Increased bleeding risk withoutĪlteration of INR. Interference with primary haemostasis – increased bleeding risk without alteration of INRĭirect mucosal injury, antiplatelet effects may also have a role. fluoxetine, paroxetine, can also inhibit warfarin metabolism Inhibition with platelet function – increased bleeding risk without alteration of INR. Serotonergic agents (SSRIs and venlafaxine) Inhibition of vitamin K synthesis by intestinal flora, inhibition of warfarin metabolismįluconazole, miconazole (including gel and vaginal preparations) Most antibiotics but especially macrolides, metronidazole, quinolones and cotrimoxazole Table 1: Some of the main medicines, medicine classes and other agents that can interact with warfarin Products without consulting their doctor or pharmacist.įor a complete list of interactions and advice on managing interactions suchĪs when to check the INR, refer to appropriate information resources such as a formulary or your PMS system. Patients should also be advised not to take any other prescribed medicines, over-the-counter medicines or food supplements/herbal It is not all-inclusive and practitioners should alwaysĬheck if there is a clinically significant interaction if they are prescribing a medicine for a person taking warfarin. Table 1 shows some of the important interactions with warfarin. To recognise that some interactions cause an increase in bleeding without alteration of the INR, e.g. Whilst most interactions involve a change in the INR, it is important Started or stopped or when the dose is altered. An interaction can occur when the interacting agent is There are many medications that can affect the INR, and even a change in diet can result in changes to the INR – either raising or lowering it.Many medicines and herbal products can interact with warfarin. The result needs to be taken in context of recent INR measurements and dose changes. An INR result higher than the desired range means the blood is “too thin”. The Prothrombin time of a normal sample of bloodĪ result of 1.0, up to 1.5, is therefore normal.Ī low INR result means your blood is ‘not thin enough’ or coagulates too easily and puts you at risk of developing a blood clot.Ī high INR result means your blood coagulates too slowly and you risk bleeding.Īn INR lower than the desired range means the blood is “not thin enough” or clots too easily.

It is important that the tube is filled to the correct level, otherwise false results may occur. The INR test is a blood test and requires a small tube of blood from a vein – approximately 4 millilitres. Artificial heart valves of the mechanical type – because of the risk of a clot forming on the valve and causing a blockage in the heart.Some cases of Heart failure (Left Ventricular, and Congestive Cardiac Failure), especially when the heart is enlarged as in some forms of cardiomyopathy.Atrial Fibrillation (AF) – an irregular heartbeat, sometimes accompanied by an enlarged left atrium – both of which predispose to the formation of blood clots in the heart, which may embolise to the blood vessels of the brain causing a cerebral infarction, a stroke – also known as a CerebroVascular Accident (CVA).Pulmonary Embolism (PE) – a clot in the lung, that has travelled through the veins (“embolised”) from a DVT formed elsewhere, such as the deep veins of the leg or pelvis.Deep Vein Thrombosis (DVT) – a clot in a deep vein, commonly of the leg.In relation to liver function tests – liver dysfunction can lead to decreased production of certain clotting factors.Monitoring as a part of warfarin therapy.The most common reasons for an INR test are:

Warfarin inr normal range