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Thyroid Replacements - levothyroxine (Synthroid) Cheat Sheet by

Used for thyroid replacement therapy in hypothyroid patients

Med Names

Prototype Med
Levoth­yroxine (Synth­roid)
Other Meds
liothy­roxine (Cytomel)
liotrix (Thyrolar)
Thyroid USP
Action: Levoth­yroxine is a synthetic form of thyroxine or T4 which is then converted to T3 in the body

Ther­apeutic Use


Adverse Drug Reacti­ons

Thyrot­oxi­cosis, Hypert­hyr­oidism (from excessive doses)
Headache, irrita­bility, insomnia
Abdominal cramping, diarrhea
Tachyc­ardia, arrhythmia
Heat intole­rance, diapho­resis
Menstrual irregu­lar­ities

Nursing Interv­ent­ions

Monitor thyroid function
Monitor for indica­tions of hypert­hyr­oidism (anxiety, tachyc­ardia, palpi- tations, tremors, altered appetite, heat intole­rance, fever, diapho­resis, weight loss)

Patient Educat­ion

Watch for and report nervou­sness, rapid heart rate, palpit­ations, trem- ors, altered appetite, heat intole­rance, fever, sweating, weight loss, and chest pain.


Recent myocardial infarction


Cardio­vas­cular disorders (hyper­ten­sion, angina pectoris, ischemic heart disease)
Renal impairment
Diabetes mellitus
Older adults


Give orally to treat hypoth­yro­idism and IV to treat myxedema coma.
Give daily on an empty stomach (at least 30–60 min before breakfast with full glass of water).
Measure baseline vital signs, weight, and height, and monitor period­ical- ly therea­fter.
Monitor for cardiac excita­bility (angina, chest pain, palpit­ations, dys- rhythm­ias).
Monitor T4 and TSH levels.
Be aware that the various formul­ations of thyroxine are not inter- change­able; instruct clients to notify the provider if a pharmacy dispens- es a different levoth­yroxine product.
Expect lifelong replac­ement therapy.


Choles­tyr­amine (Quest­ran), antacids, iron and calcium supple­ments, and sucralfate (Carafate) reduce absorp­tion, so clients should not take levoth­yroxine within 4 hr of these drugs
Food reduces absorption
Many antise­izure and antide­pre­ssant drugs, including carbam­azepine (Tegre­tol), phenytoin (Dilan­tin), phenob­arb­ital, and sertraline (Zoloft), decrease levels.
Antico­agulant effects of warfarin (Coumadin) increase.
Cardiac response to catech­ola­mines (such as epinep­hrine) increases.




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