Menadione is a synthetic, fat-soluble vitamin K analogue (Vitamin K3). It is a provitamin that is converted in the body to menaquinone (Vitamin K2). Its primary clinical role is in the prevention and treatment of hypoprothrombinemia (vitamin K deficiency) leading to coagulation disorders. Unlike natural vitamin K1 (phytonadione), menadione is water-soluble, which historically influenced its use. However, due to its association with hemolytic anemia, kernicterus in neonates, and hepatotoxicity, its systemic therapeutic use has been largely superseded by safer vitamin K1 in many countries, including India. It remains available in specific formulations and is still used in veterinary medicine and some topical applications.
Adult: Oral: 5-10 mg once or twice daily. Therapeutic dose for deficiency: 10-20 mg/day. For warfarin reversal (if K1 unavailable): 2.5-10 mg orally; effect monitored by INR after 24-48 hours. IM/SC: 5-15 mg/day (rarely used now).
Note: Oral: Administer with food to enhance absorption (especially fatty meal). Do not crush/chew tablets unless specified. Parenteral: Deep intramuscular (IM) or subcutaneous (SC) injection. Intravenous (IV) route is NOT recommended due to risk of anaphylactoid reactions. Strict aseptic technique.
Menadione serves as a provitamin. It is converted in the body to menaquinone-4 (MK-4), an active form of vitamin K. Vitamin K acts as an essential cofactor for the hepatic microsomal enzyme gamma-glutamyl carboxylase. This enzyme catalyzes the post-translational carboxylation of glutamic acid residues to gamma-carboxyglutamic acid (Gla) on the precursor proteins of coagulation factors II (prothrombin), VII, IX, and X, as well as anticoagulant proteins C and S. The carboxylation reaction is essential for these factors to bind calcium ions and subsequently bind to phospholipid surfaces, a critical step in the coagulation cascade.
Pregnancy: Category C (US FDA). Animal studies show risk. Use only if potential benefit justifies potential fetal risk, especially near term due to risk of hemolytic anemia and hyperbilirubinemia in the newborn. Vitamin K1 is preferred.
Driving: Unlikely to affect driving ability. However, dizziness has been reported rarely.
| Warfarin, Acenocoumarol | Menadione antagonizes the anticoagulant effect, reducing INR. Can lead to treatment failure or thrombosis. | Major |
| Broad-spectrum Antibiotics (e.g., Cephalosporins like cefoperazone, Nalidixic acid) | May potentiate hypoprothrombinemia, increasing bleeding risk. Menadione may be used to correct this. | Moderate |
| Orlistat, Mineral Oil | Reduces absorption of fat-soluble vitamins including menadione, potentially reducing its efficacy. | Moderate |
| Cholestyramine, Colestipol | Bile acid sequestrants bind menadione in the gut, reducing its absorption. Administer menadione at least 4 hours before or after these drugs. | Moderate |
| High-dose Salicylates (Aspirin) | May potentiate hypoprothrombinemia. | Moderate |
Same composition (Menadione (10mg)), different brands: