A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Cytomel Side Effects, and Drug Interactions - Liothyronine Sodium
Cytomel Side Effects, and Drug Interactions - Liothyronine Sodium
SIDE EFFECTS
Adverse reactions, other than those indicative of hyperthyroidism because
of therapeutic ovserdosage, either initially or during the maintenance
period are rare (see OVERDOSAGE).
In rare instances, allergic skin reactions have been reported with Cytomel
(liothyronine sodium) Tablets.
DRUG INTERACTIONS
Oral Anticoagulants: Thyroid hormones appear to increase catabolism
of vitamin K-dependent clotting factors. If oral anticoagulants are also
being given, compensatory increases in clotting factor synthesis are impaired.
Patients stabilized on oral anticoagulants who are found to require thyroid
replacement therapy should be watched very closely when thyroid is started.
If a patient is truly hypothyroid, it is likely that a reduction in anticoagulant
dosage will be required. No special precautions appear to be necessary
when oral anticoagulant therapy is begun in a patient already stabilized
on maintenance thyroid replacement therapy.
Insulin or Oral Hypoglycemics: Initiating thyroid replacement
therapy may cause increases in insulin or oral hypoglycemic requirements.
The effects seen are poorly understood and depend upon a variety of factors
such as dose and type of thyroid preparations and endocrine status of
the patient. Patients receiving insulin or oral hypoglycemics should be
closely watched during initiation of thyroid replacement therapy.
Cholestyramine: Cholestyramine binds both T4 and T3
in the intestine, thus impairing absorption of these thyroid hormones.
In vitro studies indicate that the binding is not easily removed.
Therefore, 4 to 5 hours should elapse between administration of cholestyramine
and thyroid hormones.
Estrogen, Oral Contraceptives: Estrogens tend to increase serum
thyroxine-binding globulin (TBg). In a patient with a nonfunctioning thyroid
gland who is receiving thyroid replacement therapy, free levothyroxine
may be decreased when estrogens are started thus increasing thyroid requirements.
However, if the patient's thyroid gland has sufficient function, the decreased
free thyroxine will result in a compensatory increase in thyroxine output
by the thyroid. Therefore, patients without a functioning thyroid gland
who are on thyroid replacement therapy may need to increase their thyroid
dose if estrogens or estrogen-containing oral contraceptives are given.
Tricyclic Antidepressants: Use of thyroid products with imipramine
and other tricyclic antidepressants may increase receptor sensitivity
and enhance antidepressant activity transient cardiac arrhythmias have
been observed. Thyroid hormone activity may also be enhanced.
Digitalis: Thyroid preparations may potentiate the toxic effects
of digitalis. Thyroid hormonal replacement increases metabolic rate, which
requires an increase in digitalis dosage.
Ketamine: When administered to patients on a thyroid preparation,
this parenteral anesthetic may cause hypertension and tachycardia. Use
with caution and be prepared to treat hypertension, if necessary.
Vasopressors: Thyroxine increases the adrenergic effect of catecholamines
such as epinephrine and norepinephrine. Therefore, injection of these
agents into patients receiving thyroid preparations increases the risk
of precipitating coronary insufficiency especially in patients with coronary
artery disease. Careful observation is required.
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