Acenocoumarol (Nicoumalone) - Oral

Pronunciation: a-SEN-oe-KOO-mar-ol/nye-KOO-mawl-one

Common Brand Name(s): Sintrom

Important: How To Use This Information

This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.


Acenocoumarol (also called nicoumalone) is used to prevent and treat harmful blood clots, reducing the risk of a stroke or heart attack. This medication helps to keep blood flowing smoothly in your body by decreasing the amount of clotting proteins in the blood. This medication is used to lower your risk of developing blood clots caused by conditions such as a certain type of irregular heart rhythm (atrial fibrillation), heart valve replacement, or a recent heart attack. Acenocoumarol is an anticoagulant (also known as a "blood thinner").

How To Use

Take this medication by mouth, usually once a day or as directed by your doctor. It is very important to take it exactly as prescribed.

Use this medication regularly in order to get the most benefit from it. To help you remember, take it at the same time each day. Do not increase the dose or take it more often than directed. Do not suddenly stop taking this medication unless your doctor tells you to do so. If you need to stop this medication, your doctor may direct you to gradually decrease your dose over 3 to 4 weeks.

The dosage is based on your medical condition, laboratory clotting test results, and response to treatment.

Side Effects

Nausea, vomiting, loss of appetite, or diarrhea may occur. Temporary hair loss may rarely occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication can rarely cause bleeding if it affects your blood clotting proteins too strongly. Even if your doctor stops your medication based on your test results, the risk of bleeding can persist for several days. Get medical help right away if any of these signs of serious bleeding occur:

  • unusual pain/swelling/discomfort
  • prolonged bleeding (e.g., from cuts, gums)
  • persistent nosebleeds
  • unusually heavy/prolonged menstrual flow
  • other unusual vaginal bleeding
  • unusual/easy bruising
  • dark urine (blood in the urine)
  • stomach/abdominal pain
  • black stools
  • vomit that looks like coffee grounds
  • severe headache
  • vision changes
  • confusion
  • slurred speech
  • weakness on one side of the body
  • unusual dizziness
  • fainting
  • seizures
  • bleeding inside the eye
  • fast heartbeat

This drug may rarely cause serious problems due to clumps of cholesterol that may come free from blood vessel walls. These clumps can block blood flow to parts of your body. If left untreated, this effect can lead to severe tissue damage (gangrene). Get medical help right away if any of these very serious side effects occur:

  • painful red rash
  • dark discoloration of any body part (e.g., purple toe syndrome)
  • sudden intense pain (e.g., back or muscle pain)
  • foot ulcers
  • signs of kidney problems (such as change in the amount of urine)

Tell your doctor right away if you have any serious side effects, including:

  • persistent nausea/vomiting
  • yellowing eyes/skin
  • unusual tiredness

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

  • rash
  • itching/swelling (especially of the face/tongue/throat)
  • severe dizziness
  • trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.


Before taking acenocoumarol, tell your doctor or pharmacist if you are allergic to it; or to other anticoagulants (e.g., warfarin); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

  • blood disorders (e.g., hemophilia, low platelet count)
  • bleeding problems (e.g., current ulcers)
  • recent or planned surgery/procedures
  • liver disease
  • kidney disease
  • alcohol abuse
  • tissue damage (e.g., gangrene, necrosis)
  • severe injury
  • high blood pressure
  • severe diabetes
  • congestive heart failure
  • cancer
  • collagen vascular disease (e.g., lupus, polyarteritis)
  • inflammatory disease (e.g., arthritis, vasculitis)
  • radiation therapy
  • underactive or overactive thyroid (hypothyroidism or hyperthyroidism)
  • poor nutrition
  • intestinal absorption problems
  • low blood levels of vitamin K
  • swelling of the arms/legs (edema)
  • high levels of cholesterol/blood fats
  • catheters in your body (e.g., urinary or intravenous type)
  • certain side effects with heparin treatment (heparin-induced thrombocytopenia)
  • family members who did not respond to acenocoumarol/other anticoagulant treatment
  • conditions that make it difficult to follow a treatment plan (e.g., dementia, psychosis)

Avoid alcohol while taking this drug because it may increase the risk of stomach bleeding.

Avoid getting injections into the muscles. If they must be given, limit injections to the arms.

If you have an illness or infection that causes vomiting, diarrhea, or fever for more than a few days, contact your doctor right away because these conditions can affect how well this drug works.

To lower the chance of bleeding due to getting cut, bruised, or injured, use great caution with sharp objects like safety razors and nail cutters. Use an electric razor when shaving and a soft toothbrush when brushing your teeth. Avoid activities such as contact sports.

It is important that all your doctors and dentists know that you take acenocoumarol.

Caution is advised when using this drug in the elderly because they may be more sensitive to its effects.

This medication must not be used during pregnancy. It may harm an unborn baby. Discuss reliable forms of birth control with your doctor. If you become pregnant or think you may be pregnant, tell your doctor right away. If you plan to become pregnant, talk to your doctor ahead of time. Another type of anticoagulant (e.g., heparin) is preferred during pregnancy. Consult your doctor for more information.

This medication passes into breast milk in small amounts. While there have been no reports of harm to nursing infants, consult your doctor before breast-feeding.

Drug Interactions

See also How to Use.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Many drugs and herbal products interact with acenocoumarol. Caution is advised when any medication is added to or stopped during acenocoumarol treatment. Laboratory monitoring may need to be performed more often when you start or stop taking other medications.

Some products that may interact with this drug include:

  • acetaminophen (used often or in large doses)
  • allopurinol
  • aminoglutethimide
  • amiodarone
  • anabolic steroids (e.g., danazol, oxymetholone, stanozolol)
  • other anticoagulants (e.g., heparin)
  • certain injectable cephalosporin antibiotics (e.g., cefamandole, cefotetan)
  • macrolide antibiotics (e.g., erythromycin, clarithromycin)
  • certain penicillin-type antibiotics (e.g., dicloxacillin)
  • quinolone antibiotics (e.g., ciprofloxacin, levofloxacin)
  • certain other antibiotics (e.g., chloramphenicol, neomycin, tetracycline)
  • azole antifungals (e.g., voriconazole, vaginal miconazole)
  • barbiturates (e.g., phenobarbital)
  • birth control pills/patch/ring
  • certain drugs to treat cancer (e.g., capecitabine, gefitinib, fluorouracil, vorinostat)
  • carbamazepine
  • drugs to lower cholesterol or triglycerides (e.g., cholestyramine, fenofibrate, gemfibrozil, lovastatin, simvastatin)
  • cimetidine
  • corticosteroids (e.g., prednisone)
  • diazoxide
  • disulfiram
  • estrogens
  • glucagon
  • griseofulvin
  • herbal/supplement products (e.g., bromelains, coenzyme Q, danshen, dong quai, garlic, ginkgo biloba, ginseng, St. John's wort)
  • imatinib
  • mercaptopurine
  • MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine)
  • mifepristone
  • nonsteroidal anti-inflammatory drugs (NSAIDs such as celecoxib, ibuprofen, methylsalicylate applied to the skin)
  • phenytoin
  • propafenone
  • propoxyphene
  • proton pump inhibitors (e.g., omeprazole, pantoprazole)
  • quinidine
  • quinine
  • rifamycins (e.g., rifampin, rifabutin)
  • certain sedatives (e.g., chloral hydrate, ethchlorvynol, glutethimide, meprobamate)
  • sulfa drugs
  • sulfinpyrazone
  • SSRI antidepressants (e.g., fluoxetine, fluvoxamine)
  • tamoxifen
  • tibolone
  • tipranavir
  • toremifene
  • drugs to treat thyroid disease (e.g., levothyroxine, propylthiouracil)
  • vitamins (e.g., vitamin C, vitamin E, vitamin K)
  • zafirlukast

Check all prescription and nonprescription medicine labels carefully since many contain pain relievers/fever reducers (nonsteroidal anti-inflammatory drugs-NSAIDs such as celecoxib, ibuprofen, naproxen, salicylates, aspirin) that can increase the risk of bleeding/anti-platelet effect when used with acenocoumarol. Low-dose aspirin should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention or to prevent clotting of artificial heart valves (usually at dosages of 81-325 milligrams per day). Ask your doctor or pharmacist for more details.

Continue taking related drugs (anti-platelet drugs such as clopidogrel, dipyridamole, ticlopidine) that have been prescribed for specific medical reasons unless your doctor directs you otherwise. Consult your doctor or pharmacist for more details.

While taking acenocoumarol, it is important to eat a normal, balanced diet. The amount of vitamin K in your body affects the way that acenocoumarol works. It is best to avoid sudden changes in your diet, especially unusual increases or decreases in the amount of foods high in vitamin K (e.g., liver, broccoli, cauliflower, cabbage, Brussels sprouts, kale, spinach and other green leafy vegetables, green tea, and certain vitamin supplements). It is best to avoid strict vegetarian diets that consist of foods high in vitamin K.

This medication may interfere with certain laboratory tests, possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.


If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: unusual/prolonged bleeding, blood in the urine, black stools.


Do not share this medication with others.

Laboratory and/or medical tests (e.g., blood clotting tests such as PT/INR, complete blood count) should be performed periodically to monitor your progress or check for side effects. It is important to keep all lab and medical appointments. Consult your doctor or pharmacist for more details.

Missed Dose

If you miss a dose, take it as soon as you remember if it is on the same day. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up because this could increase your risk for bleeding. Keep a record of missed doses to give to your doctor or pharmacist. Call your doctor or pharmacist if you miss 2 or more doses in a row.


Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Medical Alert

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).

Is it an emergency?

If you or someone in your care has chest pains, difficulty breathing, or severe bleeding, it could be a life-threatening emergency. Call 9-1-1 or the local emergency number immediately.
If you are concerned about a possible poisoning or exposure to a toxic substance, call Poison Control now at 1-800-567-8911.

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