AGE | Daily Dose Per Kg Body Weight
|
---|---|
0-3 months | 10-15 mcg/kg/day |
3-6 months | 8-10 mcg/kg/day |
6-12 months | 6-8 mcg/kg/day |
1-5 years | 5-6 mcg/kg/day |
6-12 years | 4-5 mcg/kg/day |
Greater than 12 years but growth and puberty incomplete | 2-3 mcg/kg/day |
Growth and puberty complete | 1.6 mcg/kg/day |
a. The dose should be adjusted based on clinical response and laboratory parameters
|
Tablet Strength | Tablet Color/Shape | Tablet Markings |
---|---|---|
25 mcg | Orange/Caplet | "25" and "GG/331" |
50 mcg | White/ Caplet | "50" and "GG/332" |
75 mcg | Violet/ Caplet | "75" and "GG/333" |
88 mcg | Olive Green/ Caplet | "88" and "GG/334" |
100 mcg | Yellow/ Caplet | "100" and "GG/335" |
112 mcg | Rose/ Caplet | "112" and "GG/336" |
125 mcg | Brown/ Caplet | "125" and "GG/337" |
137 mcg | Turquoise/ Caplet | "137" and "GG/330" |
150 mcg | Blue/ Caplet | "150" and "GG/338" |
175 mcg | Lilac/ Caplet | "175" and "GG/339" |
200 mcg | Pink/ Caplet | "200" and "GG/340" |
300 mcg | Green/ Caplet | "300" and "GG/341" |
Potential impact: Concurrent use may reduce the efficacy of levothyroxine sodium tablets by binding and delaying or preventing absorption, potentially resulting in hypothyroidism. | |
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Calcium Carbonate
Ferrous Sulfate |
Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine sodium tablets at least 4 hours apart from these agents. |
Orlistat | Monitor patients treated concomitantly with orlistat and levothyroxine sodium tablets for changes in thyroid function. |
Bile Acid Sequestrants
-Colesevelam -Cholestyramine -Colestipol Ion Exchange Resins -Kayexalate -Sevelamer |
Bile acid sequestrants and ion exchange resins are known to decrease levothyroxine absorption. Administer levothyroxine sodium tablets at least 4 hours prior to these drugs or monitor TSH levels. |
Proton Pump Inhibitors Antacids - Aluminum & Magnesium Hydroxides - Simethicone |
Gastric acidity is an essential requirement for adequate absorption of levothyroxine. Sucralfate, antacids and proton pump inhibitors may cause hypochlorhydria, affect intragastric pH, and reduce levothyroxine absorption. Monitor patients appropriately. |
Drug or Drug Class | Effect |
---|---|
Clofibrate
Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen |
These drugs may increase serum thyroxine-binding globulin (TBG) concentration. |
Androgens / Anabolic Steroids
Asparaginase Glucocorticoids Slow-Release Nicotinic Acid |
These drugs may decrease serum TBG concentration. |
Potential impact (below): Administration of these agents with levothyroxine sodium tablets results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations. | |
Salicylates (> 2 g/day) | Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T4 levels may decrease by as much as 30%. |
Other drugs:
Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs -Fenamates |
These drugs may cause protein-binding site displacement. Furosemide has been shown to inhibit the protein binding of T4 to TBG and albumin, causing an increase free T4 fraction in serum. Furosemide competes for T4-binding sites on TBG, prealbumin, and albumin, so that a single high dose can acutely lower the total T4 level. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Closely monitor thyroid hormone parameters. |
Potential impact: Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine sodium tablets requirements. | |
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Phenobarbital Rifampin | Phenobarbital has been shown to reduce the response to thyroxine. Phenobarbital increases L-thyroxine metabolism by inducing uridine 5'-diphospho-glucuronosyltransferase (UGT) and leads to a lower T4 serum levels. Changes in thyroid status may occur if barbiturates are added or withdrawn from patients being treated for hypothyroidism. Rifampin has been shown to accelerate the metabolism of levothyroxine. |
Potential impact: Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3, leading to decreased T3 levels. However, serum T4 levels are usually normal but may occasionally be slightly increased. | |
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Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day) | In patients treated with large doses of propranolol (> 160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are clinically euthyroid. Actions of particular beta-adrenergic antagonists may be impaired when a hypothyroid patient is converted to the euthyroid state. |
Glucocorticoids (e.g., Dexamethasone ≥ 4 mg/day) | Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (See above). |
Other drugs: Amiodarone | Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients. |
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25 | FD&C Yellow No. 6 Aluminum Lake |
50 | None |
75 | FD&C Blue No. 2 Aluminum Lake, D&C Red No. 27 Aluminum Lake |
88 | FD&C Blue No. 1 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake, D&C RedNo. 30 Aluminum Lake |
100 | D&C Yellow No. 10 Aluminum Lake, D&C Red Lake Blend (D&C Red No. 27 Lake and D&C Red No. 30 Lake) |
112 | D&C Red No. 27 Aluminum Lake, D&C Red No. 30 Aluminum Lake |
125 | FD&C Yellow No. 6 Aluminum Lake, FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake |
137 | FD&C Blue No. 1 Aluminum Lake |
150 | FD&C Blue No. 2 Aluminum Lake |
175 | D&C Red No. 27 Aluminum Lake, D&C Red No. 30 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake |
200 | D&C Yellow No. 10 Aluminum Lake, D&C Red No. 27 Aluminum Lake |
300 | D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake |
Hormone | Ratio in Thyroglobulin | Biologic Potency | t 1/2 (days) | Protein Binding (%)
a
|
---|---|---|---|---|
Levothyroxine (T4) | 10 - 20 | 1 | 6-7
b
|
99.96 |
Liothyronine (T3) | 1 | 4 | ≤ 2 | 99.5 |
a - Includes TBG, TBPA, and TBA
b - 3 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism |
Strength (mcg) | Color/Shape | Tablet Markings | NDC# for bottles of 30 | |
---|---|---|---|---|
137 | Turquoise/ Caplet | "137" and "GG/330" | 51655-128-52 |