Phytonadione, a synthetic form of vitamin K1, is not a single compound when administered as a medication but a formulated product containing the active ingredient and several inactive components. These inactive ingredients, or excipients, are vital for ensuring the drug's stability, shelf-life, and proper delivery. The excipients used differ greatly between injectable emulsions and oral tablets, impacting everything from manufacturing to potential allergenicity.
Ingredients in Injectable Phytonadione
Injectable phytonadione is provided as a sterile, nonpyrogenic aqueous dispersion, commonly an emulsion, suitable for intravenous, intramuscular, and subcutaneous administration. The fat-soluble nature of phytonadione necessitates the use of a surfactant to create a stable emulsion in water. The specific ingredients can vary by manufacturer, but common components found in many formulations include:
- Active Ingredient: Phytonadione (Vitamin K1), 2 or 10 mg per milliliter depending on the concentration.
- Surfactant: A fatty acid derivative, such as polyoxyl 35 castor oil or polysorbate 80, to help disperse the fat-soluble phytonadione in the aqueous solution.
- Tonicity Adjuster: Dextrose (hydrous) is often included to make the emulsion's tonicity compatible with the body's fluids.
- Preservative: Benzyl alcohol is frequently added to prevent bacterial growth. However, some versions are preservative-free, especially for neonatal use, due to the risk of toxicity in infants.
- pH Adjusters: The formulation's pH is carefully controlled, typically between 3.5 and 7.0. Agents like hydrochloric acid, glacial acetic acid, or sodium acetate anhydrous are used for this purpose.
- Solvent: Sterile water for injection serves as the primary fluid medium.
Ingredients in Oral Phytonadione Tablets
Oral formulations, such as Mephyton® tablets, are designed for ingestion and contain different inactive ingredients from the injectable versions. These excipients aid in tablet formation, binding, and disintegration, and they can include:
- Active Ingredient: Phytonadione (Vitamin K1), 5 mg per tablet.
- Binding Agents: Acacia and starch are used to bind the ingredients and hold the tablet together.
- Filling Agents: Calcium phosphate and lactose are common fillers that add bulk to the tablet.
- Lubricant: Magnesium stearate is a lubricant that prevents the tablet mixture from sticking to the manufacturing machinery during compression.
- Disintegrant: Colloidal silicon dioxide helps the tablet break apart easily in the digestive tract, allowing the active ingredient to be released.
- Glidant: Talc acts as a glidant to improve the powder flow during tableting.
Comparison of Ingredients: Injectable vs. Oral
The fundamental difference in ingredients between injectable and oral phytonadione is driven by the route of administration. Injectables require sterile, liquid-compatible components, while oral tablets use binders and fillers for solid form. This table highlights the key contrasts.
| Feature | Injectable Emulsion | Oral Tablet |
|---|---|---|
| Active Ingredient | Phytonadione (Vitamin K1) | Phytonadione (Vitamin K1) |
| Form | Sterile aqueous emulsion | Compressed solid tablet |
| Solvent/Medium | Water for injection | Binders, fillers (e.g., starch, lactose) |
| Dispersion Agent | Surfactant (Polyoxyl 35 castor oil or Polysorbate 80) | Not applicable |
| Preservative | Benzyl alcohol (in some versions) | Not typically required |
| pH Control | Yes, using agents like HCl and sodium acetate | Not applicable |
| Tonicity Agent | Dextrose | Not applicable |
| Binding/Lubricants | Not applicable | Acacia, magnesium stearate, talc |
The Role of Excipients
Excipients are not just fillers; they are crucial for a drug's efficacy and safety. For phytonadione:
- Solubilization: Because phytonadione is fat-soluble, it does not dissolve in water. Surfactants like polyoxyl 35 castor oil are used to create a micellar dispersion, allowing the emulsion to mix evenly and be administered safely via injection.
- Preservation and Stability: Excipients protect the drug. Benzyl alcohol prevents microbial contamination in multi-dose vials of injectable phytonadione. Buffering agents control the pH to prevent the oxygen-sensitive phytonadione from degrading.
- Manufacturing and Delivery: In oral tablets, excipients like binders, fillers, and lubricants ensure the raw materials can be consistently compressed into a uniform tablet shape and release the drug properly once ingested.
Considerations for Specific Formulations
It is always important to check the specific formulation's package insert, as ingredients can differ between brands and for special needs, such as for neonates. For instance, a formulation developed for neonates would typically be preservative-free to avoid benzyl alcohol toxicity risks. Intravenous fat emulsions (IVFEs) can also contain phytonadione, particularly those made with soybean oil, so the amount of vitamin K provided can vary with the IVFE type. Patients should always consult a healthcare provider to understand the specific components of their prescribed phytonadione medication.
Conclusion
In summary, the ingredients in phytonadione vitamin K are more complex than just the active vitamin itself. Injectable formulations utilize surfactants, dextrose, and preservatives in a water-based emulsion, while oral tablets rely on binders, fillers, and lubricants for solid-form delivery. The inactive components are carefully selected to ensure the drug's stability, safety, and proper delivery. Understanding these differences helps to clarify why different phytonadione products have distinct compositions and administration protocols.
Visit the FDA's website for official drug label information on MEPHYTON® (phytonadione) tablets.
