Synthroid (levothyroxine) is a synthetic thyroid hormone medication used to treat hypothyroidism and other thyroid disorders. It replaces or supplements the body’s natural thyroid hormones when the thyroid gland cannot produce enough on its own.
Generic names: Levothyroxine sodium
Brand names: Synthroid, Levoxyl, Tirosint, Euthyrox, Levothroid
Pharmacologic class: Synthetic thyroid hormone
Therapeutic class: Thyroid replacement hormone
Mechanism of action: Synthroid provides synthetic thyroxine (T4) which is converted to triiodothyronine (T3) in peripheral tissues. These hormones regulate multiple metabolic processes including growth, development, and energy expenditure.
Indications for use: Primary hypothyroidism, secondary hypothyroidism, thyroid cancer, goiter, myxedema coma, and as supplementation during pregnancy in women with hypothyroidism.
Precautions and contraindications: Untreated adrenal insufficiency, acute myocardial infarction, thyrotoxicosis, and uncorrected adrenal insufficiency. Use with caution in elderly patients, those with cardiovascular disease, and diabetes.
Drug Interactions
- Iron supplements, calcium supplements, and antacids can decrease absorption.
- Cholestyramine and colestipol bind to levothyroxine and reduce absorption
- Anticoagulants may have increased effects requiring dose adjustment
- Diabetic medications may need dose adjustments as thyroid status changes
- Estrogen and oral contraceptives may increase thyroid binding globulin
Adverse Effects
- Cardiac: tachycardia, palpitations, arrhythmias, hypertension
- CNS: headache, anxiety, tremors, insomnia
- GI: diarrhea, vomiting, abdominal cramps
- Other: heat intolerance, sweating, weight loss, muscle weakness
- Allergic reactions (rare)
Administration Considerations
Available preparations: Tablets in multiple strengths (25 mcg to 300 mcg), soft gel capsules, and oral solution
Administration timing: Best taken on an empty stomach, 30-60 minutes before breakfast or the first meal of the day
Absorption considerations: Take 4 hours apart from iron, calcium, antacids, and certain other medications
Nursing Considerations for Synthroid
Related Nursing Diagnoses
- Ineffective health maintenance related to knowledge deficit about the medication regimen
- Risk for imbalanced body temperature
- Activity intolerance related to medication adjustment
- Anxiety related to disease process and medication management
- Risk for unstable blood glucose in diabetic patients
Nursing Assessment
- Obtain baseline vital signs, including heart rate, blood pressure, and temperature.
- Assess thyroid function test results (TSH, T3, T4) before initiating therap.y
- Review cardiovascular history and current symptoms
- Assess for signs of thyroid dysfunction (fatigue, cold intolerance, weight changes)
- Evaluate the current medication list for potential interactions
Nursing Interventions
- Monitor vital signs regularly, especially during dose adjustments
- Assess for signs of therapeutic response and adverse effects
- Monitor weight changes and appetite
- Document administration times and any missed doses
- Coordinate timing with other medications that may interfere with absorption
Patient Teaching Associated with Synthroid
- Take Synthroid at the same time each day, preferably on an empty stomach in the morning.
- Wait 30-60 minutes before eating breakfast or taking other medications
- Do not switch between different brands of levothyroxine without consulting healthcare provider
- Store tablets at room temperature away from heat, moisture, and light
- Regular monitoring of thyroid levels is essential for proper dosing
- Report signs of hyperthyroidism: rapid heartbeat, chest pain, excessive sweating, anxiety, tremors
- Maintain consistent eating habits and exercise routines, as changes can affect thyroid hormone needs
- Keep all follow-up appointments for monitoring thyroid function
- If a dose is missed, take it as soon as remembered unless it’s almost time for the next dose
- Inform all healthcare providers about Synthroid therapy, especially before surgery
This is not an all-inclusive list of possible drug interactions, adverse effects, precautions, nursing considerations, or patient instructions. Please consult further with a pharmacist for complete information.
References and Sources
- Ackley, B. J., Ladwig, G. B., Makic, M. B., Martinez-Kratz, M. R., & Zanotti, M. (2023). Nursing diagnoses handbook: An evidence-based guide to planning care. St. Louis, MO: Elsevier.
- Bc, J. B. D. A., Rosenthal, L., & Yeager, J. J. (2021). Study Guide for Lehne’s Pharmacology for Nursing Care. Saunders.
- Chaker L, Bianco AC, Jonklaas J, Peeters RP. Hypothyroidism. Lancet. 2017 Sep 23;390(10101):1550-1562. doi: 10.1016/S0140-6736(17)30703-1. Epub 2017 Mar 20. PMID: 28336049; PMCID: PMC6619426.
- Harding, M. M., Kwong, J., & Hagler, D. (2022). Lewis’s Medical-Surgical Nursing: Assessment and Management of Clinical Problems, Single Volume. Elsevier.
- Ignatavicius, D. D., Rebar, C., & Heimgartner, N. M. (2023). Medical-Surgical Nursing: Concepts for Clinical Judgment and Collaborative Care. Elsevier.
- Ignatavicius, D. D., Workman, M. L., Rebar, C. R., & Heimgartner, N. M. (2020). Medical-surgical nursing: Concepts for interprofessional collaborative care. St. Louis, MO: Elsevier.
- Silvestri, L. A. (2023). Saunders comprehensive review for the NCLEX-RN examination. St. Louis, MO: Elsevier.
- Sue LY, Leung AM. Levothyroxine for the Treatment of Subclinical Hypothyroidism and Cardiovascular Disease. Front Endocrinol (Lausanne). 2020 Oct 21;11:591588. doi: 10.3389/fendo.2020.591588. PMID: 33193104; PMCID: PMC7609906.
