Drilldown: Medicines

Levothyroxine (1) · Thyroid (desiccated) (1) · Valacyclovir (1)

Armour Thyroid, NP Thyroid, Nature-Throid, WP Thyroid (1) · Synthroid, Levoxyl, Tirosint, Unithroid, Euthyrox (1) · Valtrex (1)

[[:Category:Anti-herpesvirus_agents|Anti-herpesvirus agent]] (1) · [[:Category:Antivirals|Antiviral]] (1) · [[:Category:Hormone_replacement|Hormone replacement]] (2) · [[:Category:Nucleoside_analogs|Nucleoside analog (prodrug)]] (1) · [[:Category:Thyroid_hormones|Thyroid hormone]] (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-00000016-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-00000017-QINU`"'. (1) · '"`UNIQ--vote-000005D0-QINU`"' Selectivity comes from the viral-kinase-only initial phosphorylation step, which is why uninfected cells generate minimal active drug'"`UNIQ--ref-000005D1-QINU`"'. Dose-adjust by renal function; rare crystalline nephropathy with rapid IV acyclovir. (1)

'"`UNIQ--vote-00000018-QINU`"', '"`UNIQ--vote-00000019-QINU`"' (1) · '"`UNIQ--vote-00000033-QINU`"', '"`UNIQ--vote-00000034-QINU`"', '"`UNIQ--vote-00000035-QINU`"' (1) · '"`UNIQ--vote-000005D2-QINU`"', '"`UNIQ--vote-000005D3-QINU`"', '"`UNIQ--vote-000005D4-QINU`"', '"`UNIQ--vote-000005D5-QINU`"' (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) · 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) · Initial genital herpes 1 g PO BID × 10 days; recurrent 500 mg BID × 3 days; suppression 500 mg-1 g PO daily; zoster 1 g TID × 7 days (1)

15, 30, 60, 90, 120, 180, 240, 300 mg tablets (1/4 to 5 grains; 1 grain = 60 mg) (1) · 25, 50, 75, 88, 100, 112, 125, 137, 150, 175, 200, 300 mcg tablets; oral capsule and IV/IM also available (1) · 500 mg, 1 g tablets (1)

None · Indication-specific · 40 mg/d · 10 mg/d · 20 mg/d · 80 mg/d · 10 mg/d (adults) · 100 mg/d · 4 g/d · 400 mg/d · 40 mg/d typical; up to 240 mg/d for Zollinger-Ellison · 5 mg/d · 50 mg/d · 600 mg/d · No fixed ceiling; titrate to clinical effect and tolerability with CDC opioid prescribing guidance constraints on morphine-milligram-equivalent (MME) totals · No fixed maximum; titrated to TSH target · TID per eye · Titrated to glucose; no fixed ceiling · Titrated to glucose; no fixed maximum · '''20 mg/day in adults >60 years''' per FDA's 2011-2012 QT-prolongation warning; 40 mg/day in adults ≤60

Other values:

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IV (1) · Oral (3)

Symptom relief within 24-48 hours (1) · TSH normalization 4-8 weeks (1) · TSH normalization 4-8 weeks; symptomatic improvement weeks to months (1)

8 hours per dose (1) · Steady-state at 4-6 weeks (2)

T4 ~7 days; T3 ~1 day'"`UNIQ--ref-0000001A-QINU`"' (1) · ~3 hours (acyclovir, the active metabolite); longer in renal impairment'"`UNIQ--ref-000005D6-QINU`"' (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) · Variable; reduced by food, calcium, iron, PPIs'"`UNIQ--ref-0000001B-QINU`"' (1) · ~55% bioavailability of acyclovir after valacyclovir oral (vs ~20% from oral acyclovir directly)'"`UNIQ--ref-000005D7-QINU`"' (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) · Synthetic levothyroxine is the standard-of-care in pregnancy; desiccated thyroid use in pregnancy is not well studied.'"`UNIQ--ref-0000001C-QINU`"' (1) · Widely used in pregnancy when antiviral indicated; reassuring registry data.<sup class="pcp-cn" title="This claim needs a citation.">&#91;[[Pharmacopedia:Citation needed|citation&nbsp;needed]]&#93;</sup> (1)

[[USLegal:Prescription only|Rx-only]] in US (3)