27.2 Thyroid and Antithyroid Drugs

Thyroid and antithyroid drugs play a crucial role in managing thyroid disorders. These medications help regulate hormone levels, addressing both underactive and overactive thyroid conditions. Understanding how they work is key to effective treatment.

Proper use of thyroid medications can dramatically improve quality of life for those with thyroid issues. From dosing to potential side effects, nurses need to know the ins and outs of these drugs to provide the best care for their patients.

Thyroid and Antithyroid Drugs

Key features of thyroid and antithyroid medications

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• Thyroid medications
  • Levothyroxine (Synthroid, Levoxyl) synthetic form of thyroxine (T4) used to treat hypothyroidism by replacing the missing thyroid hormone in the body
  • Liothyronine (Cytomel) synthetic form of triiodothyronine (T3) sometimes used in combination with levothyroxine to provide a more comprehensive thyroid hormone replacement therapy
• Antithyroid medications
  • Propylthiouracil (PTU) inhibits thyroid peroxidase enzyme to reduce thyroid hormone synthesis and treat hyperthyroidism, including Graves' disease, by decreasing the production of excess thyroid hormones
  • Methimazole (Tapazole) also inhibits thyroid peroxidase enzyme to reduce thyroid hormone synthesis and is preferred over PTU due to its lower risk of causing severe liver injury as a side effect

Therapeutic effects and potential side effects of thyroid hormone replacement drugs

• Therapeutic effects
  • Restores normal thyroid hormone levels in the body to alleviate symptoms of hypothyroidism (fatigue, weight gain, cold intolerance)
  • Improves overall metabolic function and quality of life for patients with hypothyroidism
• Potential side effects
  • Overtreatment may lead to symptoms of hyperthyroidism (tachycardia, palpitations, tremors, anxiety, insomnia, weight loss) if the dosage is too high
  • Allergic reactions, although rare, can cause symptoms such as rash, itching, or swelling
  • Interactions with other medications (warfarin, cholestyramine, iron supplements) may decrease absorption of levothyroxine and require dosage adjustments or timing modifications

Nursing considerations when administering antithyroid medications

• Assess for signs and symptoms of hyperthyroidism (tachycardia, tremors, heat intolerance, weight loss) before and during treatment to monitor the effectiveness of the medication and adjust dosage as needed
• Monitor thyroid function tests (TSH, free T4) regularly to ensure the medication is effectively controlling the patient's hyperthyroidism and to guide dosage adjustments based on lab results and clinical response
• Educate patients about potential side effects and the importance of regular follow-up, especially for rare but serious side effects like agranulocytosis (fever, sore throat, signs of infection) and hepatotoxicity (jaundice, abdominal pain, dark urine)
• Emphasize the importance of taking medication as prescribed and not discontinuing without consulting a healthcare provider to ensure consistent control of hyperthyroidism and prevent relapse of symptoms

Patient education plan for someone starting thyroid hormone therapy

• Explain the purpose of the medication and how it works to replace missing thyroid hormone and restore normal body functions, helping the patient understand the importance of adhering to the treatment plan
• Provide instructions on how to take the medication
  1. Take on an empty stomach, 30-60 minutes before breakfast or 4 hours after the last meal to maximize absorption
  2. Avoid taking with calcium, iron, or multivitamins, as they can interfere with absorption and reduce the effectiveness of the medication
• Discuss potential side effects (overtreatment symptoms, allergic reactions) and when to contact a healthcare provider for guidance on managing side effects or adjusting the treatment plan
• Emphasize the importance of regular follow-up and monitoring, including blood tests to assess thyroid function and adjust dosage as needed, and annual physical examinations to evaluate overall health and treatment progress
• Encourage a healthy lifestyle (balanced diet, regular exercise, stress management techniques) to support overall well-being and optimize the benefits of thyroid hormone replacement therapy