How does this medication work? What will it do for me?

Acenocoumarol belongs to the group of medications called anticoagulants. It is sometimes referred to as a "blood thinner," although it does not actually thin the blood. Acenocoumarol is used to treat and prevent blood clots in the veins by preventing blood clots from forming or from getting bigger, but it does not dissolve blood clots.

It is also used to treat atrial fibrillation (an abnormal heart rhythm) that is associated with blood clots, and to treat and prevent blood clots in the lungs. It is used along with other medications to treat blood clots in the heart and transient ischemic attacks (mini-strokes).

Acenocoumarol works by partially blocking the reuse of vitamin K in your liver. Vitamin K is needed to make clotting factors that help the blood to clot and prevent bleeding. Vitamin K is found naturally in foods such as leafy, green vegetables and certain vegetable oils. If you are taking acenocoumarol, you may continue to eat these foods but do not make any drastic changes to your diet.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Acenocoumarol is no longer being manufactured for sale in Canada and is no longer available under any brand names. This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.

How should I use this medication?

The dose of acenocoumarol is individualized by your doctor according to blood clotting time as determined by laboratory tests, called an INR, performed at regular intervals. It is very important to keep your lab appointments, as there is a narrow range between too much and too little of the medication. Too much medication may cause you to bleed more. Too little medication may let a harmful clot form.

The usual dose on the first day ranges from 8 mg to 12 mg and on the second day from 4 mg to 8 mg. The usual maintenance dose ranges from 1 mg to 10 mg once daily. Take acenocoumarol at the same time each day.

Different circumstances in your life (e.g., eating certain foods or using certain medications) can cause this medication to work more or less effectively. Ask your doctor or pharmacist for a list of these foods and medications.

It is important to manage your lifestyle appropriately when taking acenocoumarol:

  • do not make drastic changes in your diet, such as eating large amounts of green, leafy vegetables
  • do not attempt to change your weight by dieting without first checking with your health care provider
  • do not participate in any activity or sport that may result in serious injury
  • avoid drinking alcohol
  • avoid cutting yourself

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take acenocoumarol if you:

  • are allergic to acenocoumarol or any ingredients of the medication
  • are pregnant
  • are receiving injections into a muscle
  • are undergoing certain types of anesthesia
  • do not have access to laboratory facilities for regular blood testing
  • have a medical condition in which the risk of bleeding is greater than the benefits of receiving the medication, including:
    • after surgery, which is associated with increased breakdown of blood clots (e.g., lung, prostate, or uterus surgery)
    • a high risk of abortion, eclampsia, and preeclampsia (complications of pregnancy often associated with sudden onset of very high blood pressure)
    • bleeding tendencies or blood disorders
    • bleeding tendencies associated with active ulcers or bleeding of the stomach, genitourinary, or respiratory tracts, or bleeding associated with many other medical conditions
    • certain types of severe kidney and liver problems
    • recent or planned surgery of the eye or the central nervous system, or surgery associated with trauma resulting in a large open surface
    • severe high blood pressure
  • have polyarthritis
  • have senility, alcoholism, psychosis, or other conditions where the person may not be able to cooperate with taking the medication and having the necessary lab tests on a regular basis
  • have a vitamin C deficiency

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • diarrhea
  • fever
  • hives
  • itchy skin
  • loss of appetite
  • loss of hair
  • nausea
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • bleeding from cuts that take a long time to stop
  • bleeding gums
  • headaches, dizziness, or weakness
  • heavier than normal menstrual bleeding
  • nosebleeds
  • numbness or tingling of the face, hands, or feet
  • pain, swelling, or discomfort
  • paralysis
  • pink or brown urine
  • sudden shortness of breath
  • unexplained bruising
  • unusual pain or swelling

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • fainting
  • signs of a serious allergic reaction, e.g.:
    • difficulty breathing
    • hives
    • swelling of face or throat
  • signs of bleeding, e.g.:
    • bleeding in the eye
    • blood in stools
    • blood in urine
    • blood in vomit or vomit that looks like coffee grounds
    • coughing up blood
    • dark, tarry stools

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Bleeding: The most serious risk associated with acenocoumarol is bleeding in any tissue or organ. The risk of bleeding is related to the level of intensity and the duration of treatment.

It is extremely important to have regular blood tests (as recommended by your doctor) to measure your INR level. Your health care provider will adjust the dose of acenocoumarol depending on your INR level to ensure you are not receiving too little medication (which may result in blood clots forming) or too much medication (which may result in bleeding).

Kidney problems: If you have kidney problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver problems: If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Medical alert: In case of injury or accident, people taking this medication should carry a card or wear other identification (e.g., bracelet or necklace) that states they are taking this medication.

Medical conditions and other medications: Many medical conditions and medications affect the way acenocoumarol works and affect the dosing of this medication. If you have a medical condition and are taking medications, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Always check with your doctor or pharmacist before taking any new prescription or over-the-counter medication, supplement, or herbal product.

Medical procedures: Before undergoing any medical test or procedure (e.g., minor surgery, tooth extractions, angiography), be sure to tell your health care providers that you are taking this medication.

Stopping the medication: If your doctor has told you that you can stop acenocoumarol, they may recommend that you decrease your dose slowly over time. Do not suddenly stop taking this medication without discussing with your doctor first.

Pregnancy: Acenocoumarol should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Acenocoumarol passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of taking this medication have not been established for children.

Seniors: Seniors taking this medication may be more sensitive to side effects and may need closer monitoring by their doctors.

What other drugs could interact with this medication?

There may be an interaction between acenocoumarol and any of the following:

  • acetaminophen
  • alcohol
  • allopurinol
  • amiodarone
  • anticancer medications (e.g., carboplatin, cyclophosphamide, fluorouracil)
  • azathioprine
  • azithromycin
  • "azole" antifungals (e.g., fluconazole, ketoconazole, miconazole)
  • barbiturates (e.g., primidone, phenobarbital)
  • birth control pills
  • carbamazepine
  • cephalosporins (e.g., cefazolin, cefoperazone, cefotetan, cefoxitin)
  • chloral hydrate
  • chloramphenicol
  • cholestyramine
  • cimetidine
  • clarithromycin
  • clofibrate
  • corticosteroids (e.g. prednisone, dexamethasone)
  • danazol
  • delavirdine
  • dextran
  • diazoxide
  • diuretics (e.g. hydrochlorothiazide)
  • erythromycin
  • ethacrynic acid
  • fenofibrate
  • fluoxymesterone
  • flutamide
  • gemfibrozil
  • glucagon
  • griseofulvin
  • halothane
  • heparin and low-molecular weight heparins (e.g. enoxaparin, dalteparin)
  • herbs that affect blood clotting (e.g., St. John's wort, ginseng, ginkgo biloba, coenzyme Q10)
  • lidocaine
  • long-term use of narcotic pain medications (e.g. codeine, oxycodone, morphine, hydromorphone)
  • MAO inhibitors (e.g., phenelzine, tranylcypromine)
  • meprobamate
  • mercaptopurine
  • metronidazole
  • mexilitine
  • miconazole
  • nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., diclofenac, ibuprofen, naproxen, celecoxib, mefenamic acid)
  • pentoxifylline
  • phenylbutazone
  • phenytoin
  • potassium iodide
  • primaquine
  • propafenone
  • propoxyphene
  • propylthiouracil
  • quinidine
  • quinine
  • quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
  • rifabutin
  • rifampin
  • salicylates (e.g., aminosalicylic acid, sodium salicylate, acetylsalicylic acid [ASA], methyl salicylate)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., duloxetine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram)
  • "statins" (e.g., fluvastatin, lovastatin, simvastatin)
  • streptokinase
  • sulfinpyrazone
  • sulfonamides (e.g., sulfamethoxazole)
  • sulfonylureas (e.g., glyburide, chlorpropamide, tolbutamide)
  • tamoxifen
  • testosterone
  • tetracyclines (e.g., doxycycline, minocycline, tetracycline)
  • thiabendazole
  • thyroid hormones (e.g., levothyroxine, liothyronine, thyroid)
  • ticlopidine
  • tissue plasminogen activator (t-PA)
  • urokinase
  • vitamin E
  • vitamin K
  • warfarin
  • zafirkulast

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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