Antithyroid Drugs

Endocrine & Metabolic

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Examples

methimazolepropylthiouracil (PTU)

Prefix / Suffix: No consistent suffix

Physiology

Hyperthyroidism (e.g., Graves' disease) causes excess thyroid hormone, leading to weight loss, tachycardia, and heat intolerance.

Mechanism of Action

Inhibit thyroid hormone synthesis by blocking iodine organification. PTU also inhibits peripheral T4 to T3 conversion.

Indications

Hyperthyroidism (Graves' disease)
Thyroid storm (PTU preferred)
Pre-op preparation for thyroidectomy

Side Effects / Adverse Effects

Agranulocytosis (rare but serious — sore throat, fever)
Hepatotoxicity (especially PTU — black box)
Rash, pruritus
Hypothyroidism (over-treatment)

Contraindications

Pregnancy: PTU in 1st trimester, methimazole in 2nd/3rd
Severe hepatic impairment (PTU)
Bone marrow suppression

Nursing Considerations

Monitor CBC — teach to report sore throat, fever, mouth ulcers immediately (agranulocytosis)
Monitor LFTs (hepatotoxicity, especially PTU)
Effects take weeks — beta blockers used for symptom control until then
Take at consistent times daily
Methimazole preferred except in 1st trimester pregnancy and thyroid storm
Monitor TSH and free T4 regularly

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.