Thyroid Medications

• Levothyroxine

  Aka Levoxyl, Synthroid

  • MOA: produces physiologic levels of both T4 and T3
  • AE: sx of hyperthyroidism → palpitations, sweating, weight loss, diarrhea, insomnia, anxiety
  • CI: hypersensitivity, uncorrected adrenal insufficiency, nontoxic diffuse goiter or nodular thyroid disease (w/ suppressed TSH), acute MI
• Radioactive iodide

  Sodium iodide I-131

  • MOA: isotope that upon concentrating in the thyroid gland, emits beta-particles that destroy thyroid tissue
  • AE: hypothyroidism, taste loss, n/v, gastritis, tenderness/swelling/pain in neck, throat irritation, xerostomia, alopecia
  • CI: pregnancy, breastfeeding, pre-existing vomiting and diarrhea
  • Pt. C: colorless and tasteless solution
  • Use: m.c. treatment of hyperthyroidism
• Thioamide drugs

  Methimazole, Propylthiouracil

  • MOA: inhibit key steps in synthesis of T3 and T4, also inhibits organification and coupling (PTU) and peripheral conversion of T4 to T3
  • AE: rash, fever, arthralgias, agranulocytosis, hepatitis, nephritis
  • CI: breastfeeding (methimazole), caution w/ agranulocytosis, hepatotoxicity, pediatrics
  • Use: pretreatment prior to radioactive iodide therapy but d/c several days before that
• What needs to be monitored for thiomide drugs

  Thyroid function tests, CBC w/ diff, LFTs, fever, sore throat, general malaise
• Potassium iodide solution

  • MOA: block thyroid hormone release and inhibit key steps in synthesis and peripheral conversion of T4 to T3, also decreases gland size and vascularity
  • AE: allergic reaction, dose-related toxicity, metallic taste
  • CI: pregnancy, use before radioactive iodide treatment, pt with nodular goiter or adenomas
  • Use: m.c. used in Grave's disease before surgery and in thyroid storm