DRUGS USED IN HYPOTHYROIDISM by Dr.Abdul latif Mahesar

Objectives At the end of the lecture the students will be able to : At the end of the lecture the students will be able to : Classify common drugs used for treatment of hypothyroidism Classify common drugs used for treatment of hypothyroidism Details the drugs regarding, mechanism of action, pharmacological effects, clinical uses & side effects Details the drugs regarding, mechanism of action, pharmacological effects, clinical uses & side effects Recognize treatment of special cases of hypothyroidism. Recognize treatment of special cases of hypothyroidism. 7

Hypothyroidism Thyroid gland does not produce enough hormones Thyroid gland does not produce enough hormones CAUSES CAUSES Congenital ( cretinism, dwarfism) Congenital ( cretinism, dwarfism)  Autoimmune disorder ( Hashimotos thyroiditis)  Irradiation  Surgical removal of thyroid gland  Thyroid carcinoma 8

CAUSES Congenital which results to ( cretinism, dwarfism) Congenital which results to ( cretinism, dwarfism)  Autoimmune disorder ( Hashimotos thyroiditis)  Irradiation Of the gland  Surgical removal of thyroid gland  Thyroid carcinoma 9

10 HYPOTHYROIDISM People who are most at risk include those over age 50 & mainly in females People who are most at risk include those over age 50 & mainly in females Diagnosed by low plasma levels of T3 & T4 Diagnosed by low plasma levels of T3 & T4 and high levels of TSH. and high levels of TSH.

11 Manifestations of Hypothyroidism Fatigue and lack of energy Fatigue and lack of energy weight gain weight gain Dry and cold skin Dry and cold skin Dry hairs Dry hairs Constipation Constipation Slowed thinking Slowed thinking Bradycardia Bradycardia Heavy menses Heavy menses

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Treatment Replacement therapy with synthetic thyroid hormone preparations Replacement therapy with synthetic thyroid hormone preparations 17

18 Thyroid preparations LEVOTHYROXINE: (T 4 ) LEVOTHYROXINE: (T 4 ) A synthetic form of the thyroxine (T 4 ), is the drug of choice for replacement therapy. A synthetic form of the thyroxine (T 4 ), is the drug of choice for replacement therapy. Stable and has a long half life ( 7 days). Stable and has a long half life ( 7 days). Administered once daily. Administered once daily. Oral preparations available from to 0.3 mg Oral preparations available from to 0.3 mg tablets tablets Absorption is increased when hormone is given on empty stomach Parentral preparation µg. Parentral preparation µg.

19 In old patients and in patients with cardiac problems, treatment is started with reduced dosage. In old patients and in patients with cardiac problems, treatment is started with reduced dosage. Normal thyroid levels are restored within 2-3 weeks. Normal thyroid levels are restored within 2-3 weeks. levothyroxine(T4) is given in a dose of 12.5 – 25 µg/day for two weeks and then increasing it after every two weeks. levothyroxine(T4) is given in a dose of 12.5 – 25 µg/day for two weeks and then increasing it after every two weeks.

Clinical uses Hypothyroidism, regardless of etiology including : Hypothyroidism, regardless of etiology including :  Congenital  Autoimmune thyroiditis ( Hashimoto thyroiditis)  Pregnancy  Thyroid carcinoma 20

21 ADVERSE EFFECTS OF OVER DOSES ADVERSE EFFECTS OF OVER DOSES CHILDREN : Restlessness, insomnia, accelerated bone maturation. CHILDREN : Restlessness, insomnia, accelerated bone maturation. ADULTS : ADULTS : Tachycardia, palpitation, cardiac arrhythmias, tremor, restlessness, heat intolerance, headache, muscle pain Tachycardia, palpitation, cardiac arrhythmias, tremor, restlessness, heat intolerance, headache, muscle pain Change in appetite, diarrhea, weight loss

Adverse effects of under-dosing Sluggishness Sluggishness Mental dullness Mental dullness Feeling cold Feeling cold Muscle cramps Muscle cramps 22

23 Liothyronine(T 3 ) More potent (3-4 times) and rapid action than levothyroxine but has a short half life is not recommended for routine replacement therapy, it requires multiple daily doses. It should be avoided in cardiac patients. It should be avoided in cardiac patients. It is best used for short –term suppression of TSH. It is best used for short –term suppression of TSH. Oral preparation available are 5-50µg tablets Oral preparation available are 5-50µg tablets Parentral use 10µg/ml Parentral use 10µg/ml

24 MYXEDEMA COMA: Life –threatening hypothyroidism Life –threatening hypothyroidism The treatment of choice is loading dose of levothyroxine intravenously µg initially followed by 50µg daily. The treatment of choice is loading dose of levothyroxine intravenously µg initially followed by 50µg daily. I.V liothyronine for rapid response but it may provoke cardiotoxicity I.V liothyronine for rapid response but it may provoke cardiotoxicity I.V hydrocortisone may be used in case of adren al and pituitary insufficiency. I.V hydrocortisone may be used in case of adren al and pituitary insufficiency.

25 HYPOTHROIDSM AND PREGNANCY. In pregnant hypothyroid patient % increase in thyroxine is required because of elevated maternal TBG(thyroxine binding globulin) induced by estrogen and In pregnant hypothyroid patient % increase in thyroxine is required because of elevated maternal TBG(thyroxine binding globulin) induced by estrogen and because of early development of fetal brain which depends on maternal thyroxine because of early development of fetal brain which depends on maternal thyroxine

Combination drugs LIOTRIX LIOTRIX is a combination of synthetic T4 and T3 in a ratio of 4:1 that attempt to mimic the natural hormone secretions is a combination of synthetic T4 and T3 in a ratio of 4:1 that attempt to mimic the natural hormone secretions Major limitation to this product are high cost Major limitation to this product are high cost And lack of therapeutic rationale,because about 35% of T4 is peripherally converted to T3. 26