Tamoxifen

Question 1

absorption

Answer 1

well absorbed following oral administration

Question 2

distribution

Answer 2

more than 99% bound to plasma proteins, mainly albumin

Question 3

metabolism

Answer 3

extensively metabolised by CYP450 enzymes into endoxifen
- primary active metabolite

Question 4

excretion

Answer 4

mainly eliminated in faeces

Question 5

MOA

Answer 5

1. an antioestrogen that induces gonadotrophin release by occupying oestrogen receptors in the hypothalamus
2. this interferes with feedback mechanisms
3. competitively inhibits oestrogen binding to its receptor, which is essential for its activity in breast cancer cells

Question 6

indications

Answer 6

1. pre and post menopausal women with oestrogen receptor positive breast cancer
2. breast cancer

Question 7

adverse effects

Answer 7

• anaemia
• embolism and thrombosis
• hypersensitivity
• hepatic disorders

Question 8

interactions

Answer 8

• phenytoin
• warfarin

Question 9

contraindications

Answer 9

• treatment of infertility if history of idiopathic venous thromboembolism
• genetic predisposition to thromboembolism