Adjuvants are substances that are added to parenteral products (such as vaccines and injectable drugs) to enhance their effectiveness, stability, or delivery characteristics. Here are several types of adjuvants commonly used in parenteral formulations:

1. Alum

  • Type: Salts of aluminum (e.g., aluminum hydroxide, aluminum phosphate)
  • Use: Commonly used in vaccines to enhance immune response.

2. Emulsifiers

  • Type: Surfactants (e.g., polysorbates, lecithin)
  • Use: Help to stabilize emulsions and improve the solubility of hydrophobic drugs.

3. Oils

  • Type: Mineral oil, sesame oil, or synthetic oils
  • Use: Often used in depot formulations for sustained release of drugs.

4. Monophosphoryl Lipid A (MPLA)

  • Type: TLR-4 agonist
  • Use: Used to enhance immune response in vaccines.

5. Liposomes

  • Type: Phospholipid vesicles
  • Use: Encapsulate drugs to improve delivery and bioavailability.

6. Saponins

  • Type: Glycosides
  • Use: Used as immunostimulants in vaccines (e.g., Quil A).

7. CpG Oligodeoxynucleotides

  • Type: Synthetic DNA sequences
  • Use: Act as immune modulators by stimulating toll-like receptors.

8. Adjuvant Systems (AS)

  • Type: Combinations of various adjuvants (e.g., AS01, AS03)
  • Use: Designed to enhance vaccine efficacy and immunogenicity.

9. Zinc Salts

  • Type: Zinc sulfate, zinc oxide
  • Use: Can enhance stability and solubility of certain drugs.

10. Buffers

  • Type: Phosphate buffers, citrate buffers
  • Use: Maintain pH stability of the formulation.

11. Cryoprotectants

  • Type: Sugars (e.g., sucrose, trehalose)
  • Use: Protect proteins and other biologics during freeze-drying.

12. Stabilizers

  • Type: Polymers (e.g., polyvinyl alcohol, polyethylene glycol)
  • Use: Help maintain the stability of proteins and prevent aggregation.

13. Tocopherols

  • Type: Vitamin E derivatives
  • Use: Used for antioxidant properties to stabilize formulations.

14. Calcium Salts

  • Type: Calcium chloride, calcium phosphate
  • Use: May be used to enhance the immune response or stabilize proteins.

These adjuvants play crucial roles in improving the safety, efficacy, and stability of parenteral products, particularly in vaccines and biologics.