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Mephyton Dosage

Generic name: phytonadione 5mg
Dosage form: tablet
Drug classes: Anticoagulant reversal agents, Vitamins

Medically reviewed by Drugs.com. Last updated on Jul 21, 2021.

Dosing Considerations

Avoid the oral route when the clinical disorder would prevent proper absorption. Bile salts must be given with the tablets when the endogenous supply of bile to the gastrointestinal tract is deficient. The coagulant effects of Mephyton are not immediate; improvement of international normalized ratio (INR) may take 1-8 hours. Interim use of whole blood or component therapy may also be necessary if bleeding is severe.

Mephyton will not counteract the anticoagulant action of heparin.

When Mephyton is used to correct excessive anticoagulant-induced hypoprothrombinemia, anticoagulant therapy still being indicated, the patient is again faced with the clotting hazards existing prior to starting the anticoagulant therapy. Mephyton is not a clotting agent, but overzealous therapy with vitamin K1 may restore conditions which originally permitted thromboembolic phenomena. Dosage should be kept as low as possible, and prothrombin time should be checked regularly as clinical conditions indicate.

Recommended Dosage

Anticoagulant-Induced Prothrombin Deficiency in Adults

The recommended dose to correct excessively prolonged prothrombin times caused by oral anticoagulant therapy is, 2.5 to 10 mg or up to 25 mg initially. In some instances 50 mg may be required. Frequency and amount of subsequent doses should be determined by prothrombin time response or clinical condition. If, in 12 to 48 hours after oral administration, the prothrombin time has not been shortened satisfactorily, repeat the dose.

Repeated large doses of Mephyton are not warranted in liver disease if the response to initial use of the vitamin is unsatisfactory. Failure to respond to Mephyton may indicate a congenital coagulation defect or that the condition being treated is unresponsive to vitamin K.

Hypoprothrombinemia Due to Other Causes in Adults

If possible, discontinuation or reduction of the dosage of drugs interfering with coagulation mechanisms (such as salicylates, antibiotics) is suggested as an alternative to administering concurrent Mephyton. The severity of the coagulation disorder should determine whether the immediate administration of Mephyton is required in addition to discontinuation or reduction of interfering drugs.

The recommended dose is 2.5 to 25 mg or more (sometimes up to 50 mg). Evaluate INR after 6-8 hours, and repeat dose if INR remains prolonged. Modify subsequent dosage (amount and frequency) based upon the INR or clinical condition.

Further information

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