GI

Question 1

desmopressin

Answer 1

• synthetic ADH
• no vasoconstrictor effects
• used to treat cranial diabetes insipidus

Question 2

levothyroxine

Answer 2

• synthetic T4
• incomplete gastric absorption, PPIs contraindicated
• best taken on an empty stomach
• long t 1/2, metabolised to T3

Question 3

Thionamides

Answer 3

• antithyroid drugs
• carbimazole
• propylthiouracil
• inhibit iodide oxidation
• inhibit tyrosine iodination (inhibit thyroid peroxidase)
• inhibit coupling of iodotyrosines
• SEs include agranulocytosis

Question 4

carbimazole

Answer 4

• thionamide
• used for hyperthyroidism
• prodrug, metabolised to methimazole
• prevents thyroid peroxidase enzyme from oxidising I- to I/I+
  This prevents iodination of the tyrosine residues on thyroglobulin
• this reduces production of T3 and T4

Question 5

propylthiouracil

Answer 5

• thionamide
• used for hyperthyroidism
• less active and shorter t1/2 than carbimazole but better safety data for pregnancy
• can also inhibit peripheral deiodination of T4, therefore useful in thyroid storm
• impairs liver function