (100 mcg/mL)
given rapidly, and is usually well tolerated, even in the elderly. This initial
dose is followed by daily supplements of 100 to 200 mcg given intravenously.
Normal T4 levels are achieved in 24 hours followed in 3 days by threefold
elevation of T3. Oral therapy with thyroid hormone would be resumed as soon as
the clinical situation has been stabilized and the patient is able to take oral
Exogenous thyroid hormone may produce regression of
metastases from follicular and papillary carcinoma of the thyroid and is used
as ancillary therapy of these conditions with radio-active iodine. TSH should
be suppressed to low or undetectable levels. Therefore, larger amounts of
thyroid hormone than those used for replacement therapy are required. Medullary
carcinoma of the thyroid is usually unresponsive to this therapy.
Thyroid Suppression Therapy
Administration of thyroid hormone in doses higher than
those produced physiologically by the gland results in suppression of the
production of endogenous hormone. This is the basis for the thyroid suppression
test and is used as an aid in the diagnosis of patients with signs of mild
hyperthyroidism in whom base line laboratory tests appear normal, or to
demonstrate thyroid gland autonomy in patients with Grave's ophthalmopathy.
131I uptake is determined before and after the administration of the exogenous
hormone. A 50 percent or greater suppression of uptake indicates a normal
thyroid-pituitary axis and thus rules out thyroid gland autonomy. For adults, the
usual suppressive dose of levothyroxine (T4) is 1.56 mcg/kg of body weight per
day given for 7 to 10 days. These doses usually yield normal serum T4 and T3
levels and lack of response to TSH. Thyroid hormones should be administered
cautiously to patients in whom there is strong suspicion of thyroid gland
autonomy, in view of the fact that the exogenous hormone effects will be
additive to the endogenous source.
Pediatric dosage should follow the recommendations
summarized in Table 1. In infants with congenital hypothyroidism, therapy with
full doses should be instituted as soon as the diagnosis has been made.
Recommended Pediatric Dosage for Congenital
||Dose per day
||Daily dose per kg of body weight
|0 - 6 mos.
||15 - 30 mg
||4.8 - 6 mg
|6 - 12 mos.
||30 - 45 mg
||3.6 - 4.8 mg
|1 - yrs.
||45 - 60 mg
||3 - 3.6 mg
|6 - 12 yrs.
||60 - 90 mg
||2.4 - 3 mg
|Over 12 yrs.
||Over 90 mg
||1.2 - 1.8 mg
NP Thyroid® tablets (thyroid tablets, USP) are supplied
in bottles of 100 as follows: 15 mg (1/4 gr) NDC 42192-327-01, 30 mg (½ gr)
NDC 42192-329-01, 60 mg (1 gr) NDC 42192-330-01, 90 mg (1 ½ gr) NDC 42192-331-01 and 120 mg (2 gr) NDC 42192-328-01.
NP Thyroid® tablets are tan, round tablets, debossed on
one side with “AP” and a 3-digit code on the other side as follows:
30 mg (½ grain) – “329” 60 mg (1 grain) – “330”
90 mg (1 ½ grain) – “331” 120 mg (2 grain) – “328”
NP Thyroid® 15 mg tablets (1/4 gr) are tan, oval-shaped
tablets, debossed on one side with “AP” and this 3-digit code on the other
Store in a tight container protected from light and
moisture. Store between 15°-30°C (59°-86°F).
All prescription substitutions and/or recommendations
using this product shall be made subject to state and federal statutes as
applicable. Please note: This is not an Orange Book product and has not been
subjected to FDA therapeutic equivalency or other equivalency testing. No
representation is made as to generic status or bioequivalency. Each person
recommending a prescription substitution using this product shall make such
recommendations based on each such person's professional opinion and knowledge,
upon evaluating the active ingredients, excipients, inactive ingredients and
chemical information provided herein.
MANUFACTURED FOR: Acella Pharmaceuticals, LLC, Alpharetta,
GA 30005, 1-800-541-4802. Rev Jun 2018