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Vitamin K (Systemic)

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Vitamin K (Systemic)

US Brand Names


• Mephyton

Other commonly used names are: phylloquinone, phytomenadione, vitamin K 1, and vitamin K 4.


Vitamins (VYE-ta-mins) are compounds that you must have for growth and health. They are needed in only small amounts and usually are available in the foods that you eat. Vitamin K is necessary for normal clotting of the blood.

Vitamin K is found in various foods including green leafy vegetables, meat, and dairy products. If you eat a balanced diet containing these foods, you should be getting all the vitamin K you need. Little vitamin K is lost from foods with ordinary cooking.

If you are taking anticoagulant medicine (blood thinners), the amount of vitamin K in your diet may affect how well these medicines work. Your doctor or health care professional may recommend changes in your diet to help these medicines work better.

Lack of vitamin K is rare but may lead to problems with blood clotting and increased bleeding. Your doctor may treat this by prescribing vitamin K for you.

Vitamin K is routinely given to newborn infants to prevent bleeding problems.

This medicine is available only with your doctor's prescription, in the following dosage forms:


    • Phytonadione

      o Tablets (U.S.)


    • Phytonadione

      o Injection (U.S. )

Special Considerations

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For vitamin K, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to vitamin K. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.


Vitamin K has not been reported to cause birth defects or other problems in humans. However, the use of vitamin K supplements during pregnancy is not recommended because it has been reported to cause jaundice and other problems in the baby.


Vitamin K taken by the mother has not been reported to cause problems in nursing babies. You should check with your doctor if you are giving your baby an unfortified formula. In that case, the baby must get the vitamins needed some other way.


Children may be especially sensitive to the effects of vitamin K, especially menadiol or high doses of phytonadione. This may increase the chance of side effects during treatment. Newborns, especially premature babies, may be more sensitive to these effects than older children.

Older adults

Many medicines have not been tested in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information about the use of vitamin K in the elderly.

Other medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking vitamin K, it is especially important that your health care professional know if you are taking any of the following:

    • Acetohydroxamic acid (e.g., Lithostat) or

    • Antidiabetics, oral (diabetes medicine you take by mouth) or

    • Dapsone or

    • Furazolidone (e.g., Furoxone) or

    • Methyldopa (e.g., Aldomet) or

    • Nitrofurantoin (e.g., Furadantin) or

    • Primaquine or

    • Procainamide (e.g., Pronestyl) or

    • Quinidine (e.g., Quinidex) or

    • Quinine (e.g., Quinamm) or

    • Sulfonamides (sulfa medicine) or

    • Sulfoxone (e.g., Diasone)-The chance of a serious side effect may be increased, especially with menadiol

    • Anticoagulants (blood thinners)-Vitamin K decreases the effects of these medicines and is sometimes used to treat bleeding caused by anticoagulants; however, patients receiving an anticoagulant should not take any supplement that contains vitamin K (alone or in combination with other vitamins or nutrients) unless it has been ordered by their doctor

Other medical problems

The presence of other medical problems may affect the use of vitamin K. Make sure you tell your doctor if you have any other medical problems, especially:

    • Cystic fibrosis or other diseases affecting the pancreas or

    • Diarrhea (prolonged) or

    • Gallbladder disease or

    • Intestinal problems-These conditions may interfere with absorption of vitamin K into the body when it is taken by mouth; higher doses may be needed, or the medicine may have to be injected

    • Glucose-6-phosphate dehydrogenase (G6PD) deficiency-The chance of side effects may be increased, especially with menadiol

    • Liver disease-The chance of unwanted effects may be increased


Take this medicine only as directed by your doctor . Do not take more or less of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may cause serious unwanted effects, such as blood clotting problems.


The dose of these medicines will be different for different patients. Follow your doctor's orders or the directions on the label . The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets or injections that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking the medicine .

    For menadiol

    • For oral dosage form (tablets):

      o For problems with blood clotting or increased bleeding, or for dietary supplementation:

        Adults and children-The usual dose is 5 to 10 milligrams (mg) a day.

    • For injection dosage form:

      o For problems with blood clotting or increased bleeding, or for dietary supplementation:

        Adults and teenagers-The usual dose is 5 to 15 mg, injected into a muscle or under the skin, one or two times a day.

        Children-The usual dose is 5 to 10 mg, injected into a muscle or under the skin, one or two times a day.

    For phytonadione

    • For oral dosage form (tablets):

      o For problems with blood clotting or increased bleeding:

        Adults and teenagers-The usual dose is 2.5 to 25 milligrams (mg), rarely up to 50 mg. The dose may be repeated, if needed.

        Children-Use is not recommended.

    • For injection dosage form:

      o For problems with blood clotting or increased bleeding:

        Adults and teenagers-The usual dose is 2.5 to 25 mg, rarely up to 50 mg, injected under the skin. The dose may be repeated, if needed.

      o For prevention of bleeding in newborns:

        The usual dose is 0.5 to 1 mg, injected into a muscle or under the skin, right after delivery. The dose may be repeated after six to eight hours, if needed.

Missed dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses. Tell your doctor about any doses you miss .


To store this medicine:

    • Keep out of the reach of children.

    • Store away from heat and direct light.

    • Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.

    • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.


Tell all medical doctors and dentists you go to that you are taking this medicine .

Always check with your health care professional before you start or stop taking any other medicine . This includes any nonprescription (over-the-counter [OTC]) medicine, even aspirin. Other medicines may change the way this medicine affects your body.

Your doctor should check your progress at regular visits. A blood test must be taken regularly to see how fast your blood is clotting. This will help your doctor decide how much medicine you need.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

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

Less common

With menadiol or high doses of phytonadione in newbornsDecreased appetite; decreased movement or activity; difficulty in breathing; enlarged liver; general body swelling; irritability; muscle stiffness; paleness; yellow eyes or skin.


With injection onlyDifficulty in swallowing; fast or irregular breathing; lightheadedness or fainting; shortness of breath; skin rash, hives and/or itching; swelling of eyelids, face, or lips; tightness in chest; troubled breathing and/or wheezing.


Blue color or flushing or redness of skin; dizziness; fast and/or weak heartbeat; increased sweating; low blood pressure (temporary).

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

Less common

Flushing of face; redness, pain, or swelling at place of injection; skin lesions at place of injection (rare); unusual taste.

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.


This information applies to the following medicines:

1. Menadiol (men-a-DYE-ole)
2. Phytonadione (fye-toe-na-DYE-one)
January 17, 2002

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