KONAKION

Indications

• Vitamin K deficiency
• Coagulation disorders due to vitamin K deficiency
• Reversal of anticoagulation in patients on warfarin therapy
• Neonatal prophylaxis of vitamin K deficiency bleeding

Dosage

Adults: For adults, the typical dosage is 1-5 mg administered orally or via slow intravenous injection. Dosing may be adjusted based on clinical response and INR levels.

Mechanism of action

Vitamin K acts as a cofactor for the enzyme gamma-carboxylase, which catalyzes the carboxylation of specific glutamic acid residues on clotting factors II (prothrombin), VII, IX, and X. This carboxylation allows these factors to bind calcium ions, which is essential for their activation and subsequent role in the coagulation cascade. Additionally, vitamin K is involved in carboxylating matrix proteins in chondrocytes, possibly influencing bone density and vascular calcification.

Pharmacodynamics

Phytomenadione is indicated in the management of coagulation disorders resulting from vitamin K deficiency. It promotes the hepatic biosynthesis of prothrombin and other clotting factors, restoring normal clotting function. Its long duration of action and wide therapeutic index make it a safe option for patients requiring vitamin K supplementation, but monitoring of prothrombin time is essential during therapy. Hypersensitivity reactions may occur, especially with parenteral administration.

Pharmacokinetics

Phytomenadione is absorbed in the intestine and transported in the lymphatic system. It is then stored in the liver and released into circulation as needed for clotting factor synthesis. Vitamin K has a long half-life, allowing for sustained action, and is cycled in the body, contributing to its prolonged effects. The elimination occurs primarily through the hepatic pathway, and caution is advised in patients with hepatic impairment.

Contra-indications

• Hypersensitivity to phytomenadione or any of its excipients
• Severe hepatic impairment
• Hyperbilirubinaemia in neonates
• Known risk of hemolytic anemia in newborns

Adverse effects

• Anaphylactoid reactions (especially with intravenous use)
• Hypersensitivity reactions
• Flushing
• Rash
• Gastrointestinal disturbances

Interactions

• Anticoagulants (e.g., warfarin) - may require dose adjustment
• Cholestyramine - may reduce absorption of vitamin K
• Mineral oil - may interfere with absorption
• Antibiotics (e.g., cephalosporins) - may affect vitamin K synthesis by gut flora

Precautions

• Use with caution in patients with G6PD deficiency due to risk of hemolysis
• Monitor INR closely in patients with hepatic impairment
• Use intravenous preparations slowly to avoid vascular collapse
• Caution in elderly patients due to altered pharmacokinetics

Pregnancy

Use only if potential benefit outweighs risk, especially in late pregnancy due to risk of neonatal hemolytic anemia.

Breast-feeding

Present in breast milk; caution is advised if large doses are administered.

Storage

Store at room temperature, away from light and moisture. Protect from freezing.

Formulations

• Capsules (200 units, 400 units)
• Oral solutions
• Tablets (10 mg)
• Injectable solution for intravenous use

Mechanism of action

Vitamin K is a cofactor of gamma-carboxylase. Gamma carboxylase attaches carboxylic acid functional groups to glutamate, allowing precursors of factors II, VII, IX, and X to bind calcium ions. Binding of calcium ions converts these clotting factors to their active form, which are then secreted from hepatocytes into the blood, restoring normal clotting function. Vitamin K may also carboxylate matrix proteins in chondrocytes, inhibiting calcification of joints, and may increase type II collagen. The role of vitamin K in osteroarthritis, bone density, and vascular calcification is currently under investigation. Vit k is necessary for formation of prothrombinogen & other blood clotting factors in liver. During clotting, circulating prothrombin is required for production of thrombin; in turn, thrombin converts fibrinogen to fibrin, network of which constitutes clot. /vit k/ In normal animals and man, phyltonadione ... /is/ virtually devoid of pharmacodynamic activity. In Animals and man deficient in vitamin k, the pharmacological action of vitamin k is identical to its normal physiological function, that is, to promote hepatic biosynthesis of prothrombin (factor ii), proconvertin (factor vii), plasma thromboplastin component (ptc, christmas factor, factor ix), and Stuart factor (factor x). On the basis of studies of microsomal metabolism in vitro and studies in rats and mice in vivo, /it was suggested/ that vitamin K may be mutagenic by affecting the mixed-function oxidase system which metabolizes benzo(a)pyrene. Phylloquinone at a high concentration (200 umol/l) inhibited the conversion of benzo(a)pyrene to its more polar metabolites, ... . Paradoxically, at a lower concentration of phylloquinone (25 umol/l), ... the metabolism of benzo(a)pyrene was increased. In this system, therefore, .... phylloquinone could either potentiate or inhibit it, depending on the concentration. This overall weaker inhibitory effect of phylloquinone could be due to the low solubility of this lipophilic compound, but it is difficult to explain the mechanism of the enhanced metabolism of benzo(a)pyrene at lower concentrations of phylloquinone.

Pharmacodynamics

Phylloquinone is a vitamin K indicated in the treatment of coagulation disorders due to faulty formation of coagulation factors II, VII, IX, and X caused by deficiency or interference in the activity of vitamin K. It has a long duration of action as vitamin K is cycled in the body, and a wide therapeutic index as large doses can be tolerated. Patients should have their prothrombin time monitored during therapy and healthcare professionals should be aware of the increased risk of hypersensitivity reactions with parenteral administration.