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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Vitamin K [EPC]
Phytonadione is a man-made form of Vitamin K1, essential for the synthesis of blood-clotting factors. It is primarily used to treat coagulation disorders and reverse the effects of anticoagulant medications like warfarin.
Name
Phytonadione
Raw Name
PHYTONADIONE
Category
Vitamin K [EPC]
Drug Count
8
Variant Count
38
Last Verified
February 17, 2026
RxCUI
727625, 1305217, 1305222, 1670192, 312424, 198102
UNII
A034SE7857, 9E8X80D2L0, PQ6CK8PD0R, 6SO6U10H04, 1C6V77QF41, P6YC3EG204, 1O6C93RI7Z, 935E97BOY8, 25X51I8RD4, 68Y4CF58BV, 20RD1DZH99, M572600E5P, 1D1K0N0VVC, VS041H42XC, 7QWA1RIO01, 706IDJ14B7, O80TY208ZW, 18E7415PXQ, 00543AP1JV, 4QQN74LH4O, XK4IUX8MNB, U946SH95EE, WR1WPI7EW8, F7LTH1E20Y, A150AY412V, 2ZK6ZS8392, A9R10K3F2F, BR1SN1JS2W, 2679MF687A, 19F5HK2737, TLM2976OFR, 8K0I04919X, 6DU9Y533FA, 81G40H8B0T
About Phytonadione
Phytonadione is a man-made form of Vitamin K1, essential for the synthesis of blood-clotting factors. It is primarily used to treat coagulation disorders and reverse the effects of anticoagulant medications like warfarin.
Detailed information about Phytonadione
References used for this content
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Phytonadione.
Phytonadione was first isolated in the 1930s and has since become a cornerstone of hematological medicine. The United States Food and Drug Administration (FDA) first approved phytonadione (under the brand name Mephyton) in the 1950s. It serves as a critical intervention for individuals whose bodies cannot produce enough clotting factors, either due to genetic issues, malabsorption, or the presence of certain drugs that interfere with Vitamin K metabolism. Your healthcare provider may prescribe this medication if you are at risk of severe bleeding or if your blood's ability to clot has been dangerously compromised.
To understand how phytonadione works, one must understand the complex process of blood clotting. The body relies on a series of proteins called 'clotting factors' to stop bleeding after an injury. Several of these factors—specifically Factor II (prothrombin), Factor VII, Factor IX, and Factor X—are 'Vitamin K-dependent.' This means they cannot be activated without the presence of Vitamin K.
At the molecular level, phytonadione acts as a necessary cofactor for an enzyme called gamma-glutamyl carboxylase. This enzyme modifies the aforementioned clotting factors, allowing them to bind to calcium ions, which is a required step for them to participate in the coagulation cascade. Without sufficient phytonadione, these proteins remain in an inactive state (sometimes called PIVKAs, or Proteins Induced by Vitamin K Absence), and the blood cannot clot effectively. By providing an exogenous (outside) source of Vitamin K1, phytonadione restores the body's ability to produce functional clotting factors, thereby stopping or preventing hemorrhage (excessive bleeding).
The way the body processes phytonadione is highly dependent on the route of administration (oral vs. injection).
Phytonadione is FDA-approved for several critical indications:
Phytonadione is available in several formulations to suit different clinical needs:
> Important: Only your healthcare provider can determine if Phytonadione is right for your specific condition. The choice of administration route depends on the urgency of the situation and your overall health profile.
Dosage of phytonadione is highly individualized based on the patient's coagulation status, which is measured by the Prothrombin Time (PT) or International Normalized Ratio (INR) blood tests.
Phytonadione is safe and essential for pediatric use, particularly in the neonatal period.
Specific dosage adjustments for patients with kidney disease are generally not required, as phytonadione is primarily metabolized by the liver. However, these patients should be monitored closely for their overall coagulation status.
Patients with liver disease (such as cirrhosis) may not respond well to phytonadione. This is because the liver must be functional enough to use the Vitamin K to create clotting factors. If the liver is severely damaged, giving more Vitamin K may not help, and higher doses or alternative treatments like plasma may be necessary.
Older adults are often more sensitive to the effects of phytonadione, especially if they are taking multiple medications. Healthcare providers usually start with the lowest possible effective dose to avoid making the blood 'too thick' (hypercoagulable), which could lead to blood clots.
If you are taking phytonadione on a schedule and miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular timing. Do not double the dose to 'catch up.' Because phytonadione affects blood clotting, missing a dose can increase your risk of bleeding, so notify your doctor immediately if a dose is missed.
Phytonadione itself has a low toxicity profile, but an 'overdose' in the context of someone taking blood thinners can be dangerous. Too much Vitamin K can make the blood clot too easily, increasing the risk of stroke, heart attack, or deep vein thrombosis (DVT).
In the event of an accidental large ingestion, contact a Poison Control Center or seek emergency medical care immediately.
> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance, as this medication directly impacts your blood's ability to clot.
Most patients tolerate phytonadione well, especially when taken orally. However, some common reactions include:
> Warning: Stop taking Phytonadione and call your doctor immediately if you experience any of these symptoms, as they may indicate a life-threatening reaction.
Phytonadione is typically used for short-term correction of clotting issues. Long-term use is rare except in cases of permanent malabsorption. The primary risk of long-term use is the potential for 'warfarin resistance,' where it becomes very difficult for doctors to re-stabilize a patient on blood thinners because the body's Vitamin K stores are too high. There is no evidence that phytonadione causes cancer or long-term organ damage when used at appropriate clinical doses.
Phytonadione carries a significant FDA Black Box Warning regarding its intravenous and intramuscular use.
Whenever possible, the oral or subcutaneous (under the skin) routes should be used, as they carry a much lower risk of these severe reactions. If IV administration is absolutely necessary, it must be done extremely slowly (no more than 1 mg per minute).
Report any unusual symptoms to your healthcare provider immediately. If you have a history of allergies to Vitamin K or the 'vehicle' used in the injection (polyoxyethylated castor oil), ensure your medical team is aware before treatment begins.
Phytonadione is a high-alert medication because it directly alters the blood's ability to clot. It is not a 'simple vitamin supplement' when used in a clinical setting. Patients must be aware that while it prevents bleeding, it can also increase the risk of unwanted blood clots if the dose is too high or if the patient has underlying heart conditions.
As noted in the side effects section, the FDA has issued a Black Box Warning for phytonadione injections. Fatalities have occurred following intravenous and intramuscular administration. The reaction resembles anaphylactic shock and can occur upon the very first dose, even in patients with no known prior exposure to the drug. Healthcare facilities must have emergency resuscitation equipment (oxygen, epinephrine, etc.) ready whenever phytonadione is injected.
Patients receiving phytonadione require frequent blood monitoring to ensure the medication is working and that the blood is not becoming too prone to clotting.
Phytonadione generally does not affect your ability to drive or operate machinery. However, if you experience dizziness or flushing after an injection, you should wait until these symptoms subside before attempting to drive.
Alcohol should be avoided or strictly limited. Chronic alcohol use can damage the liver and interfere with the production of clotting factors, making phytonadione less effective. Furthermore, alcohol can interact with the underlying conditions (like those requiring warfarin) for which phytonadione is being prescribed.
Phytonadione is usually stopped once the INR has reached the target range or the bleeding has stopped. There is no 'withdrawal syndrome' associated with stopping phytonadione, but the risk of bleeding may return if the underlying cause of the Vitamin K deficiency has not been addressed.
> Important: Discuss all your medical conditions, especially any history of heart valve issues or blood clots, with your healthcare provider before starting Phytonadione.
There are no drugs that are strictly 'contraindicated' in the sense that they can never be used with phytonadione, but Warfarin is its primary antagonist. Using phytonadione while trying to maintain a therapeutic level of warfarin will 'cancel out' the warfarin's effect. This is only done intentionally when the warfarin level is dangerously high.
Phytonadione will directly affect the results of:
Always inform the laboratory and your doctor that you have taken phytonadione, as it will explain why these test results may have changed significantly in a short period.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, as even small changes in Vitamin K intake can have major effects on your blood's thickness.
Phytonadione should NEVER be used in the following circumstances:
In these cases, the doctor will weigh the risks against the benefits:
There is a potential for cross-sensitivity between different forms of Vitamin K. If you are allergic to 'phytonadione,' you may also react to 'menaquinone' (Vitamin K2) supplements. Additionally, because the injectable form often contains a castor oil derivative, patients with known allergies to products containing 'Cremophor' (used in some chemotherapy drugs like paclitaxel) should be treated with extreme caution.
> Important: Your healthcare provider will evaluate your complete medical history, including any history of 'thick blood' or heart valve replacements, before prescribing Phytonadione.
Phytonadione is classified as FDA Pregnancy Category C. This means that animal reproduction studies have shown an adverse effect on the fetus, or there are no adequate and well-controlled studies in humans. However, the potential benefits may warrant use of the drug in pregnant women despite potential risks.
In clinical practice, phytonadione is used in pregnancy if the mother has a severe Vitamin K deficiency or is on anticoagulants that put the fetus at risk of hemorrhage. It does not appear to be 'teratogenic' (causing birth defects) in the traditional sense, but it should only be used under strict medical supervision.
Phytonadione is excreted into breast milk in very small amounts. While it is generally considered safe for the nursing infant, it is important to note that breast milk is naturally low in Vitamin K. This is why all infants are given a Vitamin K injection at birth, regardless of whether they will be breastfed. If a nursing mother is taking high doses of phytonadione, the infant should be monitored for any unusual signs, though the risk of harm is considered very low.
Phytonadione is a standard-of-care medication in pediatrics. Its most vital role is the prevention of Vitamin K Deficiency Bleeding (VKDB) in newborns.
Patients over the age of 65 often have multiple medical conditions and take various medications that can interact with phytonadione.
No specific dose adjustments are typically required for patients with kidney disease. However, these patients are often at higher risk for cardiovascular events, so the pro-clotting effects of phytonadione must be monitored carefully. Phytonadione is not removed by hemodialysis due to its high protein binding.
In patients with liver impairment (Child-Pugh Class B or C), phytonadione may have a reduced effect. If the liver cells (hepatocytes) are damaged, they cannot process Vitamin K to make clotting factors. If a patient does not respond to an initial dose of phytonadione, it is often a sign of severe liver dysfunction rather than a 'lack of vitamin,' and further doses are unlikely to help.
> Important: Special populations, particularly newborns and the elderly, require individualized medical assessment and frequent blood testing during phytonadione therapy.
Phytonadione (Vitamin K1) is a critical component of the 'Vitamin K Cycle.' Its primary molecular role is to serve as a cofactor for the enzyme gamma-glutamyl carboxylase.
This enzyme is responsible for the post-translational modification of specific glutamate residues on several proteins. It adds a carboxyl group to these residues, converting them into gamma-carboxyglutamate (Gla). This 'Gla' residue is essential because it allows the proteins to bind to calcium. Without this calcium-binding ability, the clotting factors cannot anchor themselves to the surface of platelets at the site of an injury.
Specifically, phytonadione is required for the activation of:
| Parameter | Value |
|---|---|
| Bioavailability | 10% - 70% (Oral, varies with fat intake) |
| Protein Binding | >90% (Primarily to VLDL) |
| Half-life | 1.5 - 3 hours (Terminal phase) |
| Tmax | 4 - 6 hours (Oral) |
| Metabolism | Hepatic (Vitamin K Epoxide Reductase cycle) |
| Excretion | Fecal (40% - 50%), Renal (8% - 30%) |
Phytonadione is the prototypical member of the Vitamin K class. Related medications include Menaquinone (Vitamin K2), which is produced by bacteria and found in fermented foods, and Menadione (Vitamin K3), a synthetic form that is no longer used in human medicine due to toxicity but is sometimes used in animal feed.
Medications containing this ingredient
Common questions about Phytonadione
Phytonadione, also known as Vitamin K1, is primarily used to treat and prevent bleeding disorders caused by a lack of Vitamin K. Its most common clinical use is to reverse the effects of blood-thinning medications like warfarin when the blood becomes too thin and poses a risk of hemorrhage. It is also routinely given to newborn babies to prevent a serious condition called Vitamin K Deficiency Bleeding (VKDB). Additionally, it is used for patients who cannot absorb enough Vitamin K from their diet due to medical conditions like cystic fibrosis or liver disease. By helping the body produce essential clotting factors, it ensures that the blood can thicken and stop bleeding effectively.
For most people taking the oral tablet, side effects are very rare and mild, occasionally including a temporary upset stomach or an unusual taste in the mouth. However, when given by injection, some people may experience 'flushing' (a sudden warmth or redness in the face), sweating, or a brief feeling of dizziness. The most common reaction for the injectable form is pain or swelling at the site of the needle prick. It is important to note that while common side effects are mild, the injectable form carries a risk of a very rare but severe allergic reaction. Always tell your doctor if you feel itchy, short of breath, or lightheaded after receiving a dose.
It is generally advised to avoid or strictly limit alcohol consumption while taking phytonadione. Alcohol can interfere with the liver's ability to produce clotting factors, which may work against the purpose of the medication. Furthermore, many people taking phytonadione are doing so because they are on warfarin, and alcohol is known to cause dangerous fluctuations in warfarin levels. Drinking alcohol can increase your risk of bleeding or, conversely, increase your risk of blood clots depending on your specific health situation. Always consult your healthcare provider about whether any amount of alcohol is safe for you while being treated for clotting issues.
Phytonadione is classified as Pregnancy Category C, meaning it should only be used if the potential benefit to the mother outweighs the potential risk to the fetus. While Vitamin K is a natural substance essential for health, high pharmaceutical doses during pregnancy must be carefully managed by a doctor. It is typically used in pregnancy only to treat severe maternal deficiency or to prevent bleeding in the fetus if the mother is taking certain medications. There is no strong evidence that it causes birth defects, but it is not recommended for routine use without a specific medical indication. If you are pregnant or planning to become pregnant, discuss the necessity of this medication with your obstetrician.
The time it takes for phytonadione to work depends on how it is administered and the severity of the deficiency. When taken as an oral tablet, it usually takes between 6 and 10 hours to begin showing an effect on blood clotting tests (like the INR). If given by an intravenous (IV) injection, the process starts much faster, with initial effects often seen within 1 to 2 hours. However, it can take up to 24 hours for the full effect to be realized and for the blood's clotting ability to return to a safe range. Because the effect is not instantaneous, doctors often use other treatments like plasma if immediate, second-by-second clotting is required.
Yes, phytonadione can usually be stopped suddenly without causing a 'withdrawal' effect, as it is a vitamin and not a habit-forming drug. However, you should only stop taking it when directed to do so by your healthcare provider. If you stop taking it before your Vitamin K levels have stabilized or before your blood-thinner levels are corrected, you may be at an increased risk of dangerous bleeding. Your doctor will use blood tests to determine exactly when it is safe for you to discontinue the medication. Never stop this medication on your own if it has been prescribed for a serious clotting disorder.
If you miss a dose of phytonadione, take it as soon as you remember to ensure your blood's clotting factors remain at a safe level. However, if it is almost time for your next scheduled dose, you should skip the missed dose and continue with your regular schedule. Do not take two doses at once to make up for the one you missed, as this could potentially make your blood 'too thick' and increase the risk of a blood clot. Because this medication is critical for preventing bleeding, you should notify your doctor or pharmacist if you miss a dose so they can decide if you need an extra blood test.
There is no clinical evidence to suggest that phytonadione causes weight gain. It is a fat-soluble vitamin that helps with blood clotting and does not affect your metabolism, appetite, or fat storage in a way that would lead to increased body weight. If you notice sudden weight gain or swelling while taking this medication, it is more likely related to an underlying medical condition, such as heart or kidney issues, rather than the phytonadione itself. Always report sudden weight changes or swelling in your legs to your healthcare provider for further investigation.
Phytonadione has several important interactions with other medications that you must be aware of. It directly cancels out the effect of the blood-thinner warfarin, which is often the intended use, but it can also be affected by other drugs. Medications like orlistat (for weight loss), cholestyramine (for cholesterol), and mineral oil can prevent your body from absorbing oral phytonadione. Additionally, certain antibiotics can change the way your body produces its own Vitamin K, potentially altering how much phytonadione you need. Always provide your doctor with a full list of all prescriptions, over-the-counter drugs, and herbal supplements you are taking.
Yes, phytonadione is available as a generic medication in both tablet and injectable forms. The generic versions are bioequivalent to the brand-name versions (such as Mephyton or Vitamin K1), meaning they contain the same active ingredient and work the same way in the body. Generic phytonadione is typically much more affordable than brand-name versions and is widely covered by most insurance plans. Whether you receive the brand name or the generic, the safety warnings and the need for regular blood monitoring remain exactly the same. Consult your pharmacist to see if a generic version is appropriate for your prescription.