Drilldown: Medicines
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generic:
brand:
classes:
mechanism:
None (2) ·
Synthetic T4 (thyroxine); peripherally deiodinated to T3 (triiodothyronine), the active hormone. '"`UNIQ--vote-00000031-QINU`"' Narrow therapeutic index; brand-to-generic switches can shift TSH and require re-titration'"`UNIQ--ref-00000032-QINU`"'. (1) ·
'"`UNIQ--vote-00000032-QINU`"' Brand-to-brand and lot-to-lot variability in T3:T4 ratio is greater than with synthetic levothyroxine, which is why endocrine guidelines prefer the synthetic'"`UNIQ--ref-00000033-QINU`"'. (1)
uses:
Insomnia (sleep onset and/or sleep maintenance) in adults (FDA-approved Jan 2022) (1) ·
'"`UNIQ--vote-00000033-QINU`"', '"`UNIQ--vote-00000034-QINU`"', '"`UNIQ--vote-00000035-QINU`"' (1) ·
'"`UNIQ--vote-00000034-QINU`"', '"`UNIQ--vote-00000035-QINU`"' (1) ·
'"`UNIQ--vote-00000C4C-QINU`"', '"`UNIQ--vote-00000C4D-QINU`"' (1)
starting dose:
1.6 mcg/kg/d in young healthy adults; 25-50 mcg/d in elderly or cardiac disease, titrated by TSH at 6-8 weeks (1) ·
25 mg PO at bedtime (no titration); may increase to 50 mg if 25 mg inadequate (1) ·
25 mg PO once daily; titrate to 50 mg after 4-8 weeks if needed (1) ·
30 mg PO daily (1/2 grain); titrate by TSH at 6-8 weeks; 60 mg desiccated thyroid is approximately equivalent to 88-100 mcg levothyroxine (1)
preparations:
15, 30, 60, 90, 120, 180, 240, 300 mg tablets (1/4 to 5 grains; 1 grain = 60 mg) (1) ·
25 mg, 50 mg tablets (1) ·
25, 50 mg ER tablets; 8 mg/mL granules for oral suspension (Myrbetriq Granules, pediatric) (1) ·
25, 50, 75, 88, 100, 112, 125, 137, 150, 175, 200, 300 mcg tablets; oral capsule and IV/IM also available (1)
fda max: (Click arrow to add another value)
routes: (Click arrow to add another value)
onset:
duration:
halflife:
bioavailability:
25 mg: ~29%; 50 mg: ~35%; food reduces absorption'"`UNIQ--ref-00000C4F-QINU`"' (1) ·
40-80% (oral); reduced by food, calcium, iron, PPIs, fiber; take fasting with water'"`UNIQ--ref-00000037-QINU`"' (1) ·
Variable; reduced by food, calcium, iron, PPIs'"`UNIQ--ref-00000037-QINU`"' (1) ·
~62% (1)
pregnancy:
First-line in pregnancy; dose typically increased 25-30% due to estrogen-driven rise in TBG and fetal demand. Lactation safe at physiologic doses.<sup class="pcp-cn" title="This claim needs a citation.">[[[Pharmacopedia:Citation needed|citation needed]]]</sup> (1) ·
Limited data.<sup class="pcp-cn" title="This claim needs a citation.">[[[Pharmacopedia:Citation needed|citation needed]]]</sup> (1) ·
Limited data; avoid (1) ·
Synthetic levothyroxine is the standard-of-care in pregnancy; desiccated thyroid use in pregnancy is not well studied<sup class="pcp-cn" title="This claim needs a citation.">[[[Pharmacopedia:Citation needed|citation needed]]]</sup> (1)
Showing below up to 4 results in range #1 to #4.