Vitamin K is a crucial fat-soluble vitamin essential for blood clotting and bone health, available in the UK under several pharmaceutical trade names. The most widely recognised trade name is Konakion® MM, a phytomenadione (vitamin K1) preparation used for neonatal prophylaxis, treating deficiency states, and reversing warfarin over-anticoagulation. Understanding the different formulations and their clinical applications helps healthcare professionals prescribe appropriately and enables patients to recognise their prescribed medication. This article explores the trade names for vitamin K available in the UK, their uses, administration routes, and important safety considerations for both clinical and supplementation contexts.

What Is Vitamin K and Why Is It Important?

Vitamin K is a fat-soluble vitamin essential for blood clotting and bone health. It exists in two main forms: vitamin K1 (phylloquinone), found primarily in green leafy vegetables, and vitamin K2 (menaquinone), produced by gut bacteria and present in fermented foods. Vitamin K3 (menadione) is a synthetic compound not used in UK human medicinal products because of toxicity concerns.

The primary physiological role of vitamin K involves the activation of clotting factors in the liver, specifically factors II (prothrombin), VII, IX, and X, as well as proteins C and S. Without adequate vitamin K, the blood clotting cascade cannot function properly, leading to increased bleeding risk. This mechanism is particularly important in neonates, who have limited vitamin K stores at birth and require prophylactic supplementation to prevent vitamin K deficiency bleeding (VKDB), formerly known as haemorrhagic disease of the newborn.

Beyond haemostasis, vitamin K plays a crucial role in bone metabolism by activating osteocalcin, a protein that binds calcium to the bone matrix. Some research suggests potential involvement in cardiovascular health, though this remains under investigation with evidence still emerging. Deficiency is uncommon in healthy adults due to dietary intake and bacterial synthesis, but certain groups face increased risk: newborns, individuals with malabsorption disorders (such as coeliac disease, Crohn's disease, or cystic fibrosis), and those on long-term antibiotics that disrupt gut flora. Patients taking warfarin are not vitamin K deficient, but warfarin works by antagonising vitamin K action.

In clinical practice, vitamin K supplementation is indicated for treating or preventing deficiency states, reversing warfarin over-anticoagulation, and as prophylaxis in specific patient populations. UK clinical practice for warfarin reversal follows British Society for Haematology guidance, the BNF, and local protocols.

Common Trade Names for Vitamin K in the UK

In the UK, vitamin K preparations are available under several trade names and formulations, each suited to different clinical scenarios. The most commonly encountered pharmaceutical form is phytomenadione (vitamin K1), which is the preferred therapeutic agent due to its efficacy and safety profile.

Konakion® MM is the principal trade name for phytomenadione in the UK. It is formulated as a mixed micelle solution, designed to improve absorption and reduce the risk of anaphylactoid reactions associated with older formulations. Konakion MM is available in two strengths: 2mg in 0.2ml (primarily for neonatal use) and 10mg in 1ml (for adult administration). This preparation can be given intravenously, intramuscularly, or orally (the injection solution can be administered orally as per the SmPC). Konakion MM Paediatric specifically refers to the 2mg ampoule used for vitamin K prophylaxis in newborns, administered either intramuscularly as a single dose or orally in a multiple-dose regimen.

For oral supplementation, low-dose vitamin K products are available as food supplements, often combined with other nutrients, particularly vitamin D and calcium, marketed for bone health support. These are typically available over-the-counter in pharmacies and health food shops but are not licensed medicines for therapeutic indications.

It is important to note that vitamin K preparations for therapeutic use are prescription-only medicines (POM) when used for clinical purposes, such as warfarin reversal or treating deficiency states. Healthcare professionals should always specify the formulation, strength, and route of administration when prescribing vitamin K to ensure appropriate treatment. The subcutaneous route is generally not recommended due to variable absorption.

How to Take Vitamin K Safely

The safe administration of vitamin K depends on the clinical indication, patient age, and chosen formulation. For neonatal prophylaxis, NICE recommends that all newborns receive vitamin K to prevent VKDB. Parents can choose between a single intramuscular injection of 1mg at birth (Konakion MM Paediatric) or an oral regimen consisting of 2mg at birth, followed by 2mg at 4–7 days, and a final 2mg dose at one month for exclusively breastfed infants. The intramuscular route provides more reliable protection, whilst the oral route requires adherence to the complete schedule for effectiveness. For preterm infants or those with cholestasis, intramuscular administration is preferred, and dosing schedules may differ; healthcare professionals should follow the SmPC and local neonatal guidelines.

For warfarin reversal, the dose and route depend on the INR level and whether bleeding is present. In cases of major bleeding with elevated INR, intravenous phytomenadione 5–10mg is administered alongside prothrombin complex concentrate (PCC). For INR elevation without bleeding, smaller doses (1–5mg) may be given orally or intravenously, depending on urgency. Clinicians should follow British Society for Haematology guidance, the BNF, and local protocols for INR-specific dosing. Intravenous administration should be slow and not exceed the maximum rate specified in the SmPC to reduce the risk of anaphylactoid reactions. Facilities for managing such reactions should be immediately available.

For treating deficiency, oral phytomenadione is typically sufficient in mild cases, with doses ranging from 5–20mg daily. In malabsorption syndromes or severe deficiency, parenteral administration may be necessary. Patients with chronic conditions affecting fat absorption may require ongoing supplementation.

Important safety considerations include:

• Always administer intravenous vitamin K slowly according to SmPC guidance and monitor for allergic reactions

• Avoid intramuscular injections in patients with bleeding disorders or those on anticoagulants (except neonates)

• Subcutaneous administration is not recommended due to variable absorption

• Store ampoules protected from light

• For oral doses, take with food to enhance absorption as vitamin K is fat-soluble

• In patients on warfarin, vitamin K directly antagonises the anticoagulant effect, so dosing must be carefully calibrated

Patients should inform their GP or anticoagulation clinic before taking vitamin K supplements if they are on warfarin or other anticoagulants, as this may necessitate dose adjustments and more frequent INR monitoring.

Potential Side Effects and Interactions

Vitamin K is generally well-tolerated, with serious adverse effects being rare when administered appropriately. However, healthcare professionals and patients should be aware of potential side effects and clinically significant interactions.

Common side effects are minimal with oral administration. Some patients may experience mild gastrointestinal disturbances, including nausea or upset stomach, particularly with higher doses. These effects are typically transient and resolve without intervention.

Injection site reactions can occur with intramuscular administration, including pain, swelling, or bruising at the injection site. In neonates receiving intramuscular Konakion MM Paediatric, local reactions are usually minor and self-limiting.

Serious adverse effects are predominantly associated with intravenous administration. Anaphylactoid reactions, though rare with modern mixed micelle formulations, can occur and may include flushing, dyspnoea, chest tightness, hypotension, and in severe cases, cardiovascular collapse. This risk necessitates slow intravenous administration and immediate availability of resuscitation facilities. Intravenous vitamin K should only be used when oral administration is not feasible or when rapid reversal of anticoagulation is clinically essential.

Drug interactions are clinically significant and must be carefully managed:

• Warfarin and other coumarins: Vitamin K directly antagonises these anticoagulants by promoting synthesis of clotting factors. Whilst this interaction is therapeutically exploited in warfarin reversal, inadvertent vitamin K intake (including from dietary sources or supplements) can reduce anticoagulant efficacy and increase thrombotic risk. Patients on warfarin should maintain consistent vitamin K intake and avoid high-dose supplements without medical supervision.

• Antibiotics: Broad-spectrum antibiotics can reduce gut bacteria that synthesise vitamin K2, potentially increasing deficiency risk during prolonged courses.

• Bile acid sequestrants (cholestyramine, colestipol): These medications can impair vitamin K absorption. If co-administration is necessary, vitamin K should be taken several hours apart from these agents.

• Orlistat: This weight-loss medication reduces fat absorption and may decrease vitamin K uptake, potentially necessitating supplementation.

• Certain cephalosporins with N-methylthiotetrazole side chains can cause hypoprothrombinaemia, potentially affecting vitamin K metabolism.

When to seek medical attention: Patients should contact their GP or seek urgent care if they experience signs of allergic reaction (rash, itching, swelling, difficulty breathing) following vitamin K administration, unusual bleeding or bruising, or if taking warfarin and concerned about vitamin K intake affecting their anticoagulation control. Any patient on anticoagulation therapy should have regular INR monitoring as per their anticoagulation clinic protocol, with additional checks if vitamin K supplementation is initiated or dietary intake changes significantly.

Suspected adverse reactions to vitamin K preparations should be reported via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions