Warfarin Side Effects

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Answer the side-effect intent for warfarin without diagnosing; distinguish common from serious reactions and give safe next-step/reporting guidance.

Part of cardiovascular side effects.

What is warfarin?

Warfarin contains the active ingredient Warfarin sodium.

• Active ingredient — Warfarin sodium
• Registration number — 56/8.2/0658
• Registration holder — Biotech Laboratories (Pty) Ltd

It is approved for:

• Warfarin 5 Biotech contains the active ingredient warfarin which belongs to a group of medicines called anticoagulants
• It is used to decrease the clotting ability of the blood and therefore helps to prevent harmful clots from forming in the blood vessels
• Warfarin 5 Biotech is used to prevent and treat blood clots forming in the legs, lungs, brain or heart

Common side effects of warfarin

Not everyone gets side effects. The effects below are those listed in the South African approved leaflet, grouped using the leaflet’s own frequency wording.

Less frequent side effects

• lower-than-normal number of leukocytes (white blood cells) in the blood
• too many granulocytes (certain type of white blood cells) in the blood
• reduced blood clotting (by inhibiting vitamin K synthesis), may also increase the risk of bleeding
• diarrhoea
• nausea
• vomiting
• feeling bloated
• loss of appetite
• stomach pain
• kidney damage (leading to swelling in different parts of the body, abnormal amount of protein in the urine or difficulty passing urine). Side effects with unknown frequency
• fever
• low number of red blood cells (anaemia)
• bleeding from the nose (epistaxis)
• yellowing of the skin and white of eyes (jaundice)
• skin rash
• hair loss
• a rash of purple spots on the skin caused by internal bleeding from small blood vessels (purpura)
• painful skin lesion seen in patients with moderate to severe kidney problems
• skin redness
• skin necrosis (also called warfarin-induced skin necrosis-condition in which skin and tissue death occurs)
• arm or leg become severely damaged and may die to problems with the veins in that limb
• sores or white spots in your mouth or throat

Serious side effects and warning signs

This leaflet does not set out a separate list of serious side effects. The general warning signs below apply to any medicine.

General warning signs that apply to any medicine

How long can side effects last?

How long a side effect lasts depends on the effect, the product, how long it has been used, and the person. Some effects ease within days as the body adjusts. Others continue for as long as the product is used. A few can persist after stopping, and some need review rather than waiting.

• Settling effects — mild effects that ease over the first days or weeks of use
• Ongoing effects — effects that continue while the product is being used and improve after stopping
• Persistent effects — effects that continue after stopping and need medical review
• Delayed effects — effects that appear after weeks or months rather than immediately

Which of these applies to a particular effect is a clinical question. If a side effect is not settling, is getting worse, or is affecting your daily life, that is worth a conversation with a pharmacist or doctor regardless of how long it has been going on.

Factors that may affect side effects

The approved leaflet identifies the following cautions and factors.

Do not use it at all if

• if you are hypersensitive (allergic) to warfarin sodium or any of the other ingredients of Warfarin 5 Biotech listed in section 6.1
• if you recently had a stroke caused by bleeding in the brain
• if you have a bleeding situation
• if you have any bleeding disorder or disease
• if you had surgery within the last 72 hours or are going to have surgery in the next 72 hours
• if you have a peptic ulcer or other stomach disease that causes you to bleed internally
• if you have a severe wound
• if you have a prosthetic heart valve
• if you an infection of the heart valves
• if your kidney or liver function is impaired
• if you have high blood pressure
• if you had an aneurysm (blood vein or artery that formed a sac or burst)
• if you have inflammation (swelling) of the pericardium, which is the fluid-filled sac that surrounds your heart (pericarditis)
• if you have an abnormal amount of fluid between the heart and pericardium (pericardial perfusion)
• if you had or are going to have surgery that involves your eyes, brain, back or nerves or any other major surgeries
• if you had a baby in the last 48 hours
• if you have severe arthritis (inflammation of the joints) affecting five or more joints at the same time
• if you have a Vitamin C deficiency
• if you have the possibility of losing your baby (threatened abortion)
• if you are younger than 18 years of age, because safety has not been established
• if you are taking other medicines that increase your risk of bleeding
• if you are taking other medicines to treat and prevent blocking of a blood vessel by a blood clot
• if you are pregnant or may become pregnant or breastfeeding, you baby

Use with care, and tell your doctor, if

• if you have a genetic disorder called protein C deficiency making you prone to blood clots (thrombophilia)
• you should not stop your treatment with Warfarin 5 Biotech abruptly. Your doctor will decrease your dose gradually over three to four weeks
• if you have a Vitamin K deficiency
• medicines like Warfarin 5 Biotech, which work against vitamin K, might put you at risk for weaker bones (increased risk in fractures). You need extra attention to avoid this problem
• if you suffer from dietary deficiency, are on antibiotic treatment, suffer from vascular disease, diabetes or have allergic disorders
• if you had recent ischaemic stroke (caused by blockage of blood vessels in the brain)
• if you had an infection of the heart lining (bacterial endocarditis)
• if you previously had gastrointestinal bleeding
• if you have a higher risk of bleeding for example if you are over 65 years of age or are unsteady on your feet and more likely to fall and injure yourself
• very high blood pressure which is not controlled by medicines
• problems with circulation of blood to the brain (cerebrovascular disease)
• if you have severe heart disease, liver or kidney problems
• if you have anaemia (low haemoglobin causing extreme tiredness, breathlessness, poor resistance to infection)
• if you have a tumour or cancer
• if you had trauma, had a recent wound or injury
• if you use any anti-platelet medicines (such as clopidrogel, aspirin), because that can increase the risk of bleeding
• if you have the condition calciphylaxis, where calcium builds up inside the blood vessels of the fat and skin
• if you have an overactive thyroid gland
• if you experience a painful and prolonged erection called priapism. This problem seems to be linked to a lack of protein C, and it often happens alongside another issue called warfarin-induced skin necrosis
• if you experience a painful spot on the skin, which may look red or bleed at first. Later, it can form blisters and turn black from tissue death. People with lack of protein C levels seem to be at the highest risk
• Be cautious if you have “wet” age-related eye disease that can blur your central vision and are taking Warfarin 5 Biotech because it could make you bleed inside your eye and lead to vision loss. Regular blood tests: You will have regular blood tests to see how long it takes your blood to clot. These blood tests are very important to make sure you are taking the right dose. Blood tests will be more frequent if you have had your dose of warfarin changed, if you have started or stopped taking other medicines, or have liver or kidney problems. Warfarin 5 Biotech may be affected by: A number of things affect blood clotting and can therefore affect your Warfarin 5 Biotech treatment. It is important to follow the advice given below: The following increases the effect of Warfarin 5 Biotech
• Weight loss
• Sudden illness such as the flu or feeling run down
• Stopping smoking, thus seek medical advice before you give up smoking
• Cranberry juice and cranberry products (and possibly grapefruit juice)
• Large amounts of alcohol The following decreases the effect of Warfarin 5 Biotech
• Weight gain
• Stomach upset, diarrhoea
• Being sick (vomiting) Keep your healthcare professionals informed: Carry your anticoagulation record card with you at ALL times. Always tell any doctors, surgeons, nurses, dentists or pharmacists that you go to that you are taking Warfarin. You should also have received a booklet which includes more information about Warfarin along with a list of symptoms which need to be checked by your doctor immediately. Surgical operations: Tell your doctor you are taking Warfarin 5 Biotech. Due to the risk of bleeding, your doctor may need to lower your dose before an operation or removal of teeth. You should stop taking Warfarin 5 Biotech 3 to 5 days before and after surgery where there is a risk of severe bleeding. Make sure you tell your doctor or dentist you are taking Warfarin 5 Biotech. Depending on the reason you are using warfarin, Warfarin 5 Biotech may have to be replaced by another medicine (heparin). Children and adolescents Warfarin 5 Biotech should not be given to children 18 years and younger as the safety and effectiveness have not been established

Pregnancy and breastfeeding

• If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, please consult your doctor, pharmacist or other health care provider for advice before receiving Warfarin 5 Biotech
• Do not take Warfarin 5 Biotech if you are pregnant, may become pregnant or have had a baby within the last 48 hours
• Woman of child-bearing age who are taking Warfarin 5 Biotech should use contraception medicine during their treatment with Warfarin 5 Biotech and for at least 1 month after the final dose of Warfarin 5 Biotech
• Do not breastfeed your infant while taking Warfarin 5 Biotech

Interactions and medicines to check

The approved leaflet names these interactions.

• Fibrinolytic medicines to treat or prevent blood clots, such as alteplase, reteplase, tenecteplase, streptokinase and urokinase
• St John’s wort (Hypericum perforatum) an herbal remedy for depression. Check with your doctor first before taking these medicines:
• Clopidogrel (antiplatelet medicines to prevent or break down blood clots)
• non-steroidal-anti-inflammatory drugs (NSAIDs) for pain and inflammation including aspirin, ibuprofen, celecoxib, diclofenac, indomethacin, meloxicam
• sulfinpyrazone (for gout)
• Thrombin inhibitors (delaying blood clotting) such as bivalirudin, dabigatran
• dipyridamole (antiplatelet drugs to prevent or break down blood clots)
• heparin or medicines containing heparin, bivalirudin, fondaparinux, dabigatran, rivaroxaban, danaparoid, prostacyclin (other anticoagulants)
• Glycoprotein IIb/IIIa receptor antagonists such as eptifibatide, tirofiban and abciximab (antiplatelet drugs to prevent or break down blood clots)
• SSRI and SNRI anti-depressants such as citalopram, fluoxetine, paroxetine, venlafaxine
• glucosamine (for osteoarthritis) Medicines which increase the effect of Warfarin 5 Biotech:
• prolonged, regular use of paracetamol (for pain or inflammation)
• antibiotics such as amoxicillin, levofloxacin and tetracycline
• allopurinol (for gout)
• capecitabine, erlotinib, tamoxifen (for types of cancer)
• disulfiram (for alcohol dependence)
• ketoconazole, fluconazole, itraconazole, miconazole (for fungal infections)
• omeprazole (for stomach ulcers)
• propafenone, amiodarone, quinidine (for heart disorders)
• methylphenidate (for attention deficit disorder)
• zafirlukast (for asthma)
• bezafibrate, ciprofibrate, fenofibrate, gemfibrozil (to reduce high blood fats)
• statins such as fluvastatin to lower cholesterol (but this does not include pravastatin)
• erythromycin, sulfamethoxazole, metronidazole (for bacterial infections)
• orlistat (for obesity)
• Vitamin K (in vitamin supplements or in cod liver oil). Medicines which decrease the effect of Warfarin 5 Biotech:
• barbiturates (sedatives)
• primidone, phenytoin, carbamazepine (to treat epilepsy)
• griseofulvin (for fungal infections)
• oral contraceptives (the ‘Pill’)
• rifampicin (for tuberculosis)
• azathioprine (for inflammatory bowel disease and rheumatoid arthritis and to prevent organ rejection)
• sucralfate (for stomach ulcers)
• cholestyramine (for lowering cholesterol)
• vitamin K (an increase in the amount of your vitamin K intake could reduce the effect of Warfarin 5 Biotech). Medicines which have varying effects on Warfarin 5 Biotech:
• corticosteroids (for inflammation and many other diseases)
• nevirapine, ritonavir (for HIV infection). Warfarin 5 Biotech with food, drink and alcohol Patients should seek medical advice before undertaking any major changes in diet or using food supplements while taking Warfarin 5 Biotech. Do not drink either cranberry juice or grapefruit juice or products containing it whilst taking Warfarin 5 Biotech. Acute ingestion of a large amount of alcohol may inhibit the metabolism of Warfarin 5 Biotech and increase INR. Conversely, chronic heavy alcohol intake may induce the metabolism of Warfarin 5 Biotech

What to do if you experience side effects

If you think you are having a side effect, the response depends on how severe it is. Use the warning signs above first — if any of those apply, treat it as urgent.

If the symptom is severe or frightening

Get medical help immediately. Call 10177 for an ambulance, or 112 from a mobile phone, or go to the nearest emergency department. Take the product and its packaging with you if you can.

If the symptom is mild but bothering you

• Write down what the symptom is, when it started, and how it relates to when you take the product
• Check the leaflet that came with the product to see whether the symptom is listed
• Speak to your pharmacist — for many questions this is the fastest route to a useful answer
• Contact the prescriber if the symptom is affecting your daily life or is not settling

You can also report a suspected side effect in South Africa. Reporting does not replace getting medical advice, and you do not need to be certain the product was the cause.

When to seek urgent medical help

Some symptoms need medical attention straight away rather than an appointment in a few days. Do not wait to see whether they settle.

Get same-day medical advice if you have

• A high fever, or a rash together with feeling generally unwell
• Yellowing of the eyes or skin, or unusually dark urine
• Unusual bruising or bleeding that you cannot explain
• Severe or persistent vomiting or diarrhoea, especially if you cannot keep fluids down
• A sudden change in mood, or thoughts of harming yourself
• Any symptom that is rapidly getting worse

How to report a suspected side effect in South Africa

South Africa has an official system for reporting suspected side effects, run by the South African Health Products Regulatory Authority (SAHPRA). Reports from the public and from healthcare professionals are how safety signals get detected after a product is already in use.

Who can report

Anyone can report — you do not have to be a healthcare professional, and you do not need to prove that the product caused the problem. A suspicion is enough. Patients, caregivers and family members can all submit a report.

What to have ready

• The name of the product, its strength and form, and the batch number if you have it
• Why it was being used, and when it was started and stopped
• What the suspected reaction was, when it began, and how long it lasted
• Any other medicines, supplements or remedies being used at the same time
• Basic details about the person affected — age and sex are usually enough

How to report

SAHPRA accepts adverse reaction reports through its e-Services reporting system and through the Med Safety mobile app. Healthcare professionals can also report through the same routes. Current forms and access points are published on the SAHPRA site.

• SAHPRA Health Products Vigilance — the main vigilance and reporting hub
• SAHPRA e-Services — current adverse reaction reporting access

For a fuller walkthrough see how to report an adverse drug reaction.

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