SUMMARY

* Oral anticoagulants interfere with the vitamin K-dependent synthesis of clotting factors. Their full effects occur 72 to 96 hours after the first dose.

* Anticoagulant therapy is indicated in situations where the patient is at increased risk of a thromboembolic event. This may occur as a result of abnormalities of blood flow, or of blood vessel walls, or of the constituents of the clotting cascade.

* The optimum level of anticoagulant therapy for any condition is that which reduces the risk of thromboembolic events without producing an unacceptable risk of haemorrhage. This level varies according to the condition being treated.

* The British Society for Haematology has produced guidelines for oral anticoagulant therapy. These guidelines advise on the optimum level of anticoagulation therapy for different conditions.

* Patients should be counselled so that they have a good understanding of the aims of therapy and the risks of altering their diet or using other medicines.

* Many factors can alter a patient's response to warfarin. These include dietary changes, illness, and concomitant drug therapy. The need for anticoagulants should be re-evaluated on a regular basis.

* Concomitant use of drugs which interact with warfarin should generally be avoided; where this is not possible, the patient should be monitored closely whenever a new drug is started, the dose adjusted, or stopped.

* Studies have demonstrated that anticoagulant therapy can be managed safely and effectively in primary care. General practitioners considering such a service should discuss this with their local department of haematology.