Pharmacology: Thyroid and Pituitary Disease Drugs Flashcards
Name the modes of administration of testosterone
Sustanon - IM every 3-4 weeks)
Skin gel (testogel, tostral)
Nebido - prolonged IM injection 10-14 weeks
Oral tablets (rarely used)
What is the indication for propylthiouracil?
First line for hyperthyroidism only in first trimester of pregnancy
Describe the mechanism of action of carbimazole
Inhibition of TPO thereby blocking thyroid hormone synthesis
What is the indication for carbimazole?
First line for hyperthyroidism
What are the potential side effects of propylthiouracil?
Allergic type reactions, agranulocytis
Liver damage - cholestatic jaundice, increased liver enzymes, 1: 10 000 risk of fulminant hepatic failure (monitor LFTs)
Describe the side effects of levothyroxine
Usually occur when dose is too high, resulting in hyperthyroidism - increased appetite, weight loss, increased sweating etc.
How would you ‘safety net’ a patient on carbimazole or propylthiouracil?
Warn patient verbally and in writing to stop drug and have urgent FBC checked in the event of fever, oral ulcer or oropharyngeal infection - agranulocytosis
Why should you monitor FBC in patients prescribed testosterone?
Can cause polycythaemia - cause risk of stroke/MI
What is the indication for testosterone?
Hypopituitarism resulting in testosterone deficiency
Why should you use β-blockers with caution in asthmatics and what can you prescribe instead?
Risk of provoking bronchospasm
CCBs e.g. diltiazem can be useful instead
What is levothyroixine?
Manufactured form of thyroxine (T4)
Name 3 medications which can impair absorption of levothyroxine
PPIs, iron tablets, calcium tables
Describe the mechanism of action of propylthiouracil
Inhibits DIO1 which decreases conversion of T4 to T3
What effects may propylthiouracil have on a foetus?
Risk of aplasia cutis in early pregnancy
Risk of liver toxicity to foetus
Describe the mechanism of action of β-blockers
β-adrenoceptor blockade - reduced activity of sympathetic nervous system
Why is carbimazole contraindicated in the first trimester of pregnancy, and used in the rest of pregnancy in as low a dose as possible?
Risk of aplasia cutis in early pregnancy
Low dose to minimise other side effects on foetus when taken in pregnancy:
- Scalp abnormalities
- GI abnormalities
- Choanal and oesophageal atresia
What is the indication for β-blockers in hyperthyroidism?
Immediate symptomatic relief of thyrotoxic syptoms
Dose requirements of levothyroxine may increase by 25-50% in ________
Pregnancy
Name two side effects of carbimazole
Allergic type reactions, agranulocytosis
Why is propranalol the β-blocker of choice for symptomatic relief of hyperthyroidism?
Inhibits DIO1 as well as blocking β-adrenoceptors
Why should you check PSA in a patient before you prescribe testosterone and monitor PR exam?
Testosterone causes prostate enlargement - does not cause prostate cancer but may cause it to grow
What are the indications for levothyroxine?
Hypothyroidism and hypopituitarism
Name a potential side effect of oral testosterone
Hepatitis
What are the potential side effects of β-blockers?
Generally well tolerated
Nausea, headaches, tiredness
