|Type of medicine||Anticoagulant|
|Used for||Prevention and treatment of harmful blood clots|
Phenindione is an anticoagulant, which means that it increases the time it takes for your blood to clot. It works by reducing the effects of vitamin K, which is a vitamin your body uses in the process of blood-clotting.
Phenindione is used to prevent unwanted clots from forming if you have a condition that puts you at risk of this happening, or to dissolve any clots that have already formed in the blood vessels of your legs, lungs or heart. Another anticoagulant, called warfarin, is usually prescribed in preference to phenindione.
Before taking phenindione
Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking phenindione it is important that your doctor or pharmacist knows:
- If you are pregnant, trying for a baby or breast-feeding.
- If you have liver or kidney problems.
- If you have had a stomach ulcer.
- If you have recently had a stroke.
- If you have any cuts or wounds.
- If you have high blood pressure.
- If you have had surgery recently, or are due for surgery in the near future.
- If you have been told you have an infection of your heart called bacterial endocarditis.
- If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
- If you have ever had an allergic reaction to this or to any other medicine.
How to take phenindione
- Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack of tablets. This leaflet will give you more information about phenindione, and a full list of possible side-effects from taking it.
- Take phenindione exactly as you have been advised by your doctor or anticoagulant clinic. Phenindione tablets are available in three different strengths. Your dose may be made up of more than one strength of tablet.
- Try to take your phenindione at the same time each day to avoid missing any doses.
- If you forget to take a dose, take it as soon as you remember if it is still within 2 or 3 hours of your usual time. If you do not remember until after this time, skip the missed dose and take your next dose when it is due. Never take two doses together to make up for a forgotten dose, and remember to let your doctor know about any missed doses when you next have your blood test.
Getting the most from your treatment
- You will be given an anticoagulant record book; read this carefully, and carry it with you at all times.
- You will have regular blood tests to check how the phenindione in your blood is working - these blood tests are very important. The extent to which phenindione is working is measured by the INR (International Normalised Ratio), which is a measure of the ability of your blood to prevent clotting. The amount of phenindione that you need to take will depend upon the result of these blood tests, and this is why your dose may change from time to time.
- Changing your diet suddenly can affect your INR, especially if you begin to eat more vegetables and salad or if you change the amount of fatty foods you eat. Also, you should not begin a weight-reducing diet without discussing this with your doctor first.
- Only drink alcohol in small amounts, as this can affect the levels of phenindione in your body.
- Drinking cranberry juice can interfere with phenindione and affect your INR, so it is best if you avoid cranberry juice altogether.
- If you buy any medicines, check with a pharmacist that they are safe to take with phenindione. For example, you should not take some painkillers (such as aspirin and other anti-inflammatory painkillers) and some vitamin and herbal preparations while you are on phenindione. If you need to take a painkiller, you may take paracetamol.
- Phenindione may make your urine look pink or orange. This is completely harmless and nothing to worry about.
- Because phenindione is used to prevent blood clots from forming, you should avoid contact sports and take care not to knock, cut or bruise yourself. Let your doctor know if you have any falls or injuries.
- You should avoid getting pregnant while you are taking phenindione. If this affects you, make sure you have discussed with your doctor which types of contraception are suitable for you and your partner.
- If you are having an operation or any dental treatment, tell the person carrying out the treatment that you are taking phenindione, and show them your anticoagulant record book.
Can phenindione cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.
|Phenindione side-effects||What can I do if I experience this?|
|Diarrhoea||Drink plenty of water to replace lost fluids|
|Feeling or being sick||Stick to simple foods until this passes|
|Pink or orange-coloured urine||This is harmless|
|Hair loss, 'purple' toes, changes in the way things taste||If any of these become troublesome, speak with your doctor|
Important: if you experience either of the following, contact your doctor for advice straightaway:
- Any unusual bruising or bleeding, or any blood in your urine or stools. This is because your dose of phenindione will need to be checked.
- A severe skin rash. This may be a sign of an allergic reaction to phenindione.
If you experience any other symptoms which you think may be due to phenindione, speak with your doctor or pharmacist.
How to store phenindione
- Keep all medicines out of the reach and sight of children.
- Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
Further reading & references
- British National Formulary; 63rd Edition (Mar 2012) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
- Manufacturer's PIL, Phenindione 50 mg tablets; Manufacturer's PIL, Phenindione 50 mg tablets, Mercury Pharma Group, The electronic Medicines Compendium. Dated August 2010.
|Original Author: Helen Allen||Current Version: Helen Allen||Peer Reviewer: Prof Cathy Jackson|
|Last Checked: 19/07/2012||Document ID: 3262 Version: 23||© EMIS|
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.