A 67 year old woman with a history of breast cancer was diagnosed with Deep vein thrombosis...

A 67-year-old woman is reviewed a week after being diagnosed with having a deep vein thrombosis of her left leg. After receiving low-molecular weight heparin for 5 days she has now been started on warfarin. She has a history of depression, osteoporosis, breast cancer and type 2 diabetes. Which one of her current medications is most likely to have increased her risk of developing a deep vein thrombosis?

A. Trazadone
B. Tamoxifen
C. Sitagliptin
D. Denosumab
E. Rosuvastatin

Answer:
B. Tamoxifen

Discussion: One of the most important adverse effects of tamoxifen is the increased risk of deep vein thrombosis. Women should be counselled about this prior to starting treatment. Other adverse effect is an increased risk of endometrial cancer.

Venous thromboembolism (Risk Factors): Common predisposing factors include malignancy, pregnancy and the period following an operation.
The comprehensive list below is partly based on the 2010 SIGN venous thromboembolism (VTE) guidelines:

General
 increased risk with advancing age
 obesity
 family history of VTE
 pregnancy (especially puerperium)
 immobility
 hospitalisation
 anaesthesia
 central venous catheter: femoral >> subclavian

Underlying conditions
 malignancy
 thrombophilia: e.g. Activated protein C resistance, protein C and S deficiency
 heart failure
 antiphospholipid syndrome
 Behcet's
 polycythaemia
 nephrotic syndrome
 sickle cell disease
 paroxysmal nocturnal haemoglobinuria
 hyperviscosity syndrome
 homocystinuria

Medication
 combined oral contraceptive pill: 3rd generation more than 2nd generation
 hormone replacement therapy: the risk of VTE is higher in women taking oestrogen + progestogen preparations compared to those taking oestrogen only preparations
 raloxifene and tamoxifen
 antipsychotics (especially olanzapine) have recently been shown to be a risk factor

It should be remembered however that around 40% of patients diagnosed with a PE have no major risk factors.