Oral Anticoagulant therapy
Warfarin is the only oral anticoagulant readily available in New Zealand. There are two preparations available (Coumadin and Marevan). These have different pharmacokinetics therefore, as far as possible; patients should remain on the same product. If a product change has to be made the patient’s INR should be monitored closely. If a patient is known to be allergic to Warfarin then medical management should be discussed with a Haematologist.
Warfarin Dose
It is now recommended that patients should start warfarin on a relatively low dose, either 5mg daily or 3mg daily. In younger patients a higher dose is safe and may achieve control slightly faster.
When a patient begins warfarin treatment they will typically have blood tests every three to five working days. As their INR begins to stabilise within a desired therapeutic range the need for blood tests reduces.
Warnings
Some drugs, foods, herbs and complementary medicines can affect the effectiveness of warfarin
Pregnancy
Warfarin is not recommended during pregnancy. All pregnant women requiring treatment for thromboembolism should receive subcutaneous LMWH treatment until delivery. After delivery warfarin can be used.
Breastfeeding
Warfarin is excreted in breast milk in very low amounts but is not considered to be a risk to the infant. It is recommended that pregnant patients be advised by a haematologist and an obstetrician, as well as their GP.