Thyroid Drugs Flashcards
Thyroid hormone preparations
Levothyroxine
Liothyronine
Liotrix
Thyroid desiccated
Thyroid hormone preparations - MoA
Binds to receptors causing increased gene transcription that leads to increased levels of proteins for growth, development, heat production.
Thyroid hormone preparations - Contraindications
Lithium: inhibit release of thyroid hormones
Amiodarone: cause either hyper/hypothyroidsm
Levothyroxine - Classification
Synthetic T4
Levothyroxine - MoA
Converted to T3 in tissues, effects from both thyroid hormones
Levothyroxine - Clinical use
Hypothyroidism (DOC).
TSH suppression in thyroid nodules, diffuse goiters, thyroid cancer (DOC).
Myxedema coma (IV)
Levothyroxine - Adverse effects
Hyperthyroidism in high doses
Levothyroxine - Interactions
Aluminum hydroxide, Ca2+-supplements, cholestyramine, ferrous sulfate, sucralfate decrease absorption.
Coffee, soy, dietary fiber: reduced absorption
Increased TSH:levothyroxine not sufficinent.
Liothyronine - Classification
Synthetic T3
Liothyronine - MoA
Does not increase plasma T4 –> difficult to monitor response to treatment.
Liotrix - Classification
T4+T3 (4:1)
Thyroid desiccated - Classifiaction
Natural pig T4+T3
Antithyroid agents
Thioamide drugs: Methimazole Propylthiouracil β-adrenoceptor antagonists Iodide salts RAI
Antithyroid agents - Clinical use
Hyperthyroidism
Thioamide drugs - MoA
Inhibit synthesis of thyroid hormones by inhibition thyroperoxidase-catalysed steps.
Inhibition of hormone synthesis and depletion of glandular stores.
Thioamide drugs - Clinical use
Graves disease: induce remission or control symptoms before surgery/RAI.
When do you need to check for agranulocytosis in the case of thioamide drugs?
In case of fever, malaise, sore throat, flulike-symptoms
Thioamide drugs - Adverse effects
Relapse (esp pt with thyroid-stimulating antibodies)
Pruritic maculopapular rash, arthralgia, fever.
Lupus erythematosus-like syndrome, hepatitis, GI distress.
Transient leukopenia, agranulocytosis.
Liver injury, fatal liver failure
Cross-sensitivity
Which thioamide drug is contraindicated during pregnancy because of birth defects?
Methimazole
Methimazole - Adverse effects
Birth defects
Propylthiouracil - MoA
Also inhibit conversion of T4 –>T3 in peripheral tissue.
Propylthiouracil - Clinical use
DOC just before and during 1st trimester
Propylthiouracil - Adverse effects
Increased incidence of liver failure
β-adrenoceptor antagonists
Propanolol
β-adrenoceptor antagonists - MoA
inhibit conversion of T4 –>T3
Reduce cardiovascular stimulation ass with hyperthyroidism (arrhythmias, palpitations, tachycardia)
β-adrenoceptor antagonists - Clinical use
Severe thyrotoxicosis (thyroid storm) Symptomatic (control cardiovascular symptoms) in hyperthyroidism before surgery/RAI treatment.
Iodide salts
Potassium iodine
Sodium iodine
Iodide salts - MoA
Inhibit release of thyroid hormones
Iodide salts - Clinical use
After RAI to inhibit radioactive thyroid hormone release.
Iodide salts - Adverse effects
Skin rashes, hypersensitivity reactions, salivary gland swelling, metallic taste, sore gums, GI discomfort
Iodide salts - Contraindications
Should not be used before RAI treatment because nonradioactive iodide compete with I for uptake by the thyroid gland.
Pregnancy
Thyrotropin alfa - Classification
Recombinant human thyrotropin
Thyrotropin alfa - Clinical use
Increase thyroid gland uptake of RAI in diagnosis and treatment of thyroid conditions
What happens if you start Levothyroxine treatment with too high dose?
Cardiovascular stress
Sodium iodine - Contraindication
Pretreatment with thioamide drugs and pregnancy
