Dosing and uses of Thyrolar (liotrix)
Adult dosage forms and strengths
Each 60 mg tablet will replace approximately 60-65 mg (1 grain) of desicated thyroid
Liothyronine sodium (T3) is approximately 4 times as potent as levothyroxine (T4)
tablet, T3/T4
- Thyrolar 1/4 (15mg): 3.1/12.5mcg
- Thyrolar 1/2 (30mg): 6.25/25mcg
- Thyrolar 1 (60mg): 12.5/50mcg
- Thyrolar 2 (120mg): 25/100mcg
- Thyrolar 3 (180mg): 37.5/150mcg
Hypothyroidism
1 tab of Thyrolar 1/2 daily; follow with increments of 1 tab of Thyrolar 1/4 q2-3wk
Lower starting dose of 1 tab recommended in long-standing myxedema, especially if cardiovascular impairment suspected where extreme caution recommended
Maintenance: 1 tab Thyrolar 1 to 1 tab Thyrolar 2 per day; failure to respond to tab Thyrolar 3 may suggest lack of compliance or malabsorption
Adjust dose within the first 4 weeks of therapy after proper clinical laboratory evaluations where serum levels of T4 bound and free TSH are measured
Administer before breakfast
Pediatric dosage forms and strengths
Each 60 mg tablet will replace approximately 60-65 mg (1 grain) of desicated thyroid
Liothyronine sodium (T3) is approximately 4 times as potent as levothyroxine (T4)
tablet, T3/T4
- Thyrolar 1/4 (15mg): 3.1/12.5mcg
- Thyrolar 1/2 (30mg): 6.25/25mcg
- Thyrolar 1 (60mg): 12.5/50mcg
- Thyrolar 2 (120mg): 25/100mcg
- Thyrolar 3 (180mg): 37.5/150mcg
Congenital Hypothyroidism
0-6 months: 3.1/12.5 to 6.25/25 PO;
6-12 months: 6.25/25 to 9.35/37.5 PO;
1-5 years: 9.35/37.5-12.5/50 mcg PO;
6-12 years: 12.5/50-18.75/75 mcg PO;
>12 years: >18.75/75 mcg PO;
Administration: Before breakfast
Thyrolar (liotrix) adverse (side) effects
Frequency not defined
Arrhythmias
Increased blood pressure
Chest pain
Palpitation
Anxiety
Headache
Urticaria
Changes in menstrual cycle
Insomnia
Hyperhydrosis pruritus
Tachycardia
Nervousness
Tremor
Cramps
Increased appetite
Weight loss
Diarrhea
Warnings
Black box warnings
Thyroid hormones, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss
In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.
Contraindications
Hypersensitivity to thyroid hormone
Acute MI uncomplicated by hypothyroidism, untreated thyrotoxicosis, untreated adrenal insufficiency
Treatment of obesity
Cautions
Caution in angina, cardiovascular disease, HTN, endocrine disorders, elderly
Use caution in patients with adrenal insufficiency (symptoms may become exagerated or aggravated)
Euthroid withdrawn from U.S. market
Use caution in patients with myxedema (symptoms may become exagerated or aggravated)
No advantage over levothyroxine & may do more harm (T3 overdosage) than good
Not for the treatment of female infertility in euthyroid patients
Pregnancy and lactation
Pregnancy category: A
Lactation: Small amount excreted into breast milk, use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Thyrolar (liotrix)
Mechanism of action
Natural thyroid hormone; increases basal metabolic rate, increases utilization and mobilization of glycogen store, promotes gluconeogenesis
Pharmacokinetics
Half-Life (T4): 6-7 days (euthyroid); 3-4 days (hyperthyroid); 9-10 days (hypothyroid)
Half-life (T3): 2.5 days
Onset: 48 hr
Absorption: 40-80% (T4); 95% (T3)
Max effect: 8-10 days
Peak Plasma Time: 12-48 hr
Bioavailability: 50-95%
Protein Bound: 99% (T4)
Metabolism: Liver, also in kidney & intestinal walls
Metabolites: Triiodothyronine (T3)
Excretion: Urine (major), feces
