Hypothyroidism

Question 1

L T4

Answer 1

1. Levothyroxine, used for hypothyroidism
2. PK:
   - A: oral or iv
   Onet of action: oral 2 - 5/7; IV Within 6 to 8hr
   Unpredictable/erratic absortion rate: 40 to 80% ( maybe decreased with age and with food)
   - D: >99% plasma protein bonding
   - M: in liver 80% to T3;
   In kidney and peripheral can be converted to T3
   Conjugation also occurs
   Undergoes enterohepatic recirculation
   - E: 80% in kidney, 20% in faeces

Question 2

What mat happen if a pt accidentally overdosing LT4?

Answer 2

1. In adults, cardiac arrest, HTN, tachycardiac, palpitation, heat intolerance, hyperactivity, insomnia, irritbility and LOW
2. In children, insomnia, restlessness, accelerated growth and bone maturation may occur

Question 3

A pt brought by ambulance because: AMS, hypothermia,
Blood results shown multiple organ failure, TFT shown hypothryoidism, what should be given ?

Answer 3

1. Pt is having myxoedema coma
2. Liothyronine (LT3 should be given)

Question 4

The properties of liothyronine :

Answer 4

1. Available in oral or IV form
2. Onset of action: 3hr
3. A: well absorbed (95% in 4hr)
4. D: >99% plasma protein bonding
5. M: In liver (to be deiodinated and conjugated metabolites)
6. T1/2: 1 to 2 days
7. E: in urine

Question 5

ADE of LT3:

Answer 5

1. Cardiac arrythmia
2. Tachycardia
3. Hypotension
4. Myocardial infarction

Question 6

What may decrease the absorption of LT4?

Answer 6

1. Fe, Ca, Al, I, Mg, Zinc , Se(selenium)
2. Cholestyramune
3. Sucrafate , antacide
4. Kelp tablets (Iodine)
5. Fibre, caffeine, soya

Question 7

Conditions that may increase levothyroxine bonding:

Answer 7

1. Pregnancy
2. estrogen hormone replacement therapy

Question 8

Drugs effect maybe enhanced by LT 4:

Answer 8

1. Wardarin
2. Amitriptyline

Question 9

LT4 + propranolol:

Answer 9

Decrease the effects of propranolol