DRUGS USED IN HYPOTHYROIDISM

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 Congenital ( cretinism, dwarfism) Congenital ( cretinism, dwarfism)  Autoimmune disorder ( Hashimotos thyroiditis)  Irradiation  Surgical removal of thyroid gland  Thyroid carcinoma 8

9 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

10 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 16

17 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 Parnteral preparation µg. Parnteral preparation µg.

18 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. Restore normal thyroid levels within 2-3 weeks. Restore normal thyroid levels within 2-3 weeks. levothyroxine is given in a dose of 12.5 – 25 µg/day for two weeks and then increasing it after every two weeks. levothyroxine 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 19

20 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 21

22 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 therapy. It is best used for short –term therapy. Oral preparation available are 5-50µg tablets Oral preparation available are 5-50µg tablets Parnteral use 10µg/ml Parnteral use 10µg/ml

LIOTRIX Combination of syntheticT4 & T3 in a ratio 4:1 that attempt to mimic the natural hormonal secretion. Combination of syntheticT4 & T3 in a ratio 4:1 that attempt to mimic the natural hormonal secretion. The major limitations to this product are high cost & lack of therapeutic rationale because 35% of T4 is peripherally converted to T3 The major limitations to this product are high cost & lack of therapeutic rationale because 35% of T4 is peripherally converted to T3 23

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 induced by estrogen and In pregnant hypothyroid patient % increase in thyroxine is required because of elevated maternal TBG 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