1. Clinical Overview
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with hemolytic anemia, kernicterus in neonates, and hepatotoxicity, its systemic therapeutic use has been largely superseded by safer vitamin K1 in many countries, including India.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.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: Prothrombin time (PT) correction begins within 6-12 hours. Parenteral: More rapid, with effects seen within 1-2 hours. | The effect on coagulation factors lasts approximately 24 hours, but full synthesis of new coagulation factors (II, VII, IX, X) takes up to 24-48 hours for complete normalization of PT. | Oral bioavailability is variable and highly dependent on bile salts for absorption from the intestine. In the presence of normal biliary function, it is moderately absorbed. Parenteral administration provides 100% bioavailability. |
2. Mechanism of Action
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.
3. Indications & Uses
- Treatment of hypoprothrombinemia (vitamin K deficiency) due to obstructive jaundice, biliary fistula, malabsorption syndromes (e.g., celiac disease, sprue)
- Prophylaxis and treatment of hemorrhagic disease in adults (though Vitamin K1 is preferred)
- Correction of excessive anticoagulation induced by vitamin K antagonist drugs (e.g., warfarin) ONLY when Vitamin K1 is not available and under strict monitoring (not first-line).
4. Dosage & Administration
Adult Dosage: 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).
Administration: 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.
5. Side Effects
Common side effects may include:
- Gastrointestinal upset (nausea, vomiting)
- Altered taste sensation
- Flushing sensation (especially with IV, which is contraindicated)
- Pain and swelling at injection site (for parenteral forms).
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| 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 |
7. Patient Counselling
- DO take the tablet with food, preferably a meal containing some fat, to improve absorption.
- DO inform all your doctors and dentists that you are taking this medication, especially if you are on blood thinners (e.g., warfarin).
- DO keep follow-up appointments for blood tests (PT/INR) as advised.
- DO NOT take it if you are pregnant, planning pregnancy, or breastfeeding without consulting your doctor.
- DO NOT give this medicine to infants or children unless specifically prescribed by a pediatric specialist.
- DO NOT take double doses to make up for a missed dose.
8. Toxicology & Storage
Overdose: Symptoms of hypervitaminosis K: Hemolytic anemia (fatigue, pallor, jaundice), hepatotoxicity (nausea, vomiting, right upper quadrant pain, elevated liver enzymes), hyperbilirubinemia, kernicterus in infants, methemoglobinemia (cyanosis, dyspnea).
Storage: Store in a cool, dry place, protected from light and moisture. Keep away from children. Do not freeze. Store tablets in their original blister pack or container. For injections, store as per manufacturer's instructions (usually at room temperature, protected from light). Do not use if the solution is discolored or contains particles.