Drilldown: Medicines

Cyanocobalamin (vitamin B12) (1) · Folic acid (folate, pteroylglutamic acid) (1) · Levothyroxine (1)

Folvite; mostly generic (1) · Many OTC and Rx; Nascobal (intranasal); generic injection (1) · Synthroid, Levoxyl, Tirosint, Unithroid, Euthyrox (1)

[[:Category:B-vitamins|B-vitamin]] (2) · [[:Category:Hematinics|Hematinic]] (2) · [[:Category:Hormone_replacement|Hormone replacement]] (1) · [[:Category:Thyroid_hormones|Thyroid hormone]] (1) · [[:Category:Vitamins|Vitamin]] (2)

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-00000033-QINU`"', '"`UNIQ--vote-00000034-QINU`"', '"`UNIQ--vote-00000035-QINU`"' (1) · '"`UNIQ--vote-000005B3-QINU`"', '"`UNIQ--vote-000005B4-QINU`"', '"`UNIQ--vote-000005B5-QINU`"', '"`UNIQ--vote-000005B6-QINU`"' (1) · '"`UNIQ--vote-00000607-QINU`"', '"`UNIQ--vote-00000608-QINU`"', '"`UNIQ--vote-00000609-QINU`"', '"`UNIQ--vote-0000060A-QINU`"' (1)

0.4 mg PO daily (general prevention); 0.8-1 mg/d in pregnancy; 4 mg/d for women with prior NTD-affected pregnancy; 1 mg/d during methotrexate therapy (1) · 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) · Replacement: 1000 mcg IM daily for 1 week, then weekly for 4 weeks, then monthly; or 1000-2000 mcg PO daily (effective even in pernicious anemia via passive diffusion); intranasal 500 mcg weekly (1)

0.4, 0.8, 1 mg OTC; 1 mg Rx; 5 mg/mL injection (1) · 100, 250, 500, 1000, 5000 mcg tablets (OTC and Rx); 1000 mcg/mL injection; intranasal spray; sublingual (1) · 25, 50, 75, 88, 100, 112, 125, 137, 150, 175, 200, 300 mcg tablets; oral capsule and IV/IM also available (1)

1 mg/d typical Rx; higher in specific indications (1) · No fixed maximum; titrated to TSH target (1) · No strict ceiling; water-soluble vitamin, low toxicity (1)

None · Oral · IV · topical · IM · intranasal · rectal · Subcutaneous · Topical ophthalmic · ophthalmic · intramuscular · intravenous · transdermal · vaginal · Subcutaneous (abdomen · sublingual · thigh · inhaled · SC · intra-articular

Other values:

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Hematologic response within days (1) · Reticulocyte response at 3-5 days; neurologic recovery weeks to months (and may be incomplete if longstanding) (1) · TSH normalization 4-8 weeks; symptomatic improvement weeks to months (1)

None · 24 hours · 4-6 hours · 12 hours · 6-8 hours · Daily dosing · 8-12 hours · 12-24 hours · Hours · Hours per application · 24 hours (HS dosing) · 24 hours (once-daily dosing) · 24 h · N/A · N/A (replacement) · Variable · ~7-8 hours · 3-5 hours · 4-6 hours (IR); 24 hours (ER) · 6-12 hours

Other values:

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~0.5 hours plasma; tissue retention longer (1) · ~6 days (plasma); hepatic stores last 3-5 years (1) · ~7 days (euthyroid); longer in hypothyroidism (~9-10 days), shorter in hyperthyroidism'"`UNIQ--ref-00000036-QINU`"' (1)

40-80% (oral); reduced by food, calcium, iron, PPIs, fiber; take fasting with water'"`UNIQ--ref-00000037-QINU`"' (1) · High (oral) (1) · Oral ~1-3% via passive diffusion at high doses (independent of intrinsic factor); IM/SC ~100% (1)

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.">&#91;[[Pharmacopedia:Citation needed|citation&nbsp;needed]]&#93;</sup> (1) · Routinely supplemented in pregnancy and preconception to prevent neural tube defects.<sup class="pcp-cn" title="This claim needs a citation.">&#91;[[Pharmacopedia:Citation needed|citation&nbsp;needed]]&#93;</sup> (1) · Routinely supplemented in vegan pregnancies and pernicious anemia.<sup class="pcp-cn" title="This claim needs a citation.">&#91;[[Pharmacopedia:Citation needed|citation&nbsp;needed]]&#93;</sup> (1)

OTC (low-dose) and [[USLegal:Prescription only|Rx-only]] (1 mg, injectable) in US (1) · OTC (low/mid-dose oral) and [[USLegal:Prescription only|Rx-only]] (injection, intranasal) in US (1) · [[USLegal:Prescription only|Rx-only]] in US (1)