Thyroid Hormones & Drug Interactions PDF

Anti/thyroid drug inetractions Action of Thyroid Hormons Synthesis and Secretion of Thyroid Hormones  Thyroid hormones essential for physical, mental and sexual peroxidase enzyme development...

Anti/thyroid drug inetractions Action of Thyroid Hormons Synthesis and Secretion of Thyroid Hormones  Thyroid hormones essential for physical, mental and sexual peroxidase enzyme development 1. Iodide uptake iodine  Facilitate normal physical growth By O2 consumption & metabolic rate 2. Organification of iodine : is the incorporation of iodine into iodine Glucose absorption, uptake & utilization for the production of thyroid hormone. Heart Rate, Cardiac output Cholesterol & fat and glycogen deposition 3. iodine + Tyrosine MIT monoiodotyrosine DIT di-iodotyrosine 4. MIT + DIT T3 2 DIT T4 which are stored in colloid and released by protease enzyme All these steps are controlled by TSH, which are regulated by feed back mechanism Hypothyroidism Hyperthyroidism or thyrotoxicosis Inadequate secretion of thyroid hormones  May occur due to excessive production of thyroid hormones Treatment of Hypothyroidism  It is characterized by metabolism in all body tissues.  Levothyroxin ( L thyroxine T4 or tetraiodothyronine less potent thyroid  Occurs more often in female than male. hormone used for replacement and suppression  The most common cause of hyperthyroidism is Graves disease  Liothyronine ( T3 tri iodothyronine) a more potent thyroid hormone/ expensive, rapid onset used for myxedema coma An autoimmune disorder in which an abnormal thyroid receptor binds to TSH  Liotrix (T4: T3) ( 4: 1) used for replacement receptor causes uncontrolled thyroid hormone production  D-thyroxin weak effect on heart , used to decrease cholesterol level in euthyroid patients Thyroid hormones + Cholestyramine Medications: Cholestyramine may absorption of thyroid hormones Primary treatment options 1. Thioamides Thyroid hormones + estrogen or OCs Such as Propyl thiouracil, Carbimazole which is converted into , Methimazole Estrogen may effects of thyroid hormones 2. Surgery Is considered the treatment of choice in case of malignancy, esophageal Thyroid hormones + antidiabetic drugs obstruction, respiratory difficulties Thyroid hormone may hypoglycemic effects 1. Thioamides Thyroid hormone + Orlistat antiobesity drug Mechanism of actions orlistat may cause risk of hypothyroidism Inhibit peroxidase enzyme Inhibit organification of iodide Thyroid hormones + alpha lipoic acid Inhibit coupling of iodotyrosine Leading to thyroxine which increase TSH alpha lipoic acid may effects of thyroid hormones by interfering with the conversion of T4 to T3 Uses In mild cases of thyrotoxicosis Thyroid hormones + Rifampin (enzyme inducer) Before surgery may metabolism of thyroid hormones and their effects With radioactive iodine until its effect appears Side effects Leukocytopenia, increase sizes of glands Allergy ( rash, fever, hepatitis and nephritis) Joint pain Thioamides drugs drug interactions Propyl thiouracil + warfarin Propyl thiouracil may effect of vitamin K, thus excessive bleeding may result if taken with warfarin Propyl thiouracil + Digoxin Propyl thiouracil may increase serum digoxin which leads to cardiac arrhythmia, Must reduce dose of digoxin if taken concurrently Adjuct to primary therpy include 1. Ionic inhibitors (K Perchlorate & Thiocyanate ) They compete with iodide uptake leading to thyroxin. Action is antagonized by excess iodide 2. Iodides ( Lugol’s iodine & KI) Inhibit action of TSH Inhibit iodine binding and protease enzyme so size and vascularity of the gland Uses Preoperative to decrease size and vascularity of the gland In thyrotoxic crisis with propranolol Prophylaxis to prevent goitre Side effects may cause : Iodism: Results from overdose or prolonged use of iodine causes ( lacrimation, rhinitis , salivation, cough, diarrhea) 3. Radioactive iodine Such as I 131 Is concentrated in glands & destroys thyroid follicles, acts after 3 months Uses Hyperthyroidism in old age or recurrence Failure of other therapy Metastic cancer thyroid Side effects: hypothyroidism 4. Adrenergic antagonist (B) Propranolol Used to relief adrenergic symptoms of hyperthyroidism Control these symptoms preoperative & with radioactive iodine & with thyrotoxic crisis