3 Thyroid Medications
Review how levothyroxine, methimazole, and propylthiouracil are used and the administration, monitoring, interaction, and safety concerns associated with each.
replacement and administration
is replacement therapy for hypothyroidism. Food can affect its absorption, so take it consistently on an empty stomach. Iron and calcium can bind the medication and reduce absorption; separate from agents such as iron by at least 4 hours.
monitoring and excess
For adults with primary hypothyroidism, reassess about 6–8 weeks after a dose change. Once the dose is stable, periodic follow-up is still needed.
New palpitations, tremor, heat intolerance, or insomnia may indicate excessive thyroid-hormone replacement. Have symptoms and thyroid status reviewed rather than changing the dose independently.
and thyroid tests
can interfere with some laboratory assays used to measure thyroid hormones and , producing misleading results. Tell the clinician about use and follow clinician or laboratory instructions about holding it before testing.
Methimazole safety and interaction
Methimazole reduces new thyroid-hormone production. Fever or severe sore throat can signal , a rare but potentially life-threatening reduction in white blood cells associated with antithyroid drugs. Seek prompt medical advice and evaluation, including a white blood cell count with differential; contact the prescriber before taking further doses.
Methimazole can increase the effect of oral anticoagulants such as . PT/INR monitoring may need attention, particularly when treatment or thyroid status changes.
and liver injury
reduces new thyroid-hormone production and carries a boxed warning for severe, sometimes fatal liver injury. Yellowing of the eyes, dark urine, or pain in the right upper abdomen requires prompt medical evaluation. When symptoms of hepatic dysfunction occur, the drug label advises discontinuing PTU and obtaining liver tests.