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.
Cytomel (liothyronine sodium) Tablets are intended for
oral administration; once-a-day dosage is recommended. Although liothyronine
sodium has a rapid cutoff, its metabolic effects persist for a few days
Recommended starting dosage is 25 mcg daily. Daily dosage
then may be increased by up to 25 mcg every 1 or 2 weeks. Usual maintenance
dose is 25 to75 mcg daily.
The rapid onset and dissipation of action of liothyronine
sodium (T3), as compared with levothyroxine sodium (T4), has led some
clinicians to prefer its use in patients who might be more susceptible to the untoward
effects of thyroid medication. However, the wide swings in serum T levels that
follow its administration and the possibility of more pronounced cardiovascular
side effects tend to counterbalance the stated advantages.
Cytomel (liothyronine sodium) Tablets may be used in
preference to levothyroxine (T4) during radioisotope 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 to T3 is suspected.
Recommended starting dosage is 5 mcg daily. This may be
increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is
reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks until a
satisfactory therapeutic response is attained. Usual maintenance dose is 50 to
100 mcg daily.
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.
An intravenous preparation of liothyronine sodium is recommended
for use in myxedema coma/precoma.
Recommended starting dosage is 5 mcg daily, with a 5 mcg
increment every 3 to 4 days until the desired response is achieved. Infants a
few months old may require only 20 mcg daily for maintenance. At 1 year, 50 mcg
daily may be required. Above 3 years, full adult dosage may be necessary (see PRECAUTIONS
; Pediatric Use).
Simple (non-toxic) Goiter
Recommended starting dosage is 5 mcg daily. This dosage
may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is
reached, dosage may be increased every week or two by 12.5 or 25 mcg. Usual
maintenance dosage is 75 mcg daily.
In the elderly or in pediatric patients, therapy
should be started with 5 mcg daily and increased only by 5 mcg increments at
the recommended intervals.
When switching a patient to Cytomel (liothyronine sodium)
Tablets from thyroid, L-thyroxine or thyroglobulin, discontinue the other
medication, initiate Cytomel at a low dosage, and increase gradually according
to the patient's response. When selecting a starting dosage, bear in mind that
this drug has a rapid onset of action, and that residual effects of the other
thyroid preparation may persist for the first several weeks of therapy.
Thyroid Supression 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 baseline laboratory tests appear normal or to
demonstrate thyroid gland autonomy in patients with Graves' ophthalmopathy. I
uptake is determined before and after the administration of the exogenous hormone.
A 50% or greater suppression of uptake indicates a normal thyroid-pituitary
axis and thus rules out thyroid gland autonomy.
Cytomel (liothyronine sodium) Tablets are given in doses
of 75 to 100 mcg/day for 7 days, and radioactive iodine uptake is determined
before and after administration of the hormone. If thyroid function is under
normal control, the radioiodine uptake will drop significantly after treatment.
Cytomel (liothyronine sodium) Tablets should be administered cautiously to
patients in whom there is a strong suspicion of thyroid gland autonomy, in view
of the fact that the exogenous hormone effects will be additive to the
Cytomel (liothyronine sodium) Tablets: 5 mcg in bottles
of 100; 25 mcg in bottles of 100; and 50 mcg in bottles of 100.
5 mcg 100's: NDC 60793-115-01
25 mcg 100's: NDC 60793-116-01
50 mcg 100's: NDC 60793-117-01
Store between 15° and 30°C (59° and 86°F).
Distributed by:Â Â Pfizer Inc, New York, 10017. Revised: June 2016